FX loops: When does an amp need one??

[makinrose]

Hello Mr. Makinrose

I believe your own history of modification requests answers your question. The gain preceding the effects loop does not matter, and what the player seems to desire is that the guitar signal hit a tube grid before anything else, be warmed up, then go to the effects.

For example, in a Fender Twin Reverb amplifier, one might wish to add  the Equal Weighting mod from TUT1 first, then add the effects loop between the channel mix point and the input to the reverb block. I believe KOC suggests this as the preferred order for an effects loop and a reverb. Each of the two-stage preamp channels actually has significant raw gain, but players do not really push them that hard. Consider that in most Fender amps the second stage drives the power amplifier input, which only requires 2-3V peak to be driven to clipping.

In a Fender Twin Reverb, the reverb block adds a bit of gain overall to the related channel, so the second stage is working less hard. Inserting the Equal Weighting mod reduces the output of each preamp, so they are both back up to what the Normal channel output level might have been in the stock configuration.

With all of the desk-top recording systems people have, there is an increasing demand for warming stages before or after processing, and these stage are usually tube gain stages set either for low gain, or with attenuators either at the input or the output or both.

Cheers

Thanks for the reply and all the helpful remarks.  I guess one of the things I'm weighing is amount of benefit that adding the loop would having vs. other features in a cleaner amp.   For example, having a loop vs. tremolo or tube reverb....there's only so much room.  Another concern is whether the loop in a cleaner design is going to have a big enough benefit vs. putting pedal through the front end especially considering many players are going to have drive pedals in front.  While I like the idea of hitting a tube grid first is the person playing it going hear a difference?  This may be case of build-and-see but I would be interested what other's experiences are.