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Old 22nd February 2012, 11:30 PM   #1
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Default Grounding issue between turntable and tube amp

Hello all. Long time lurker but first time poster. Anyway, I searched and couldn't find any previous threads relating to my particular issue. I recently purchased some tube gear (Yaqin MS-22b and Yaqin MC-10T). I was listening to the amp through my ipod the day I got it and it sounds great. But, the thing is that when I tried to listen to some vinyl, I get real bad grounding buzz. This only happens if the turntable (Thorens 147) is hooked up to the pre-amp. As soon as I unplug the rca's from the pre, the buzz goes away. The table is grounded to the pre-amp correctly and I've switched out interconnects between all three with the same results. My next step is to try another turntable (Pro-ject Xpression) but I'm afraid I'll get the same results.

Could this be an issue with the two different tubes that the pre-amp (12ax7) and the amp (12at7) have, or is it the turntable itself? I do have everything plugged into a Panamax power conditioner. Any advice would be appreciated.

Thanks
Stephen
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Old 23rd February 2012, 11:02 AM   #2
DF96 is offline DF96  England
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If you only get buzz when the turntable is connected then it can't be a valve fault. Probably a grounding problem. Does the turntable have a separate audio ground wire - most do. This needs to be grounded at the phono preamp. Any CFLs near the turntable? They can generate buzz.
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Old 23rd February 2012, 12:28 PM   #3
pointy is offline pointy  United Kingdom
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Have you tried a continuity test on the arms wires
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Old 23rd February 2012, 01:45 PM   #4
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"I do have everything plugged into a Panamax power conditioner."

Try plugging the turntable into the wall and leave the rest in the power conditioner. Some power conditioners do funny things with the ground in an attempt to remove noise riding on it. You could also try not plugging the phono stage into the pc.
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Old 23rd February 2012, 01:48 PM   #5
DF96 is offline DF96  England
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Yes, try it with just normal audio gear plugged into a normal power supply - no iPods, PCs, TVs, power conditioners etc.
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Old 23rd February 2012, 02:49 PM   #6
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Thanks guys, I'll give all those a try. The Thorens does have a grounding wire which is hooked up to the pre. I'll unplug the TT and try to plug it in somewhere else as well as moving the pre to another location. Right now its on a shelf below the TT and above the amp. I need to get another rack and re-arrange some equip. I'll let you know.

Thanks
Stephen
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Old 23rd February 2012, 04:29 PM   #7
kevinkr is offline kevinkr  United States
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Hi Steffner,
Welcome to the forum!

One other potential issue here is whether or not the cartridge grounds are also connected to the TT chassis creating a ground loop between the arm/cartridge ground and the TT chassis GND. This is easily checked with a DMM - there should be no continuity between the chassis and RCA plugs.

Another thing to look at is whether or not someone has replaced the line cord with a 3 wire grounded cord and connected the ground wire to the chassis. In this case leaving the ground wire unconnected to the pre-amp may solve the issue provided that the cartridge grounds are not connected to the chassis at some point.

I mention this because I have had a Thorens table where the cabling also carried the chassis ground through the RCA plugs, and I had to cut the link when I installed a separate ground lead to prevent a loop.
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Old 23rd February 2012, 05:34 PM   #8
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I'll have to recheck the grounding inside the TT. I rewired the tonearm some time ago and ran one wire directly from the headshell interconnect to RCA's I had Mounted on the back of the unit. The grounds (I believe) were grounded to a little PCB board. I'm pretty sure I just re-soldered the grounds from the cartridge to the old ground leads on the board.

I was running it for about 2 years like this hooked up to my Cambridge Audio 640 going into my HT receiver with no issues. In fact I did take the old pre and hooked it up to the TT/Amp with no issues. Which leads me to believe thats its a grouding issue. I'll have to try my other TT to see what that yields.

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