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[gibbyj]

Hi,
I bought a used ASUS Xonar Essense STX card, for use on Windows 10 with my Kawai virtual piano controller/keyboard and Pianoteq virtual piano software.  I use the line outputs of the card and the Uni Xonar driver with ASIO (installed with low-latency mode).  I've solved a lot of small problems but still have 2 questions:

1. The output of the STX card seems to be 2v, but the full-volume input to my Parasound HCA-600 amp is only .9v.  The speakers are quite loud...   So it seems I need to lower the output of the card, or turn down the gain adjustment on the amp.  Do you lower the max output of the card in the mixer section?  Does this affect the S/N ratio, which of course I want to maximize?  I did turn down the gain on the amp, but I read that it is better to have that gain set high, to maximize the S/N ratio.

2. Pianoteq defaults the ASIO buffer size based on what I set in the Uni Zonar ASIO window.  When I set the Unizonar ASIO latency to 1ms, Pianoteq sets its buffer size to 48 so it gets exactly 1ms latency, but that is not an optimal buffer size, and I have to change it to 1.3 ms/64 samples which is optimal.  I would like to be able to set the Uni Zonar ASIO latency to 1.3 ms, or 64 sample buffer, but the only choices I see are 1ms or 2ms.  Is there a solution to this, or will I always have to reset the buffer size back to 64 when I start Pianoteq?  (If I just leave it running and hibernate, maybe it will stay set to 64.)

Thanks!
John

[mwillems]

I can't speak to your number 2), but WRT to 1), if you want to maximize SNR, you want to turn down the volume at the amp rather than at the DAC if you have a choice.  Lowering the DACs volume will reduce the SNR of the DAC to some extent, whereas using a well designed analog volume control on the amp should have no meaningful effect on the SNR of the system.  If your amp has a digital volume control (or a poorly designed analog volume control), then you're going to lose some SNR no matter where you set the volume, so set the volume where it's most convenient for you.

Another potential solution is to use a passive inline line-level attenuator with a fixed attenuation.  If you get a well-designed one it will match the output of the DAC to the amp's input with no significant change in the SNR (just a little Johnson noise from the resistors, but you won't ever get away from that even with a well-designed analog volume control).  I use in-line attenuators for my setup and can recommend them if you need fixed attenuation between DAC and amp.

[gibbyj]

That's very helpful, thanks.  I thought I might be missing some configuration parameter or something; good to know this is a common problem and what the best fixes are.  For now, I'll turn down the gain controls on the amp.  I'm buying an active crossover from Marchand Electronics; maybe he can help me deal with this in a good way, too. 
As for my #2, it is not that bad a problem.  But I'm going to try configuring the latency in the registry.
Thanks again!

[jimwallen]

Burson Audio's Cable+ in-line between my STX II and preamp works magic in the sound quality!  https://www.bursonaudio.com/

I've also modded my card with their Supreme Op Amps. It's another jump in sound quality.
-jim

[rts100x5]

If you want some serious SQ dump the Xonar and get a CLARO HALO XT .... then load it with the BURSON OpAmps as the other post did ... I have the ULtimate sound card.