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Topic starter
My March Audio stereo P452 is a few years old, has been and still is performing wonderfully, but has recently developed a slight click in one channel only when the preamp is muted (which shorts the inputs), as if there was DC in the circuit. By reversing the input XLRs & the click staying on the same side I've established that the click is caused by the power amp, not the pre. Its very low level, similar to the sound of a switching relay. Wondering if anyone else has a similar problem & if it should be attended to given that there's no problem with actual performance?
Having spent decades with Valve amps & being eventually terrified by clicks that turn into loud bangs and sparks resembling a volcano, I worry about even the slightest abnormal sound!
Update - I checked for any voltage & found low level DC actually on both channels, but stronger on one, when not muted. Right side is 0.03v and left side is 0.01v. Only noticing the left side click on mute when I put my ear right up against the speaker. Not changing sides when reversing the inputs. Next step, I'll check for any dc on the output cables from the pre-amp, although Audio Research says the pre output is capacitor coupled to avoid any dc.
Posted : 06/02/2026 4:31 pm
@Michael It's a bit surprising that the issue is affecting the Left channel with less DC offset but they're negligible amounts anyway, have you been experiencing any popping noises at all?
Posted : 09/02/2026 4:10 pm
Topic starter
Oniiz86 wrote:
@Michael It's a bit surprising that the issue is affecting the Left channel with less DC offset but they're negligible amounts anyway, have you been experiencing any popping noises at all?
There's no problem at all with the sound, which remains truly stunning - but as I wrote in my post above there's the click when I mute the preamp. Now I know its in both channels, but I only noticed the louder right channel until today! It may be nothing to worry about, but it doesn't seem right!
Posted : 09/02/2026 4:16 pm
If
Michael wrote:
There's no problem at all with the sound, which remains truly stunning - but as I wrote in my post above there's the click when I mute the preamp. Now I know its in both channels, but I only noticed the louder right channel until today! It may be nothing to worry about, but it doesn't seem right!
If your pre amp uses the technique of shorting the output on mute, any tiny voltage (normally harmless) that has accumulated on the pre output (could be caused by coupling cap leakage) will suddenly go to zero. A tiny click will result.
Bottom line is that it's not a good mute technique in this respect. It's not an amplifier fault.
BTW a small DC offset on amplifier speaker outputs is perfectly normal. In fact 1mV and 3mV is extremely low and not related to the click.
Posted : 09/02/2026 9:52 pm
Topic starter
That's reassuring, thanks Alan.
Posted : 10/02/2026 4:42 am
0.03V is 30mV... right??
The mute circuit (the shorting-to-ground one) would short both ends of an XLR cable to ground, not only the pre-amp end - it's the same cable. It doesn't matter where the shorting relay (or transistor) is placed along that cable. With this in mind, could it be that your amp has higher DC levels at your input buffer IC INV (NONINV) pins? Maybe the stored energy in your amp's sound-coupling/DC-blocking caps is higher?
I do not understand why you'd blame pre-amp by default...??
I expected something along the lines of: "Okay, I will test my amp. Please send it in for a check." No??
Posted : 19/02/2026 1:09 pm