right mark audio test on DIY ADAT convertor, need some help

pilo

Active member
Joined
Jun 11, 2004
Messages
41
Hi everyone!

So here a link to the test generated by right audio mark:
http://membres.lycos.fr/blendinpulse/adat/test/DIGI32_8 Out (1+2)(1)_9.htm

there are previous tests in http://membres.lycos.fr/blendinpulse/adat/test, but this one is the last one. I move the dac far from the psu to decrease noise level.

As you can see, there are, I think, harmonics, 50/100/150/200/250/300/350/400/450/500/550Hz... and I would like to know where they come from? anybody as an idea?

I also have another problem : when I put a TRS jack in the output and plug it in the input, it seems that there's a lot of noise, I have to touch the TRS metal case and then everything is fine (so yes during test my hand is on the TRS ;)). When I plug my amp on the convertor, can hear digital noise in the speaker : if i increase amp colume, the noise doesn't increase, and if I touch the output jack, or the cable going thru the amp, the noise disapear... any idea? I think it's because the digital ground of pcb is not connected to the case by the skrew (the analog and digital ground are seperate on the psu PCB, but I start to think of another psu for digital, with a seperate transformer).

thank you!

Pilo
 

PRR

Well-known member
Joined
Jan 30, 2010
Messages
11,144
Location
Maine USA
> I think it's because the digital ground of pcb is not connected to the case

I think so too.
 

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