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Linn LP12 ground
Linn LP12 ground
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Old 2nd March 2020, 09:49 AM   #1
landiepete is offline landiepete  Belgium
diyAudio Member
Join Date: Aug 2014
Location: Belgium
Default Linn LP12 ground

Hello everyone,

I know this has been done to death, which is exactly why I'm unable to sift through the interwebs on this one. There is simply too much.

Here goes. I own an older Linn LP 12 with a Valhalla that I don't use very much. It has a Linn Troika MC. I had to replace the Valhalla a while back, but shelved the unit.

I reconnected it over the weekend. As the amplifier does not have a MC input, I use a Pro-Ject Phono box DS+ with amplification set to 60 dB. The amp is earthed.
Unfortunately, it hummed like a SOB. I started searching the 'net, and it appears to be a problem that's been around for decades. Funny, it hadn't bothered me when using direct amp connections (different amps). Or at least I think it didn't. Equally unfortunately, the solutions proposed in many many posts on various websites and forums sound like snake oil proffered by people who seem to lack a basic understanding of electricity.

So I opened it back up, and noticed a really funky earth/ground arrangement. The ground wire from the plug is connected to the metal cross brace where the Valhalla is mounted. OK. There's a thin black wire connecting the metal bearingplate to the brace. OK. The signal ground is run from the arm plug outside with the RCA's for connection to the phono pre-amp, which is also standard fare. But now, there is a small black wire with an eyelet - I assume is the arm ground - that is also connected to the chassis ground, which I find mightily strange. Especially since the arm is mounted on a wooden armboard and thus isolated from the metal frame. As soon as I disconneced this wire the hum all but disappeared. When I disconnected the signal ground from the phono pre-amp it became very quiet.

I am now contemplating extending the 'arm ground' to go outside with the signal ground and both connecting them o the pre-amp to there is equipotential on everything coming from the arm.

Your thoughts ? Thanks, Pete
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Old 23rd March 2020, 07:23 AM   #2
landiepete is offline landiepete  Belgium
diyAudio Member
Join Date: Aug 2014
Location: Belgium
I replaced the arm cable with a better made one I bought on the bay. I left the arm fround unconnected inside the base, but did connect the external ground wire to the phono pre amp. Problem solved.
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Old 23rd March 2020, 07:41 AM   #3
warrjon is offline warrjon  Australia
diyAudio Member
Join Date: Feb 2011
Location: Terang Vic
I had a1983 LP12 Ittok and Troika these are a pretty good rig. If it's quiet lifting the ground wire leave it.

Grounding and hum can be individual to the setup. The mains earth for instance can be a source of grounding back to the amp. Having multiple paths with different potentials is where the problem lies.

I changed the tomearm on my current rig (Technics SP10) and the thing BUZZED like crazy getting worse to the centre. Adding a ground to the TT frame tamed the buzz. This ground was not needed with my EPA100.
SP10, ...... DIY Linear tonearm, ......Stanton 881s with D3000 stylus, .....BHL phono,.........Pass B1,
MODULUS 86 power amps x4,.............Active line level OX,......... bi-amped OB speakers with Mark Audio Alpair 12P
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