Beginners oscilloscope for audio - Page 1
Forum section: electronics / testgear

author: stev.dk
author_rank: Regular Contributor
timestamp: April 11, 2013, 01:32:05 pm
content: I am repairing and upgrading guitar and hifi amplifiers, and i want to take it to the next level, and get myself a scope for that. I only know, that i wontneeda scope with digital storage, cause im only going to be reading sine waves (potentially clipping or turning into square waves), in real time. I really dont want to overbuy this, and get features i wont need for this purpose. If getting a cheap used analog scope is sufficient, i'll stick with that.What analog bandwidth is recommended/needed for repairing audio equipment?When measuring a continuous sine wave loop, is equivalent time sampling enough (im thinking cheaper scope)?What else to look for in a scope, wich sole purpose is displaying sine waves; ex. setting bias to controle clipping/checking for distortion ect. finding clipping in circuit, to replace bad part, or adjust bias.

author: nctnico
author_rank: Super Contributor
timestamp: April 11, 2013, 02:38:54 pm
content: I'd still recommend a digital scope because it can also display low frequency waves. Don't expect a scope to be accurate either. Its excellent for watching whether a signal is seriously clipped but for measuring levels you need an AC voltmeter and for distortion you'd need a distortion analyser.

author: ddavidebor
author_rank: Super Contributor
timestamp: April 11, 2013, 03:46:05 pm
content: Go for the cheapest chinese scope

author: smashedProton
author_rank: Frequent Contributor
timestamp: April 11, 2013, 07:10:45 pm
content: Pc sound card! They are optimized for audio. That combined with a Meter and a solder station should have you in Business

author: c4757p
author_rank: Super Contributor
timestamp: April 11, 2013, 07:13:56 pm
content: Quote from: smashedProton on April 11, 2013, 07:10:45 pmMost don't do DC, nor do they have anything you could ever call a "bandwidth" to point out parasitic oscillations and such. Look in the right places and you can find a used, proper scope for peanuts.

author: valentinc
author_rank: Regular Contributor
timestamp: April 11, 2013, 09:02:37 pm
content: For audio, an analog bandwidth of several hundred Khz should be enough (for sine waves). Although, one thing I want to mention is DON'T buy the DSO nano oscilloscope... for several reasons: it doesn't have AC coupling, the input front end is very basic, the sampling rate is very poor, the trigger at low frequencies does not work at all... And above all these, it's pretty expensive too for what it can do.Equivalent time sampling only works for repetitive signals, so you won't be able to see glitches... And it's slower too (as regards of refresh rate)In my opinion you should buy an analog scope with 10 Mhz analog bandwidth or so ... You can get them pretty cheap on ebay...

author: PaulAm
author_rank: Frequent Contributor
timestamp: April 11, 2013, 09:40:55 pm
content: Just about any decent quality analog scope will work for audio. You might want to look for a Tektronix 5000 or 7000 series and pick up appropriate plugins. The 5000 series were fairly low bandwidth, but they're fine for audio work. They tend to be pretty cheap.There's a spectrum analyzer plugin for the 5000 series that covers 20hz to 100KHz which might be of some interest. That plugin sells for $100-150.

author: stev.dk
author_rank: Regular Contributor
timestamp: April 11, 2013, 10:52:50 pm
content: Thanks for your reply's so far.The Tektronix 5000, is way to expensive. This is only amateur work on a hobby level, and i do not have the funds for a professional scope like the tektronix.I've been looking at owon, rigol, uni-t and atten;s entry level scopes at 100MHz, at a price range around £300. There really is no market for used analog oscilloscopes (or digital for that matter) in Denmark. There are a couple of 20MHz (unknown brand) analog scopes at £50-£120, but there's no other info on them. There is one Agilent 54621A 60MHz at £330, but that seems like a lot for a old analog scope. Getting large and heavy analog scopes sent from outside dk is too expensive, and just not worth it in my price range.

author: ben_r_
author_rank: Frequent Contributor
timestamp: April 11, 2013, 10:55:05 pm
content: Quote from: stev.dk on April 11, 2013, 10:52:50 pmI think maybe you were looking at the current 5000 series line up and what that poster meant was an older (much older and used) model from the 5000 series that would cover the range you are looking for.

author: PaulAm
author_rank: Frequent Contributor
timestamp: April 11, 2013, 11:26:54 pm
content: Indeed. You should be able to find an older 5000 series for $50 US, more or less. I just mentioned those because they tend to be cheap.Any of the Tektronix 4xx series would be fine and they're floating around the 100-150 range in working condition. Maybe less if you run across someone who just wants to see it go to a good home.

author: nanofrog
author_rank: Super Contributor
timestamp: April 11, 2013, 11:58:12 pm
content: Any working 20MHz analog scope would be suitable. More than enough bandwidth, and has better vertical resolution than an inexpensive digital (you'd want 12bit or better to get equivalent vertical resolution, and that's rather expensive). There are tradeoffs of course (have to use a camera to get a screen image into a document if you wish), but you don't *need* a digital scope for audio at all. And such an analog scope would be less expensive than a Rigol 1052E.

author: nctnico
author_rank: Super Contributor
timestamp: April 12, 2013, 12:19:55 am
content: You don't need high vertical resolution. An oscilloscope's vertical DC accuracy is at best 3%. An oscilloscope is for examining waveforms not for accurate measurements!

author: vk6zgo
author_rank: Super Contributor
timestamp: April 12, 2013, 01:59:48 am
content: I'm not sure if they are available in Denmark,but new "El Cheapo" Chinese analog 'scopes are ,or were until recently,available in Oz!They are a bit cruddy,but will do the job.The single channel 10MHz one is around $A135 ,so expect similar prices in your country.There may be a few of these around secondhand,from people who have upgraded to 100Mhz 'scopes.Another thought is to look out for a Philips 'scope.Philips stuff was pretty much endemic throughout Europe back in the day,& are usually rugged,well performing units.

author: commongrounder
author_rank: Frequent Contributor
timestamp: April 12, 2013, 11:32:39 pm
content: I run a business doing what you would like to try out, and just wanted to add that you should be sure that any 'scope you find has a suitably high input voltage rating. Since you might want to probe around interstage and output stage tube circuits, having your probe/scope be able to withstand several hundred volts is a necessity. I own a trusty old Sencore SC3100 analog scope. It has a 2 kilovolt (!) maximum AC+DC input rating with the supplied probe, and does a decent job of dbm, ac, dc, frequency and peak to peak readings on a separate LCD screen. I don't know if they were ever available where you are, though. They do show up on the 'bay. At the very least, get a set of 100x scope probes to help any 'scope withstand B+ voltages in tube amps (and present a very high 100 megohm load impedance, too). I do have a digital scope too, to get screen shots and more extensive waveform measurements. Both types have their strengths and weaknesses. Best of Luck!

author: mzacharias
author_rank: Frequent Contributor
timestamp: April 13, 2013, 10:35:56 am
content: For audio work a BK Precision 1472C or a newer 1477 can be found on eBay often for much less than 100.00. Nice thing about these is they go to 20 volts per division, excellent for looking directly at the output of big power amps. They are a 15mHz bandwidth so don't expect to be able to do FM front end work. Really reliable though, real workhorses.

author: stev.dk
author_rank: Regular Contributor
timestamp: April 16, 2013, 12:08:14 pm
content: Thx for your answers. I have bought a Gould OS1420. I found it on a danish "used items" site, very cheap - and the former owner used it for the exact same purpose. I also found a manual for it online. It's an analog two channel, dual trace, 20MHz, digital storage scope. It has 1024 x 8-bit storage per channel, not sure if this is usefull in any way, but im most likely not going to be using the storage function anyway.