THD meter circuit needed

[Martin Czech]

:::    Another posible way is to use a A/D converter on your PC.  Again, you
:::will need to get a sound card that exceeds what you are attempting to
:::measure, but I am pretty sure you can get one that will be better that 100
:::dB S/N.  Once you A/D the signal, you can process it with an FFT.  This
:::would probably give much more acurate results.


I have now tryed a couple of pricey sound cards.
In order to record some live event directly to hard disk.
The result: the amount of useable bits is sometimes 13
or 14, but never 15 and beyond. The reason is hf-noise
and clock subharmonics as well as the unbalanced inputs.

We ended up with the good old trusty Sony dat...

That's why I proposed the optical in card.
Some of them seem to produce artefacts as well...


m.c.