User´s Manual - Lake People MIC-AMP F35/II Bedienungsanleitung

GENERAL INFORMATION
The LAKE PEOPLE MIC AMP F35 is an extre-
mely low-noise, dual microphone preamplifier
with excellent specifications.
Due to its versatile concept and high level capa-
pility it is also suitable for line signal boosting
and balancing.
Gain is controlled via two knobs per channel: a
twelve-step rotary switch sets coarse gain in 6-
dB steps from 0 to +66 dB. A center-detented
potentiometer allows fine adjustment within a
range of +/-9 dB.
Each channel is equipped with switches for
- phantom powering,
- pad,
- phase reverse and
- lo cut.
The state of all these switches is reported by
LEDs.
The lo-cut switch activates the lo-cut control for
filter adjustment. Filter frequency can be set in-
dividually from 10 to 250 Hz.
A dB-linear, ten-segment LED bargraph dis-
plays the output level over a range of 30 dB.
Display sensitivity can be adjusted to the user's
requirements.
A clip LED starts flashing at levels above +20
dBu and thus reliably warns against distortion.
The electronically balanced inputs and outputs
are situated on the rear panel.
Each channel is equipped with two outputs.
As an option, the MIC AMP F35 can be equip-
ped with transformer balanced outputs.
THE CASE
The grounded case is crafted from 3mm alu-
minium and 1.25 mm steel sheet. This con-
struction offers a maximum of mechanical stabi-
lity and withstands even rough environmental
conditions. Internal signal ground and protective
earth are connected via a high ogmic RC com-
bination.
POWER SUPPLY
The unit is connected to mains via a built-in
IEC-CEE socket with integrated fuse holder.
Voltage can be switched internally between 230
and 115 VAC.
The "POWER"-switch is situated on the front
panel. Power-on status is indicated by a LED
next to the power switch.
The internal supply voltage of +/-18 VDC ensu-
res a maximum of headroom. The 48 V phan-
tom powering voltage is regulated.
THE AMPLIFIER STAGE:
THEORY AND PRACTICE
The MIC AMP F35's gain is effected by a so
called instrumentation amplifier. It is represen-
ted by an IC specially designed for this task, di-
stinguishing itself by very low noise figures and
a high gain/bandwidth product.
When gain is set to +60 dB (x1000), the amount
of noise added is only 2-3 dB more than the
(theoretically) achievable minimum.
The gain/bandwidth product (GBW) and the
slew rate are basically responsible for the sonic
quality of an amplifier. The higher they are, the
more transparent the sound becomes.
Slew rate is 10V/s, while the GBW is calculated
from the frequency response at a certain gain
ratio.
The MIC AMP F35's internal linear frequency
response at +60 dB gain exceeds 200 kHz. The
resulting GBW is as high as 200 MHz (200.000
Hz x 1000).
SIGNAL PATH AND CONTROLS
THE INPUT
The balanced inputs ares situated on the rear
panel, fitted with XLR type sockets. They are
denoted "INPUT 1" and "INPUT 2". The inputs
accept balanced as well as unbalanced audio
signals. XLR wiring corresponds to international
standard with
- Pin 1 = ground,
- Pin 2 = + (in phase) and
- Pin 3 = - (out of phase).
If an unbalanced source must be connected,
one of the phases (preferably the negative one)
should be connected to signal ground.
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