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Overview
Why use an external processing channel?
The shortest signal path is the best way to get a signal to tape. In most cases, the
shortest path is: mic to preamp to compressor to EQ to tape deck. The signal doesn’t
even go through the mixer! This isn’t a new concept, but it has become more relevant
with the availability of affordable mixing consoles. As their name implies, most
affordable mixers excel in signal routing and mixing capabilities. However, they are not
necessarily your best option for the actual recording of tracks. While their onboard
circuitry is nearly always clean and quiet, the simple truth is that the Pro Channel has a
better sounding and more flexible collection of circuits. Mixer manufacturers need to
make trade-offs betweeen price and performance. Imagine the price of your mixer if
each channel’s EQ cost over $200 (and we’re not talking about those of you who have
one of those $250,000+ consoles)! The use of external processing (equalizers, preamps
and compressors) has sonic and practical benefits when you consider that most
recording is done one or two channels at a time. For those of us on a budget, it just
doesn’t make sense to spend a ton of money on a “Cadillac” console when a budget
mixer and a few pieces of external gear is more cost effective. Even those engineers
who regularly work on “big” consoles use external EQs, compressors and preamps!
The goal of any recording is to get the sounds right before you commit them to tape.
The Pro Channel exists to help you get it right so you don’t have to “fix it in the mix.”
Design Notes
The Pro Channel is a multi-purpose tool for audio engineering and recording. Enclosed
in a two rack space (2U) chassis are three independent circuits featuring a tube-based
analog preamplifier, a VCA-less compressor switchable between optical or variable-mu
control element, and a semi-parametric, four-band, tube-based equalizer. Used as a
direct recording channel, a mic/line preamp, or a DI (direct) box, the Pro Channel is
designed to work seamlessly with any recording, sound-reinforcement, or electronic
instrument setup. A R T’s Pro Channel circuitry is a hybrid design utilizing the latest,
most advanced, solid-state and tube technology. With a transformerless design, the Pro
Channel maintains exceptional signal integrity and extremely low noise. The
compressor circuit follows the preamp and the equalizer follows the compressor
(although you can change the order of the circuits by utilizing the insert points). While
the preamp is always active, the compressor and equalizer may be individually
bypassed. The preamplifier’s active balanced solid-state input provides extremely low
noise and excellent CMRR. The ¼” input has a high impedance, which prevents the
loading of any device connected to it and makes the Pro Channel perfect for DI or line
level applications. The preamplifier’s second stage 12AX7a tube runs on a regulated
DC voltage providing an additional 20dB of gain. Our design enables the tube to
overload before the input or output stage. This allows you to manipulate the tube gain
to meet different sonic requirements. The compression circuit features a VCA-less
design and utilizes either optical (Vactrol®) or variable-mu dual triode electronics for
superior musical performance. The compressor is soft knee by design. Although it is
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