doubt about effect loops

[noobiePT]

hello all! i have some doubts about where to place the effect loop in an amplifier. the only thing i know is that the signal circuit should be away from the power, but where exatly should i put the effect loop? right next to the input jack? a bit far away, after the eq. pots?
many thanks

[teemuk]

This totally depends on the circuit you have and the way in which you want the effect loop to operate. There are no exact rules but few general practices exist:

- FX loops typically should be operated at a signal amplitude level that is equal to so-called "line level". Note that there are various standards of what "line level " is.

- The stage feeding the FX loop should have adequate buffering capabilities because it may need to drive long cables and moderately low impedances.

- FX loop is typically configured so that the effects in it are the "last in chain" before the power amplifier. In other words, you generally do not introduce further signal processing (such as distortion) after the effect loop (as this may "muddy" the signal). Loop effects are typically stuff like EQs, delays, reverbs or dynamic processors that do not benefit from distortion taking place after them. Sometimes you may have some more "transparent" effects e.g. reverb, compressing after the loop but as I said, the rules are not absolute.


Edit: After re-reading your post I got the impression that you are actually talking about the physical placement. Trying to answer this question is even more vague without seeing the exact layout. The FX loop typically has signal levels of about 0.3 - 1V RMS (and it should be well buffered) so it shouldn't be very prone for catching interference and can be placed a bit closer to power supply than the input stages. However, all this depends so much about the circuit and the layout that it is impossible to say anything precise without knowing more of the details.

[noobiePT]

yes, i was talking about fisical placement sorry.
the layout is what im working on, im gonna build a combo and so i'll put the power transformers outside of the chassis, which should reduce possible interference. as you said, if the fx loop doesnt catch much interference, i'll probably put it after the eq. pots and before the powerswitch, and the power section away as possible, i think it will be well placed
gonna try the layout that way, and then show to see if its fine
thanks