home made sound card

[whiz]

Hello i'm new here! i have recently finished a USB sound card
the device uses the PCM2902 chip and i can say it works good enough!
(i would rate it 7/10) but as far as i now it can get a little better than that...

i have loopback tested my PCB with Real Mark audio analyser and these are the results

frequency Response, db: +0,15, -0,06
noise level, dbA: -83,8
dynamic range, dbA: 81,5
THD %: 0,214
IMD+ Noice, %: 0,180
stereo crosstalk, db: -88,0


And these are i'm after for...

frequency Response, db: +0,15, -0,05
noise level, dbA: -85,5
dynamic range, dbA: 85,0
THD %: 0,0089
IMD+ Noice, %: 0,018
stereo crosstalk, db: -88,9

the IC can do better than that! the specs say that it can provide ADC SNR=89db and DAC SNR=96db

i'm sure the designing of the PCB is one factor, but my PCB is full of lelon and capxcon and i believe that is one more reason i can't compite other PCM2902 PCBs

if someone knows what kind and which brand capacitors i sould use i would like to help me!

[gonzo0815]

Re: home made sound card

In Audio Equipement, some purist like to use some Solid Polymer caps, e.g Oscon. This is not only due to their very low Esr, some of those are using OFC coper leads, wich will help in reducing the ESL and may be doing some magic HIFI woodo.
Then there are some specially audio caps, with some zinc or thinfoil. But i don`t know if that is good for anything. I personally would try some good low esr long endurance caps from an respectable brand (e.g. Rubycon, BC, Panasonic) an test it. If there are some improvements, may be those Oscons are worth a try. But in generally, i am not shure, if those bigger caps are the problem. May be there are some smaller decoupling caps missing. But for that, i leave it to the more knowledgeable people here.

[whiz]

Re: home made sound card

thank you for your answer! i partially improved the performace by
changing usb cable! yes! that's right!

i've tasted it 3-4 times and all results are almost the same!

Frequency response, dB: +0.15, -0.06
Noise level, dBA: -84.4
Dynamic range, dBA: 81.1
THD, %: 0.097 (!)
IMD + Noise, %: 0.173
Stereo crosstalk, dB: -88.0
IMD at 10 kHz, %: 0.135

[Logistics]

Re: home made sound card

I'm looking at the datasheet for the PCM2902, right now. What type capacitors and what values did you use for C9, C10, C11 and C12?