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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.