Ideal processor placement: before and after amp, <i>not</i> in amp's fx loop

Ideal processor placement: before and after amp, not in amp's fx loop

There is an effects processor now (December 1998) that brags about permitting you to put some of its stages before your guitar amp's preamp, and some other stages in the amp's effects loop. Their ad banner poses this as a question: "Which is the best position for your processor: before the amp, or in the amp's effects loop? Answer: both!" But they don't get it. Both positions are equally dissonant, as far as the placement of heavy time-based effects relative to heavy power tube saturation. The correct answer is, the best position for your processor is *neither* before the amp nor in the amp's effects loop; the best position is after the amp, and before the amp -- but not in the amp's effects loop. This is the way they do it in professional recording studios and stage setups, when you take into account the total signal path from guitar to tape:

Processor stage1: before the amp: Wah, EQ, phaser, compressor
Amps' preamp Distortion and then tone controls
Amp's effects send
Processor stage 2: in amp's fx loop: [optional effects here - not many effects are best here - phaser could go here, time-effects could go here *if* you want a crapped-out power tube saturation sound as a special effect]
Amp's effects return
Power tubes directly driving a mic'd guitar speaker
Processor stage 3: after the amp: Compression, EQ, stereo time-based effects

Most guitarists' thinking stops at the guitar speaker. In the studio, the producer thinks of the rig as extending all the way to tape saturation (that is so far down the line, you can't even monitor it real-time). No wonder most guitarists can't get a decent sound when combining effects with an amp; they restrict themselves to placing all the processing before the guitar speaker, which is really only 2/3 of the way through the *total* chain. On stage, there is also a mixer with an effects loop; that's where heavy time effects must be placed if the clarity of amp tone is to be preserved.

If I could eliminate any of the 3 positions for the processor, I would eliminate the one in the amp's effects loop. You need a processor before the amp's preamp, because that is the only way you can control the distortion voicing, via pre-distortion filtering and compression. And you need a processor after the amp, because that's the only place you can safely put heavy time effects and equalize the speaker cabinet (and with MIDI, control the overall volume of the amp's completed sound). But you don't really need processing between the amp's preamp distortion and saturating power tubes; the amp already has an equalizer (tone controls) placed there, so the one important processing stage at that point is already provided by the amp. If your amp has poor tone controls, then I would recommend placing an EQ in the amp's effects loop, but that is really the only thing needed there. You *can* safely put filtering there, without introducing intermodulation distortion, such as:

wah/phase/vibe
preamp distortion
wah/phase/vibe
power stage saturation
wah/phase/vibe
mixer

So, I disapprove of effects loops in amps, given that the amp has decent tone controls. All they do is encourage people to put time effects before power tube saturation -- resulting in garbled tone, which would be avoided by adding time effects through the mixer, after the amp tone has been securely established all the way through the guitar speakers.

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