Shure A15BT User Guide

Model A15BT User Guide

BRIDGING TRANSFORMER

The A15BT matches, bridges, or isolates balanced and unbalanced
devices of different impedances and levels.

Impedance: XLR socket (Female), 33,000Ω

Unbalancing: Either end can be unbalanced by connecting pins 1 and 3.
Voltage difference: From 33,000Ω to 7500Ω, 6.4 dB

MEDIUM-IMPEDANCE SELECTION

As supplied, the A15BT XLR plug is at 7500Ω. To convert to 600Ω, refer
to Figure 1 and proceed as follows:

1. Remove the three-pin plug element by turning the screw counterclock­wise and withdrawing the element from the case.

2. Remove the GREEN lead pin jack from pin 3, and insulate the jack and
bare lead.

3. Remove the tape from the pin jack on the WHITE lead and push the jack
firmly onto pin 3.

4. Replace the plug element in the housing and fasten the screw firmly in
place (turn clockwise).

XLR plug (Male), 7500Ω, easily converted to 600Ω.

From 33,000Ω to 600Ω, 17.4 dB.

2005, Shure Incorporated
27C1916 (Rev. 4)

Printed in U.S.A

TYPICAL APPLICATIONS

To connect the 600W line output of a preamplifier, mixer, or recorder to a
high-level, high-impedance, unbalanced (Aux) input:

Connect the 600Ω output to the 33,000Ω XLR socket of the A15BT.
Unbalance the the XLR plug on the A15BT and convert it to 7500Ω or
600Ω to provide the proper level and best signal-to-noise ratio. Connect
the A15BT to the Aux input. In this configuration, the A15BT “bridges” the
600Ω line output. Refer to the table on the back page for the maximum in­put level to the A15BT.

To match a high-impedance microphone output to a medium-impedance
(approximately 10,000W) input on a reel-to-reel or cassette recorder:

Unbalance both ends of the A15BT. Connect the microphone output to the
33,000Ω XLR socket. Connect the 7,500Ω XLR plug to the recorder.

For an unbalanced Aux input to accept a balanced low-impedance output:

Unbalance the 33,000Ω XLR socket on the A15BT and connect it to the
Aux input. Convert the XLR plug to 7500Ω or 600Ω and connect it to the
balanced low-impedance device.

When a balanced 600W line output is needed on a unit with an Aux output
(such as the Shure SCM268):

Unbalance the A15BT 33,000Ω XLR socket and connect it to the Aux out­put. The A15BT XLR plug offers a balanced line output at both 600Ω (at
about a –20 dBm level) and 7500Ω.

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