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  #1  
Old 22nd January 2013, 09:17 PM
JonnyCJ JonnyCJ is offline
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Default One for the brains amongst us !

It's the dreaded speaker hum. (Pre 3 and Phono 3 through QUAD II's)

It only appears when Phono, Tuner, Aux, Tape or mute are selected on the Pre. Selecting CD eliminates it totally.

So far I've eliminated the valves in the Pre and Phono by swapping them back to the JJ originals and the hum remains.

Removing the ground wire on the tone arm from the Phono increases the hum, but changes the pitch slightly. Connecting the ground wire to the chassis ground on the Pre gives the same tone hum as having it connected to the Phono.

Not sure what that evidence tells you, but hopefully someone will be able to deduce where lies the source of hum.

Source is a Garrard 301 and speakers are ESL 57's

Thanks in advance !

Jonny
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  #2  
Old 23rd January 2013, 09:40 AM
John Caswell John Caswell is offline
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Default Re: One for the brains amongst us !

Hi Jonny,
First remove ALL sources from PreIII, Is the hum still there, and whether the volume is up or down
Then plug each source in one by one to see which if any or all give you the hum.
Report back.

John
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  #3  
Old 23rd January 2013, 06:02 PM
JonnyCJ JonnyCJ is offline
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Default Re: One for the brains amongst us !

Results as follows - only sources are CD and TT.

All disconnected - no hum

CD connected only - no hum

Phono 3 connected - hum

As each interconnect goes into the Pre 3 from the Phono 3 the hum appears equally on each speaker. Hum is increased as the volume is turned up.

Tonearm cable disconnected & ground wire disconnected from Phono 3 - hum stays the same.

Effectively it appears that the hum is caused by the connections from the Phono 3 to the Pre 3.

I've tried putting the Phono and Pre on separate shelves of my hifi rack, with 25mm slate in between and this makes no difference. The power unit is on a 3rd shelf, again with 25mm slate in between.

Incidentally, when the cd is playing but Phono 2 is selected (the input selection for the TT) I can hear the CD track very faintly.

Hopefully that gives you some food for thought !

Many thanks

Jonny

Last edited by JonnyCJ; 23rd January 2013 at 07:53 PM.
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Old 23rd January 2013, 09:23 PM
JonnyCJ JonnyCJ is offline
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Default Re: One for the brains amongst us !

Just been reading some of the hum threads on the Problems page and have eliminated the wallwart that was plugged into the Tacima multi socket mains conditioner.

More info - the hum occurs on the Phono 2 output only, which is the MC selector.
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  #5  
Old 23rd January 2013, 10:47 PM
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Greg. Greg. is online now
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Default Re: One for the brains amongst us !

Your post is a little confusing. You start talking about Phono 3 and then talk about Phono 2. Which are you using?

Where is Pre 3 located in respect of your power amp and what is that power amp? Regardless of thick slate, how far apart are they? How close is Phono 2?3 to you power amp?
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Old 24th January 2013, 07:34 AM
bob orbell bob orbell is offline
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Default Re: One for the brains amongst us !

Hi Greg. I think Jonny means no 2 input, on phono 3, Jonny, dose the hum go away when no 1 is selected, if so you may have something wrong with the grounding of the SUT's. BOB
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Old 24th January 2013, 10:53 AM
JonnyCJ JonnyCJ is offline
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Default Re: One for the brains amongst us !

Sorry for the confusion - I was talking about the Phono 2 selection on my Phono 3.

When Phono 1 is selected the hum goes away completely and I'm left with just a bit of very faint valve crackle.

The PSU is a PSU 3 and is on a separate 25mm slate shelf directly below the PRE 3. They're approx 100mm apart vertically. The Phono 3 is to the right of the Pre 3 on the same shelf with a gap of approx 150mm.

If I move the Phono 3 away from the Pre 3 the hum becomes a little louder. This places it more directly underneath the QUAD II monoblock.

Could it be an earth issue with the QUAD ?
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Old 24th January 2013, 12:07 PM
bob orbell bob orbell is offline
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Default Re: One for the brains amongst us !

Jonny, it sounds like your SUT's are picking up EMF from the Quad, can you move the Quad's well away from Pre and Phono? BOB
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  #9  
Old 24th January 2013, 12:27 PM
John Caswell John Caswell is offline
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Default Re: One for the brains amongst us !

Jonny you haven't said if it is MM or MC. If MC felonies are compounded
As moving nearer the Quads causes hum to increase as I suspect moving it nearer PSU III will also do the same.
Phono III with SUT needs a good 30cm or more from ANY power transformer to be quiet and hum free, this is because it has so much gain built in to it. I think you may have to juggle components around to achieve this. Can you not place the Quads on the floor for instance
John
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Old 24th January 2013, 12:34 PM
justin brown justin brown is offline
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Default Re: One for the brains amongst us !

Apologies Jonny for using this space- but I have sent you a pm John (about my 300b); I have lost your email address.

Justin.
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