Unison pre removes (ground loop?) noise... how??

[JFAT]

I have a synthesizer connected to input 1 (line in) of my Apollo 8. The synthesizer is also connected via USB to the computer for midi purposes.

When no plugins are on the UAD channel strip, I get a constant crackly / hissy noise coming through the channel (actually reads as audio input and can be recorded). This is not too unexpected USB (ground?) issues with noise seem to be fairly common. The thing is, as soon as I put a unison pre on the channel strip, the noise goes away completely. I can even turn the channel up to max and I don't hear the noise. This has been the case with all of the 3 unison pre's I've tried.

Adding the same preamp plugin into a non-unison slot does NOT have this effect.

Is there any practical explanation for why this could even be the case? Ideally I figure out why Unison removes the noise, so I can try in some way to mitigate the noise when not using Unison.

Thanks!
Jacob

 

[Matt Hepworth]

I have a synthesizer connected to input 1 (line in) of my Apollo 8. The synthesizer is also connected via USB to the computer for midi purposes.

When no plugins are on the UAD channel strip, I get a constant crackly / hissy noise coming through the channel (actually reads as audio input and can be recorded). This is not too unexpected USB (ground?) issues with noise seem to be fairly common. The thing is, as soon as I put a unison pre on the channel strip, the noise goes away completely. I can even turn the channel up to max and I don't hear the noise. This has been the case with all of the 3 unison pre's I've tried.

Adding the same preamp plugin into a non-unison slot does NOT have this effect.

Is there any practical explanation for why this could even be the case? Ideally I figure out why Unison removes the noise, so I can try in some way to mitigate the noise when not using Unison.

Thanks!
Jacob

Weird. Impedance change should not be a significant reducer of noise, or is it possible you're overloading the line input unless there's a Unison pre? What does the meter on the front of the hardware show when Unison is not inserted?

 

[klasaine]

Hmm?
"Crackly, hissy" noise is not in my experience ground loop hum.
Can you record the noise and post it here.