TL Audio PA-2001 VALVE, INDIGO PA-2001 User Manual

T L Audio

INDIGO SERIES

User Manual

PA-2001 VALVE PRE-AMPLIFIER

Tony Larking Professional Sales Limited,

Letchworth, England.

Tel: [phone]. International [phone].

Fax: [phone]. International [phone].

INTRODUCTION

The T L Audio Indigo Series combines classic valve techniques with low noise solid
state circuitry to produce audio processing units offering very high quality signal paths
with comprehensive control facilities and the unique valve sound.

The PA-2001 is a four channel valve microphone pre-amplifier. Featuring very low
noise and an exceptionally wide bandwidth, it provides continuously variable input
and output gain controls, high pass filter and phase reverse switches, and
independently switched +48V phantom power.

The block diagram of one channel of the unit is shown in fig.1. The microphone input
socket is a balanced XLR connector, with phantom power applied via a front panel
switch. The gain of the input stages is controlled by a continuously variable rotary
control providing between 10 and 60dB of gain. A switchable 12dB per octave high
pass filter is provided to reduce unwanted background low frequency noise, such as
traffic rumble or wind effects.

The second stage of the pre-amplifier consists of both sections of a twin triode valve
(vacuum tube), which has a variable signal level depending on the setting of the input
gain control. Thus the characteristic valve sound may be subtlety introduced or used to
effect by turning up the input gain. A variable intensity peak LED monitors the output
of the triode circuit to indicate the headroom available. The LED will begin to glow
when a signal 6dB above normal line up level is present, and will be fully illuminated
when there is 10 dB of headroom remaining.

Phase reverse may be applied, prior to the output level control which allows matching
to the sensitivity of the following equipment (e.g. mixing console or tape machine).
The combination of input and output gain controls allows optimisation of the
operating level in the valve stages, to produce a clean uncoloured sound through to a
signal with a degree of valve warmth added.

Each channel has a balanced line level output on an XLR socket at a nominal level of
+4dBu, and an unbalanced output on a jack socket at a nominal level of -10dBu.

Please read this manual fully before installing or operating the Pre-Amplifier.

PRECAUTIONS

The T L Audio PA-2001 Pre-Amplifier requires 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 correct operating voltage is selected on the rear panel
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.