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Hum on right channel
Hum on right channel
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Old 3rd February 2018, 07:04 PM   #1
02GF74 is offline 02GF74  United Kingdom
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Default Hum on right channel

Not sure if this is the correct section.

My set is as below.
Cyrus dad3 cd --> MF m1 dac --> Chinese 6j1 valve buffer --> cyrus pre --> krell

Connection to dac is optical toslink.
In and out of valve buffer is van den hul d102.

Now I wanted to try different cables so I have two pairs of van damme silver plated cables with wbt phono connectors.

When I replace both pairs of vdH, there is a hum on right hand speaker.
I've checked vD cables with dvm and 0 ohm so nothing to indicate a fault. I've also swapped them around and hum is the same, I. E. It does not follow a cable.

Now here is the weird bit.

I replaced the vD cable, right one going from buffer to pre with the vdH or a cheap lead, hum stops.

WTF is going on?
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Old 4th February 2018, 10:20 AM   #2
AndrewT is offline AndrewT  Scotland
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laying the cables different distances apart changes the loop area of the loop formed in the input section where the source has a common Signal Return.

If you change the loop area to VERY SMALL, you will reduce the interference picked up on the two connected returns.

Do this for both cable types and see if you can measure any difference in H+N at the outputs.
BTW,
your ears/brain are NOT any good at measuring. Use a voltmeter.

Download D.Joffe's paper on HBRR+HBRL. He explains why the interference and a solution.
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Old 4th February 2018, 10:35 AM   #3
02GF74 is offline 02GF74  United Kingdom
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I kinda follow that - I did try moving the cables away from the mains leads and to be at right angle to mains lead, no difference, admittedly I did not try to make the loops smaller (vD cables are 0.5m whereas vnH are 1.0m so the vD have smaller loop .... BUT why does it happen with 4 van Damme cables but not with 3 van Damme and 1 other cable?

Photo below shows the set up.

Orange cable is the van Damme - nothing usual about it.

Valve buffer connected with 4 van den Hul D102, 4 yellow cables.
Upper two cables are output, lowest two are input., It is the input right (lowermost cable, red mark on socket) that when replaced, makes the hum go away.
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File Type: jpg cables.jpg (100.5 KB, 81 views)
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Old 4th February 2018, 10:43 AM   #4
epicyclic is offline epicyclic  United Kingdom
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Do the VD phonos touch each other when the others don't
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Old 4th February 2018, 10:47 AM   #5
02GF74 is offline 02GF74  United Kingdom
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Oops, should have mentioned that. That was my thought too as the WBT connector are of larger diameter, so first I put pieces of paper to insulate them, then I removed all the outer body barrels (they are screw on type that allow tightening of the outer onto the phono socket) and it made no difference.
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Old 4th February 2018, 11:29 AM   #6
AndrewT is offline AndrewT  Scotland
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Have you read D.Joffe's paper yet?
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Old 9th February 2018, 05:14 PM   #7
02GF74 is offline 02GF74  United Kingdom
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I did find one paper, no sure if it is the one you refer to but I can't see how it would explain my problem, only difference in the leads is that one is silver plated copper and other is copper.
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Old 9th February 2018, 05:19 PM   #8
scottjoplin is offline scottjoplin  Wales
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This is the one he was referring to https://www.updatemydynaco.com/docum...lemsRev1p4.pdf
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Old 9th February 2018, 05:21 PM   #9
02GF74 is offline 02GF74  United Kingdom
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Yes that's the one I found.

Circuit is the same but different cable metals so how does it help?
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Old 9th February 2018, 05:29 PM   #10
scottjoplin is offline scottjoplin  Wales
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It does sound like a cross channel ground loop, the one cable that stops the hum probably has a slightly higher resistance on the screen which is enough to stop the current flowing
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