Author Topic: Weird preamp issue! I touch the input knob or volume knob & hum/buzz appears  (Read 5562 times)

Offline sleepyguy24

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Hey everyone.

Has anyone encountered an issue like this before. I have a 12AU7 based tube preamp and if I leave the volume at normal listening & turn off the music when I touch the volume control or input control I hear a buzz coming from both speakers. When I stop touching either control the buzz stops.

The volume is a stepped one and at each time I adjust the volume I hear a pop or staticy type of noise from the speakers. I'm going to give the internals a round of deoxit later but am wondering if there is a bigger problem at hand. The preamp is about 9 years old and has seen normal usage.

Thanks in advance & if any other details are needed please let me know.

Offline jimbones

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ground issue? Did this just start happening, any changes in the set up?
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Offline sleepyguy24

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ground issue? Did this just start happening, any changes in the set up?


Evening Jim

You got my mind thinking some more on this. This weird buzzing just started happening. Before I was using this preamp as a tube buffer. It was between an Oppo BDP 83 and a refurbed Accuphase C200. When I was using it as a tube buffer Volume was set as a fixed point as well as the input. It was barely touched and when I did touch the controls nothing was heard. Now I'm bringing it back to full preamp duty as the right channel on my Accuphase is acting up.

Regarding the ground loop. Good point. I may have to test that theory out more. For kicks I took an Ebtech Hum X and put it on the preamp. Still had the weird buzzing issue.

Info about the Ebtech btw

http://www.ebtechaudio.com/humxdes.html

Also this buzzing happens only when I touch the volume control and input control only. If I touch the power knob, which is made of the same material, no buzzing. If I touch the phono inputs or outputs no buzzing. Real weird.

Well Thanks again for the ideas. You got me thinking about more potential issues. Best of luck with that MiniDSP24. I found a video on youtube where a guy was explaining stuff about it and told him of your issue. No word yet.

Offline jimbones

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go back to the original config and see if it still happens. BTW, MMA Rulz.  :rofl:
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Offline richidoo

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Sounds like internal ground issue some joint has come loose or gotten dirty. DeOxit is a good idea, do the RCAs and the PC contacts too. Wiggle the tube sockets to clean the tube pins.

It might be exacerbated recently with cold temps and lower humidity making more static electricity.
Good luck Dean

Offline Response Audio

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Sounds to me like you need a better ground from the volume control body. This is a common problem. If the body of the volume control does not have a good ground, you will experience exactly what you described.
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Offline sleepyguy24

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Sounds to me like you need a better ground from the volume control body. This is a common problem. If the body of the volume control does not have a good ground, you will experience exactly what you described.

Thanks for the advice. You are right on the money. The volume control didn't have a good ground and there were issues with the volume control itself. I had to have it changed out entirely and some re-wiring done. All is good now. I have to get used to the new volume control that was installed. It is thick. I feel I need a socket wrench to turn the volume to where I want it.

Offline BobM

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Does it happen on all source settings or only one? It may not be the preamp that has a grounding issue, it may be the source component grounding to the preamp through your RCA's and causing the hum.

Laugh and the world laughs with you. Cry and you'll have to blow your nose.

Offline sleepyguy24

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Does it happen on all source settings or only one? It may not be the preamp that has a grounding issue, it may be the source component grounding to the preamp through your RCA's and causing the hum.


Evening Bob

The hum happened on all source settings. I was using 2 inputs and no matter what source I switched to there was a very bad hum. Thanks to SG Custom Sound it is sounding great again. I wish you all could feel this volume control. Very sturdy.

Offline tmazz

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