LYNDKRAFT TUBE-TECH MP 2A User Manual

Lydkraft ApS

Mose Allé 20, DK 2610 Rødovre

Denmark

1

TUBE-TECH MP 2A

microphone pre-amplifier

Description

The TUBE-TECH microphone preamplifier MP 2A is a two-channel microphone and
instrument preamplifier.

Each amplifier consists of a microphone input transformer (with a static screen) with a
step-up of +10 dB, a dual tube preamplifier with a stepped gain (2dB/step passive and
10dB passive/active), an output amplifier with two dual tubes in push-pull and an
output transformer (with a static screen).

The microphone inputs are provided with a switchable -20dB attenuation PAD and
switchable +48 V PHANTOM-power, three selectable input IMPEDANCEs (600,
1200,2400 Ohm), and a PHASE reversal switch.

The microphone input is capable of accepting 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 the
input transformer. The gain range for this input is +10dB to +60dB. When in use, the
microphone input is disabled.

A high pass filter (LOW CUT) for the microphone and the DI input is switchable
between off, 20Hz and 40Hz. It is advisable to use this filter in environments with high
levels of very low frequency disturbances.

Gain errors between the two channels are less than 0.5 dB at any gain setting.

The two amplifier circuits are completely separated and the cross talk between
channels is below -60 dB ranging from 20 Hz to 20 kHz.

An Overload indication (RED LED) lights up when the output level exceeds +26 dBU.

(130530)

Lydkraft ApS

Mose Allé 20, DK 2610 Rødovre

Denmark

2

CONTROLS:

GAIN: The gain switches have a range from +20dB to +70dB.
Coarse gain 10dB/steps (20-60ddB) and
Fine gain 2dB/step (+10/-10dB).

LF cut: The high pass filter is selectable between off, 20Hz (12dB/octave) and
40Hz (6dB/octave).

Phantom: The phantom switch switches the +48V DC power on and off.
The +48V DC is supplied to the microphone input via two 6,81 KΩ resistors.

PAD: This switch places a -20dB attenuation between the microphone and
the input transformer.

PHASE: Reverses the phase by 180 degrees on the mic input.
The DI input is unaffected.

IMPEDANCE: The mic. input load impedance can be selected between 600, 1200 and 2400

Ohm.

(130530)