ATI Technologies SUM100 Maintenance Manual
SUM100
LINE/SUM/LINE AMPLIFIER
OPERATING AND MAINTENANCE MANUAL
© Copyright 1997-2005, Audio Technologies Incorporated - Printed in USA
Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax 856-719-9903 | www.
audio.com
DESCRIPTION
The SUM100 Summing Amplifier is an inexpensive, high performance amplifier
that is designed as a line level stereo to mono summing amplifier. It is also useful
as a gain block, and as an impedance converter and summing for IHF (RCA
type) signals.
The inputs provide balanced 40Kohm bridging impedance for line levels up to
+24dBm. The high input impedance allows the SUM100 inputs to also bridge 10dBu (hi-fi, RCA plug) lines without loading.
Front panel, screwdriver adjust, full range gain controls provide 26dB gain at full
clockwise rotation, unity gain at twelve o’clock and a smooth audio taper to full
off. The output driver is a servo controlled, ground-sensing circuit, which will
supply over +22dBm to 600 ohm balanced loads and +20dBu to high impedance,
unbalanced loads. The SUM100 uses rugged XLR type input and output
connectors.
Loop-through DC connectors allow several NANOAMPS to share a single
external 24VDC power supply. Battery packs and DC-DC converters for portable
use are also available.
Up to three amplifiers will mount side-by-side in only one rack unit using the
available rack mounting kits. NANOAMPS may also be neatly stacked or
mounted side by- side on your desk with the available angled desk mounting kits.
CIRCUIT DESCRIPTION
INPUT STAGES
The balanced input stages of the SUM100 Line Amplifier utilize a FET input
LF347 quad op-amp in a clean, quiet inverting instrumentation amplifier
configuration. Input levels up to +24dBm will be handled without clipping, excess
levels cause only clean clipping without hang-up or phase reversal. Equal -6dB
gains from both HI and LO inputs allow unbalanced sources to be easily
accommodated. Bridging impedance is a high 40Kohms with good CMR. Linear
panel adjust trimpots for both left and right signals are designed to be operated at
their 12 o’clock position for maximum resolution.
SUMMING AMPLIFIER
Left and right signals are combined in an active summing network (A1B) which
yields unity gain for each individual signal, three dB gain (RMS summation) for
program audio signals and six dB gain for correlated inputs.
Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax 856-719-9903 | www.
audio.com
GAIN STAGE
A low noise NE5532 section (A1A) provides 26dB maximum gain. A linear control
is used in a unique circuit configuration to provide a wide range logarithmic
MASTER gain control characteristic in a variable gain stage with optimum noise
performance. Output noise at unity gain is low enough to allow performance to
exceed 16-bit digital dynamic range even at -10dBu nominal output. Unity overall
gain is achieved at approximately 12 o’clock pot position.
LINE OUTPUT
The balanced output stage of the SUM100 utilizes a unique active balanced
output driver IC, the Analog Devices SSM2142, that senses whether the
connected load is balanced and floating or is unbalanced due to either side being
grounded. A balanced output load will be driven with equal and antiphase levels
on the HI and LO output lines.
An unbalanced (one side grounded) load will cause the driver IC to shut off the
signal output to the grounded side of the load and double the output level applied
to the other side, thus maintaining equal output to either type of load. The output
stage provides 6dB gain and will drive loads of 600 ohms and higher. Nominal
output is +4dBm with clipping at +22dBm (10Vrms) into 600 ohm balanced loads
for 18dB nominal headroom. Maximum output is reduced to +20dBu (7.8Vrms)
when driving an unbalanced load since the full output swing of only one driver is
available. This still provides a very comfortable 30dB of headroom above the
typical -10dBu nominal unbalanced signal.
POWER SUPPLY
The SUM100 requires 22 to 30VDC and are designed to share a common
external 24VDC "Wall Wart" type power supply. A pair of loop-thru DC
connectors on the rear of each module permits several units to be daisy-chained
with P/N20602-1 DC power cables to a single power supply. The WA100-1 and
WA100-2 (230VAC) are 400Ma supplies. The SUM100 draws 70mA. Any
combination of amplifiers, which add up to less than the supply rating, can be
powered by a single supply.
INSTALLATION
UNPACKING
Inspect the equipment. If there is any visible damage to the unit or to the box it
came in, contact the factory but do not return anything to ATI without prior
authorization and shipping instructions. It may be necessary to have the shipping
Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax 856-719-9903 | www.
audio.com
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