Re: Running through effects loop
The mix control on the units themselves determines how much of the output signal is the effect and how much of it is just passing the incoming signal to the output. You set these according to the effect you're going for. If you're using a slapback setting for the delay, setting its mix to 100% wet will give you only the effected signal and no source/dry signal: you'll hit the string but won't hear an immediate response.
In a similar vein, setting the reverb mix to 100% wet with a high predelay and a large room will give you a decent reverse reverb effect, but again, you won't hear an immediate response.
The Send/Return levels on the amp CAN be set so there is no volume change when turning the effects on/off (which I would think you should do rather than turning the loop itself on/off).
The Send sends signal to the Return, and the Return (typically) sends the signal to the power section. I would guess the Send's level control affects the signal going out of the Send, and the Return's level control affects the level of the signal coming into the Return? I'm not familiar with this amp, but I've seen similar controls on rack gear for decades, which employed two different methods.
This would be so you can get a specific mix when running your Send out to either another head or power amp or recording input and not overload the input to that unit, and so that underpowered gear coming into the Return that may not have an output level control (or an effective range) could be boosted somewhat to a matched level.
You'd have to know the amp's specific setup of how the loop works to determine why it's like that, but in general, yes, you do want the loop to have the same volume Off as it does On. Unless you're running some sort of signal boost in the loop for solos.
