I've been pulling my hair out for the last few weeks because I thought the Effects Loop Return input jack of my amp was broken. When I have my HD500 set to Combo Power Amp mode and plug the L/Mono output into the effects return, it sounded just horrible.... very thin and distant. Hard to explain, but I tried everything... felt like I was playing through a 5W amp. Literally took my entire amp apart to look at the soldering on the jack !
So this morning, I had an epiphany that it might be due to the effects return input on the amp being stereo (meaning a TRS cable, instead of a regular instrument cable). I tried it and sweet baby Jesus it sounds 10,000x better !!!
I'm posting this because I'm still not clear if my setup is correct or perhaps I've just arrived at the point of insanity, trying to get this thing working.
Here is the setup that gave me horrible sound:
HD500 L/Mono Output --> Instrument Cable --> Effects Loop Return
Here is the setup that gives me fantastic sound:
HD500 L Output -->
(cable that merges two TS instrument cables into a single stereo TRS cable) ---> Effects Loop Return
HD500 R Output -->
I'm using a POD HD500 with a Randall RX100RG2 Combo Amp