ATI Technologies SDA200 Operating instructions

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© Copyright 2011, ATI Audio Inc.
SDA200 and SMDA200
STEREO DISTRIBUTION AMPLIFIER
MODULES for SYSTEM 10K
OPERATING AND MAINTENANCE MANUAL

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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

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channel’s gain over a 4dB range above and below the nominal stage gain of
22dB.
Board mounted DIP switch S1 provides four normally open switch sections to
independently direct the left and right input signals to either or both output
amplifiers. Resistive mixing allows both left and right inputs to be summed (L+R)
into either or both outputs.
The output stages consist of a bridged pair of high current output ICs
(NE5532AN) that provide the first 20ma. of output current directly. Above that
level, the complimentary class B output booster transistors take over. This simple
but unique, wide bandwidth, high slew rate design provides effective class AB
operation with minimal crossover distortion from a power output stage operating
in true class B with zero quiescent power dissipation. The outputs provide 3.5dB
of stage gain, 6dB additional due to the balanced configuration and 3.5dB of
output loss through the build-out resistors when loaded by 600 ohms.
The HI and LO amplifier outputs are split into four isolated balanced outputs
through 150 ohm build-out resistors. The build-out resistors are individually
bypassed to prevent RF pickup on an output line from affecting the operation of
the DA. The build-out resistors totally isolate disturbances on one output line
from all other outputs. All outputs will tolerate short circuits across the outputs, or
to ground, without damage. However since all outputs are driven by active
stages, DO NOT CONNECT EITHER HI or LO OUTPUT TERMINALS TO
GROUND or to the grounded side of an unbalanced load to avoid excessive
power supply loading and loss of headroom. Instead, connect the unbalanced
load between the HI output and DC GROUND (rather than HI and LO) or use a
transformer output equipped DA module such as an ATI MIDA100-1 or isolate
the unbalanced load through a balanced-to-unbalanced converter such as an ATI
L1000-1 Line Amplifier or an isolation transformer.
The SMDA200 includes a bargraph peak-reading meter. Front panel switches S2
and S3 select input or output and either Left, Right or the L+R sum signal. A4A
sums and amplifies the switch output with a 3dB gain reduction allowance for the
L+R rms sum. The meter circuit is designed for equal input and output levels and
as shipped is calibrated by R71 for +4dBm at 0VU. A4B and A4C form an active
full wave meter rectifier driving the LED bargraph with a range of 12dB above
and 15dB below 0VU in 3dB increments. The display and circuit time constants
approximate PPM ballistics. The meter driver, A5, is a National LM3915 and A6
is a General Instrument MV50164 ten segment LED display.
Unregulated input power at ±18VDC nominal is filtered and limited to 16VDC
maximum by zener diodes CR2 and CR3. Power indicator LED CR5 detects the
loss of either power supply voltage. On-board fuses, PI and F2, (3/8 A) protect
the main power buss from module faults. Zener diode CR1 provides 11VDC
maximum to the meter display.

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An electrostatic shield is mounted to the PC board just behind the panel to shield
the low level circuitry. To achieve optimum shielding, SYSTEM 10K modules
should be mounted side-by-side starting on the left side of the rack frame with no
spaces left between modules. Panel retaining screws should be tight to
effectively ground the panel to the frame.
All parts with the exception of panels, shields and PC boards are standard
distributor items but are also available from ATI stock. A1 and A4 are National
LF347N quad bi-fet ICs interchangeable with TI TL074 and others. A2 and A3
are Signetics, TI or Exar NE5532AN dual, high output audio opamps. The output
boost transistors are GE D44C3 (NPN) and D45C3 (PNP).
INSTALLATION
A mating connector assembly is included with each amplifier module. The
connector assemblies may have been pre-assembled to the RM100 rack frame if
ordered together. If not, they should be mounted to the rear of the frame using
the (4) M2.5X6mm screws supplied. Install modules starting from the extreme left
(opposite power supplies); leave no spaces between modules to achieve the
most effective shielding. Plug on the DC power buss connector to the polarized
3-pin receptacle at the top of the connector assembly.
To make a connection to the 3.5mm modular connectors using Belden #8451
cable or equivalent cable with 22 to 24 gauge inner conductors, strip back the foil
shield about 1" to 1 1/2" exposing the inner conductors and shield drain wire.
Remove shield and cut off the drain wire. All connectors and 3.5mm modular
connectors are marked clearly for function and polarity.
The output ground connections "G" are used for connecting the LO side of
unbalanced, single ended, one-side grounded loads. They must NOT be used to
terminate the shields of the cables connected to the outputs or inputs since this
would degrade the RF immunity of the system by routing intercepted RF and
other noise pickup directly into the module. Cable shields should instead be tied
to studio ground at a punch block, Christmas tree block or jack field interconnect
point and allowed to float at the input and outputs of the DA.
All inputs, whether balanced or unbalanced should be treated and wired as
balanced sources to achieve maximum immunity to hum, noise and RF which
may be picked up on the input wiring. All inputs should use two-conductor-plus-
foil shielded cable. Connect source HI to DA input HI, connect source LO or GND
to the DA input LO, tie cable shield to source or studio ground (allow shield to
float at the DA) and make sure there is a connection from the source chassis to
the studio ground.

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SPECIFICATIONS
Specifications reflect performance in a typical SYSTEM 10K consisting of ten
mixed distribution amplifier modules and two PS100 power supplies mounted
together in an RM100 rack frame.
INPUT
Channels
2 (Configurable as Dual Mono or Single Stereo)
Input Impedance
>30 K ohm balanced
CMR Range
+20V
CMR Ratio
>90 dB @60Hz
OUTPUT
Channels
8 total Mono or 4 per Stereo Input Channel
Output Impedance
<600 ohm
Output-to-Output isolation
>70 dB, 20Hz to 20kHz
Nominal Output Level
+4dBm @ 600 ohm = 0 VU Indication
Maximum Output Level
+24dBm @ 600 ohm
Headphone Output
10Vrms maximum through 150 ohms
PERFORMANCE
S/N Ratio
>90dB (unweighted) 20Hz to 20kHz
Gain Range
-4 to +24 dB Front Panel Adjustable
Frequency Response
<-0.25, +0dB 20Hz to 20kHz
Total Harmonic Distortion
<0.025% @ 1kHz
Intermodulation Distortion
<0.05% @ 1kHz
Channel Crosstalk
>90 dB @ 1KHz
ENVIRONMENTAL
Power Supply
120 or 230 VAC ±10% @50/60 Hz (determined by
power supply wiring)
Operating Temperature
0 deg C to 40 deg C
Humidity
0 to 90% non-condensing

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One Year Limited Warranty
ATI warrants this product to be free from defects in materials and workmanship to its original
owner for a period of one year from date of purchase. ATI will repair or replace such product or
part thereof, which upon inspection by ATI, is found to be defective in materials or workmanship.
The Proper Return Authorization Number must be obtained from ATI in advance of return.
Contact ATI at 856-626-3480 or email [email protected] to receive the number and
instructions for return of your unit.
A written statement providing the name, address, daytime telephone number and email address
of the original owner, together with receipt from the original purchase, and a brief description of
any claimed defects, must accompany all returns. Parts or product for which replacement is made
shall become the property of ATI.
The customer shall be responsible for costs of transportation and insurance to the factory of ATI,
and shall be required to prepay such costs.
ATI shall use reasonable efforts to repair or replace any product covered by this limited warranty
within thirty days of receipt. In the event repair or replacement shall require more than thirty days,
ATI shall notify the customer accordingly. ATI reserves the right to replace any product that has
been discontinued from its product line with a new product of comparable value and function.
This warranty shall be void in the event a covered product has been damaged, or failure is
caused by or attributable to acts of God, abuse, accident, misuse, improper or abnormal usage,
failure to follow instructions, improper installation or maintenance, alteration, or lightning, power
fluctuations and other incidental or environmental conditions. Further, product malfunction or
deterioration due to normal wear is not covered by this warranty.
ATI DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WHETHER OF
MERCHANTABILITY OF FITNESS FOR A PARTICULAR USE, EXCEPT AS EXPRESSLY SET
FORTH HEREIN. THE SOLE OBLIGATION OF ATI UNDER THIS LIMITED WARRANTY SHALL
BE TO REPAIR OR REPLACE THE COVERED PRODUCT, IN ACCORDANCE WITH THE
TERMS SET FORTH HEREIN. ATI EXPRESSLY DISCLAIMS ANY LOST PROFITS, GENERAL,
SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHICH MAY RESULT FROM
BREACH OF ANY WARRANTY, OR ARISING OUT OF THE USE OR INABILITY TO USE ANY
ATI PRODUCT.
Some states do not allow the exclusion or limitation of incidental or consequential damages or
limitation on how long an implied warranty lasts, so the above limitations and exclusions may not
apply to you.
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ATI reserves the right to modify or discontinue, without prior notice to you, any model or style
product.
If warranty problems arise, or if you need assistance in using your product contact us.