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Analog Disovery as Audio Analyzer

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RobK_NL:

--- Quote from: jaxbird on December 10, 2015, 06:31:51 pm ---This is the board I'm testing here: (it's a small class D amplifier)

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It would be interesting to see if you can actually measure any difference between the two channels, seeing as how you've got a broken filter inductor on channel 2  :)

c4757p:

--- Quote from: rjeberhardt on December 11, 2015, 11:49:16 am ---Can you do intermodulation distortion with that kit?  I've often thought that intermodulation is more significant than THD especially when you see how THD rises at higher frequencies.  Music is almost never just a single tone.

Russell.

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That should be possible, in theory.

jaxbird:

--- Quote from: rjeberhardt on December 11, 2015, 11:49:16 am ---Can you do intermodulation distortion with that kit?  I've often thought that intermodulation is more significant than THD especially when you see how THD rises at higher frequencies.  Music is almost never just a single tone.

Russell.

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--- Quote from: c4757p on December 11, 2015, 02:46:48 pm ---That should be possible, in theory.

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Indeed, should be doable, and a feature I surely will add. The Discovery unit includes a dual 100Msps DAC and the API exposes functions to produce regular waves (sine, square, triangle plus modulation) but not multitone directly, however it is possible to pass a 4k sample buffer and have it played back at a specified sample rate, so the challenge would be producing a continuous/repeating buffer with 2 tones without glitches. Should be doable with the common 19+20kHz test signal.

Then just display the spectrum from e.g. 20Hz to 30kHz and it should give a good view of the intermodulation distortion performance.

Another option would be to just combine the two waveform channel outputs with some resistors to form the dual tone test signal. (this I have tried already and it works fine)

If anyone got a good formula for creating a continuous/glitch free buffer with 2 or more frequencies, I'd be grateful as it would save some time :)

jaxbird:

--- Quote from: miguelvp on December 11, 2015, 04:28:26 am ---Nice, Also I'm going to upgrade to Waveforms 2015 since I saw the new Analog Digital Discovery 2 and had a link to the updated software, but have not had a chance.

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Thanks, Just installed the Waveforms 2015 version 3.1.5, the UX is better and it's easier to access/switch between instruments. Have not done a lot of testing, but it appears they have actually removed some features  :o, or maybe I just can't find them.

Really I just wanted to know if they made any API changes, but everything I've written is compatible, so it seems no API changes, the API already had the features needed for a variable output PSU as now available in Discovery V2.

diyaudio:

--- Quote from: jaxbird on December 10, 2015, 05:30:03 pm ---First off, I know a lot of people on this board got some some misconception that audio is not engineering and everything sounds the same due to many of Dave's comments on the subject.

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:-DD my alias gets me into shit every time with some members around here, yet i have no association with audio only.

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