o-scope advice. audio

[chipss]

hello,
I am looking at getting a scope, used for audio, tube amps, 9 volt stomp boxes, and have started to build some pro audio gear, mic pre amps, compressors, eq's and a few mics, I have read  use an older crt type, am Leary of what I am seeing on say e-bay, used and tested to work,  vrs new smaller units, but wonder what would be good for audio, price wise looking $400 to say 600, the  DS1054Z  sure seems to be well liked but not sure if it fits what I will be using it for.

thanks for your time.

[james_s]

For audio, practically any scope will work. I would be nervous about poking around in a tube amp with an expensive DSO, although it can be done with proper probes. Personally I think I'd look for an inexpensive used analog scope in good condition, you don't need a lot of bandwidth for audio. Even a very low end 5MHz scope from the 70s would probably do the job, although if you're going to pay money for it you can probably find something reputable like a Tektronix.

[ohdsp]

Again a good old used analog scope would be just fine for basic audio work. Assuming you pick up a reasonable cost one, such as a Tek/HP or Gould (which I have and seems pretty alright) or something like a Hitachi, you can always invest in a DSO in the future if you need one. Have seen things like Gould/Hitachi's cheap/free if you dig around enough (including in skips!) but your mileage may vary...

[alsetalokin4017]

While I love analog scopes and have several myself (three working, plus one not so much), for the purposes and budget stated I would have to recommend the Rigol z-box.

Especially if you are doing work for customers. It is so much easier to store, display, print waveform images with the DSO than it ever would be with any analog scope-camera combination. The single-shot capability of the DSO is worth the price right there. Bench space, power consumption, factory and vendor warranties, four channels, probes supplied with purchase... all of these factors argue for the Rigol z-box instead of a used analog scope.

Although for 600 dollars you might be able to get a pretty decent analog scope that probably originally cost more than my house did....

Any (working) scope is better than no scope at all, and with 600 dollars to spend you might even be able to get a DSO that is "better" than the Rigol z-box.

[james_s]

I wouldn't pay $600 for any analog scope, but the thing is you can get a nice analog scope for $100 or less, occasionally even for free. If I were just working on audio gear that's what I'd do, and then use some of the money saved to get a HV differential probe for poking around in tube amps. Single shot capture and saving waveforms are great features but that isn't something I recall ever needing while working on audio gear.

[rstofer]

It would seem to me that the DS1054Z is a great place to start and I certainly like mine but...

I am underwhelmed with the FFT function.  It may be user error (ask around) but what I get on the screen isn't impressive.  Furthermore, for audio, I would think that FFT is going to be something you want since you ultimately want to talk about THD when discussing amplifiers.

https://www.microsemi.com/document-portal/doc_view/134813-an30-basic-total-harmonic-distortion-thd-measurement

Ask others around here specifically about their experiences with FFT in the audio range and whether the DS1054Z is useful for that function.  Maybe try to get a sceenshot of something in the audio spectrum.  My stuff is trash but I suspect it is user error!

If I were doing FFT, or audio of any kind except probing a vacuum tube amplifier, I would use the Digilent Analog Discovery 2.  It does a fantastic job on just about everything but the FFT is especially good.  The problem is, most who haven't used it consider it some kind of toy.  Yes, it is a little clunky by the time you add the BNC adapter and a couple of probes but it does a terrific job of displaying and analyzing waveforms.

http://store.digilentinc.com/analog-discovery-2-pro-bundle/

There is a substantial advantage to having a 27" screen versus a tiny 8", particularly when you get on in years.

As to the higher voltages of a vacuum tube amplifier, I suspect the x10 probes will tame that pretty well up to a maximum of 250v.  If the plate voltage is higher than that, you will need x100 probes.  Not a big deal, they're all over eBay.  Just remember, when you are using the BNC adapter, one side of the scope probe is grounded so the maximum input voltage after the probe divider (x1, x10, x100) is 25V.  I use x10 for everything (better frequency response, less loading of the circuit) but I don't work with vacuum tubes.

[james_s]

FFT tends to be a bit of an afterthought on DSOs. FFT on my TDS784C is quite good, but it still can't touch the output from a real spectrum analyzer. Fortunately audio spectrum analyzers tend to be relatively cheap compared to the RF variety. A friend of mine does a lot of contract work on vintage audio gear for a recording studio and has an old (HP I think) audio spectrum analyzer, Tek 465B analog scope, and some sort of audio distortion test set that along with a Fluke true RMS multimeter are pretty much all he needs. An LCR meter and ESR meter for checking capacitors are handy too.

[chipss]

This is all great stuff guys, thank you.

Yes the fft is something I have thought about, and I have seen its pretty bad on scopes in the price range I am looking at.

 I just purchased  a 2015 keithly that has thd. 
 
With some gear have used a computer program called insight, a plug in for pro tools, a music recording and mixing program,  that has a Spectrum Analyzer, and a few other tools like a 3d Spectrogram, a waterfall type  plot I find very useful.  with the pro audio stuff I build,  it is made to run into this program anyway.  yet someday hope to own a stand alone.

kind of seems like it would be a good idea to own both a newer DSO, and a analog scope. I can see how both would be useful.

I have built clones of old classic analog music type gear, and so far have done so with basically  only a DMM, and bumbled my way though the builds, with only one failure, that I never did figure out, anyway  The parts cost on some of this stuff is very expensive,  and I am wanting to build more complex circuits,  become better at troubleshooting, and learn something along the way.

Thank you all for your time.

[mzacharias]

On the off-chance the OP comes back here, I would just mention that  if there is any chance of working on CD players, observing the eye-pattern kind of requires a 40mHz or better bandwidth, and if you plan on troubleshooting FM tuners at some point, 100mHz minimum is preferred.

[jeroen79]

milli-Hertz?
But you're correct, these parts work way beyond 20 kHz.

But what functions does the OP need at a minimum?
And which would be a nice extra?

[james_s]

kind of seems like it would be a good idea to own both a newer DSO, and a analog scope. I can see how both would be useful.

That's what I have. Well, it's an older DSO but it was high end at the time so it's still quite good. I mostly use the DSO now but I'm glad I had the analog scope first. Even a 250MHz analog scope is still pretty cheap.

[tautech]

This is all great stuff guys, thank you.

Yes the fft is something I have thought about, and I have seen its pretty bad on scopes in the price range I am looking at.

In all that you have seen. 

That may be about to change....1Mpts FFT 200 MHz SDS1202X-E @ $ 379
Soon to be released if you are not in a hurry.
Some discussion here:
https://www.eevblog.com/forum/testgear/new-siglent-sds1000x-e-oscilloscope-based-on-xilinx-zynq-7000-soc-architecture/