replace AV9 for system coherence

EJ Funk -- Tue, 10/07/2008 - 14:56

For almost two years, I have used an ARCAM AV9 controller, an ARCAM DV79 disc player and an (Audio Research) ARC 150M.5 amp for both film and music. My main speakers are Wilson Sohpia 2's with ProAc speakers filling out the remaining spots. Recently, I incorporated an ARC LS26 preamp and an ARC CD5 into the system for two channel music.

My question centers around the continuned use of the AV9 within this system. The AV9 does not have balanced connections so I use unbalanced RCA terminated interconnects to link it with the LS26; however, I use balanced interconnects or XLR's from the LS 26 for connecting to the CD5 and to the 150M. An AV dealer suggested trading out the AV9 for a controller that provides balanced connections for a more coherent system. He suggested a B&K Reference 70, but I am not familiar with it and, because it is quite new, cannot find much in the way of reviews.

Because I subscribe to TAS and read TAS reviews, I know that the editors and I assume some readers are familiar with the ARCAM AV9 and the ARC 150M.5 and some products from B&K. Does it make sense to switch to a new controller, and, if so what are some appropriate alternatives---the B&K, etc? Thanks for some thoughtful suggestions.

Robert Harley -- Wed, 10/08/2008 - 09:50

I've been using the AV9 for some time in a system that sometimes includes balanced connections.

First, there's no inherent advantage in having a system that's completely balanced unless all the components in that system are truly balanced internally. Here's what happens in many "balanced" preamplifiers and controllers: the balanced input is converted to unbalanced by an active amplifier stage (called a "differential amplifier") and the preamp or controller acts on this unbalanced signal. At the output, the unbalanced signal is converted to balanced with another active amplifier stage (called a "phase splitter"). In this scheme, two additional and unnecessary active amplifier stages are introduced---and these are usually op-amps. The result is more electronics in the signal path and degraded sound quality.

Such a product has two signal paths (left and right in a stereo preamplifier) or eight signal paths (in a multichannel controller). If the product were truly balanced, it would require double the audio circuitry: four signal paths for a stereo preamp and 16 signal paths for a multichannel controller. Each phase of the balanced signal (left +, left -, right +, right -) requires its own audio circuitry and independent signal path. Not only must the product have double the audio circuitry, but the components in each half of the balanced signal path must be precisely matched to each other---which adds expense.

The reason manufacturers offer such products is so that the products are compatible with balanced-output sources and balanced-input power amplifiers without spending the money to create a truly balanced product.

This might be more information than you need, but the short answer is that you're just fine mixing balanced and unbalanced connections in your system. Moreover, the AV9 is an outstanding unit; to get anything better would require a big jump in cost. The reason to replace the AV9 at some point is for a controller with Dolby Digital Plus, Dolby TrueHD and DTS-HD decoding.