Unused channels on a multi channel amp

That's what I'm doing at the moment. I have a pair of speakers biamped with a 5 channel power amp, with the full blessing of the manufacturer. You simply don't use what you don't need. No need to cap anything.

Also, if the multichannel amp uses a single power supply, particularly if it is not especially large, the amp might actually sound better the fewer channels you use. You would have fewer channels drawing the available power from the common power supply.

Just remember that any channel with signal input to it must have a speaker hooked up. If you can turn the gain down on the unused channels is may help alleviate stress on the power supply???

Elevick, a channel with NO input CANNOT stress the pwr. supply. This doesn`t even qualify for Urban Legend status.

A long time ago all amps liked to see a load connected. Maybe more true with tube amps than SS. Today seems to be a different story. I sometimes use a HT receiver with an external amp so that none of the receiver's amp channels are in use. Some think it sounds best when the power supply isn't taxed so heavily. Makes sense to me. And it neither urban nor legend.

For optimum results, unused channels should have their inputs shunted with a reasonably low value resistor ( 100 - 500 ohms or so ). The unused output stages of those channels should also be shunted. You can use the same value resistors as you used on the inputs, so long as they are at least 50+ ohms ( at minimum ) and rated for a minimum of a 1/4 watt of power.

Shunting the input resistively shuts down the potential for the input stage to pick up RFI and / or EMI based noises. Otherwise, once these noises were picked up, they would be fed into other stages of the amp. Not only could such noise cross-contaminate the channels being used, such an occurance could either send the "unused" channel into oscillation and / or produce output power. By "closing" the input via the shunt resistor, that path into the amplifier via the unused channel is effectively stifled.

Shunting the output with an impedance much higher than what the amp would normally see with a speaker presents a load to the amp whether it needs it or not. Many amps DO produce low level leakage with / without a signal present. As such, the resistor acts as a load and helps to stabilize that channel and potentially extend the life of the associated circuitry. By using a higher value resistor, current flow is minimized and a high powered resistor isn't necessary.

From an electrical standpoint, one can only gain from such an approach. From a sonic standpoint, the benefits will vary with the environment that the gear is in and the design of the gear / system itself. From a monetary standpoint, it may help to preserve your investment in a multi-channel amp.

If you are even reasonably handy and not afraid to do basic DIY, shunting both the inputs and output stages of quite a few unused channels of an amp shouldn't set you back more than $10 at most. This is based on RCA / single ended shunts, as XLR / balanced connectors cost significantly more. In most designs, shunting either the RCA / XLR inputs will achieve similar results, so there's no need to do both at the same time. Sean
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