ATI Audio BU400B - Manual (Page 3)

Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax 856-719-9903 | www. audio.com
CIRCUIT DESCRIPTION
INPUT STAGES
The balanced input stages of the BU400 and BI100 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 gains from both HI and LO inputs
allow unbalanced sources to be easily accommodated. Bridging impedance is a high
40Kohms with good CMR.
LEVEL CONTROLS
Each IHF and balanced output is controlled by its' own front panel potentiometer.
These controls are factory set for standard IHF level of -10dBu (.25V) and Pro level of
+4dBm.
LINE OUTPUT
Balanced output stages of the BI100 and UB400 utilize a unique active balanced
output driver IC, the SSM2142, which 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
will drive loads of 600 ohms and higher. Nominal output is +4dBm with clipping at
+22dBm into balanced loads. Maximum output at clipping is reduced by 6dB when
driving an unbalanced load, since the full output swing of only one driver is available.
POWER SUPPLY
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 WA100-1 power supply. The WA100 is a 400mA supply. The BI100 and
the UB400 each draw 70mA and the BU400 draws 40mA. Any combination, which
adds up to less than 400mA, can be powered by a single supply. They incorporate an
"artificial ground" power supply splitting circuit to track the DC input voltage and
provide a center point voltage reference for the audio stages.