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minh_827 16th September 2005 06:15 AM

krell kas power suppy hum
My krell kas mono-block power suppy has a noticible hum when it is on stanby. I've read somewhere that it is the power supply filter caps that has gone bad. Is the filter caps the main big caps in the power supply and is it fairly easy to change? I don't want to send the amp back to krell cause it would costs a lot and it would be more fun to do it myself. Does anyone have a simillar experience they can share with me or can help me with this problem?
Thanks Minh

Jozua 16th September 2005 07:37 AM


My experience has been that at peak power periods- especially round about suppertime my Krell amp transformers tend to hum. Also when somebody close to me is doing some welding in his backyard. The best is possibly to switch off during these periods.


amplifierguru 16th September 2005 07:55 AM

Sounds like poor design under the guise of 'audiophile' to me!
:D :D :D :D :D :D

CBS240 16th September 2005 08:04 AM

I guess poor design includes pi$$ poor PSRR.:D

amplifierguru 16th September 2005 08:14 AM

Hi CBS240,

Yes indeed that's exactly what it sounds like! :D :D
But hey, they're getting something special ... I'm sure they know what they're doing?


minh_827 16th September 2005 08:49 AM

amplifierguru, cbs
What are u guys talking about and how is it going to help me.

amplifierguru 16th September 2005 09:00 AM

Sorry Minh,

A couple of armchaire critics I guess, playing old favourites! Maybe a good power filter is in order.

Or ask (pester) Krell about it!


minh_827 16th September 2005 09:11 AM

2 Attachment(s)
My power supply is seperated from the amplification part. So when the amp is off the power suppy is still on.

peranders 16th September 2005 09:27 AM

All transformers hum more or less, by nature but some may hum more. Toroid transformers may also be very sensitive againt DC on the mains and "DC" is simply unsymmetrical waveform coming from hairdryers, microwave ovens and other "non-resistive" loads.

Jozua 16th September 2005 09:38 AM


I would love to have those Krells- I used to drool over that model in the magazines.

I have the KSA100 and KSA200s. So far I like the KSA100 best.

Personally I would suggest that you send those specialized amps to Krell or their agents for an overall service- also they are quite "old" by modern standards and possibly in need of service. The design of those models are also quite complex and I would not suggest that a novice fiddle inside them.

My gut feeling is that it possibly is a dry soldering joint in the power supply. Years ago my KSA 100 transformer sounded as if there was loose wire inside- all it took was a resolder of the mains wire on the inside of the connecting IEE connector plug.



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