How does processor loop work?

If you have a cassette deck, or other tape deck or device such as a cd recorder, which can both record and play back, the preamp's tape out connectors (left and right) would be connected to the input (record) connectors of the deck (left and right, respectively), and the deck's output (playback) connectors (left and right) would be connected to the preamp's tape in connectors (left and right, respectively).

That allows the signal from the source component (phono, cdp, tuner, etc.) which is selected on the preamp to be routed to the tape deck input for recording. To play back from the tape deck, or to monitor the recorded signal directly from the tape as it is being recorded (which requires a deck with separate record and playback heads), you then select the monitor or tape position of the preamp's monitor/input or tape/source switch (or whatever similar designation it may have).

It's the same idea for the processor loop, allowing you to connect an external equalizer or other processor in the signal path. A processor loop and a tape loop, in fact, would be functionally and technically identical, differing only in terms of the nomenclature appearing on the front panel and the rear connectors, and in terms of which comes first in the signal path (I'd assume the tape loop is first in preamps that provide both, so that the processor could act on signals being played back from the tape deck).

Hope that helps. Regards,
-- Al

Ah, so the processor loop really is for the external parametric equalizer. Not processor in "pre/pro", but a sound processor. And processor loop can't be used to provide HT integration. That was a source of confusion, as I've seen mentions to processor loop when people asked for two channel and HT integration. Thanks for clearing it up.

Theo, if you connect the pass through output to the pre/pro, how will you connect the rest of the system? The power amp has one set of input, and can't connect both the preamp and pre/pro to it at the same time.

Yes, it's easy for all of this to be confusing, because the terminology tends to be used loosely and inconsistently. But properly speaking a processor loop and a home theater unity gain bypass are two completely different things.

A processor loop, as I indicated, allows an equalizer or any other external signal processing device to be inserted into the signal path of a 2-channel system. It is located ahead of the volume control in the preamp or integrated amp.

A home theater bypass allows the home theater system to utilize the 2-channel main speakers as part of its overall speaker system, by feeding its two front-main line-level outputs into the home theater bypass/unity gain INPUTS of the 2-channel preamp. When home theater bypass is selected on the 2-channel preamp, the volume control (and all other controls) on the 2-channel preamp are bypassed, so that the home theater unit's volume control (and only that volume control) will control the volume of all speakers.

Hope that clarifies things a little more.

Regards,
-- Al