I have a Velodyne Microvee sub that, a couple of years ago, started humming for a couple of minutes after being powered on every time it was switched on (AC power applied and main power switch moved from off to on).
The solution was quite simple, rarely switch it off 😂.
Lately though it has got worse with the period that it hums for after switch on getting longer until, today, it wouldn’t stop humming at all.
The hum is classic mains (or harmonic of mains).
Opening it up, there is no evidence of physically damaged components (Main PSU caps are not puffed up for example).
Anyone have any suggestions? I’m especially curious as to whether the fact that it previously only hummed for a while after power on might give any clues? To me, it suggests PSU issues but I don’t know where to start.
I’ve seen a few threads on this sub developing a hum problem so it seems like a vulnerability of the design. I’ve not been able to find a commonly reported root cause though.
The solution was quite simple, rarely switch it off 😂.
Lately though it has got worse with the period that it hums for after switch on getting longer until, today, it wouldn’t stop humming at all.
The hum is classic mains (or harmonic of mains).
Opening it up, there is no evidence of physically damaged components (Main PSU caps are not puffed up for example).
Anyone have any suggestions? I’m especially curious as to whether the fact that it previously only hummed for a while after power on might give any clues? To me, it suggests PSU issues but I don’t know where to start.
I’ve seen a few threads on this sub developing a hum problem so it seems like a vulnerability of the design. I’ve not been able to find a commonly reported root cause though.
FYI, I've checked the power rails and there is no visible droop on the voltage over the main cap bank on the PSU board. So, looks unlikely that this is a PSU issue? I guess that was always likely the case though since the issue resolves after a few minutes. I'm not aware of bulk decoupling electrolytics having that kind of behaviour.
I also applied local heat to the power amp board itself in the hope of stimulating a change in behaviour (possibly speeding up the noise resolution after turn on. I did not observe any change in the recovery time.
Lastly, I should add that, the longer the amp has been switched off, the longer it takes to recover after startup. After a day being switched off, it'll take a few minutes to quieten down. With a quick on-off-on power cycle, it can be just a few seconds.
I also applied local heat to the power amp board itself in the hope of stimulating a change in behaviour (possibly speeding up the noise resolution after turn on. I did not observe any change in the recovery time.
Lastly, I should add that, the longer the amp has been switched off, the longer it takes to recover after startup. After a day being switched off, it'll take a few minutes to quieten down. With a quick on-off-on power cycle, it can be just a few seconds.