T L Audio User Manual C1 VALVE COMPRESSOR Tony Larking Professional Sales Limited, Letchworth, England. Tel: 01462 490600. International +44 1462 490600. Fax: 01462 490700. International +44 1462 490700.
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.
PRECAUTIONS The T L Audio Valve Compressor requires very little installation, but like all electrical equipment, care must be taken to ensure reliable, safe operation.
INSTALLATION AC Mains Supply. The equaliser is fitted with an internationally approved 3 pin IEC connector. A mating socket with power cord is provided with the unit, wired as follows: Brown: Live. Blue: Neutral. Green/Yellow: Earth (Ground). All mains wiring should be performed by a qualified electrician with all power switched off, and the earth connection must be used. Before connecting the unit to the supply, check that the voltage selector switch on the rear panel is correctly set.
When using unbalanced signals, the signal ground may be obtained by linking pins 1 and 3 in the mating XLR connector. Good quality screened cable should be used, particularly for microphone or low level sources, to prevent hum or noise pickup. Unbalanced Line Inputs. An unbalanced line level input is provided for each channel, on a 0.25” mono jack socket. The mating plugs should be wired as follows: - Tip = Signal Phase (“+” or “hot”). - Screen = Ground. Auxiliary Inputs.
- Pin 2 = Signal Phase (“+” or “hot”), - Pin 3 = Signal Non-Phase (“-” or “cold”). If an unbalanced output is required, pins 1 and 3 should both be connected to ground. Nominal Output Level. A switch on the rear panel allows the output to be matched to equipment at a nominal operating level of +4dBu or -10dBu. Most professional equipment requires +4dBu (approximately 1.2V rms), but some small mixing consoles, portable tape recorders or domestic audio equipment require -10dBu (approximately 225mV rms).
OPERATION. Front Panel. The front panel controls for one channel are identified in fig.2. Input Stage. Ensure that the correct input connector, mic or line, is being used and that the front panel switch is set to the appropriate position. Note that both mic and line inputs may be connected at the same time, but only one is selected. The input selector switch selects between the line input, mic input, mic with +48V phantom power (signalled by a red LED), and the Aux input.
Compressor Operation. A compressor functions by reducing the gain of the signal when it exceeds a certain level, or threshold. The amount of gain reduction may be fairly gentle through to limiting, where the signal is clamped at the threshold level. The amount of gain reduction is determined by the ratio control, which is calibrated as a ratio of the output to input signals. The gain of the signal is reduced by a voltage-controlled circuit.
Ratio. The ratio may be varied from 1:1.5 (very gentle compression) to 1:30 (near limiting). The compressor normally operates with a “soft-knee”, i.e. the compression is gradually introduced as the signal passes the threshold, in which case the ratio refers to the compression eventually obtained. Gain Make-Up. Up to 20dB of gain make-up may be applied, to retain the subjective loudness of the signal. Stereo Operation. In normal 2 channel operation, the controls operate independently for each channel.
SPECIFICATIONS Mic Input: Electronically balanced, input impedance greater than 10Kohm, to suit 150-600 ohm microphones. 48V phantom power available, indicated by red LED. Gain range +16 to +60dB. Noise (EIN): -126Bu at maximum gain with a 150 ohm termination, measured 22Hz-22KHz unweighted. Maximum input level +10dBu. 3 pin female XLR connector. Line Input: Electronically balanced, unbalanced compatible, with input impedance greater than 5Kohm.
Compressor: Threshold -20dBu to +20dBu, Attack 0.5msec to 50msec, Release 40msec to 4 seconds, Ratio 1:1.5 to 1:30, Gain Make-Up 0 to +20dB. Stereo Operation: Ganged Threshold, Attack, Release and Ratio controls, Linked control voltages. VU Meters: Switchable to output level or compression, 0VU = +4dBu. Outputs: Electronically balanced, unbalanced compatible. Rear panel selectable for +4dBu or -10dBu nominal level. Output impedance less than 10 ohms.
Dynamic Range: 106dB. Distortion: THD+N: IMD: 0.05%, 10Hz-40KHz. 0.03%. (Line input at 0dBu and 0dB gain with compressor in, after 10 minute warm up time). Sidechain Insertion Points: Unbalanced, switched 3 pin jack socket, tip = send, ring = return. Nominal level -2dBu. Output impedance 47 ohms. Return input impedance 10Kohms. Power Requirements: Rear panel selectable for 220-240V 50Hz or 110-120V 60Hz operation. Rear panel fuse 20mm, 1AT. Power consumption 30VA typical.
SERVICE Should the compressor require service, it must be taken or posted to an authorised dealer. Please retain the original packing for possible future use, and ensure the unit is suitably protected during transit. The manufacturer cannot accept responsibility for damage caused during transportation. The compressor is protected by a limited warranty for a period of one year from the date of purchase. During this period, any faults due to defective materials or workmanship will be repaired free of charge.
