Analog Discovery USB Oscilloscope

[diegocw]

Hello everyone, I've been reading some of your posts lately and I must say this is a very nice forum to visit and learn new things. Thank you all for that.

I recently got an Analog Discovery to take some measurements and learn some more about how my pedals work, and generally how audio signals travel inside the circuit and change their characteristics along the way.

My main question is: Which measurements would you recommend me to do? It sounds very basic, but I want to know what to look for. I want tips!

Until now I have measured:

- with the Network Analysis tool, which shows the Transfer function of the circuit a.k.a Bode Plot (Magnitude and Phase across the frequency spectrum). Should I only care about measuring from around 10Hz to 20kHz or even less? Or is it also important to consider radio frequencies?

- with the Spectrum Analyzer, which shows the harmonic content of a signal. With this tool you can input a pure sinusoidal signal from 1kHz in to a distortion pedal and look the harmonic content of the signal at the output of the distortion pedal. That way I could SEE the fact that different distortion circuits create odd or even harmonics.

- with the Sweep tool, I made several sweeps from sinusoidal signals and see how the amplitude changes depending on the frequency. (the same that you see with the Bode plot, but with a different representation.

I have done some other things but too, but I would really like to know what YOU guys think about this and recommend.

Diego

[GibsonGM]

Hi.  Welcome to the forum!   The basic measurements are always valuable to learn! 

How about: input a sine wave to some gain-producing circuit, like a distortion. Maybe .1V AC.    Then, measure both input and output; set up so you can see both.    Note how the signal changes at output as you increase the gain (distortion) -  observe the rounding over of the sine wave, and see it become more square wave, and then actually square.  This is what distortion looks like.
You can also probe inside a distortion or such circuit, and see how each state is amplifying and possibly distorting...this is a big use for O scopes (signal quality, amplitude...).

- Build a Class A transistor amplifier, with a BJT or similar.   Adjust the bias and you will see how the wave shape changes (output) as you go into other classes of operation.    This can help a person understand why and how transistors (and other things) are set up to operate in the way they are.

- Measure an AC signal...maybe the output of a pedal with high gain, when you input a small voltage, as described above.  Use your meter.  See what it reads, AC.    Then measure with the scope - you will find it probably is not the same!  If your meter is RMS, it will average (root mean square) the AC signal...the O scope shows all - you can see the peaks, and note they are higher than the meter reads. 

- Look up "oscilloscope octopus"...maybe you can make one, if you feel OK with making a couple of mains connections.  Neat tool.  Ask if you are unsure of how the transformer should be connected (!)

These are simple but very useful applications of a scope, ones that we would use on pedals or amps pretty frequently to troubleshoot or explore.  I don't really know what the Analog Discovery is capable of, LOL...sounds like quite a bit!  But don't forget to learn the basics, as you'll probably use them more than most functions.

I'd LOVE to be able to sweep filters and stuff - looks great!

[karbomusic]

If you are talking about the device made by Digilent, it is an excellent, excellent device. I have the Electronics Explorer version that comes with the breadboard.

[diegocw]

Thank you for your answer! Cool, those are things i'll do! In case you wonder how to build an audio bench with an Analog discovery 2. You can watch this videos! and I recommend this videos to everyone who has an USB Oscilloscope.

https://youtu.be/dFj_fa78y7c

I'm planing on making a short series of measurements on different pedals/circuits and upload the screenshots.