Oscilloscope for audio repairing and studying - Page 1
Forum section: electronics / beginners

author: gis
author_rank: Contributor
timestamp: October 15, 2013, 01:17:48 pm
content: Hi everybody,as said in the subject I'm wondering which oscilloscope to buy for mainly audio circuits troubleshooting.Suddenly last time I used oscilloscopes send me back to school, five years ago: Hameg CRT stuff, with the possibility of acquire waveforms to a connected computer.The things I usually put hands on are live service audio and lights materials, analog pedal("pedal" as in "for guitars, basses, keyboards")effects.Actually using ears, intuition and step by step troubleshooting, I'd like to invest some money on an oscilloscope to get some things done faster (and better).The things mentioned above are not my main occupation (I'm a live sound engineer, backliner and light technician), but I'd like to invest some money and energy in these directions to diversify my revenues.Two oscilloscopes I putted eyes on...used Tektronix 2445B, calibrated, 2x 100MHz probes490€ shippednew Rigol DS2072830€ shipped, 3 years warrantyI usually try to spend "more but once", but I'm actually afraid I can't understand now what I'll really need, and afraid to "throw away" money.So... some hints from the community will be really, really appreciated!Thanks to anyone for reading!Giovanni aka "gis", from Italy

author: David_AVD
author_rank: Super Contributor
timestamp: October 15, 2013, 08:23:34 pm
content: A used dual channel 20MHz analog oscilloscope should be fine for audio use. They can be had for very little money these days.

author: deth502
author_rank: Frequent Contributor
timestamp: October 15, 2013, 10:02:26 pm
content: Quote from: David_AVD on October 15, 2013, 08:23:34 pmthis, but dont expect them to be very "portable".if your looking for something to drag around with you, although i despise them with every ounce of my being, a pc based scope may be the best option for you.i have one of those small "mp3 player" type dso, and i know most feel the same about them as i do about the pc based ones, but i find it very useful for field use observing basic waveforms and logic signals. not sure if one of those would have the resolution you would need for top shelf audio work.if your looking to do bench work now and possibly be portable in the future, then im back to agreeing with david. cheap cro bench model, and while you learn to use it, you can get a feel for what it does, what you need it to do, what it dosent do, and what you dont need, so then, if, in the future, you decide you need something smaller and more portable like the rigol, or a pocket dso, or a pc based scope, you will have a better idea of what to look for to meet your needs.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 15, 2013, 10:32:55 pm
content: I think almost any scope should work for audio repair. Certainly the two choices you have listed should serve very well. I would be tempted to save some money and go with the Rigol DS1102E, (or even 1052E) but the DS2072 does have a bigger screen, faster update rate, and intensity graduated display. These features make the DS2072 clearly superior, but whether the superiority is worth the price difference is a question only you can answer.An old analog scope should do well, and may be very inexpensive. It is very big and heavy, though.The biggest advantage of a digital scope over analog is its ability to handle transient one-shot events. These are very common in digital circuits (communications protocols) but if you're testing analog gear, you can usually make things work well enough by using a repetitive waveform on an analog scope.Even on repetitive signals, digital scopes offer some advantages of easy measurement functions, easy waveform capture for computer analysis, easy screen capture for illustrations, small size on the bench, etc.Don't forget to allocate some money for at least a basic signal generator. For audio use, a basic sine, square, and triangle generator up to 100kHz or more should be enough, though arbitrary waveform generators are popular and not much more expensive. Modern DDS generators give very accurate and stable frequency, with good waveforms, but old used analog generators can also work, and may be cheaper. I have the GW Instek SFG-1003, which is inexpensive and does its job well.

author: gis
author_rank: Contributor
timestamp: October 16, 2013, 09:26:01 am
content: Thank you all!Portable is fundamental but pocket is not (just put it in the back of my car and go); this because I'mafraid of little screens(reason why I won't buy a Rigol DS1052E or a DSO nano; isn't it like having lots of horsepower on a car with just two gears?)or not-standalone units(so no computer-based scopes).AG6QRsaid well, I still need to buy a decent signal generator, a new solder unit, most common components to replace... so staying on tight budget is (quite) a must.Storing waveforms and troubleshooting most common digital protocols who'd be nice (I made some programming on uCs and RS232, SPI, I2C; and I like to get back into), but I think I can buy a pc-based scope later if I'll really need, at least for the last thing?Found a non-calibrated used Hameg HM 303-6 on auction that's actually on 150€,a calibrated used Tektronix 2440 actually at 170€,a calibrated used Hameg 1005 actually at 200€.I also saw the Rigol DS1074Z for 535€, with three years warranty... really don't know if the extra 300€ are worth the DS2072, and the two channels less.I'm a bit confused.Also by theBW and sample rate of the DSOs, measures that I use everyday in my job, butI don't have the numerical perception for analog and digital troubleshooting.

author: DL8RI
author_rank: Regular Contributor
timestamp: October 16, 2013, 09:46:20 am
content: Hi,I would by a cheap, used scope, 20MHz, 50€. Perfect for Audio and indestructible.A DSO is not so good for audio-measurements because of the lack of vertical resolution. The 8 Bits of most scopes are not nearly enough to get a "real" Picture of the performance of an amplifier. If you think about Using FFTs and so on, you will get not enough dynamic range for real Measurements.Soundcards are often recommended, but they are very limited:Small input-range, build in HF-Noise-Generator (=PC), no DC, most HiFi-Amps have a Gain-BW up to ~400kHz, no real physical knobs and so on.The old, analog HAMEG-instruments have one advantage: They are nearly always reparable. Hameg uses mostly "common" Parts you get from every store, no fancy custom-labeled ICs. On the backside they are quite expensive on ebay.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 16, 2013, 09:51:44 am
content: For analog repair work and trouble shooting, you may actually prefer an old analog CRO over a modern DSO. If for instance you want to look at cross over distortion in any kind of detail while adjusting amplifier balance, then a CRO is superior. The reason is that an old analog scope generally couldn't care less about vertical channel overvoltage. The scope will recover quite quickly from each overload on every half period.A DSO on the other hand may give all kinds of trouble if you attempt to magnify a small portion of a signal to fill the whole screen vertically.  They can mostly do this to some degree, but not in any way like a CRO can. So if you want 1V to fill your screen vertically, while examining a 20Vpp signal, then an old CRO may be the better fit. Actually I haven't tried this with a current, high quality mid range scope, like an Agilent 3000X series. They may have improved lately.

author: gis
author_rank: Contributor
timestamp: October 16, 2013, 10:32:10 am
content: Quote from: DL8RI on October 16, 2013, 09:46:20 amReally good to know, thanks!Quote from: ElectroIrradiator on October 16, 2013, 09:51:44 amYou got me, thanks!

author: gis
author_rank: Contributor
timestamp: October 16, 2013, 08:01:25 pm
content: Just bought a Tektronix 2440 for 350€...

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 16, 2013, 08:13:45 pm
content: Quote from: gis on October 16, 2013, 08:01:25 pmThat is a really, really old DSO...

author: DL8RI
author_rank: Regular Contributor
timestamp: October 17, 2013, 06:04:49 am
content: Well, it's a good scope although it's old, a bit expensive maybe... But for audio it's not really the best choice.

author: gis
author_rank: Contributor
timestamp: October 17, 2013, 07:35:54 am
content: In this period I'm always on a hurry, and this is always a good way to make mistakes.I read Tektronix 2440 and believed it was a brother of the 2445.8 bit resolution...

author: BravoV
author_rank: Super Contributor
timestamp: October 17, 2013, 08:00:02 am
content: Feel sorry for you, and too bad you did not do deep enough homework on reading various old Tektronix scopes before making any hard decision.Don't mean to scare you, in reality on buying a really old scope, that 2440 DSO which could be out of calibration by now, or worst may suddenly die after you used it just for few days because of old age, and leaving you without any guarantee at all and possibly no or really hard to find spare parts and that presumably you know to fix it too which may take some time.I hope you really learned from this expensive lesson and to be honest looking at your current condition, the DS1052E suddenly looks far more better choice isn't it ?

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 17, 2013, 08:26:47 am
content: Quote from: BravoV on October 17, 2013, 08:00:02 amI would suggest the DS1052E may not be a good choice for the OP. It doesn't have intensity modulation of the waveform, which makes displaying many forms of complex analog signals problematic, to say the least. Same issue will plague the 2440, plus the Tektronix has an awfully low waveform update rate IIRC.A DS1074Z, a DS2072, or any scope with similar capabilities, would have been my 'minimalist' choice for a new instrument for analog work.

author: BravoV
author_rank: Super Contributor
timestamp: October 17, 2013, 08:37:34 am
content: Quote from: ElectroIrradiator on October 17, 2013, 08:26:47 amAgree, what I mean is with his current condition with the 2440 DSO is more like a really risky gamble, with so many vulnerabilities and weaknesses compared to a "NEW" DS1052E even though it doesn't fit in properly with his needs on intensity, c'mon, you just can't deny the fact that with 1 year manufacturer guarantee + a properly & freshly calibrated scope will make you sleep much-much better at night.Quote from: ElectroIrradiator on October 17, 2013, 08:26:47 amHe has budget limitation on that part.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 17, 2013, 08:49:43 am
content: Quote from: BravoV on October 17, 2013, 08:37:34 amYep, presented that way your suggestion makes perfect sense.Quote from: BravoV on October 17, 2013, 08:37:34 amI'm aware of that, which is why I would also have suggested an old, easily repairable dual channel 20MHz scope. My personal experience here is mostly with old Philips models, not as much Hameg. At leastsome(emphasis on 'some') of Philips' PM32xx models are built from nothing but through hole jellybean components, and single sided PCBs.

author: gis
author_rank: Contributor
timestamp: October 17, 2013, 09:06:11 am
content: A colleague of mine is telling me that 2440 will be nice for low frequency inspections, where analogue can't properly or easily trigger.When I told him about 8 bits samples depth, he said it won't be a substantial problem.I'm getting more confused, not having enough oscilloscope use experience.

author: BravoV
author_rank: Super Contributor
timestamp: October 17, 2013, 09:07:43 am
content: Quote from: ElectroIrradiator on October 17, 2013, 08:49:43 amYeah, too bad he ignored suggestions on choosing much-much cheaper lower freq analog scope for 1st timer, instead of trying to get higher speed scope but without doing his homework properly and slipped out of track at last minute.

author: gis
author_rank: Contributor
timestamp: October 17, 2013, 09:25:02 am
content: I wrote to the seller and he said no problem if I won't buy, just told him if so or if he can supply some other instrument.Could I ask your opinion on these?Quote from: gis on October 17, 2013, 09:06:11 amAgain, thank you so much.

author: madshaman
author_rank: Frequent Contributor
timestamp: October 17, 2013, 12:46:51 pm
content: Quote from: gis on October 17, 2013, 09:25:02 amBack out man, back out!1: €350 is too much for a Tek2440 unless it's in perfect condition and calibrated and you *want* one specifically.2: the Tek 2440 has really slow acquisition.3: For audio work, imvho, being able to visualise the spectral content is more important than seeing waveforms in the time domain. The Tek 2440 will let you do that via a computer and FFT (do you have a gpib interface?) but at low frequencies, the data you'll get by FFT-ing the output of the Tek 2440 is going to be suspect at best; I'd say that's even true of modern DSOs with 8-bit acquisition. So, you might as well go for a pure analog scope where you can see the time-domain better (vs a Tek 2440).The Tek2440 is 300Mhz analog bandwidth so you're looking at a Tek 485 (350 Mhz), a Tek 2465 (300 Mhz) or a Tek 2467 (350Mhz), rhe additions of "A" or "B" suffixes indicate a bandwidth boost and a later model.Pricewise a used Tek 2445 is near the price of a used Tek 2465, so I would go for the latter for significant bandwidth increase.You might want to think about stalking eBay for a used DSA and maybe a used distortion analyser like the HP331A.edit: later <-> earlier

author: gis
author_rank: Contributor
timestamp: October 23, 2013, 01:29:11 pm
content: Quote from: DL8RI on October 16, 2013, 09:46:20 amFound anHAMEG HM 204-2on auction, now at 83€ shipped. Will spend up to 150€ shipped have sense?Does anybody know if this model corresponds toDL8RI's hint above?Thanks!

author: Sigmoid
author_rank: Frequent Contributor
timestamp: October 23, 2013, 04:20:03 pm
content: Honestly, I've thought long about getting an analog scope, but in the end went with the ds1052e. Don't worry about the screen size, it's not smaller than an analog CRT - and you'll get used to it quick. It's perfectly adequate.As for portability, it IS quite portable, and doesn't take too much space.

author: madshaman
author_rank: Frequent Contributor
timestamp: October 24, 2013, 06:19:29 am
content: CRO's aren't always as bulky and heavy as most people think.I have a couple Tek 2236s, one that's a permanent fixture on my bench. They're *extremely* light and easily moved.

author: gis
author_rank: Contributor
timestamp: October 24, 2013, 08:27:11 am
content: Sigmoid, but what you say about 8bit resolution ADC if, for example, I want to see a little distortion over a 50 volts wave?

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 24, 2013, 02:57:43 pm
content: Quote from: gis on October 24, 2013, 08:27:11 amHandle it the same way you would handle it on an analog scope. You can't easily see small details on a tiny analog screen with the full 50V range shown, so you would adjust the vertical scale and position knobs to zoom in on the area of interest. Likewise, you can adjust the scale and position on a digital scope to get the analog front end amplifiers to send the area of interest to the 8 bit ADC.

author: gis
author_rank: Contributor
timestamp: October 24, 2013, 03:23:50 pm
content: Quote from: AG6QR on October 24, 2013, 02:57:43 pmSo it will be enough to understand the waveform and make some measures.But when I see the Rigol DS1052E at 330€ shipped and the Rigol DS1074Z at 530€ shipped... an old CRO Hameg could be fine.And I think I can sell it later at quite the same price I'll buy it; I don't think the DS1052E will be reselled as well as the 20MHz analog one.

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2013, 08:55:57 pm
content: A used 20MHz analog oscilloscope will be fine for general audio use. Like you say, you can always sell it again later if you want. Even if you do get a digital oscilloscope later, the old analog one is still handy to keep and will owe you little.

author: dyazdani
author_rank: Newbie
timestamp: October 26, 2013, 04:19:04 pm
content: I bought an old (very) Tek 465, it works fine and I was willing to risk the $100USD on it. That said, I'd drop the extra on a Rigol or something else new if I was using it a lot.

author: gis
author_rank: Contributor
timestamp: October 29, 2013, 11:21:46 pm
content: Hi guys,finally bought an Hameg HM204-2 with probes for 105€ plus shipping! Just few minor scratches, so happy!But poorly packaged, it arrived with the right front high pushed inside, component tester socket missing, shaft-to-potentiometer connections broken...I started thinking about sparing some money and buying the Rigol DS1074Z, with its nice three years warranty!PS: Hameg is really nice engineered inside!

author: sipo75
author_rank: Contributor
timestamp: October 30, 2013, 10:26:03 am
content: Quote from: gis on October 29, 2013, 11:21:46 pmNot sure how bad the damage is but it sounds bad. Don't hesitate to request some compensation.I am pretty much going through the same process - bought a few oscilloscopes. In the end I think I will need a sound card for serious audio analysis. Something like the esi juli@. But having the oscilloscopes around is a big plus.Good luck with your new scope(s).

author: manzini
author_rank: Regular Contributor
timestamp: October 30, 2013, 03:34:03 pm
content: For hobbiyst Audio repairs, I use the Peter Millet's sound scope / AC RMS kit, that include a signal gen, through a good 24/192 RME external interface or firewire Echo Audio (I have and love both).Cheap and happy.this: Sound Card Interface / AC RMS voltmeterhttp://www.pmillett.com/ATEST.htmps: and a cheap real scope for some else (no DC coupling)

author: gis
author_rank: Contributor
timestamp: October 31, 2013, 11:03:15 am
content: Thanks everybody for the hints!Look at the poor 204...

author: Shock
author_rank: Super Contributor
timestamp: October 31, 2013, 06:55:04 pm
content: I own a couple of Philips PM3065 100Mhz scopes.I went for this model as it seemed to be the later end of the analog era right before the hybrids and fairly cheap.Can someone please check and comment on the attached specs for audio usage?

author: DL8RI
author_rank: Regular Contributor
timestamp: October 31, 2013, 09:46:21 pm
content: Nice for Audio and "general work"I also have one of these (the 55) unfortunately with an error in the Powersupply and without the handle.But i will definitely repair it, these scopes are pretty lightweight for an analog scope, perfect for "service"One debate over them is always the knobs. Some hate this Units for these "up-down"-switches, some love them.Or i'll get one of this hybrid-scopes even nicer with GPIB and all the fancy digital stuffQuote from: gis on October 31, 2013, 11:03:15 amUh, thatsBut the damage doesn't seem to be to severe, looks somehow fixable.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 31, 2013, 10:03:10 pm
content: Quote from: DL8RI on October 31, 2013, 09:46:21 pmI would be a bit worried about internal damage or misalignment of the CRT after a knock like that. They are built to be fairly rugged, but there are limits...

author: tony3d
author_rank: Frequent Contributor
timestamp: November 01, 2013, 10:43:17 am
content: Quote from: gis on October 15, 2013, 01:17:48 pmThis owon should be fine, and it's only $236.00!http://www.amazon.com/gp/aw/d/B007T6XNCA/ref=mp_s_a_1_1?qid=1383302484&sr=8-1&pi=AC_SX110_SY165_QL70

author: Eddie
author_rank: Newbie
timestamp: November 01, 2013, 04:27:08 pm
content: For audio work you cannot go past the Rigol DS1102E it is a pleasure to operate and once you get used to the menus you you will get faster in using the device.What I like about it is that it is portable, nice and light as in weight and it was not that expensive, and yes I am most pleased with mine, the old CRO I had was heavy, took far too long to heat up and the controls were in need of replacing.

author: ErikTheNorwegian
author_rank: Frequent Contributor
timestamp: November 01, 2013, 04:52:57 pm
content: I`m doing a lot of audio work, and do prefeer analog scope for that. Easier to work with. Caputures glitzes way faster-