Tait TB7100, Service Manual

Page: 55 / 370

TB7100 Service Manual Circuit Descriptions 55
© Tait Electronics Limited October 2005
Auxiliary Audio
Output
The source for the auxiliary audio output signal
CDC AUD TAP OUT
is provided
by IC204 (
RAMPDAC
ball). The DAC output of IC204 is low-pass filtered to
remove high-frequency artefacts. The low-pass filter, formed by IC201
(pins 1 to 3), R219, R220, R221, R224, C206, C208 and C210, is a third-
order Butterworth type with a cut frequency of approximately 12 kHz.
The output of the low-pass filter is amplified by 6dB by a buffer amplifier,
IC201 (pins 5 to 7), and fed via R207 and R208 to drive the
CDC AUD TAP
OUT
interface line. The DC bias for this signal path is provided by IC204 and
is approximately 1.2 V when operational. The offset at
CDC AUD TAP OUT
is
approximately 2.4 V owing to the gain of the buffer amplifier.