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RE: Humming amps :(


  • To: <ukha_d@xxxxxxx>
  • Subject: RE: Humming amps :(
  • From: "Keith Doxey" <ukha@xxxxxxx>
  • Date: Sun, 13 Jul 2003 17:22:03 +0100
  • Mailing-list: list ukha_d@xxxxxxx; contact ukha_d-owner@xxxxxxx
  • Reply-to: ukha_d@xxxxxxx

Hi Matthew,

Depends on the construction of the amp but they will be reasonable large or
very large.

Could be "Can" type electrolytic capacitors fixed to the chassis
with a
bracket that grips the body, could also be Radial or Axial electrolytics
mounted directly to a PCB.

They will normally be > 4700uF with a working voltage > 50V DC. A
conventional linear power supply consists of...

MAINS > Transformer > Bridge Rectifier > Smoothing Capacitors >
Regulation
(optional)

Apart from a persistant background hum, another sign of failing PSU Caps is
that the amp no longer seems as punchy and will clip more easily on
transients because the power supply has less reserve power to cope with the
peaks.

In one of my homebuilt amps the main smoothing capacitors are 22000uF 100V.
Playing it at normal listening level in the lounge I can turn the power off
and it will keep playing for about 20 seconds. Thats what you call a power
supply!

Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: Matthew Norman [mailto:mafiu@xxxxxxx]
> Sent: 13 July 2003 12:35
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Humming amps :(
>
>
> This is interesting - I've had similar on my amp for a while.
>  What sort of
> caps are we looking for?  I assume they will be in the psu circuit
> somewhere?
>
> Matthew
>



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