I've been spending the last month struggling with the effect loop, while the lead channel is on, on my 6505. I can't get anything to sound good through it. Originally I was using a mxr carbon copy and it always just sounded like it was just adding more noise to the signal than delay. I just thought my issue was with the carbon copy until I got an m13 a realized it was more or less the same deal. Nothing cuts through the gain without adding a ton of noise/tone loss.
In my neverending battle to fix this I changed out the V3 tube to a 12at7. It cleared everything up a bit, but not much. I also tried a Morley effect loop corrector which helped a little, but killed my overall volume. I think my issue is with the 6505 sending way to hot of a signal(-10 dbV) to the effect which my understanding the m13 and most stompboxes are at -20dbV, which is why I tried the Morley ELC.
Now I just picked up a Nova System, with the thought that I would have more internal control of the ins and outs and while the effects come through a little more it was very high pitched and sounded pretty damn bad too.
Pretty much I'm open to any tips or help regarding any of this, but I guess more specifically I was wondering what settings with the nova system has worked for others. Maybe some sample patch settings as well? Any help is greatly appreciated because righy now I'm on the verge of selling the 6505, which sucks because tonally it's a monster
You need to watch the impedance with the gear you put into the FX loop on the 6505. I found this out the hard way. The 6505 expects to see "normal" guitar FX in the loop, so it wants to see a high impedance on the device(s) where they connect to the "send" and a low impedance where they connect to the return.
Your descriptions makes it sound as if you are returning the signal to the amp with a high output impedance. Use the connection on the unit that you would connect to the front end of a guitar amp (low output impedance), and you should be good.
Impedance is the one thing that people tend to overlook with signal chains, and it is AT LEAST as important as establishing unity gain due to its influence on the high frequencies (mismatch can cause treble loss or treble boost).