[sdiy] How to measure 1-bit DAC performance?

[Richie Burnett]

I'd put some sinewaves through it at various frequencies and levels, and then look at the spectrum of the analogue output to assess the performance in terms of harmonic distortion, noise floor and any other spectral components that shouldn't be present.

-Richie,

Sent from my Xperia SP on O2

---- Scott Gravenhorst wrote ----

>
>I make basic measurements which include spectrum using free RightMark
>Audio Analyzer (on a PC).  I had been working with someone who wanted
>to use a one bit first order delta-sigma DAC on an FPGA project and I
>was able to show that there were large amounts of harmonic signal
>present even though the input to the DAC was a sine wave.  RMAA is
>probably not the best, but I think it's output would be better than
>looking at wigglies on an oscope.
>
>Tom Wiltshire <tom at electricdruid.net> wrote:
>>Hi All,
>>
>>I've been using the PWM output module on the PIC chips as a cheap 
>>DAC for years. It does this job reasonably well, all things 
>>considered. Whilst the quality and 10-bit resolution aren't 
>>great, it's cheap and convenient, and those are big pluses. 
>>
>>However, I've been looking at using the NCO peripheral as a Pulse 
>>Density Modulated output instead. This would in theory produce a 
>>higher frequency output and allow a greater resolution. 
>>
>>In order to determine if the results I can get out of it are 
>>genuinely an improvement, I need to be able to accurately measure 
>>the performance of both styles of "DAC". 
>>
>>How would I do this?
>>
>>My current method is to send an incrementing count to the DAC and 
>>then have a look at the post-reconstruction filter output on a 
>>'scope. How wiggly the line is is my measure of quality! Not very 
>>exact! 
>>
>>I've got a digital oscilloscope, a multimeter, and a laptop. No 
>>other test equipment is available, unless I make it. 
>>
>>Thanks,
>>Tom
>>
>>
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>
>-- ScottG
>________________________________________________________________________
>-- Scott Gravenhorst
>-- http://scott.joviansynth.com/
>-- When the going gets tough, the tough use the command line.
>-- Matt 21:22
>
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