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#1
23rd January 2008, 05:56 PM
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Phono3S hum
Hello everyone and a happy new year
I am having a bit of a problem with my newly built Phono3s and Pre3. When I switch to Phono 2 ie the moving coil I/P I get a hum which gets louder the more I turn up the volume. If I switch to either the Phono 1 I/P or mute no hum but I do get a sort of mush, which is the best way I can describe the sound, again this gets louder the more I turn up the volume. I have used option 1 on the Phono3s build and have a DNM Aciore cartridge which I belive to be 5mV O/P. The other problem I have is with the Pre3 I do not have to turn the volume up very far on any I/P before the sound becomes to loud. The power amps are WAD 300B PSE. Any advice would be most welcome. Thanks Archie 
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#2
23rd January 2008, 06:37 PM
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Re: Phono3S hum
Hi Archie-i'm still trying to find the hum on my Phono3s,but its not the same as you describe !
Try the shunt mod (see FAQ ) on your volume pot and that will help. Philip
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Philip. Everything in this post is my honest opinion based on what i thought I knew at that very moment in time. 
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#3
23rd January 2008, 07:02 PM
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Re: Phono3S hum
Hi ArchieH,
refering to your hi vol problem, check out this thread http://www.wduk.worldomain.net/forum...ead.php?t=3830 where we discussed matching the PRE3 to WAD amps. I used the mod recommended to attenuate the PRE3 output into my amp and it works well. Cheers, Jeremy.
__________________
We're all in control with a nice tight proportional band!
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#4
23rd January 2008, 11:12 PM
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Re: Phono3S hum
Hi Archie
Let us do one thing at a time. I am pretty sure that the "mush" you describe is standard high gain valve shot noise so initailly do not worry about it. So............... Does the Phono III Hum with the pickup leads removed from the inputs? Do you have the cover bolted on and earthed as I said in another thread? John - Dr John
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#5
24th January 2008, 06:18 PM
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Re: Phono3S hum
Hi all
Just back from work, thanks for your replys. Dr john I think I will go with your suggestion of one thing at a time I will check the earthing to the cover and let you know. thanks Archie
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#6
24th January 2008, 07:15 PM
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Re: Phono3S hum
Dr John
Checked my earthing and found cover was not earthed at all, also clips holding MC transformers were not earthed. Hum now on both phono 1 and phono 2 I/P and mute position no change if I disconnect the turntable also no change if I earth Phono3s to either Pre3 or Psu3. Have I done something to make things worse or am I on the right track with some way to go ? Archie
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