Manual

Lydkraft ApS
Mose Allé 20, DK 2610 Rødovre
Denmark
TUBE
-
TECH PM 1A
Microphone pre
-
amplifier Module
Description
The
TUBE
-
TECH microphone preamplifier PM 1A
is a combined microphone and
DI preamplifier.
The amplifier consists of a microphone input transformer (with a static screen) wi
th
a step
-
up of +10 dB, a dual tube preamplifier with a coarse stepped gain 20
-
60dB
(10dB/step), a fine stepped gain +/
-
10dB (2dB/step) giving a total gain range of
+10
-
70dB, an output amplifier with two dual tubes in push
-
pull and an output
transfor
mer
(with a static screen).
The microphone inputs are provided with a switchable
-
20dB atte
nuation PAD, a
selectable input impedance 600/1200/2400 Ohms, a switchable phase reverse and
switchable +48 V phantom
-
power.
The microphone input is capable of accept
ing levels of up to +6 dBU (1.55V) at 40
Hz without the
PAD
and +26 dBU (15.5V) at 40 Hz with the
PAD
, so the
microphone input can be used as a unity gain line amplifier.
The high impedance
DI
input is unbalanced and placed in the circuit directly after
t
he input transformer.
The gain range for this input is +10dB to +60dB.
When in use,
the microphone input is disabled.
A high pass filter for the microphone and the DI input is switch
able between
off
,
20
Hz
and
40 Hz
.
It is advisable to use this filter in
environments with high levels of
very low frequency disturbances.
(
071221 JGP)