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 Post subject: System Hum
PostPosted: Nov Fri 15, 2019 5:09 pm 
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Location: Zeeland MI
I have a Garrard RC-210 changer that I run though either my Heathkit EA-3, or Knight Kit amp. There is the typical low level hum with either amp. My question is, what is a good way to cut that down? These older changers don't have a separate ground lead. Should I attach a wire to the base and then connect to a screw on the amp?
RW

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 Post subject: Re: System Hum
PostPosted: Nov Sat 16, 2019 1:28 am 
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Location: Metzger Oregon
I, too, have a Garrard RC-210 and I believe it does have a ground wire, though honestly it's been a long time since I have used it, and I can't say for sure. My dad bought this changer new, so if there is a ground wire it has been there since the 60s.


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 Post subject: Re: System Hum
PostPosted: Nov Sat 16, 2019 1:30 am 
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Location: Eastlake, Michigan
Can't hurt. Just run a wire from the changer chassis to a ground screw on the amp.


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 Post subject: Re: System Hum
PostPosted: Nov Sat 16, 2019 1:52 am 
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Alright. As I thought. Thanks.
RW

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 Post subject: Re: System Hum
PostPosted: Dec Sat 21, 2019 5:17 am 
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Location: Powell River BC Canada
You should check to see if the changer ground is connected to the
ground pin of the RCA plug,

Old amps may have an elaborate routing for the shield side of the magnetic cartridge
inputs. An additional loop back to ground may cause more problems.

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 Post subject: Re: System Hum
PostPosted: Jan Wed 01, 2020 8:30 pm 
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Location: Sunbury, Ohio 43074
60hz him in these systems is usually traceable to a low level ac voltage being carried on the shield. In this case, the cartridge wire shield. A direct wire ground from the reciever or amp to the turntable may help or may make it worse. It depends on if the cartridge wire assembly is grounded at the turntable or not

Try it and see......can’t really hurt. Use a decent gauge wire though. #18 at minimum. #14 better

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 Post subject: Re: System Hum
PostPosted: Jan Wed 01, 2020 10:27 pm 
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18 I have...no 14. I used to have access at my old job...nice stuff...
RW

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 Post subject: Re: System Hum
PostPosted: Jan Thu 02, 2020 1:09 am 
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Ok...here's the deal. It has a stereo cartridge that is wired for mono...followed the correct instructions in the manual. There are two sets of shielded cables from it. I've included a picture to show the grounding...the green wire is connected to ground terminal on the output side of the wiring terminal, but not on the side where the cart wiring is...should I put a jumper there? The green wire does connect to the changer.
RW


Attachments:
garrard.jpg
garrard.jpg [ 227.02 KiB | Viewed 779 times ]

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 Post subject: Re: System Hum
PostPosted: Jan Thu 02, 2020 3:25 am 
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Location: Sunbury, Ohio 43074
I can't figure out from your description what's been wired to what, and how.

Is it a stereo cartridge that you are summing into a mono? Normally I'd not expect to see the shield hooked up at the cartridge end of things... it could be floating, or it could be grounded I suppose.

If it is floating (as in not connected at the cartridge end) I'd leave it that way. The odd thing though is from the photo, that looks like coax, not shielded balanced audio cable. What is that cable now?

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 Post subject: Re: System Hum
PostPosted: Jan Thu 02, 2020 5:11 am 
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It was already wired for summing from the seller. The cable also came with it. Has a molded on RCA plug. I've nothing else to it except a new stylus about 3 years ago.

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 Post subject: Re: System Hum
PostPosted: Jan Thu 02, 2020 1:17 pm 
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Location: Sunbury, Ohio 43074
As with all such questions, there are several answers, and even several correct answers. Not knowing exactly what you have now, it's impossible to say whether or not it can be improved. Can you draw out a schematic of exactly what currently exists? The link below is just ONE of many dozens of possible wiring diagrams. This particular one is a stereo setup, but summing it to mono is really no trick.

The trick is getting both the grounding, and the shielding, correct. Those two things are not necessarily the same.

Do a google search for "turntable cartridge wiring" and read a bunch of them. And do try and draw out what you have, even if it's a hand sketch that you take a picture of to post here.

https://www.vinylengine.com/turntable_forum/viewtopic.php?t=94688

Attachment:
TT Cartridge Wiring.docx [811.76 KiB]
Downloaded 24 times
. This is a sample of a "typical" cartridge wiring. I'd rewire the turntable this way, and use an RCA Y cable to sum to mono at the amplifier.

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