Question

Does the PreSonus Studio 192 work as a standalone preamp?

Level meter for input signal is okay but I get outup signal only when I start UC Surface

Within studio 192 setup, there is a stand alone mode with 2 options (Preamp and DAC)

But preamp mode doesn't work for me.

Answer 1

The interesting thing here is that the Studio 192 is not designed to be a stand alone rack mixer.  It won't mix in stand alone mode.  The HP1, HP2 and Main Outs are discrete channels from UC Surface and your DAW.  

The stand alone functionality will work channel to channel.  Direct In and Out.  

Preamp Mode = So input 1 to Line Out 1, input 2 to Line Out 2, input 3 to Line Out 3, etc...

DAC Mode = ADAT inputs 1 thru 8 will correspond respectively to the analog Line Out 1 thru 8.

Answer 2

http://support.presonus.com/entries/106466946-Can-the-Studio-192-be-used-stand-alone-