If I have a gain-y pedal in the FX loop of my HD500, turning the FX Loop off causes the noise level to go up.
Specifically I'm using a Bogner Red pedal, and I'm trying to use my HD500 into the power amp of a Fender Deluxe. I'd like to be able to assign the FX Loop and a preamp on the HD500 to A/B, so I can go from a medium gain modeling preamp to the high-gain Bogner with one footswitch.
GTR -> HD500, pregain FX - FX out - Bogner red - FX in - HD500 preamp* - post gain FX - main out - Power Amp In
Pod set to Combo Pwr Amp
So far I've confirmed:
The noise is coming from the pedal being in the FX loop. Turning the pedal off always gets rid of the hiss. Patching the FX loop into itself does not cause hiss. Pedal straight into amp does not cause hiss**
Hiss happens when the fx loop is set to both line and stomp levels. The hiss goes down when set to stomp, but so does the volume of the pedal (which is no good as I'm using it as a preamp).
The hiss also happens if I have BOTH the FX loop and amp enabled but turned off. It does NOT happen if I have either one disabled.
*The HD500 modeling preamp and the Bogner red are set to never be on simultaneously.
**Unless I have the gain cranked, and even then it causes significantly less hiss than if in the FX loop.