User manual TL AUDIO A1

[. . . ] T L Audio User Manual Ebony Series A1 Dual Pre-Amp TL Audio Limited, Letchworth, England. www. tlaudio. co. uk email: info@tlaudio. co. uk TABLE OF CONTENTS TABLE OF CONTENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 WHY CLASS-A?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] Such an arrangement is referred to as "floating" or "ground-free". Balanced signals require 3 pin connectors, such as XLR's or TRS jack plugs, carrying the phase and non-phase signals, plus a screening ground connection. Naturally, the Ebony Series features balanced, ground-free signals for all line inputs and outputs, as well as insertion points where present. The range is also compatible with unbalanced equipment, as described above. The A1 Dual Pre-Amp. The Ebony Series A1 Pre-Amp features two independent channels, with each channel offering mic and instrument inputs. 3 The block diagram of one of the channels is shown in fig. 1. A discrete Class A electronically balanced mic input amplifier is used, delivering superior audio performance with very low noise, low distortion and wide bandwidth. The mic input is suitable for low impedance (150-600 ohm) microphones, with a gain control range of +16 to +60dB. Front panel switches provides 48V phantom power, and 30dB pad for high output mic applications. The front panel mounted jack socket is suitable for a variety of sources, including electric guitar, acoustic pickup and keyboard. The instrument input has high/low switching, and a dedicated valve input stage. Phase reverse and high pass filter switches are provided, affecting both mic and instrument inputs. The tube stage has a variable drive control, with the signal level indicated by the variable intensity "Drive" LED and "Peak" LED. Use of this feature typically introduces 1% to 10% harmonic distortion, predominately second harmonic, without changing the output level from the unit. The tube stage can be selected or bypassed as required. A VU meter is provided, which can be selected to either channel, and input or output signals. The meter is also provided with a "+10dB" switch, which keeps the reading on the scale when driving a high level out (to a DAW, for example). In the +10 mode, 0VU is calibrated as +14dBu out. Please read this manual fully before installing or operating the Pre-Amp. 4 PRECAUTIONS The T L Audio Ebony Series units require very little installation, but like all electrical equipment, care must be taken to ensure reliable, safe operation. The following points should always be observed: - All mains wiring should be installed and checked by a qualified electrician, - Ensure the mains operating voltage stated on the rear panel is correct before connecting to the mains supply, - Never operate the unit with any cover removed, - Do not expose to rain or moisture, as this may present an electric shock hazard, - Replace the fuse with the correct type and rating only. Warning: This equipment must be earthed. 5 BLOCK DIAGRAM. 6 INSTALLATION AC Mains Supply. The unit is fitted with an internationally approved 3 pin IEC connector. A mating socket with power cord and mains plug is supplied. All mains wiring should be performed by a qualified electrician with all power switched off, and the earth connection must be used. Please note that when using this unit with alternate supply voltages (in foreign countries, for example) the internal wiring of the unit may be set for 115V (accepting voltages in the range 110V to 120V, 60Hz AC) or to 230V (for voltages in the range 220V to 240V, 50Hz AC). If the wiring needs to be changed, the unit must be taken to an approved service centre. [. . . ] Experiment with the tube warmth rotary knob. Turn the rotary knob level up so that the Drive LED glows brighter - you should notice an audible change in sound character as the tube stage is driven harder. This variation in tone is one of the great strengths of the Ebony A1 - you have the option of running it very clean, or nice and warm as you increase the valve drive via the `Tube Warmth' control. 11 SPECIFICATION. Mic Input: Discrete Class A circuitry from input to output (unless Tube stage In). Gain Range: +16dB to +60dB (-14dB to +30dB with pad), Maximum Input level: +10dBu (without pad), +30dB (with pad), Frequency Response: 10Hz to 40KHz, +0, -0. 5dB, @ 40dB gain, Distortion (THD + Noise): 0. 025%, 20Hz to 20KHz @ 40dB gain, Noise (EIN): -127dBu unweighted, 22Hz to 22KHz, 150 ohm source termination. Instrument Input: Tube input stage, plus discrete Class A circuitry to output. [. . . ]