Music plays after amp is turned off.

[Killjoy99]

I've just finished testing my P101 and everything checks out alright. The only issue I am having is that once the power switch is turned off the amplifier continues to pay music. This goes on for around 30+ seconds without a change is the sound or volume of the music. I'm assuming this is due to the capacitors in the power supply but how can this be stopped.

The power supply was built just for testing the amplifiers so it is only +- 17V. The trafo is connected to two 63V 10,000MFD filter caps and than goes to the amp.

Will this change or even go away once the final supply voltage of +-70V is applied? I will also have 15,000 MFD per rail on the final supply.

Any Ideas?

[richie00boy]

If you increase the voltage the stay on period will last even longer. The only way to get around this is to fit a relay in the speaker output that is controlled from the AC supply. Alternatively look into ESP P33 as it does this and more.

[rabbitz]

Turn the volume control down and turn the music off.

Easy.

[darkfenriz]

use dual switch- turning off power and turning off the speaker

why do you find it a 'problem' anyway?

[sivan_and]

The only way to get around this is to fit a relay in the speaker output that is controlled from the AC supply

Add a bleeder resistor,to discharge the caps!!

[richie00boy]

If you add a bleeder to make any noticeable impact on the discharge period then you will simply be wasting that capacity of the PSU, making it unavailable for it's actual smoothing job.

[mAJORD]

mine does the same thing (p101) but makes a horrid feedback style sreech before dying out. not sure why

[Coulomb]

Originally posted by richie00boy
If you add a bleeder to make any noticeable impact on the discharge period then you will simply be wasting that capacity of the PSU, making it unavailable for it's actual smoothing job.

Humm untrue, I use high Value resistors for discharging capacitors all the time. Depending on the rail voltage anywhere from 5K to 20 K per rail, usually 5 or 10 Watt. This is far to high to load up a power supply but will expedite the discharge time.

There are really two issues here; For safety reasons High Value caps should always be discharged given thier capacity to store enormous amounts of energy. As far as muting the sound after power off, the previously mentioned relay or speaker protection circuit will work. I do not like to break the signal path after the output device so I would mute the input signal with a low voltage high quality relay and a 10K resistor.

Regards

Anthony

[rabbitz]

The P101 I've got is quiet on startup and shutdown. I did try a dual power supply once which made some disgusting noises on shutdown. I found using Rod's suggested power supply had no problems.

Another case for turning the volume down before switching off.

[sivan_and]

The bleeder resistor will load the PSU and reduce the switching noise of the rectifier diodes,whenever the amplifier operated with small output power.The peak spike current (diodes conducting only at the peak of a/c waveform) will be somewhat broadened with a bleeder resister.Why add a small switching circuit to put this load whenever the amp output is low.the attack time should be very slow, and disengaged fast, a small relay or Mosfet can be used for switching.
will try to post such a circuit soon....