“I wanted my home theater system to be able to select the upstairs system as a source, and vice versa.”
Jane and I live in a fairly large house with five bedrooms and two floors. Upstairs in the living room is a nice little two-channel system with a CD changer and library. Downstairs is the theater room. In our shared office is a little mini-system. Music sometimes gets a serious listen, but more often it's the soundtrack to our lives as we read, write, work, or play.
It wasn't uncommon to have all three systems tuned to the same radio station. But we always thought it'd be nice to put a stack of CDs in the upstairs changer on shuffle play and have the music follow us throughout the house. Or wouldn't it be nice to put one of the Grateful Dead DVD concerts on the home theater and be able to listen to it upstairs?
When you research "whole house audio" or "distributed audio" on the net or in magazines, you find a mind numbing array of multiple zone audio distribution systems, in-wall speakers, and wall-mounted keypads and IR receivers. Sites are happy to refer you to contractors willing to do the project.
This was not at all what I had in mind!
Back when I was at Caltech in Ruddock House, anyone who was lucky enough to have a stereo had the option of joining an ad hoc network of people who were sharing audio. I wasn't one of those lucky souls, but I remember well how various students could select the "house system" as their music source. I never knew how they decided who got to feed the net, or exactly how the electrical loads were managed. It didn't always work perfectly, but it was fun.
I wanted to be able to do something like that. I wanted my home theater system to be able to select the upstairs system as a source, and vice versa. I wanted the office mini-system to be able to pick either of the other systems as a source. That way if I'm working in the office and Jane is writing upstairs, I can listen to her CDs with my own volume control, or I can play my own choices.
Whole house audio systems typically work by bunching a group of amplifiers in a closet somewhere, then sending speaker wire and control cable to each room where you want audio. Part of the reason for that design is that speaker level audio is fairly noise immune. Even if the wiring runs near power lines or electrically noisy appliances, it shouldn't affect the sound.
The plan I had in mind would involve distributing line level audio, like that distributed between your receiver and cassette deck or VCR. The problem is that line level audio has very little immunity to noise. The audio in a home stereo is unbalanced — there's one hot line and a ground shield. Shielded cables can pick up noise and RF on their shields, have ground loops, and make terrible 60 Hz or 120 Hz hums.
The solution is to distribute balanced audio, which uses two hot wires to carry the audio signal in opposing polarities. This is how the pros distribute unamplified audio signals around in huge noisy installations like arenas and broadcast studios. Balanced audio can be distributed using twisted pair cable, such as CAT5 ethernet cable.
I found exactly the device I needed from a company in Mountlake Terrace, Washington, called AudioControl.
The magic device is a box that converts home stereo unbalanced audio to a 600 ohm balanced audio signal and vice versa. It comes in three flavors — one that transmits four channels (BLD-10), one that receives four channels (BLR-10), and a transceiver (BLX-10) that sends on two pairs and receives on two pairs. (Find them here)
They knew exactly what they were doing at AudioControl. CAT5 cable has four twisted pairs, which makes it perfect for a pair of BLX-10's.
Since the AudioControl balanced receiver inputs have a good high impedance, you can even drive several receivers from one transmitter just by wiring them in parallel. There's no need for an audio distribution amp to send audio to several destinations.
The hard part is trying to actually buy these devices. AudioControl won't sell them to you directly, and most of their dealers are A/V contractors who don't expect to be selling them retail.
Luckily I found a dealer in Oakland who was willing to take a telephone order for a pair of BLX-10s and ship them to me. It shouldn't be hard to find someone near you from AudioControl's dealer locator. (But hey, AudioControl, consider selling direct!)
I ran one CAT5 cable from the upstairs stereo to the downstairs theater room, and hooked up some cheap interconnect cables to an unused input and output on each receiver. Voila! The upstairs system could select whatever was playing downstairs, and vice versa. The sound quality was perfect — no extra noise or coloration of any sort.
Next came the office system. I ordered a BLR-10 four-channel receiver, since the office system wouldn't be acting as a source. All I needed to do then is run CAT5 from the office system to the theater rack. I could tap all four channels of audio right there. Now the mini-system in the office can play a CD, tune a radio station, or play whatever's on the upstairs or downstairs stereos.
It's quite heavenly!
During the baseball playoffs, we'd even switch the upstairs system to play the TV audio from downstairs.
AudioControl now also has systems for distributing video along with audio on CAT5 twisted pair cable.
What I don't understand is why anyone would want one of these multi-zone stereo closets with speaker wire and control keypads going all over the house.