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Amp noise on shut down, thump on start up.

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Posted on October 31, 2009 at 12:22:15
Rick7
Audiophile

Posts: 153
Location: So. California
Joined: November 17, 2005
 I have a Times One 400 Watt SS Amp.
When I power it down - it send a weird signal through the speakers.
A little whine and a thump. Both sides, each a little different.
There is also a thump when powering on.
My Hafler P4000 does not do this.

What causes this and is it an easy fix?

My Powered Tannoy System 10's do something similar. (different room)

Thank you,
Rick

EDIT - It happens @ 5 secs after shut down. Left side then right. Actually sounds like a motorcycle engine/dirtbike for a second or 2 - winding down.
RE: Amp noise on shut down, thump on start up., posted on October 31, 2009 at 14:51:19
Ron Oehlert
Audiophile

Posts: 4649
Joined: December 18, 2003
 The current arcing of power switch contacts during Make or Break provides an operating current signal that gets amplified thru circut & thus heard via speakers. A proper capacitor across the power transformers' primary winding can act as a Mute filter at the source for this electrical switch noise. If you understood what I wrote, then the fix is easy to implement; if you have further questions, then it is NOT a simple DIY fix & involves Dangerous Voltages that can Kill you.

RE: Amp noise on shut down, thump on start up., posted on October 31, 2009 at 15:05:15
Rick7
Audiophile

Posts: 153
Location: So. California
Joined: November 17, 2005
 I meant simple - as in someone can do it for me. And not cost a fortune.

The switch is on the front and is orange colored.
The light flickers a little when on.

It happens @ 5 secs after shut down. Left side then right. Actually sounds like a motorcycle engine/dirtbike for a second or 2 - winding down.

I can't find the original builders of this amp.

Do you know any reliable Amp repair places in L.A.?

Rick

RE: Amp noise on shut down, thump on start up., posted on November 2, 2009 at 22:39:29
JoeKool
Audiophile

Posts: 426
Location: NYC
Joined: May 9, 2003
 My Adcom 555 does that on shut down, its normal as the ps-caps are drained of its charge. Your Hafler probably have a muting or delay start circuit so you don't get that turn on thump or the "whining" sound on shut down.
I wouldn't be too concerned.

RE: Amp noise on shut down, thump on start up., posted on November 2, 2009 at 23:36:21
Rick7
Audiophile

Posts: 153
Location: So. California
Joined: November 17, 2005
 Thank you for the help.
I think I will try to record it and post the audio file for people to hear.
It's probably not going to hurt my speakers.

Rick7

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