ATI ML200 User Manual

Audio Technologies Inc. ■ Tel: [phone] ■ [e-mail] ■ www.

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ML200

MICROPHONE AMPLIFIER

OPERATING AND MAINTENANCE MANUAL

© Copyright 2008, Audio Technologies Inc.

Audio Technologies Inc. ■ Toll Free 800-922-8001 ■ [e-mail] ■ www.

audio.com

GENERAL

The NANOAMP Series ML200 dual channel microphone preamplifier is an in
expensive high performance, low noise amplifier designed to cleanly boost
professional microphones to balanced line level. ML200 is ideal to drive long
lines in the presence of high hum and noise or as an auxiliary rack mounted
preamplifier to convert mixer high level inputs to microphone levels.

The ML200 provides two outputs at either line or microphone level to drive
balanced and unbalanced lines. HI and LO preamp gain levels are front panel
selectable for each channel. Peak indicators monitor preamp and output circuit
levels. Switched phantom microphone power is provided and all audio
connections are made using XLR type connectors.

The ML200 accepts microphone inputs from –76dBm to +18 dBm thru a high
impedance (20Kohms) balanced, low noise, transformerless (no ringing)
instrumentation amplifier input (A1, A2) and drives servo balanced 600 ohm
(minimum load) outputs (A4, A5) to+4 dBm balanced line level (+22 dBm
maximum). The servo-balanced outputs automatically detect single-ended (one
side grounded) loads; remove drive from the grounded output and double the
signal applied to the ungrounded output thus maintaining equal gain for both
types of loading.

An internal input gain setting DIP switch used in conjunction with the front panel
HI – LO gain selector optimized the preamplifier stage gain, noise and headroom
for the microphone outputs rated at –60, -50, or -40 dBm (HI) or –40, -30, or –10
dBm (LO). Thirty dB if input headroom is provided in the HI position allowing 10,
20, or 30 dBm additional range, if necessary. The Master Gain controls (R23,
R24) adjust the output line level. Individual internal jumper plug output
attenuators (P1, P2) provide –50 dBm microphone level outputs, if desired.

PEAK indicators for each channel monitors both the preamp stage output level
(before the MASTER level controls) and the output drive voltage. The PEAK
indicators operate at 4 to 5 dB below clipping and track varying supply voltages.
If turning down the output level with the MASTER, do not turn off the PEAK
indicator when a reduction of input stage gain with HI – LO switch is indicated.

Phantom microphone power at regulated +20.2 VDC from A6 is selected with a
front panel switch and is sufficient for most powered microphone. +48 VDC
phantom power is also available as an inexperienced plug-in option (PH48-1);
consult factory.

NANOAMPS require 22 to 3- VDC and are designed to share a common external
24 VDC “Wall Wart” type power supply. A pair of loop-thru DC connectors on the
rear of each module permit several units to be daisy-chained with P/N20602-1
DC power cables to a single power supply. The WA100-1 and the WA100-2 (230

Audio Technologies Inc. ■ Toll Free 800-922-8001 ■ [e-mail] ■ www.

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VAC) are 400 mA supplies. The DA103 and the DMA103 both draw about 100
mA at full output. Any combination of NANOAMPS, which add up to less than
the supply rating, can be powered by a single supply.

INSTALLATION

WIRING

Audio Connectors balanced XLR type inputs are outputs are wired with pins 2 as
HI and 3 pins as LOW. Pin 1 is cable shield and ground connection.

Active balanced outputs and inputs require a reference ground connection to the
source or receiving device for proper operation. This ground can provide by the
rack frame or a studio ground bus connection if the cable shield does not carry it
through.

GROUNDING

Operation in high RF broadcast environments required special attention to
grounding and shielding. The chassis must be grounded directly to good, low
impedance studio ground system. Input and output connections must be
properly shielded and free of ground loops. It may even be necessary to add
shielding and free to the DC input leads to avoid RF pickup.

POWER DISTRIBUTION

Multiple NANOAMPS sharing a single wall-wart power supply should be looped
through each other using the DC interconnect cables P/N20602-1. Hum and
noise performance of the units can be degraded by poor DC ground connections
between units sharing a common supply. Use of the recommended rack and
desk mounting kits will assure a good ground connection between units by firmly
strapping their chassis together.

CAUTION!

The outer shell of the DC interconnect cables is positive relative to the chassis.
Do not allow a DC cable plugged into a powered unit to hang loose where it can
short against chassis or rack frame.