TL Audio A1 - Manual (Page 5)

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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.