Oscilloscope for audio signals - Page 1
Forum section: electronics / beginners

author: sorrycharlie
author_rank: Newbie
timestamp: August 24, 2022, 10:02:53 pm
content: Hi there. I’m looking at purchasing an old oscilloscope. I’m looking at a few models but most look like the BWD 506. I’m hoping to run audio through it, I’ve got a few analog synthesisers, I just wanna see the waveforms. I’m going to be honest, I know very little about the subject and I will be basing the purchase solely on the looks, I like the vintage look.My question is, will these old units do what I want, simply display the different oscillator patterns. Also, how would I do this, what type of cabling would be required to get the signal into the scope and from where would it come from the synthesiser?Thank you and sorry for my ignorance.

author: Zenith
author_rank: Frequent Contributor
timestamp: August 24, 2022, 10:38:42 pm
content: From the late 80s to around 10 years back, the basic entry level scope was dual trace 20MHz with very similar ones around by all sorts of makers; Hameg, Goldstar, Topward, B&K, plus others, and string of rebadged ones.That's plenty enough bandwidth for audio. Hameg have a good reputation. £40-£50 on ebay UK, I don't know what the Oz market is like. It's best if you can see it working and see it doesn't have problems with dodgy switches and so on.If you want the real vintage look go for a valve scope, but unless you are into fixing them, which I'd guess you are not, not a good idea.You feed a signal to a scope either with a cable - usually a BNC cable - or a scope probe. A cheap scope probe should be fine for what you want (£10).I can't advise on where the signal should come from in the synthesiser - not enough information. Presumably it has an output socket, or you could find somewhere to clip on a scope probe.

author: sorrycharlie
author_rank: Newbie
timestamp: August 24, 2022, 10:58:12 pm
content: Ah wonderful, thanks for the replies! Ok I think this answers my question perfectly. Thanks again.

author: wizard69
author_rank: Super Contributor
timestamp: August 26, 2022, 06:16:32 pm
content: QuoteAs much as I'm with you on this I have to warn you about the reliability issues associated with such hardware. Unless you can find one in working order I wouldn't be quick to buy. Some of these scopes can be repaired but it is often far from trivial effort wise. I say this looking at the partially working scopes that I have that i might get 'around to it' for repairs. If you do go this route I actually like the look of old Tektronx scopes. Tek's newer scopes kinda loose it for me looks wise. Frankly If I was doing something like this I'd would want an older analog scope for the looks also.If you skip the old scopes you will have to consider one of the lower cost ho-hum scopes on the market or a new technology option. This is literally a case of buying for looks as that seems to be what is important here. Almost everything on the market will do as a waveform display monitor as the band width requirements are not high. However if it is a digital scope look closely at the specs, you will likely benefit from higher sample rates.As for new technology digitizers/scopes as USB dongles for the PC are a thing. This flips the "look" part of the requirement on its head so maybe not your cup of tea at all. However once you get past ultra modern you do have some advantages. While not small, the "dongles" are much smaller than most scopes these days. The small size can help especially if you have a laptop in use already

author: Terry Bites
author_rank: Super Contributor
timestamp: September 05, 2022, 01:36:04 pm
content: For audio you usually wont need a smart digital, fast or precise scope. If its cheap and it works, it will probably do. People seem to be unloading anlog scopes like they're an infectious disease on ebay etc.

author: rstofer
author_rank: Super Contributor
timestamp: September 05, 2022, 02:39:48 pm
content: One way to think about price is the difference between supply and demand. Those analog scopes on eBay are there because nobody wants an old analog scope that likely needs a lot of rework just to get a trace. Look at the shipping cost...Yes, I have an old Tektronix 485 350 MHz scope but I bought it for the bandwidth, not the neat features of the Rigol DS1054Z which I bought a few years back. There is simply no comparison between the capabilities of a modern DSO and an old analog scope.Look at the Siglent SDS 1202X-E for $359 (in US) with free shipping. When you look at the old heavyweights, consider any shipping charges.https://www.amazon.com/Siglent-Technologies-SDS1202X-Oscilloscope-Channels/dp/B06XZML6RDSure, that's more expensive than a $150 eBay scope but it's highly capable, decent bandwidth (200 MHz but only 2 channels) and has onscreen measurements an old analog can only dream of. Not to mention FFT for looking into harmonic problems.These new entry level DSOs are amazing! And they're not likely to need a lot of rework to get a trace.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: September 05, 2022, 03:38:26 pm
content: This is just my opinion having owned both digital and analog scopes.Analog scopes are much, much easier to use at audio frequencies.10-20 MHz scopes are really cheap. Here in the US, I think I can pick one up that is working for maybe $20-$50.This is my opinion only: I saw some Ausie ebay for that BWD scope and I think the prices they want are nuts.Make sure you can get the correct probes usually the scope has the capacitance of the probe next to the BNC input. Match it closely with the probe.Almost always you would use 10X probes to sample the signal. Don't direct connect anything until you are comfortable with your equipment, even though scopes like your BWD have direct connections.I have spent hours fixing the inputs of scopes that have been blown. ( I would never admit to doing this myself, however, HA!)Again probes are really cheap.for low freq scopes. Chinese probes are mostly just fine.Try local hamfests or whatever Craigslist thing you have available.Turn it on and make sure you can see a good trace. Brightness counts.Most scopes have a little connector for a probe on the front panel so you can observe a square wave. If you can, try it on the scope you are buying. Note the Cal on the BWDGet the one with the biggest screen you can.The Tektronix 465...475...485 are really good scopes and are probably the benchmark of analog scopes. But getting one in good working order is pretty difficult.These things are 100 plus MHz, so you do not need them, I have one. Complicated and hard to fix.I used to have a Tektronix "School" scope that was 15 MHz, had a really nice big screen and was just great for audio. Also hard to hurt it since it was made for use in schools.Kinda looked like your one channel BWD 506, nice big screen. It might actually be a close copy, lots of folks copies lots of Tek scopes.Here is a nice quote about BWD :While the use of commonly available components to build equipment had the effect of limiting performance, it means that BWD equipment is still serviceable, making it popular with Australian electronics hobbyists.I have been disappointed in the digital scopes analyzing audio. Maybe I just have not tried the right one. It takes too long for them to "acquire" the signal and most of these scopes are high freq and need a bandwidth filter to adequately show audio.