Usage Examples
The
ANALOG
switches select from four sources to be listened to. The
selected source is sent to the “Functions” group and the “A-MTR” feed on
the back panel. The fourth analog selection is a built in D/A converter which
is fed by the selected “Digital” switch.
The “Functions” group allows channel phase reversal, speaker mutes, mono,
volume dim, alternate speaker selection, and a VU meter offset (to keep
from thrashing the meter movements when listening to high level program
material). The volume control is a 21 position stepped attenuator. It was
decided in the design process to use an attenuator for its accuracy and
repeatability. It was also found that attenuators provide consistent sound
quality at all volume settings whereas pots tend to change sonic
characteristics and balance depending on the setting. Pots also require DC
blocking to reduce scratching noises on adjustment. The gain of most power
amps today is set very high so the attenuator range is set for about 30 dB of
loss. Since it is desirable to occasionally listen to the noise floor, which
requires unity gain at the volume control, the last two steps are pretty big.
Please use caution near the top of the volume control.
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