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DAC for industrial vibration data
- Thread starter cedric
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yes of course. You could get another raise if you do.Should I add DC test signal to Multitone?
- Joined
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BTW, I checked and at least the Babyface ADC does not accept DC input.
Woohoo!! Another raise!
Created this WAV file -- a dc step, 3 seconds long.
Played through an Apple USB-C headphone dongle.
Played through my Thinkpad headphone output. [Edit] Note the time scale difference between the Thinkpad headphone output trace and the Apple dongle output trace.
Played through an Apple USB-C headphone dongle.
Played through my Thinkpad headphone output. [Edit] Note the time scale difference between the Thinkpad headphone output trace and the Apple dongle output trace.
Last edited:
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Publishing DC files is not a good idea, IMHO. You don't hear anything playing them, but your phones and speakers might get destroyed...
As already mentioned here analyzing the DC coupled outputs of modern DACs is limited by the AC coupled ADCs. And measuring is also anything but easy, as most systems/methods are not suitable to give accurate frequency response curves that low. Trying single value measurements still runs into the integration time issues mentioned by KSTR.
That said I had some fun with the ADI-2/4 Pro to measure its analog input stage (including ADC). With 47 µF coupling capacitor and 45 kOhm input resistance (unbalanced), or 90k balanced, corner frequency of the high pass is around 70 mHz only (0.07 Hz). And I managed to measure it- no way to do this with a stepped sine sweep, though. This is the AP Log Chirp set with special parameters.
As already mentioned here analyzing the DC coupled outputs of modern DACs is limited by the AC coupled ADCs. And measuring is also anything but easy, as most systems/methods are not suitable to give accurate frequency response curves that low. Trying single value measurements still runs into the integration time issues mentioned by KSTR.
That said I had some fun with the ADI-2/4 Pro to measure its analog input stage (including ADC). With 47 µF coupling capacitor and 45 kOhm input resistance (unbalanced), or 90k balanced, corner frequency of the high pass is around 70 mHz only (0.07 Hz). And I managed to measure it- no way to do this with a stepped sine sweep, though. This is the AP Log Chirp set with special parameters.
- Thread Starter
- #67
Well. I ended up with a Topping DX3 Pro+. I am achieving a peak voltage of ~3.02V, which we round to 3V and at <1% error is suitable for our needs and use, for example, 3V is 30 engineering units, i.e. 0.1V/EU. Two dummy values are added to the raw data eg +/-30, then the data is converted to a wave file so 0dBFS or 32,768 references the value 30.
Due to the various incoming files being various sampling rates, I used Audacity which I assuming is it resampling on the fly to 44.1kHz.
Audacity allows me to move a file to the left or right channel which outputs to channel 1 or 2 on the data acquisition unit, clearly see the waveform and/or spectrum and other nice controls over playback. With the DAC on dual mode the line out goes to the voltage in of the data acquisition unit and the headphone out goes to speakers with their own volume control. Everything always at 0dBFS.
The left channel can sometimes produce very slightly higher levels than the right channel when fed the same signal, I think this is frequency dependent. I also noticed when only using the right channel, the left channel gets some cross-talk, more so than the other way around.
Some very low freqs eg 3 hertz near full voltage cause a HP err on the DAC, but these amplitudes at low freqs I would never expect to see in our data so no issues there.
More testing to be done, but this looks to be a suitable method for now. Thanks for all the input and discussion.
Due to the various incoming files being various sampling rates, I used Audacity which I assuming is it resampling on the fly to 44.1kHz.
Audacity allows me to move a file to the left or right channel which outputs to channel 1 or 2 on the data acquisition unit, clearly see the waveform and/or spectrum and other nice controls over playback. With the DAC on dual mode the line out goes to the voltage in of the data acquisition unit and the headphone out goes to speakers with their own volume control. Everything always at 0dBFS.
The left channel can sometimes produce very slightly higher levels than the right channel when fed the same signal, I think this is frequency dependent. I also noticed when only using the right channel, the left channel gets some cross-talk, more so than the other way around.
Some very low freqs eg 3 hertz near full voltage cause a HP err on the DAC, but these amplitudes at low freqs I would never expect to see in our data so no issues there.
More testing to be done, but this looks to be a suitable method for now. Thanks for all the input and discussion.
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