Two-Channel Music Playback
on Home Theater Systems
This is a common situation. How do you play two channel fare on a home theater system if you’re into the best two channel reproduction possible?
First let’s look at the challenges. Many listeners are more attuned to the purity of two channel music reproduction than they are their theater programming. In some regards it is two different experiences. The ambience, imaging, etc. of a theater system are addressed not by reproducing an acoustical event like much of two channel, but rather by producing, synthesizing if you will, its own environment. Theater systems are not typically focused on, or even concerned with, the purity of the two channel signal.
The obvious solution is two separate systems which I have long done. However that requires both the space and the duplication of some of the equipment. There are various ways to address it and we’ll start with the least expensive, albeit most compromised.
Surround receivers, especially moderately priced ones, are using one power supply for all of the channels and often for the digital processing as well. The first step is to simply add a decent quality two channel amplifier to the mix. This is done by disconnecting the speakers from the amplifier output of the left and right front channels and using the pre out low level connection to the new power amp. This obviously provides better amplification to the two front speakers but it also has the benefit of removing some of the load from the power supply in the receiver and improves the sound in those channels.
One thing you want to keep in mind is that a surround receiver or processor tends to think in digital terms. On most, all of the inputs are digitized by default. Of course you want that on your Dolby and DTS sources but not so much on your analog sources, especially turntables. Many receivers allow you to designate an input and tell it not to do digital processing. If you do change it to analog you want to be aware that on virtually all receivers both the subwoofer and surround channels are done in the digital domain. So a more pure sound but no sub, no surround on that input. Both are still present on other inputs.
A better way to do two channel in a theater environment is to go a step beyond the dedicated two channel amp and provide a two channel preamp for your music playback. This requires that the preamp has a home theater pass through input. These can either be a dedicated input or the ability to program an individual input to pass the signal straight through. You now take the pre out of your surround receiver and connect it to the appropriate input of the two channel preamp. When you select this input the signals goes from your surround piece into the preamp, passes through, and on to the power amp.
It essentially makes the preamp invisible to the signal with no effect, including volume control. However when you select the input on the preamp that has, for example, your turntable connected to it, the signal never sees the surround and digital part of the system. You have a pure two channel system with source, preamp, power amp, and speakers. The best of both worlds in one system. The only downside is you can’t listen to two channel movies while the kids watch a movie. That becomes a discussion about headphones…