2x 2.1 in USB DAC (Asus Xonar U5) Problem!

[0menchild]

I've recently been interested in having surround sound but my knowledge is really limited when it comes to this subject.
Anyhow I have myself 2 completely working sets of "Logitech Z4" and wanted to rig it to 4.2(?).

At first I bought a generic USB DAC, 2x "RCA to 3.5mm" and 2x "3.5mm splitters".
But Hindsight caught up with me and made me realize that the speakers from each set was powered trough the subwoffer.. But it worked! Problem was doh that I had to tinker with the drivers to get it to work and once I got the sound it was limited to unsatisfying quality.

So I returned it and saw the "Asus Xonar U5" and all the praise it got so I bought it. But then my current problem appeared. The volume is extremely low even on the highest setting and the sub is not automatically specified. It was almost like the Xonar couldn't provide enough power to the speakers but that made no sense since the generic lowend DAC was able to provide enough power to run all the 4 speakers (sub's have it's own power source).

So I ask this great community for help. What can I do to fix this depressing mess?

/Omen

 

[ssddx]

soundcards are not designed to handle much of a speaker load. normally they can handle speakers up to a few watts rms at most so they do not need very strong amplifiers. of course some have headphone amplifiers built in to them but this is unrelated and is not going to help so you can ignore. anything more than this and pc speakers have their own amplifier integrated. generally soundcards are only outputting low level power on the outputs as they expect an amplifier after this when using speakers..

it sounds like you are disconnecting them from the amplifier included in the package (inside the subwoofer) and hooking them up directly using rca to 3.5mm connectors. having low volume output is a sure sign that the amplifier is not strong enough to support this. this falls into line with what i said above.

so, how could you make it work with a soundcard like the u5? use the amp inside the subwoofers. however be advised this would create an odd form of 4.2 where the two subs may not both trigger at the same time. the one will trigger on front sounds while the other would trigger on rear sounds. this may not sound terrible depending on where you place the subs in relation to your head. in settings it will be 4.0/4.1 quadraphonic.

if you wanted to isolate the subwoofers completely from the speakers instead of having it pull information from the same line (dedicated lfe channel) then instead of a soundcard you would want to be using two 2.0 speaker amplifiers or a single 4.0 speaker amplifier. given that car audio is often a 4ohm impedance load you may be able to get one of those cheap low output $20-30 4 channel car amps to work for you with the speakers. likewise you might be able to find another generic low power output multi channel amplifier for a reasonable price. you could use some rca to speaker wire adapters. suitable wpc would be at most around 8.5 (what the speakers are listed at) so i'd say a 20-40 watt (5-10wpc) amplifier with 4 channels would work fine at 4ohm load.

as said before, two cheap 2.0 amplifiers would also work. same approximate wattage as above would be fine. they make ones as cheap as $10. two volume knobs, but eh.. not too big of a deal