How to? Add a Pre/amp for 2ch to a HT receiver

The pass-thru bypasses the circuitry and volume control in the preamp. You should also be able to use the tape loop.

Yes, the "pass through" has no gain, so it just gives your amp whatever showed up at the input. This is useful for setting the level controls of your pre/processor so you get consistent results. Plus there is less distortion since you bypass the vol. control on the preamp. You will however be feeding the same amp for 2 ch and for 5 ch., so you will probably want a 2 channel amp and a 3 channel amp.