Bob the Tech had this McIntosh C41 preamplifier in for a loudness repair. The customer complained of lack of bass response in one channel.
A relay controls the engagement of the loudness circuit. Normally the relay is closed, bypassing the loudness circuit. This passes all frequencies through the circuit at the same level, as set by the volume control.
Opening the relay engages a high-cut filter that attenuates only the high frequencies. This provides the effect of a low frequency boost when listening at low volume. We isolated the issue to a fault relay (stuck open) in one channel. The result is that the affected channel always had loudness engaged. The enhanced low frequency response in that channel made the other channel’s low frequencies sound weak.
The pictures are not that thrilling, but replacing the relay, black box left, had both channels operating the same way, and the unit sounded great.
If your McIntosh C41 is having loudness issues or for any of your McIntosh repair needs, contact Bob the Tech Audio.
