Noisy Amp

[ostripper]

but this is not a short burst of sound, it sound more like an aircraft crashing! (not joking), and lasts about 5-6 seconds

Did it start doing this all of a sudden, or did this errata increase
gradually (over the months/years)??
OS

[vento]

Originally posted by ostripper


Did it start doing this all of a sudden, or did this errata increase
gradually (over the months/years)??
OS

Hi ostripper,
Can’t answer that one as it had the fault when I bought it, and was unaware of the problem.

Had a look on the net for circuit diagram, and ‘Hen’s Teeth’ spring to mind.

[nigelwright7557]

Originally posted by lineup
This is quite normal.
And nothing to be very afraid of.
At power off the big electrolytic capacitors take some short time to dis-charge.

A way to avoid this would be to use an output relay.
This relay should immidiately disconnect speakers when OFF switch pressed.
This is probably how most commercial amplifiers do it.

Along with a delay to connect speakers at POWER ON.
To let everything get charged, settled and stable, before connect the speakers.
This will avoid any 'pop' sounds at power on.

I use a microcontroller and a relay to do this.
The micro gives a 3 second delay to the relay on power up.
It also looks for looks for DC output (fault state) and disconnects the speakers if a fault state is found.

[Nico Ras]

Originally posted by lineup


I is more serious than I first thought.
5-6 seconds ... hmmm
If you can provide more info, somebody may figure out what is the trouble.
At least we now know what amplifier: Music Fidelity E10

Hi Line-up, I was joking with my comment of course.


I came across a problem many years ago on a guitar amp which may or may not be similar, but what happened was that a little while after turning power off a whistling sound came from the speaker and died down as the capacitors discharged.

The problem lay in one rail discharging quicker than the other and the amplifier became unstable as it got to some threshold voltage.

The reason for the unequal discharge was that all pilot lights were connected only to one rail of the power supply.

Regards

Nico