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In Reply to: Re: Terraplane Buzz posted by smart845 on January 12, 2007 at 00:36:33:
You are talking about the common mode choke on the filament supply. Not the Power Supply choke.Mine too buzzed, I too am on 240V - drove me nuts. I built my DRDs myself and added the Star Chief upgrade.
I eventually took it to someone with a scope and he traced it to the common mode chokes which are supposed to be an upgrade to the standard DRD. Once the chokes were removed the amps were dead quiet.
They are indeed excellent amplifiers.
Follow Ups:
Hi Furry,yes I should have been a bit more specific. Weird how this happens with 220V. Anyone know why? It also made the wirewound resistor vibrate and get hot too!
It does seem unlikely on the face of it, but it might be the 50Hz rather than the 220v that is a cause. Not knowing the parts in question, I could not speculate any further.
<> I think you are almost certainly right, on the secondary side of the Power transformer the voltage should be identical to that in the US versions, but the AC frequency on the filaments would be different, it doesn't seem like American owners are experiencing this problem.
I can't begin to imagine why the mains AC frequency should make a difference though.
Thank you everyone for the suggestions.In my amps the buzz is low level and the same in both amps. I am located in North Amercia.
Did you build them yourself?This is wild speculation, but the only thing I can think of is that the Power Supply rectifier diodes are buzzing, which is normal, but with the chassis closed shouldn't really be audible. If somehow this buzzing vibration is being transferred to the top or bottom plate and causing it to vibrate in sympathy then it may be audible.
If you think this might be the case then mechanically decoupling the PSU module from the rest of the chassis with rubber washers or grommets might be the remedy. I'd be wary about any damping to the diodes themselves though because they need to be able to dissipate heat effectively.
The amplifiers were assembled by Ron Welborne himself. Yes, the chassis is closed. The buzz is not loud, but can be heard in a reasonably quiet room three feet from the chassis.
Son House
Hmm. Not really sure what to suggest. I have to virtually stick my ear on my star chiefs to hear the diode switching-noise.With any luck it will diminish in your amps. If not I suppose you can post on DIY asylum and see if there is a competent DIY guy in your area who can have a look for you, or you can send 'em back to Ron...
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