After my receiver died, I bought a new pre/pro but needed 2 more channels of amplification for my HT surrounds. I stumbled upon the cheap-as-mud Audiosource AMP100, a 50 wpc job that's normally used for "zone 2" amplification like background music. It also comes with its own volume knob.
Obviously, I'm more intent on controlling volume and speaker balance with the processor, but what should I set the amp volume control at? If I set it to full do I risk clipping, or is the amp volume knob redundant and should be set all the way up (the way you would on, say, a sub crossover knob)?
Frank, the volume control is a variable resistor which controls the amount of voltage which is let in from the pre-amplifier to be multiplied by the fixed gain factor(again, there are no "gain controls")of the amplifier. If it's set at max it lets essentially all of the voltage through and the overall volume level is controlled by the level controls for the various channels in the pre-amp. So yes, the use of the amplifier volume control is redundant and it should be left wide open.
I'll add one caveat to John's post. There are some amps that when their volume controls are turned all the way up, they go past unity, and the pre-amp stage is actually boosting the voltage that's being delivered to the amplifier.
You're receiver should have a manual test test tone mode. Activate that for your main channels, and then with the volume control on this external amp set at half, move to the one of these additional channels. Switch back and forth, comparing the two (if you have a SPL meter, it'll be even easier). You're don't have to be exact if you'll be using the auto setup later, but the idea is to bring up the volume control on the amp until the speakers it is driving seem about even in output compared to the mains. If the volume control is almost all the way up, turn it the rest of the way, but if you're only at something like 3/4 and already as loud as the mains stop there.
So what John said is right in most cases, but not all. Just so you're aware.
I actually did do the setup with an SPL meter. Even with the amp at full volume, the surrounds (QS4s) still needed to be upped by 5-6 dB to match the mains. No problems so far after 2 days of re-calibrating everything.
Sure, Frank; the Amp-100 is a power amplifier(not a receiver or integrated amplifier)and has no pre-amp section. Your separate pre/pro boosts the voltage from the source material and sends it to the amplifier for a further increase. The amount of voltage output from the pre/pro is of course controlled by its own level adjustments and there's no need to complicate things by using two level controls.
Anyone looking for additional amplification for surround speakers should check out Partsexpress.com. They have some son-of-T-Amps for sale,like the Dayton DTA 100a, 50 wpc T-Amp (with power supply) for $89.00, or a 20 wpc Lepai Tripath (with power supply) for about $25.
Either should be plenty for a pair of QS4s or QS8s.
I mean really, for footsteps, flyovers, chopper chop, ricochets, brass cartridges hitting the floor, these amps are just fine.