[JN] buzz goes away when volume is mid way.

BBands bbands at gmail.com
Thu Apr 18 10:30:59 CDT 2019


Does the brand of the milk can make a difference? (Apologies...)

On Wed, Apr 17, 2019 at 9:04 PM Paul Seymour via Sound <sound at soundlist.org>
wrote:

> Thanks Stephen & all Joe's !
>
> this suggestion RE earthing the top plate got me thinking.
> I have a wooden top and I have placed the rectifier too close
> to the 6sn7s.  In hindsight.  I noticed when going to earth the
> valve plate socket that just my hand between the rectifier
> and the 6sn7 almost fixed it. To further test it I placed an old
> metal milk tin over the 6sn7 and then earthed it with a lead.
>
> GONE. Quiet as a mouse.  See pics.
> It was radiation from the rectifier. I might build an earth cage for
> it but until then I put "flashing"   aluminium with sticky back under
> the top and screwed and earth wire into it. The flashing is around
> the 6sn7. Cured about 95% of it just with this.   I guess it only
> affected 1 channel  due to the orientation of the tubes.
>
> Many thanks,
> Paul.
>
>
> [image: image.png]
>
>
> [image: image.png]
>
> On Thu, Apr 18, 2019 at 3:37 AM Stephen Robinson via Sound <
> sound at soundlist.org> wrote:
>
>> I had something not too dissimilar recently and it was cured by earthing
>> the plate the valves and transformers were mounted on; that wasn't the case
>> work. Is the pot case earthed?
>>
>> Cheers,
>>
>> Stephen
>> On 17/04/2019 18:04, Paul Seymour via Sound wrote:
>>
>>
>> Hi Jo's
>>
>> can I ask for your wisdom, I am stumped on this one.
>>
>> I have a pre amp, similar to JELabs preamp with the 76 tube,
>> except I have all 6SN7's.
>>
>> I have this BUZZ in right channel only.
>> I switched inputs and output's and always this channel
>> of the pre amp has the buzz.
>>
>> *Strangely if I turn up the volume pot on the pre amp *
>> *to mid way the buzz vanishes. (* Pot is on the input and
>> I've swapped inputs as said and it's the same result so it's
>> not the phono stage prior. )
>>
>> *If the vol pot goes right up the buzz comes back.*
>> *Only in the middle does the buzz disappear. *
>>
>> This bizarre symptom must point to something, but what?
>>
>> thanks,
>> Paul.
>>
>>
>>
>> --
>> Paul.
>>
>>
>>
>>
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>
>
> --
> Paul.
>
>
>
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