TL Audio C-1 - Manual (Page 5)

INTRODUCTION
The T L Audio Valve Compressor combines classic valve techniques with low noise
solid state circuitry to produce a unit offering a fully controllable compressor on each
of its two channels. Both channels feature balanced and unbalanced line level inputs,
plus a mic input with switchable 48V phantom powering. Further flexibility is
provided from a front panel auxiliary input which accepts mono or stereo keyboard
and guitar inputs. Typical applications include direct recording to tape, instrument
preamplifier, use as outboard equipment during mixdown, and as a main stereo
compressor for monitoring and PA systems.
The block diagram of one of the channels is shown in fig.1. A solid state,
electronically balanced input amplifier is used, to achieve state of the art performance
with very low noise, low distortion and wide bandwidth. The input includes a
switchable second order high pass filter, -3dB at 90Hz, to remove unwanted LF noise.
A triode valve is used as a second stage voltage amplifier, to obtain the classic valve
sound and gradual overdrive characteristics.
Two XLR input sockets are provided per channel, for mic and line inputs. The mic
input is suitable for low impedance (150-600 ohm) microphones, with a gain control
range of +16 to +60dB. 48V phantom power is available on each channel. The line
input has an effective overall gain range of -10 to +35dB, allowing the valve stages to
be fully driven from line level signals in the range -20 to +20dBu.
A front panel mounted auxiliary jack socket for each channel allows mic or line level
inputs to be easily connected to the compressor. The aux input may be used for a
stereo keyboard or mono guitar, etc.
An insertion point is provided in the sidechain circuit to allow an equaliser or other
processor to be used for frequency conscious compression, etc. The insertion point is
unbalanced, at a nominal operating level of -2dBu. The sidechain processing is solid
state, whilst a second triode valve stage is employed in the compressor circuit.
The compressors feature continuously variable controls for threshold, attack, release,
ratio and gain make-up. A certain degree of programme dependant variation is
incorporated, particularly of the attack and release times. Full stereo operation is
supported, with ganged controls and linked control voltages. The compressors may be
by-passed for A-B comparison.
Twin illuminated VU meters are provided, which may be switched to monitor the
output signal level or compression applied. A solid state, electronically balanced
output stage with XLR connector completes the channel. Dedicated unbalanced
outputs are also provided on jack sockets. The outputs are switchable for +4dBu or -
10dBu nominal output level.
Please read this manual fully before installing or operating the Compressor.