ATI SDA200 User Manual

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

audio.com

© Copyright 2011, ATI Audio Inc.

SDA200 and SMDA200

STEREO DISTRIBUTION AMPLIFIER

MODULES for SYSTEM 10K

OPERATING AND MAINTENANCE MANUAL

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

audio.com

DESCRIPTION

The SDA200 and SMDA200 modules are both two-input and eight-output audio
distribution amplifiers designed as plug-in components for the SYSTEM 10K
Modular Audio Distribution System. The SYSTEM 10K provides proper mounting,
shielding and power for a family of interchangeable amplifier modules.
Performance to published specifications and operational life of these modules
are covered by ATI's standard warranty on the SYSTEM 10K only when they are
used as part of a SYSTEM 10K consisting of an RM100 Rack Enclosure and
PS100 Power Supplies.

The SDA200 and SMDA200 modules feature eight active balanced outputs in
two groups of four. Both output groups are controlled together by a single, stereo,
full range, audio taper level control. Individual left and right multi-turn trimmers
provide fine matching adjustment with a limited range of ±4dB.

A board mounted DIP switch selects normal left/right stereo outputs or can select
either the left or the right input to drive all eight outputs or can even be used to
sum both left and right (L+R) inputs into either or both sets of outputs. By
reversing the phase of the right input signal on the external connector, an L-R
difference signal can be generated in the same manner.

A TRS (tip-ring-shield) stereo headphone output jack is mounted on the front
panel. Both low and high impedance stereo headphones will be driven properly
without output loading.

The SMDA200 incorporates an LED peak-indicating bargraph meter which is
switchable to either the inputs or the outputs and will monitor either the Left
Channel, the Right Channel or the Left plus Right (L+R) Sum signal as selected
by a pair of front panel switches.

CIRCUIT OPERATION

The audio input lines are bridged by a 30,000 ohm active balanced differential
input stage with a loss of 2.5dB. The bridging resistor network is split and heavily
bypassed for maximum RF protection. Trimmers R13 and R14 null out common
mode hum inputs and are factory set to 90dB. To field-adjust, apply a 60 Hz input
to HI and LO input terminals together referenced to ground and adjust the
trimmer to null the output. The input stage will bridge a +24dBm input line without
clipping. The input stages use two sections of a quad bi-fet LF347N IC.

A full range, ganged stereo OUTPUT control, R23 and R24, adjusts both
channels simultaneously; unity channel gain is at 50 percent rotation. Individual
multi-turn trimpots, R17 and R18, allow fine TRIM and precise matching of each