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The Tube PAC (PreAmplifier/Compressor) is a multi-purpose tool
for audio engineering and recording. Enclosed in a table-top (and
1/2 rack-able) chassis are two independent circuits featuring a
tube-based analog preamplifier and a VCA-less, tube-based
compressor with optical gain reduction control. Used as a mic/line
preamp or as a DI (direct) box, the Tube PAC is designed to work
seamlessly with any recording, sound-reinforcement, or electronic
instrument setup.
A R T’s Tube PAC circuitry is a hybrid design utilizing the latest,
most advanced, solid-state and tube technology. Using a trans-
formerless design throughout, the Tube PAC maintains exception-
al signal integrity and extremely low noise. The compressor circuit
follows the preamp. While the preamp is always active, the com-
pressor may be bypassed.
The preamplifier’s active balanced solid-state input provides
extremely low noise and excellent CMRR. The 1/4” input has a
high impedance, which prevents the loading of any device con-
nected to it and makes the Tube PAC perfect for DI or line level
applications. The preamplifier’s second stage 12AX7a tube runs
on a regulated DC voltage providing an additional 40dB of gain.
Our design causes the tube to overload before the input or output
stage. This allows you to manipulate the tube gain to meet differ-
ent sonic requirements.
The compression circuit features a VCA-less design and utilizes
optical electronics (Vactrol) coupled with a 12AX7 vacuum tube
gain stage for superior musical performance. The compressor is
soft knee by design. Although it is capable of providing a thor-
oughly “squashed” signal, it was designed to excel in areas where
transparent and musical dynamics control is desired. The beauty
of the optical/tube design is its ability to apply heavy amounts of
compression without pumping and breathing like VCA-based
compressors. In many cases you will hear the results of the com-
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