[linux-audio-dev] Anyone else ever run a THD test on Jamin?

[Dan Mills]

Hi all, 
While hacking around with aliasing effects in digital compressors (Yes
it is real, yes you can hear it!), I happened to run a 10Khz sine wave
into jamin  with an instance of Jaaa hooked up to the output.

The results were 'interesting' as it appears that jamin introduces
easily measurable harmonic distortion even with all compressors and eq
bypassed! Switching the master bypass in jamin however does make the
effect go away. 

This was at a level of -26dbFS with no boost and with the limiter
bypassed.  

I say 'harmonic distortion', but it really is not quite that as it
appears as a series of narrow spikes every few hundred Hz. 

Further checks show that the same effect appears with the test tone
turned down to 2.5Khz and that eq bypass has no effect.

Now with a single tone we are looking at per 'harmonic' energy almost a
hundred db down on the test tone, but there are a lot of these spikes
and they increase in number as additional inputs are added, so there
might be quite a lot of energy here all told. 

Anyone have any ideas? This thing should be linear under these
conditions!

Regards, Dan.

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