ATI BU400B User Manual

BU400, BU400B, UB400B,

UB400B, & BI400

IHF-PRO INTERFACE AMPLIFIER

OPERATING AND MAINTENANCE MANUAL

audio.com

GENERAL

Consumer audio equipment can offer unique features, good performance and attractive pricing making it very desirable for professional use. Unfortunately, RF pickup, ground coupled cross talk, high frequency roll off, hum loops and distortion are often the results of the direct connection of low level unbalanced IHF outputs into the 600 ohm balanced systems used in studio or broadcast environments. Consumer and semi-professional equipment can be identified by their use of RCA type connectors, typical of home hi-fi equipment, for their IHF inputs and outputs. Professional systems typically use XLR type connectors or hard-wired connections.

The BI100, BU400 and UB400 are interface amplifiers designed to interconnect consumer grade and semi-professional equipment into professional, balanced, low impedance audio systems.

The BI100 is a bi - directional stereo interface, which bridges a stereo pair of professional 600 ohm balanced or unbalanced +4dBm lines and converts those signals to a nominal .25volt IHF level (-10dBu). The IHF output can feed, for example, the record inputs of a consumer grade cassette or DAT recorder. Simultaneously the BI100 also converts the unbalanced, high impedance, stereo, .25-volt IHF playback outputs from the tape deck to a +4dBm output capable of driving balanced or unbalanced lines of 600 ohms or greater line impedance.

The UB400 is a uni - directional four-channel interface that converts four IHF level signals into four balanced professional outputs. The UB400 is particularly useful in protecting the four, eight or sixteen main or monitoring IHF outputs of low cost mixers and tape decks. The UB400 is also a very low cost way to interconnect two CD players into a balanced system.

The BU400 is also a uni - directional four channel interface but it converts four balanced professional signals into IHF levels suitable for feeding the line inputs of a multi-channel tape deck, DAT machine or mixer.

Several of these can comfortably share a single external WA100, 24VDC / 400mA. wall-mount AC/DC power supply. Battery packs for remote or back-up use are planned for this product line. Check your dealer or a current price list for availability. Up to three of these products will mount side-by-side in only one rack unit using the available rack mounting kits. They may also be neatly stacked or mounted side-byside on your desk with the available angled desk mounting kits.

The BI100, UB400 and BU400 use rugged XLR type connectors for the balanced inputs and outputs. Gold plated RCA type jacks mate to the IHF world.

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.

audio.com

+ 4 hidden pages