Analog vs digital scope - Page 1
Forum section: electronics / testgear

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 03:03:48 am
content: New member here and I am looking to get my first oscilloscope. Last time I touched one was in school in the early 80's, sad.Anyway, I have a vintage Fender guitar amp and it needs work. I am going to replace the tubes, recap it, the standard stuff. Might do more on tone controls, hum/noise reduction and who knows what else. I just got a bug to buy a scope to help in this project and if for nothing else for the fun of it and just have around for other projects I might get into.Since its been a long time since I have used one, I could use a little advice. I thought about going to ebay and just getting a cheap old analog scope. Then started looking at the modern DSOs and holy cow the things they can do nowadays. I saw some under $400 that did FFT, wave sampling and storage, and well I am sure you all know.So my question is: which is moreappropriatefor working on an old tube amplifier, analog or digital? An old analog ebay scope might run around 200 with shipping but 200 more gets me a DSO with so much more functionality, but it might not be the best tool for the job. I am definitely leaning towards a DSO unless there is some real limitations with them for tube work (upwards of 500vdc).I am not asking which scope I should buy, this is a more fundamental question - which type. And once I know which type, I can search this forum for threads on particular ones.Sorry, maybe I should have searched for the "analog vs dso" already, so I will do that now. But if you have thoughts or a link to a discussion it would be appreciated.

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 09, 2020, 03:20:14 am
content: Welcome!Digital scopes have replaced analog scopes in every way, shape and form. Sure, some still prefer analog and that’s fine but there aren't many upsides to older analog scopes that are getting long in the tooth. Big, noisy, hot and no storage. I still like my thirty year old 2245A and still use it. But, I took it out of the box, new, all those years ago. My daily driver is a TDS220, maybe second gen digital. Not great but okay. I use them both, it just depends. The newer stuff is way better with respect to performance, I don’t understand why they they still fetch $200 and more on eBay. I guess there’s a different flavor for everyone.IMO, If I had no scope and was going to do amplifier work, I’d buy a modern digital and a differential probe to work on tube stuff. The bigger screens, compact size and overall performance make it a no brainer.I’ll also add that at 700 volts, I wouldn’t trust my life to a $8 Chinese probe. Don’t go cheap when it comes to probes and safety.

author: bob91343
author_rank: Super Contributor
timestamp: April 09, 2020, 04:30:15 am
content: I have both and sometimes one is better than the other. Certainly analog is more intuitive and when working on audio gear is probably the simplest way to go. For more sophisticated measurements the digital can give a new functionality.Some waves are difficult to display on either but I have had more success with analog, especially when trying to view an amplitude modulated signal. And of course the gremlin called aliasing only exists on digital units.

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 04:58:44 am
content: I'll always have a soft spot for my Tek 465, and the XY mode still beats that on any DSO I've ever used. Despite that, I'd say digital hands down, there are a very few niche applications (like XY) where analog is superior, for everything else digital is the way to go. I also still see some value in a beginner playing with an analog scope but if you already know how to use a scope then there's not much to be gainedThe one reason I'd say to maybe go with an analog scope is price, if you're on a tight budget sometimes you can find an analog scope for peanuts, occasionally free. If the price is right, it will do the job you're trying to do.

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 05:03:04 am
content: Quote from: WattsThat on April 09, 2020, 03:20:14 amI don't understand that either. I'd consider paying $100 for a good condition TDS220 because I'm a long time Tek fan, but $200+? That's just nuts, at that price I'd toss in another $150 and get a 4 channel Rigol with a nice color display, factory new.

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 09, 2020, 05:17:04 am
content: QuoteThat occurs when you don’t have enough samples to display a digitized waveform. That’s not going to occur at audio frequencies with a modern 70MHz digital scope, pretty much the bottom end of any decent scope in today’s market. Looking at any modulated waveform, for example audio, without a consistent amplitude and or frequency, is a perfect example of where digital storage comes to the rescue with being able to examine any part of the waveform at a desired sweep speed. So long as you capture the event with enough samples in memory, you can look at it fourteen ways to Sunday. That’s not going to happen with an analog scope

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2020, 07:54:26 am
content: Quote from: ToddW on April 09, 2020, 03:03:48 amThere's no such thing. Any that are still working are hoarded by Gollums.

author: AndyC_772
author_rank: Super Contributor
timestamp: April 09, 2020, 08:11:48 am
content: Look at probes first, *then* worry about what scope to connect them to. Any normal bench scope measures voltage with respect to ground, which in turn is connected through to mains earth, and I wouldn't personally want to have an earthed lead flapping about inside a high voltage amp even if I was measuring an earth referenced signal.I have one of these, which I'd use to protect both myself and my scope when measuring anything with more than about 50V on it. It's good for 700V; you may want more.https://www.picotech.com/accessories/high-voltage-active-differential-probes/25-mhz-700-v-differential-probe

author: jxjbsd
author_rank: Regular Contributor
timestamp: April 09, 2020, 08:41:11 am
content: The requirement of audio measurement to oscilloscope is very low. Any oscilloscope with 1MHz input bandwidth or above can be competent. To measure the electronic tube amplifier, only a 100:1, 1kV pressure probe is needed, which is competent.Analog scope： Tek 2245A 2246A 2247Adigital scope Rigol1054Z

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2020, 08:55:44 am
content: Quote from: ToddW on April 09, 2020, 03:03:48 amStart by understanding how to use scopessafely. There are voltages around tubes that can destroy a scope, and which could seriously harm a scope's user.In particular learn how about different probes, and look at the prices of them. That may or may not limit your options. FFI, have a look at the safety references inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/QuoteThe key question isn't "which is better". More useful question are "which are good enough" and "what else do I want to spend my money on".If looking at audio, understand the consequences of 8-bit digitisers and a scope's linearity specification w.r.t. noise and distortion andyourmeasurements.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 09:58:04 am
content: The simple answer to the original question is digital. WattsThat has already explained why aliasing isn't even a consideration at audio frequencies. Rigol havesome great deals right nowand you could pick up a DS1054Z for a little over $300 and have a 5 year warranty. You could hack it but there's no point for what you're doing, 70 MHz bandwidth is just fine and they give you all the extra options such as serial decoding for free.The comment about using a high voltage differential probe adapter is VERY good advice which I would follow. If you want to cheap out, you can set your Rigol probes to x10 (a tiny slide switch on the side of the probe) but if you accidentally switch that back to x1 and overvolt the scope input, you'll be SOL.

author: MarkMLl
author_rank: Frequent Contributor
timestamp: April 09, 2020, 10:08:24 am
content: A few weeks ago I had a hankering for an analogue 'scope that I once owned. I needed to display two signals with a fixed phase offset plus jitter, and this 'scope was a true dual-beam with a delay line in one of the analogue inputs.Now I broadly agree with what everybody else has said about the superiority of digital 'scopes, which of course apart from anything else have the overwhelming advantage that you can usually capture a pretty picture for your notes. But just now and again...MarkMLl

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 10:18:32 am
content: The HV differential probe suggested seems overpriced - you can get the Micsig DP10013 for $179 on Amazon and they also have several x100 HV passive probes for around $25 (yes, you can set a x100 multiplier on the DS1054Z on the channel menu). The DP10013 will offer better protection IMHO and get you away from ground loop issues but the x100 HV probe will also get the job done for a lot less money.

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2020, 10:21:35 am
content: Quote from: Gandalf_Sr on April 09, 2020, 09:58:04 amI'm in two minds over this recommendation. The Rigol is an awesome deal but the OP specifically wants to do audio work and look at hums and distortions so a good FFT is important. FFT is the Rigols's achilles heel.Cue the resident Siglent salesman ...(although after watching this video the Siglent doesn't really look like a stellar performer either)Another option is the Analog Discovery II. The AD2 willdestroyboth of those 'scope in FFT performance as well as doing frequency sweeps, Bode plots, etc. With the right probes there's no reason not to use it with a high voltage tube amp (consult here if you're unsure of any part of how to probe that).The AD2 also (a) Cheaper than a DSO, and (b)Highlyrecommended for the sort of people who "just got a bug to buy a scope to help in this project and if for nothing else for the fun of it and just have around for other projects I might get into."The only real downside to the AD2 is that it needs to be used together with a PC/Laptop.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 10:40:10 am
content: I'm not a big FFT user but having stuck with the Siglent FFT video for the first 10 minutes, I then cross-compared with the Rigol DS1000Z video below; seems to me that the Rigol's FFT responds faster and the video is pushing MHz into the scope.

author: Electro Detective
author_rank: Super Contributor
timestamp: April 09, 2020, 11:01:34 am
content: Pushing past for a minute...Reading through OP ToddW's requirements, I would roll with a cheap 100% working generic badged 20 Mhz CRT scope that has its combined owner/service/cal manual supplied,and a decent affordable high voltage differential probe (buy once, cry less)saving yourself the ordeal of learning about oscilloscope safety and pesky earth/ground/neutral relationshipswith a half chance of escaping the tragedy of taking out all your gear on your first serious probing sessionThis humble setup is more than good enough for the requirements described, SAFE/R, and FUN!Any future upgrade path may be the ADDITION of a pricier DSO that can do the few things most CRT scopes can'tBut if the CRT scope gets it done, don't blow money on a novelty scope you can do without, for now

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2020, 11:02:47 am
content: Quote from: Electro Detective on April 09, 2020, 11:01:34 amAnd you get that mythical beast, where...?

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2020, 11:05:14 am
content: Quote from: Gandalf_Sr on April 09, 2020, 10:40:10 amYep. There's very few videos showing their FFTs but judging by those two there's not as much difference as people claim.

author: jxjbsd
author_rank: Regular Contributor
timestamp: April 09, 2020, 11:25:17 am
content: If you want to study noise distortion and FFT, a 196k / 24bit sound card is a good choice

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2020, 11:27:56 am
content: Quote from: Gandalf_Sr on April 09, 2020, 10:40:10 amFaster response isn't always better. Sometimes you want more details which is where the Rigol doesn't deliver at all. Getting the FFT faster on the Siglent is likely a matter of selecting a shorter memory length (if possible). But for audio analysis there are better tools anyway.To get back at the OP's question: definitely DSO combined with a differential probe. One of the things you can do with a DSO is sweep an amplifier through a frequency band look at the response of the tone control. Or look at the low frequency response; a analog scope is pretty much useless below 20Hz or so. Another problem is that analog scopes are so old nowadays that most of them are restauration projects.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 01:20:15 pm
content: The Norwegian Blue prefers kippin' on 'is back!

author: free_electron
author_rank: Super Contributor
timestamp: April 09, 2020, 01:46:05 pm
content: Quote from: jxjbsd on April 09, 2020, 11:25:17 amtube amps , guitar amps. they are all about distortion ! the more the better. Some guitarists prefer their amp to sound like a cat being milked using pliers ...if all you want to do is recapping , invest in a good soldering iron . A scope is useless. you can look at signals. so what ? what do you think you will learn from it ? Scopes are used to troubleshoot or characterize during design. Recapping is neither.

author: 2N3055
author_rank: Super Contributor
timestamp: April 09, 2020, 01:51:04 pm
content: One big advantage of digital scope that is rarely mentioned is capability to create and save reference waveforms, and easy saving of screen shots for documentation purposes.. That, together with single shot captures, makes digital scope more useful.Only thing that analog scope excels at is a scope art..

author: Fungus
author_rank: Super Contributor
timestamp: April 09, 2020, 01:55:25 pm
content: Quote from: free_electron on April 09, 2020, 01:46:05 pmSure, but engineers want to measure it.Quote from: free_electron on April 09, 2020, 01:46:05 pmI imagine the same sorts of things everybody else learns when they own an oscilloscope.

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 02:55:29 pm
content: Thanks to all for the feedback. Think I will get some kind of DSO around 300- 400 bucks. Also looking into safe ways to measure high amp voltages - iso transformers, diff probes, 100x probes, understanding mains, grounds, neutrals, etc.I would like to use a scope on my tube amp to see the various AC/DC voltages and forms, ripple, signal inputs, preamp stages, noise at different locations and different modes, effects of changing RC circuits, reverb/vibrator stuff, etc. Scope could be overkill but the new DSOs are just so damn pretty.................I also fly RC helicopters. I have one bird that I can't even get off the ground because it goes into ground resonance funky chicken mode before I get enough power to lift off. Wonder if I could rig a sensor to it and hook up to scope to see an FFT to get a better understanding of mechanical frequencies going on. There is the tail rotor, main blades, drive shaft, electric motor etc.Anyway, my first project is the tube amp. I will play around with the scope on it and sure there will be other uses in the future. Not much risk for a few 100 bucks.Pro-AA763-schematic.pdf(499.54 kB - downloaded 126 times.)

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 02:59:00 pm
content: Sounds like the OP's immediate project is a guitar tube amp, and in the future he's interested in expanding into electronics hobby-type stuff.Since money is rarely no object for most folks, I'd suggest the first question is how much do you want to spend? And if you're going to work on amps and power supplies you MUST first decide to spend at least $180 on a differential probe for safety reasons, as others have said. This allows you to work on any line voltage stuff like amps and power supplies and so on.Now, since only you know your future plans in this area, you need to decide if you want to stick to working on guitar amps or branch off into other stuff. Is it a hobby, or a business, or what? Do you want to expand into a bunch of different areas to learn? Only you can determine what you want and need for the future.If you're gonna branch out and don't have much or any equipment right now, keep in mind you're gonna be into this for at least probably $1,000. That's $200 for a differential probe, $400+ for a good scope, and another $400 for assorted stuff.But if you're just gonna mess with your guitar amp and call it a day, that's a whole different thing.Regarding analog vs. digital, if you have any interest in moving forward with this as a hobby or learning about electronics or whatever you should consider a digital scope. You can't really learn about and understand electronics without a scope. And it's far easier, IMO, to be able to access your scope via PC and save waveforms and compare with other waveforms and simultaneously compare multiple signals in order to truly understand stuff by using a digital scope.But it all depends on what you'll need going forward.

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 03:13:37 pm
content: Quote from: engrguy42 on April 09, 2020, 02:59:00 pm

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 03:23:26 pm
content: ToddW,I've done a load of work with RC Helicopters, I own several but haven't flown for a year or more. Are you sure that you have the Gyro setup properly or is it flybarless? Give me more info (open a new thread is probably best) and I can help.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 03:25:42 pm
content: ToddW, based on your response I'd suggest you look at the following:Differential scope probe:"Micsig DP10013 High Voltage Differential ProbeMicsig DP10013 High Voltage Differential Probe is designed for professionals and experts like you to be used with most oscilloscopes in the market. It allows you to safely measure floating voltages up to 1,300V and has a bandwidth up to 100 MHz. DP10013 can work in two different attenuation ranges: 500X for a maximum test voltage of 1300V and 50X for a maximum test voltage of 130V."Especially since you said you're relatively unfamiliar with the whole electronics thing, I think it's extremely important that you consider something like this. It can prevent personal injury and equipment damage, especially if you don't have it ingrained into your brain to double and triple check your circuit connections before powering stuff on.I'd also recommend you take a look at the Rigol DS1054z scope. VERY good bang for the buck and gives you a lot for future stuff you might want to get involved in. Cost around $400.

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 04:03:44 pm
content: Differential probes don't have to be expensive. I have two Tek 100MHz models, one is a P5205 and the other is I think a P5210. I think I paid $120 for one of them and $100 for the other, both were as-is untested but both worked perfectly. I did have to open one up and tweak the offset pot for one of the ranges but the other had no problem at all.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 04:39:23 pm
content: Quote from: james_s on April 09, 2020, 04:03:44 pmWill those Tek probes work with a non-Tek scope? I can see they've got the fancy Tek connector and not a standard BNC on them. They also appear to be going for around $400 on eBay.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 04:52:27 pm
content: The McSig I posted is only $180 and has standard BNC

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 04:57:49 pm
content: Quote from: Gandalf_Sr on April 09, 2020, 04:39:23 pmThe P5205 and P5210 have the TekProbe interface which I specifically wanted because I have Tek scopes and that allows the scope to automatically configure itself.There is an otherwise identical P5200 that has a plain BNC and a separate power jack, and there are adapters to go from TekProbe to standard BNC. As for prices, well it's ebay so prices are all over the place. There were loads of people asking $400+ for them when I bought mine but I don't think any of them were moving. Eventually one came up for a more reasonable price so I put in an offer and it was accepted in both cases.Anyway my point is simply that deals turn up occasionally if you look for them, it's a gamble though, the probes I bought could have easily had one of the obsolete ICs be defective.

author: 2N3055
author_rank: Super Contributor
timestamp: April 09, 2020, 05:09:07 pm
content: Quote from: james_s on April 09, 2020, 04:57:49 pmWell, the point is that for 180 USD you get something that is brand new, has warranty, works great and is no lottery.Also, hi voltage diff probe is pretty much safety equipment, and I like to be able to trust it to be safe and not in unknown state.

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 05:28:46 pm
content: True but not one that's good for 100MHz, and not one that has a TekProbe interface, which in my case was highly desirable.I pretty much exclusively buy used A-list gear though, I think my ESR meter is the only significant piece of test equipment I bought new and that was back before ebay was a thing.

author: 2N3055
author_rank: Super Contributor
timestamp: April 09, 2020, 05:35:30 pm
content: Micsig DP10013 is 100MHz..And most people explicitly don't want TekProbe because they don't have a scope that has it..I do get that you did best choice for your situation..

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 07:03:54 pm
content: Quote from: Gandalf_Sr on April 09, 2020, 03:23:26 pmHey Gandalf - thanks for the offer. I haven't flown mine for a few years either but will get back to it someday and will look you up. The bird is an MSH 500 FBL. I balanced everything as well as I could, tried pretty common FBL settings, different surfaces, etc. Things worked great up to about half throttle, smooth. Then a bare increase in rpm and it would start into ground resonance and I would have to immediately cut the power and things would still get dicey. Anyway, probably shouldn't start a discussion here about it. Later in the year I hope to get her out and if needed will look you up. Thanks again.

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 07:10:52 pm
content: So if I understand this correctly, the HV diff scope probe actually has a diff amp inside it. So that means you can test between any two points in a circuit and not have to always reference to ground. Also has high input Z to provide some safety to HV, but is not actually isolated. So the difference between it and a 100x probe is the ability to do diff probe measurement and better protection from HV. Do I have this right? 100x probe about $40, diff probe at least $100 more. But it sounds like the extra $100 or so would be worth it.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 07:18:33 pm
content: Quote from: ToddW on April 09, 2020, 07:10:52 pmYou have it right

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2020, 07:19:50 pm
content: For full information read, and re-read the safety references I gave earlier. That will help you overcome your misunderstandings below.Abbreviated points...Quote from: ToddW on April 09, 2020, 07:10:52 pmMostly correct.QuoteFalse and false.QuoteYes.QuoteAlmost certainly for fiddling around inside tube amplifiers.Don't forget you will need one HV differential probe per channel, and they work equally well with digitising and analogue scopes.In your situation I would first spend the money on probes, and whatever is left over I would spend on a scope.Unless you want post-processing such as FFT or to look at PSU startup transients, an analogue scope probably just as usable as a digitising scope. If you go that route, ensure it is fully working and expect to pay around £1 or USD1 per MHz.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 07:23:09 pm
content: Uh oh, here we go...I'm gettin' outta here

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 07:53:13 pm
content: QuoteFalse and false.Guess I misunderstood Dave

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 09, 2020, 08:08:16 pm
content: Quote from: Fungus on April 09, 2020, 07:54:26 amHey, i resemble that remark. Yes, collecting things can get out of control.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2020, 08:50:15 pm
content: Quote from: ToddW on April 09, 2020, 07:53:13 pmGuess you didn't bother to read the safety references - they were produced by professional companies to ensure you don't make noises and flashes when using their equipment.Hints: they aren't that high impedance, the impedance has nothing to do with isolation, and they are (or ought to be) isolated.(And your quoting is incorrect!)

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2020, 09:19:49 pm
content: I didn't think they were actually isolated? It's been a while since I've watched the video explaining them though.I was only vaguely aware of their existence until about a year ago but now that I have one I find it to be indispensable for poking around inside line powered stuff.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 09:30:06 pm
content: A teardown of my McSig differential probe shows each differential input lead has five, 1 Meg resistors in series before going into the differential circuitry. The only isolation is a DC/DC converter that isolates the ground from the USB ground that provides power to the differential probe circuitry. Otherwise the probe is not isolated.Not saying they're all that way (though it seems the one referenced in the Dave video is similar), but in neither case are they isolated from ground. I think Dave even confirmed that for his LeCroy.And a Techtronix reference I have lying around somewhere also says that differential probes have a resistive path to ground. Therefore, not isolated.So no, in general it's safe to assume they're not isolated, and do have a high input impedance (5 Meg + 5 Meg) to provide safety.

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 09:49:22 pm
content: Quote from: tggzzz on April 09, 2020, 08:50:15 pmI will read your provided references and appreciate you posting them. Just haven't got around to it yet. I just had come across Dave's video on the diff probe and wanted to see if I understood it. Looks like not completely, and there is always more to learn, like from your references. Which I suspect will contain more info than just diff probes.

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2020, 09:50:37 pm
content: Quote from: engrguy42 on April 09, 2020, 09:30:06 pmSuch high resistance values are isolation. It is possible to come up with an 'isolated' circuit (using a transformer for example) which has effectively a lesser degree of isolation due to creepage/clearance paths. The use of a string of high value / high voltage resistors is a well proven technique and most (if not all) of the high voltage differential probes out there are made this way.The thing to look for on a differential probe is a CAT rating. That means it is safe to use up to the specified voltage.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 09:55:19 pm
content: Quote from: nctnico on April 09, 2020, 09:50:37 pmSeems to me that with those high resistance values the whole issue of isolation becomes, while technically true, a bit irrelevant. Other than, as Techtronix says, if the circuit has leakage currents then (non-isolated) diff probes might not be the best choice:"Differential probes provide a safe method to adapt agrounded oscilloscope to make floating measurements.In addition to the safety benefits, the use of these probescan improve measurement quality. Differential probesprovide balanced measurement input capacitance soany point in the circuit can be safely probed with eitherlead. Differential probes also typically have better CMRRperformance at higher frequencies than voltageisolators.Another benefit is the full use of the oscilloscope’smultiple channels with the simultaneous viewing ofmultiple signals, referenced to different voltages.Trade-OffsThe probes still have a resistive path to ground- so if acircuit is sensitive to leakage currents then differentialprobes may not be the best solution.Other trade-offs include an added layer of cost -depending on the oscilloscope capability an independentpower supply may be required, adding cost and bulk.The gain and offset characteristics must be factoredmanually into every measurement."

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 10:05:45 pm
content: There goes another perfectly good thread... sigh!

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2020, 10:08:48 pm
content: Quote from: engrguy42 on April 09, 2020, 09:55:19 pmWell, every probe using whatever isolation method will have some resistive and capacitive leakage to ground. The only way to really avoid having any leakage is to use a probe with an optical interface for both the signal and power. But even then you'll influence the circuit due to the capacitance and inductance of the electrical leads and circuit. In reality most high voltage circuits have a low enough impedance where a bit of leakage to ground doesn't matter.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 09, 2020, 10:15:22 pm
content: To all intents and purposes, the high voltage differential probes are very high input impedance (many Meg Ohms) even though not actually isolated. The OP could use them without worry and that's why I said he was right in his/her summary.

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 10:33:27 pm
content: Quote from: engrguy42 on April 09, 2020, 09:55:19 pmJust read that too. But don't know what in a tube amp would be sensitive to leakage currents.

author: ToddW
author_rank: Contributor
timestamp: April 09, 2020, 10:36:22 pm
content: Quote from: Gandalf_Sr on April 09, 2020, 10:05:45 pmThis is the best thread eva!

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 10:50:23 pm
content: Quote from: ToddW on April 09, 2020, 10:36:22 pmOkay, but more importantly...Long ago I had a Fender guitar and electronic amp. We're talkin' late 1970's. And at the time the guitar world scoffed at electronic amps, and said tubes are the only way to go. Kinda like the guys who were conviced that vinyl records were vastly better than all that digital rubbish. But personally I was amazed at how good the electronic guitar amps sounded. I forget the brand...So does anyone make tubes anymore? Or are they just recycled from old equipment like Ham radios and stuff?

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 10:56:16 pm
content: Hold on...It was a Crate G-40C. Beauty.

author: 0culus
author_rank: Super Contributor
timestamp: April 09, 2020, 11:06:58 pm
content: Quote from: engrguy42 on April 09, 2020, 10:50:23 pmYes, there are plenty of then still being made. Nowadays the cork sniffers prefer hand wired point to point construction over PCBs. Gotta get them toanzzz! I have an Egnater 15W head (definitely PCB construction) and 1x12 cab. It sounds freakin awesome and it's light enough to carry to a friend's house for jamming without breaking your back. I thought you were asking about tubeamps...but to answer your question, yes, tubes are still being made. Mostly in China, Russia, and Eastern Europe last I heard. They tend to not be as well made as the stuff made in the golden age of vacuum tubes, but they work fine for guitar amp use where the running parameters tend to shorten their lives anyway, as opposed to say a Tektronix 5xx series oscilloscope where the original tubes often still work fine because they were well made to begin with and are used strictly in a linear regime.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 09, 2020, 11:14:40 pm
content: Wow, I never dreamed that tubes were still around, much less tube amps. Is Marshall still a big player?So who uses tubes now? I assumed that the Ham radio world had pretty much dried up long ago (?), and the only folks using tubes would be the hobbyists fixing old scopes and radios and amps and stuff.

author: 0culus
author_rank: Super Contributor
timestamp: April 09, 2020, 11:32:34 pm
content: Audiophiles and guitar players mostly. The former annoy me because they rape classic test equipment for tubes.Marshall is still around, yes.

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 09, 2020, 11:37:54 pm
content: Where can you find the “The technology the 1900’s meets the the technology of the 2000’s”?That’s where you can buy overpriced vacuum tubes from an online store.https://tubedepot.com/A matched pair of old stock 300b’s will only set you back $10,000.00. But hey, they’re good for 40 watts each.https://tubedepot.com/products/nos-western-electric-300b-black-plate-1961-matched-pairThey don’t call ‘em audiofools fur nuttin. With my apologies for helping to drag the thread off topic.

author: ToddW
author_rank: Contributor
timestamp: April 10, 2020, 12:51:46 am
content: Tell me your not jealous.[ Specified attachment is not available ]

author: james_s
author_rank: Super Contributor
timestamp: April 10, 2020, 04:22:28 am
content: Quote from: engrguy42 on April 09, 2020, 11:14:40 pmHave you been living under a rock? There are many thousands of tube amplifiers in service, a mix of vintage stuff and modern boutique equipment, both hifi and guitar amplifiers, they're as popular today as they've been any time in the past 40 years if not more so. Not all of the old types are still made but modern versions of many of the popular audio tubes are still manufactured. There are even high end $$$ audiophile tubes hand made in small quantities. Musicians and audiophiles are the primary users, then of course there are millions of vintage items out there. I have at least 3 vintage tube radios.A quick google search for "tube amplifier" comes up with dozens and dozens of sites.

author: Cubdriver
author_rank: Unknown
timestamp: April 10, 2020, 07:02:30 am
content: Quote from: engrguy42 on April 09, 2020, 11:14:40 pmTubes are definitely still around and popular. I've built several tube-type audio and guitar amp kits over the past several years.Dynaco ST 70 clone:Transcendent T-16 Output Transformerless amplifier:Encore and LF guitar amp kits from Allan Amplification and a tweed 5F1 kit from Tube Depot. Also have a pair of VTA M-125s in the build queue.As for differential scope probes, over a few years I bought a pair of Dave's EEVBlog HVP-70s. The don't come out to play too often, but are very useful when they do.-Pat

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 10, 2020, 10:34:19 am
content: Quote from: james_s on April 10, 2020, 04:22:28 amLiving under a rock?? How the hell would anyone know that tubes are still used without going out of their way to investigate? Y'know, like going to a club or concert where some guy happens to be using a tube amp and go up on stage and say "hey, are those tubes in there?"Or spending time, as you say, searching google asking "hey, do tubes still exist?".Most/all of my limited youtube time is looking at tech stuff, and the only thing I've stumbled on about tubes is the guy who does these 50 year old tube radios and stuff, which, honestly, is a big yawn for me. I never had any interest in tubes.So back to the basic question: WHY? Why does anyone care about or use tubes? Is it just a boomer hobbyist or "I love old stuff" thing, or do people actually think there's a benefit?

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 10:57:16 am
content: Probably the same reason people collect old cars, telephones, home computers, etc, etc.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 10, 2020, 12:02:43 pm
content: Quote from: engrguy42 on April 10, 2020, 10:34:19 amApparently, musicians think that the sound of tube amplifiers is better than silicon. I didn't realize until recently that the sound we associated with stars such as Jimmy Hendrix was where they had a specific effects pedal combined with a specific (almost always tube in the 'good' old days) amplifier. Such asthe Fuzz Face.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2020, 12:14:19 pm
content: Quote from: engrguy42 on April 10, 2020, 10:34:19 amYou know CRT oscilloscopes are still around, even though they're "worse".Quote from: engrguy42 on April 10, 2020, 10:34:19 amThey give a different sound. Audiophiles call it "warmer" but really it's just noise/distortion.Why would you want that? Depends on who you are.Using a tube amp if you're a musician/guitar player it's no different then using a distortion pedal. It overdrives, it distorts, it gives you the sound you want.If you're an "audiophile" it's usually a sign that you grew up in the 1970s when amplifiers were crap and that'swhat your ears are accustomed to hearing. Amplifiers without "warmth" sound cold and clinical to you, despite being better.nb. A similar thing is happening in the younger generation. Their "warmth" is the all nasty artifacts caused by audio compression. Audio sounds worse to them without it.https://www.google.com/search?q=youngsters+prefer+mp3+to+lossless

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2020, 12:18:36 pm
content: Quote from: Gandalf_Sr on April 10, 2020, 12:02:43 pmItisbetter when you're a musician. Using a distorted amplifier is no different than turning a knob on a synthesizer, putting a mute in the end of a trumpet, pressing a pedal on a piano, etc., etc. It's what gives you your particular sound.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 12:45:54 pm
content: Quote from: Gandalf_Sr on April 10, 2020, 12:02:43 pmYou are seeing this wrong. The 'amplifier' together with the guitar is the musical instrument. Not just the guitar.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 10, 2020, 12:46:50 pm
content: I guess I assumed that whatever people believe sounds "better", at the end of the day it's pretty much just a waveform. And presumably you can reproduce that with newer electronics.I was never sure if the "tubes sound better" thing was an actual thing or just what people want to believe. Like I said, way back when there were those who were convinced that vinyl records sounded better than CD's and all that digital stuff.I recall reading that Van Halen (a rock guitar god, IMO) never used any distortion effects to get his "brown sound". I suppose it's one of those things that's so difficult to prove that people can argue about it until the end of time. Like they've been doing since when I was a kid decades ago.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 01:01:53 pm
content: Quote from: engrguy42 on April 10, 2020, 12:46:50 pmOfcourse you can reproduce that with newer electronics. Tubes tend to clip softer resulting in even harmonics which are more pleasant to listen to.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 10, 2020, 01:06:33 pm
content: Quote from: nctnico on April 10, 2020, 01:01:53 pmSo all the audio tube amp afficionados are wasting their time?Uh oh....

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 01:17:50 pm
content: Quote from: engrguy42 on April 10, 2020, 01:06:33 pmThis is getting wildly off-topic...It can be a great hobby. Years ago I bought a piece of test equipment from an electronics enthousiast. He had build two huge horn loudspeakers (the size of a big fridge) which where extremely efficient. According to him this meant that the voice coils (self wound!) where operating in a very linear area so distortion from the speakers was minimal. He drove these from a (self build) class-A tube amplifier able of delivering just a few Watts. And yet he could crank the volume up to club-like sound levels. He also build his own turn table in which he used the ball from a ball-point-pen as a bearing for the arm. All in all very impressive!

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 10, 2020, 01:59:34 pm
content: As nctnico said...This is getting wildly off-topic...

author: exe
author_rank: Unknown
timestamp: April 10, 2020, 02:05:04 pm
content: Quote from: bob91343 on April 09, 2020, 04:30:15 amPeak detect to the rescue.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2020, 02:43:59 pm
content: Quote from: engrguy42 on April 10, 2020, 01:06:33 pmPretty much, yes. A DSP can do that at the push of a button.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 10, 2020, 02:57:36 pm
content: Quote from: Gandalf_Sr on April 10, 2020, 01:59:34 pmYou mean like threads about "what did you buy today?" and "what's on your phone?"In any case, it seems reasonable that the OP's original question was already answered, and he doesn't seem too concerned about staying on topic, so do we really need to call in the topic police?

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2020, 04:00:46 pm
content: The argumentagainsttube amps for listening to recorded music is (of course) that you're not hearing what the artist intended.The same goes for vinyl records: They also add "warmth". If you're listening to an old LP then you're simply not listening to what the artist created in his studio.(...because they wear out a bit every time you play them, and the grooves simply can't reproduce the sharp edges of electronically created sounds)

author: MarkMLl
author_rank: Frequent Contributor
timestamp: April 10, 2020, 04:16:07 pm
content: Quote from: Fungus on April 10, 2020, 04:00:46 pmNot as fast as the artists. Listening to later concerts by- as a genre example- certain prog rock bands with the performers trying to sing in the same register as they did in their heyday can be downright embarrassing.MarkMLl

author: james_s
author_rank: Super Contributor
timestamp: April 10, 2020, 04:18:26 pm
content: Quote from: engrguy42 on April 10, 2020, 10:34:19 amBecause they're so prolific that I'm not sure how anyone with even a passing interest in electronics or music could miss them. Vintage tube hifi gear is worth a fortune. Virtually every company that makes guitar amps or effects pedals has at least one model that uses tubes.Tube audio gear definitely sounds different, whether that's "better" is purely subjective. Yes you can simulate the waveforms and get a similar sound but that's not the same, musicians are artists and many want the real deal. It's similar to how vintage synths like the Roland 606, 808 and others are now highly sought after and valuable despite the fact that the sound they produce can be emulated by modern devices.Personally I just think it's neat, there's something almost magical about glowing glass bottles that can manipulate electrons, a radio that can play music without a piece of silicon anywhere. The high voltages and evacuated glass appeal to the mad scientist in me. Also I like old stuff, I'm a generation younger than the boomers but I'm still old enough to remember when stuff was actually well made and built to be repairable and I've watched things get just a little cheaper, a little lighter, a little flimsier each year as pennies are shaved off the cost. I tend to automatically equate new to cheap and crappy while old stuff is solid and high quality. Obviously with things like computers tech was advancing quickly so newer has clear advantages but pretty much anything else I'll pick a well cared for vintage one over a new one any day. I have a lot of stuff much older than I am and I hope when I'm gone that someone else can keep enjoying it as I have.

author: james_s
author_rank: Super Contributor
timestamp: April 10, 2020, 04:27:46 pm
content: Quote from: Fungus on April 10, 2020, 04:00:46 pmThey certainly can wear out, although played with a good quality stylus on a properly adjusted turntable a record can last a very long time. There have been tests where they replayed the same record hundreds of times, inspecting the record under a microscope and did not observe any wear. The stylus only passes any one particular part of the groove once per play so it's not as though it's sitting there grinding away at it.You're never listening to what the artist created no matter what you use to reproduce the sound. Speakers greatly color the audio as do room acoustics. Listening to music at home is never going to sound the same as it sounded live, that's just reality. What sounds better to an individual is subjective and all that really matters anyway.I'm not going to argue that vinyl sounds better than digital but after somebody gave me a decent turntable, (not high end audiophool voodoo, just a late 80s Technics) I was actually really impressed with how good a vinyl record could sound. I remembered them from when I was a kid as being scratchy but now I have some that are in nice shape and they sound very good. 90% of the time when I listen to music it's MP3s but I still play records, it's a different experience, it's fun. I browse through the record bin whenever I'm at a thrift store, never know what you'll find. They've gotten more expensive in the last couple years though as the post-millennial hipsters have discovered vinyl.

author: ToddW
author_rank: Contributor
timestamp: April 10, 2020, 04:40:04 pm
content: OK, some notes for this thread by OP (me)1. My initial questions have been answered about analog vs digital scopes and probes for HV diff measurements. I have a good feel for what you are getting with both types and reference material out the ying yang for safety, probe selection, etc.2. I am working with a tube amp because that's what I have, its worth about $3k, it was given to me by my grandfather, is a simple device and the tubes look cool when they are hot.3. Thread has veered off the rails considerably but I don't really mind at all. It seems damn near impossible to keep a thread on target. I got a ton of good info so I am happy. If I have more questions about other topics, I will start new threads.Carry on.

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2020, 04:57:09 pm
content: Quote from: james_s on April 10, 2020, 04:27:46 pmHeadphones?

author: james_s
author_rank: Super Contributor
timestamp: April 10, 2020, 04:59:48 pm
content: Quote from: Fungus on April 10, 2020, 04:57:09 pmThat can be an improvement but those are also going to color the sound. It's still a mechanical device, the impedance is going to vary wildly depending on frequency, the housing is going to have its own acoustics.None of that really matters though if it sounds good to the listener.

author: tggzzz
author_rank: Super Contributor
timestamp: April 10, 2020, 05:39:16 pm
content: Quote from: Fungus on April 10, 2020, 04:57:09 pmThe microphone position is rather important tooFor an orchestra, is the "right position" for the microphone in the violins, with the conductor, in the first row, or the Nth row etc. That question is rhetorical!

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2020, 05:47:01 pm
content: Quote from: tggzzz on April 10, 2020, 05:39:16 pmAbout six feet above the conductor's head and twelve feet behind him.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 10, 2020, 05:49:58 pm
content: @ToddW, I didn't see it mentioned here, but the Siglent SDS1202X-E is a good low cost choice as well, especially due to the more accurate FFT to evaluate harmonics on audio.Sure, Rigol is making a sale on their DS1202Z-E for $299, but for $80 more I think you can get a more modern and featured platform - that and independent controls for each channel.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 06:07:53 pm
content: Quote from: tggzzz on April 10, 2020, 05:39:16 pmThe answer is all and then getting it mixed so it sounds right again. Due to reflections some harmonics of the sound may get dampened. One of my early electronics mentors used to work for an organ manufacturer. At some point they recorded a church organ, analysed the wave forms and re-made those digitally. It sounded like crap. After some pondering they re-did the recordings but this time at various points in the church and using those recordings they got it right.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 10, 2020, 07:37:32 pm
content: Quote from: Fungus on April 10, 2020, 04:00:46 pmjust a consideration while wandering around, near, on, or off-topic ....Analog electronics and media can degrade/does degrade over time but we should be careful about blanket assessments. For example, it is likely that any artist who created or finalized something in a studio in the 1950s and early 1960s (which encompasses a lot of great music) decided what to publish/release based on not only listening in the the studio with tube amps but even the reel to reel recorders that captured their music (live somewhere or in the studio) had tubes - so the artists had to decide what they created while relying on tubes. And when they got their first copy of vinyl at home to listen on their hifi, they were again listening to tubes - so I think they must have adjusted the entire recording process to best reflect whatever they intended to the extent feasible.

author: Electro Fan
author_rank: Super Contributor
timestamp: April 10, 2020, 07:51:54 pm
content: Quote from: nctnico on April 10, 2020, 06:07:53 pmAs a long time hifier back to college days I am very sure that as important as the quality of the recording is and as important as the system is (cd player or turntable, tonearm, cartridge, preamp, amp, speakers, etc), the placement of the speakers and listening position in the room and especially the room acoustics can make a big difference in frequency response, and more. The room (size, shape, materials) might be an even bigger contributor to the final result than the system. Reflections and nulls will definitely impact frequency response and other factors that will influence a listener's ability to discern audible details - such as the ability to recreate spatial imaging (side to side and front to back). So, if the goal is to accurately reproduce the original (ie, achieve High Fidelity) the system and the room acoustics both need some attention.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 10, 2020, 08:14:06 pm
content: I agree that all of these deep hi-fi technicalities are extra important.Especially when listening to Billie Eilish mumble thru "Bad Guy".

author: james_s
author_rank: Super Contributor
timestamp: April 10, 2020, 09:21:29 pm
content: Quote from: nctnico on April 10, 2020, 06:07:53 pmBut how do you define what sounds "right"? There are some things that people would almost universally agree sound "bad", but there are variables throughout the entire process, all of which color the sound in one way or another and what sounds best to one person may be different than what sounds best to someone else.Either way most people don't care about quality or technical perfection. This is easy to see by the fact that cheap garbage has always outsold quality gear by orders of magnitude. Back in the CRT days when Sony's Trinitron was the undisputed king, places like KMart must have sold 200 Emerson, Funai or whatever else was the cheapest crap they had to offer for every one Trinitron sold. Today good quality audio gear is still available (I don't mean audiophool, just good quality midrange stuff) but the vast majority of people listen to music from a $20 bluetooth speaker or the tinny speakers in their laptop. Most people just don't care about the quality and there's nothing really wrong with that, what bothers me is when they act like there's something wrong with those who do care.

author: ToddW
author_rank: Contributor
timestamp: April 10, 2020, 10:30:48 pm
content: Quote from: rsjsouza on April 10, 2020, 05:49:58 pmYes, I have looked at that one and it looks pretty nice. Basically looking at half a dozen or so in this price range that are common and have reviews on here. One thing I am considering now is that you can get some scopes with a built in function generator, a slot for a digital signal probe interface and other stuff. More money but killing birds with one stone. It has been interesting just researching all the new stuff scopes have to offer and comparisons between different units.Also looking at NI Multisim. Looks like you can get it for a free 30 day eval. Also, I have seen it come up on places like ebay for like $70 but I wonder how the license would work out. Would think NI would have it locked down to the original/registered owner. Anybody know?

author: tautech
author_rank: Super Contributor
timestamp: April 10, 2020, 10:45:55 pm
content: Quote from: ToddW on April 10, 2020, 10:30:48 pmOnly you know how far down the electronics rabbit hole you will venture and you can get all the extras as standalone units but it does all start to add up. SDS1104X-E is worth considering as you can add an AWG and 16ch MSO when you're ready or the budget allows.These are scopes that have provision for growth when you are ready.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 10:48:48 pm
content: Quote from: ToddW on April 10, 2020, 10:30:48 pmDigital channels are nice if you work on digital circuits. However the builtin function generators aren't worth the money due to very limited amplitude. Nowadays you can buy decent function generators for around $100 (Feeltech FY6900 for example).If you are into simulation then LTspice is a good place to start. There are also several high end packages made available for free.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 10, 2020, 11:41:11 pm
content: Quote from: nctnico on April 10, 2020, 10:48:48 pmAbsolutely. I'll second both of those. You MUST get LTSpice. It's a law or something. I never do any design stuff without first simulating in LTSpice. You can learn a ton.And the Feeltech, Juntech, Koolertron, whatever, Chinese re-branded function generators are really awesome for the price ($100). And the included software for making arbitrary waveforms on your PC is crazy good.

author: nctnico
author_rank: Super Contributor
timestamp: April 11, 2020, 12:17:29 am
content: I found 'superspice' and 'micro cap spice'. I have the feeling that these packages may be better and have a better UI compared the LTspice.https://www.anasoft.co.uk/http://www.spectrum-soft.com/index.shtm

author: tggzzz
author_rank: Super Contributor
timestamp: April 11, 2020, 12:37:26 am
content: Quote from: nctnico on April 11, 2020, 12:17:29 amMicrocap has a good reputation, and is now free as in beer. I have not used it, and only use an old version of LTSpice. There have been some mutterings about the later versions of LTSpice.I believe neither is now supported by the original author.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 11, 2020, 12:44:53 am
content: Quote from: nctnico on April 10, 2020, 10:48:48 pmNot only that but, given you are in the US, you can get really good test gear for very reasonable prices - nothing blocks you from getting a good low distortion analog audio signal generator or a very decent Synthesized one like the HP3314A or a Wavetek 273/5/7 or the Feeltech mentioned by Nico above - I have one and its size and features turned it into my get go function generator.BTW, I bought mine for about $60 shipped, as it was the model on its way out (6600-30MHz) when the 6800 was already being sold.

author: nctnico
author_rank: Super Contributor
timestamp: April 11, 2020, 01:31:10 am
content: The HP3314A and Wavetek are more likely to be projects by themselves due to their age. I used to own a 3314A about a decade ago but it is loud, large and very old. I needed to fix mine. It is very easy to forget equipment which was excellent 30 years ago is now old and flaky. I keep needing to remind myself regulary.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 11, 2020, 10:06:33 am
content: Quote from: nctnico on April 11, 2020, 01:31:10 amWith patience and careful search, the old gear can be had for really cheap around here, thus in some cases it is worth the risk (both my 3314A and the Wavetek 275 were about half of the Feeltech's price), but you are correct they may come with the need for some TLC (mine didn't and so far they are working well). If the OP is interested in investigating this option, the track record of failures reported can help - I don't recall anything outstanding with these particular models, apart from the Rifa capacitors and the need for recapping.However, don't forget thst even the Feeltechs can become a project on themselves as well - lots of hacking info around this website due to its limitations and under specifications. Its great advantage is its size and the huge number of features.All in all, my opinion is that the right answer is always case by case and never generally applied.

author: nctnico
author_rank: Super Contributor
timestamp: April 11, 2020, 10:35:12 am
content: The HP3314A has reed relais which became 'sticky' in my unit. I had to replace all of them. Either way you can't deny that really old gear is very likely to fail. Personally I avoid equipment which is older than 15 years.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 11, 2020, 11:24:31 am
content: Quote from: nctnico on April 11, 2020, 10:35:12 amNo equipment is free from problems, including the Feeltech. You have to live with some risk. The answer is always somewhere in between and the OP has added options by living in the US (test gear Heaven).

author: joeqsmith
author_rank: Super Contributor
timestamp: April 11, 2020, 06:06:03 pm
content: Quote from: nctnico on April 11, 2020, 10:35:12 amLet me just say, as a hobbyist if I used this criteria for my home lab, outside of a few handheld DMMs and a soldering iron, things wout ne sparse. I couldn't afford to buy the same level of equipment I own new. Restoring old equipment gives me an opportunity to learn more than just the basics about it.The OP is working on a "vintage Fender guitar amp and it needs work." and I see no reason they should buy a newer product. Of course, we don't all enjoy playing with older equipment and not everyone is going to have the skills required to service them. You also loose the latest marketing glitter.

author: james_s
author_rank: Super Contributor
timestamp: April 11, 2020, 06:42:23 pm
content: Quote from: nctnico on April 11, 2020, 10:35:12 amI avoid equipment that's younger than about 15 years. Usually I buy untested/as-is stuff because the gamble is kind of fun, I've been surprised at how often it works perfectly. Once I've repaired a piece of gear it has been extremely rare that it has ever caused me any trouble again later, I can't actually think of even one repeat failure that I've had. I don't make a living off my personal gear though, it's all just hobby toys. This is something that I've noticed a lot of professionals have some difficulty understanding. If one of my scopes or meters or whatever breaks down I'll use one of the others. If I haven't got a backup I'll work on the gear instead of the project I had in mind that evening, either way it's not holding up my paychecks.While not necessarily the case with test equipment, general life experience has been that new stuff feels cheap and falls apart after a few years while old stuff just keeps going for years or decades and is usually much easier to repair. I know more than one person who has been through two washing machines in the time I've had mine that I got for free 15 years ago because a few cracked solder joints on the motor inverter was going to cost the original owner $400 to have repaired.

author: Fungus
author_rank: Super Contributor
timestamp: April 11, 2020, 09:07:02 pm
content: Quote from: joeqsmith on April 11, 2020, 06:06:03 pmThe main problem is that you need a certain amount of test gear to do those repairs. If you've got nothing and you buy something that's a dud you may not be able to repair it. Telling test-gear-newbies to buy old gear seems counter-productive to me.Another problem is that it requires a certain amount of knowledge/practice which they may not have.Maybe the best bet is to buy a Rigol DS1054Z, fix up some old gear, sell the Rigol.

author: 0culus
author_rank: Super Contributor
timestamp: April 11, 2020, 09:14:31 pm
content: Quote from: Fungus on April 11, 2020, 09:07:02 pmThat could be a good approach. There's two big reasons why I think buying and repairing old gear is good: (1) at least for HP and Tektronix, there's sizeable communities of people who are willing to help (and aid in finding unobtainium parts if needed) if you're stumped and (2) there's much to learn from studying the operating and service manuals from the days when they gave full schematics and theories of operation.The other thing is that HP and Tek made stuff extremely well. As long as it's in decent shape (i.e. not from that ebay seller in israel that apparently dredges stuff from shipwrecks), chances are most problems that one encounters are trivial. Re-seat boards, look for cold solder joints, replace some caps. Once done, you have a professional quality instrument that should serve many more years, at a fraction of the cost.

author: nctnico
author_rank: Super Contributor
timestamp: April 11, 2020, 09:26:50 pm
content: Quote from: 0culus on April 11, 2020, 09:14:31 pmYou are definitely overrating / idolising such equipment. Old HP and Tektronix gear isn't that good and it can act up. For example: in older HP gear you can find wires soldered directly into the board (including the ones for mains). I've had several pieces of equipment where I could pull the wires out or where many strands where already broken by vibration due to handling. So if your hobby is to repair / restore old equipment (and I'm doing my fair share of that) getting really old equipment can be fun but if you want equipment for the sole purpose of making measurement then I'd look for newer ones.

author: 0culus
author_rank: Super Contributor
timestamp: April 11, 2020, 09:52:48 pm
content: Quote from: nctnico on April 11, 2020, 09:26:50 pmOverrating/idolizing huh?Seriously? So you encountered some instruments that were abused in a harsh environment, so you're going to throw the baby out with the bathwater based on N = several? Yes, I am an hobbyist, but I have a lab full of the best of ca 1965-1990 from both HP and Tek, all working perfectly fine and in spec that says you're wrong.HP and Tek made top of the line gear that, up until the 90s at least, is very repairable, and when it restored to good working orderstill works just fine today, and I didn't have to get second mortgage to afford any of it. What you are saying makes perfect sense for abusiness, but most of us here are not businesses and we either can't afford (or can't justify) purchase of the newest and best.If you're happy with the latest cheaply made plastic toys from China, that's fine, but I am not and I'll wager that given the popularity of the TEA thread here a lot of others are not either. That Rigol DS1054Z certainly is attractively priced now, but won't be repairable and will simply become e-waste in a decade or two. I'd be willing to bet you that most, if not all, of my HP and Tek equipment will still be working at that time while already being many decades older.

author: Cubdriver
author_rank: Unknown
timestamp: April 11, 2020, 10:53:33 pm
content: Quote from: 0culus on April 11, 2020, 09:52:48 pmAgreed! I have an awful lot of 30+ year old gear that "isn't that good" but yet is somehow working just fine with minimal if any work on my part. And if it DOES decide to crap out, there are manuals with extensive detail on the circuitry and its operation that enable me to troubleshoot and repair it.Is it perfect, and absolutely trouble free? No, it's not - nothing is. But it's certainly nowhere near as unreliable and failure prone as you purport in this thread. Seems to me I read a fair bit about some of the Chinese gear you're suggesting having all sorts of software bugs right out of the box. Sure, they're eventually fixed, but I'd prefer to fix my old stuff than to buy new and need to fix that with firmware updates and the like. To each his own, but given my choice I prefer buying older lab-quality gear made by the manufacturers that OWNED the industrial/scientific/government markets for such things for pennies on the dollar compared to its new cost even if it requires a bit of fettling to get/keep it working to new, cheap gear made in the far east. Others may feel differently, and I'm fine with that, but strongly disagree with the characterization of vintage gear from the companies that drove the market for it as something that "isn't that good".-Pat

author: james_s
author_rank: Super Contributor
timestamp: April 12, 2020, 12:29:25 am
content: Quote from: Fungus on April 11, 2020, 09:07:02 pmOr just keep it. I mean it's a nice little scope, it's compact, inexpensive and easily replaceable. I've been tempted to buy a DS1054Z myself although I really can't justify a need for one. It just seems like it would be a handy little scope I could put in the car and take with me somewhere and not have to worry too much about my A-list gear getting damaged or stolen. If I had no scope at all it or something like it is probably what I'd buy to start out.The older Tek, HP, etc gear is just a joy to use, it has that superb fit & finish and attention to detail that you just don't get with inexpensive test equipment. It cost a fortune when it was new and it still feels svelte and expensive. It's like driving an older high end Mercedes or Bentley or something, it doesn't really get you around any better than a cheap newer car but it's got comfort and style and feels great.

author: MarkMLl
author_rank: Frequent Contributor
timestamp: April 12, 2020, 07:36:53 am
content: Quote from: james_s on April 11, 2020, 06:42:23 pmOlder kit has the advantage that it's not likely to be based on an operating system loaded from disc (or SSD) plus applications that are effectively unrepairable when the original medium fails.I had enormous fun with a couple of Tek salesmen when they brought out their first logic analyzer based on Windows '95: I moved the taskbar from the bottom to the side of the screen and they panicked thinking it was broken in a way beyond their ken.MarkMLl

author: nctnico
author_rank: Super Contributor
timestamp: April 12, 2020, 09:49:54 am
content: Quote from: MarkMLl on April 12, 2020, 07:36:53 amLike firmware isn't stored in flash or epromsWhen I get an older piece of equipment which has seated EPROMs/ Flash memories the first thing I do is create images of them.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 12, 2020, 02:01:10 pm
content: Quote from: Fungus on April 11, 2020, 09:07:02 pmTo be clear, I wasn't telling anyone what to do but rather offering my experience to NCTNICO. In the case of the OP's vintage amplifier, I suggest they take it to a proper shop to have it serviced.

author: ToddW
author_rank: Contributor
timestamp: April 12, 2020, 07:14:34 pm
content: To be clear, I wasn't telling anyone what to do but rather offering my experience to NCTNICO. In the case of the OP's vintage amplifier, I suggest they take it to a proper shop to have it serviced.It might come to me taking it to the shop. But after looking over the schematics and reading forums, there is a lot I can check out myself with just a DMM. The circuit is pretty simple and I am isolating and testing one stage at a time. So far I isolated the secondary of the power transformer and found I am getting proper voltages from the 3 circuits on the secondary - main power, tube heater circuit, and GZ34 heater circuit. Next will hook back up DC filtering caps and check B+. Then throw in drop resistors and check b2 and b3 and so on. Also recapping the elect caps as I go. So, unless there is something really odd with the unit, I have a good chance of getting it back up and running.

author: james_s
author_rank: Super Contributor
timestamp: April 12, 2020, 07:21:32 pm
content: I repaired things for years before I ever had a useful oscilloscope. Even today it's rare that I'd reach for a scope when working on audio gear unless I suspect oscillation. Normally a multimeter and ESR meter are the only measurement tools I need for most repairs.

author: Shock
author_rank: Super Contributor
timestamp: April 12, 2020, 09:44:59 pm
content: Lot of people trying to justify the existence of their analog scopes. Nobodys saying you have to surrender it to own a digital. If a dude wants to look at some audio signals let him do it on whatever he wants. No harm in buying an oscilloscope if you have the money.The Rigol DS1054Z are good bang for buck as a learning, diagnosis tool and better than wasting $100 on buying something that needs immediately repairing or is bottom of the heap in terms of brand/quality.Saying the Rigol will be not repairable etc is a joke, we already have threads on people repairing them. Overall they have proven they are quite reliable and people have worked on the firmware recovery side of things. It's not like repairing a DS1054Z is harder than any other digital oscilloscope. If anything equipment that is really common is even easier to repair with community help.

author: marcus h
author_rank: Contributor
timestamp: April 13, 2020, 10:10:01 am
content: Quote from: 0culus on April 11, 2020, 09:52:48 pmIs that really so? What specific parts do you consider irreplaceable or not repairable?QuoteFrom an economic standpoint many repairs don't make sense today unless you are a hobbyist. And this includes both vintage and modern stuff.I readily believe that one can solve most problems with gear from the 70s to 90s - but with higher integration we see an increasing number of custom ASICs in practically all electronics devices - and that includes test gear. Everything that isn't off the shelve can be quite problematic.When I just consider the videos Dave put out we see specialized parts made by/for HP (for example). Can you always get replacements? In "decades"?Of course you can cannibalize other machines - but the same is true for the Rigols.In fact, I believe that twenty years from now on people will havethe exact same discussionand talk about the "legendary 1054Z" and preferring it to what will then be available.

author: Fungus
author_rank: Super Contributor
timestamp: April 13, 2020, 10:39:59 am
content: Quote from: marcus h on April 13, 2020, 10:10:01 amThe main board might be tough to fix if you zap it with 1000V.There's no reason for it to fail in normal use though, most likely it will be the power supply or knobs/buttons that die.Quote from: marcus h on April 13, 2020, 10:10:01 amRigol has recently upped the warranty to five years:https://www.rigolna.com/products/digital-oscilloscopes/1000z/

author: nctnico
author_rank: Super Contributor
timestamp: April 13, 2020, 10:43:25 am
content: Quote from: marcus h on April 13, 2020, 10:10:01 amModern equipment not being repairable is utter rubbish. Lots of older HP and Tek gear has specialised parts which do fail and are unobtainium. A modern low end oscilloscope OTOH is completely build from off-the-shelve parts. You can replace everything if you want! But in the end the most likely parts to fail are the ones which are under stress and that is the power supply and the analog front-end (if the oscilloscope sees some abuse).

author: Gyro
author_rank: Super Contributor
timestamp: April 13, 2020, 11:11:19 am
content: Quote from: marcus h on April 13, 2020, 10:10:01 amI highly doubt it. It's about a step change in fundamental technology, not just another DSO model.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: April 13, 2020, 01:24:57 pm
content: Quote from: 0culus on April 11, 2020, 09:52:48 pmI have to agree with Nico here. Because from my view (as industrial user and someone who had to deal with the service side of a large amount of test equipment) modern test equipment is, in general, a lot more reliable, durable and capable than kit made back in the old days. And this has nothing to do with abuse or 'harsh environments'.For example, when analog scopes were still a thing we had a lot of failures with certain HP scopes (i.e. 1980 Series), and the Tek 7000 Series has often been the literal pain in the ass because many of the modules were so fragile that they spent more time with Tektronix then with usIn fact, the Tek 7000 Series has been by far the worst in terms of reliability than any other scope I have seen over the decades. As a result, we had to keep a lot of spare mainframes and especially modules, so we had something to work with when another component had to be sent back for repair or calibration and adjustmentIt wasn't just scopes. For example, the HP 8672A RF synthesizer and the venerable HP 8566A/B spectrum analyzers weren't exactly trouble-free, either, although still better than the Tek 492P spectrum analyzers we also had.For some reason hobbyists like you always seem to assume that the old kit you buy for cheap or get for free never had a fault when it was with its original owners. But a lot of the old kit was pretty service intensive when used in a professional environment, which is what it was built for. Then years later these instruments get discarded (often not too long after they had another repair to extend their life just long enough until the replacement instrument becomes available), and a lot of them eventually end up with hobbyists. Which then put a lot less use on them and who don't care about their calibration, and when this use pattern results in few new faults this is then talked up as some miraculous superiority of old equipment.Having said that, there were lots of instruments which worked fine with no repair until their retirement, like most of the Philips analog scopes, the R&S FSM spactrum analyzers or the various HP function generators we had. A lot of simpler instruments survived without needing a single repair (although regular adjustment was still a thing). But many more complex instruments were pretty demanding back then.QuoteYes and no. A lot of very old kit has special-made parts, from mechanical switches for which spares have to be individually manufactured to unobtainium ICs for which the only source is to canibalize another antique instrument in the hope the part taken from it is in better condition than the one it replaces.All this is fine if this is for a hobby like collecting and restoring vintage test equipment. But even if that hobby is electronics and the particular instrument is supposed to be the tool to fix something else then the fragility and lack of spares is already a problem.There's a reason why old kit is often so cheap or often even free.QuoteThis may be the case, but even for hobbyists there is still the choice of buying some antique which very likely will be way past the zenith of its life time, or a new modern-day entry-level instrument which is cheap because it's made from commodity parts, and which will come with some 3 or 5 years of warranty.And in general, the latter is the better choice.QuoteThe thing is that this $400 Rigol DS1054z will very likely still work fine in 20+ years, and it's not unlikely that it will do so even without needing any repairs. But even if it fails it can be repaired, because it's made from COTS components which are used in a lot of other devices and which are a dime a dozen.This isn't necessarily true for more expensive instrument (i.e. Keysight DSO-X scopes, which use proprietary ASICs) but even here the lack of mechanical wear (aside from electro migration of course) means the useful service life will most certainly be in excess of 20 years.The reality is that most modern test equipment will have little problems to survive for decades, not only because mechanical switches and the need for manual adjustment is gone for many instruments. The only real limit will be the durability of plastics and rubber parts, and that is already a problem for a lot of the old test equipment today.The other thing to consider is that the service life is only one part of a test instrument. The other is technological obsolescence, i.e. the lack of functionality that today is expected from a similar instrument. For analog scopes, this would be things like single-shot acquisitions or measurements, and for older DSOs this would be functionality like serial decode. It's pretty irrelevant if an old instrument still works if it lacks the required functionality.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 13, 2020, 05:15:39 pm
content: WuerstchenhundIt was long but what a great summary of the subject raised by the OP - brilliant!