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Old 20th December 2002, 07:20 PM   #1
G is offline G  United States
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Default Question about using RCA jacks.

Hi All,

I have a question for the gallery. When I first got interested in tube DIY i used to frequent the Bottlehead forum a lot. I seem to remember reading that if you connect a .1uF cap from the signal negative of a chassis mount RCA jack to the chassis as well as using a wire to establish the signal negative for it's corresponding channel that there was some benefit to be had. Is this true? Has anyone used this "trick of the trade"? Also I plan on soldering a chassis ground wire to the approximate center of my chassis and to the star ground point of my amplifier. Is the spot that I choose for the chassis ground connection crucial when using the star grounding method?

Gavin Haley
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Old 20th December 2002, 07:49 PM   #2
Joel is offline Joel  United States
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The best thing to do is to connect the RCA jack directly to the chassis (no insulation). The negative side of the input jack is the only point on the chassis that all the grounds should be then tied to (via a heavy bus wire).
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Old 20th December 2002, 08:21 PM   #3
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Default GROUNDING

Hi,

What good is a cap going to do there?
It will ground AC at the negative side of the input but a wire grounds AC and DC to the ground already.

Joel,

One hell of a way to upset a grounding scheme is to use uninsulated RCA connectors.

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Old 20th December 2002, 08:35 PM   #4
tiroth is offline tiroth  United States
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Well, chassis ground may not be chosen as the same as small signal ground. Unless you enjoy circulating currents in the chassis.

CW says that if chassis ground differs from signal ground you ensure they are grounded in AC but you prevent DC currents from flowing. Is this a good strategy? hmmm....

I think this has been discussed before.
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Old 20th December 2002, 08:38 PM   #5
Joel is offline Joel  United States
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Frank, the point of lowest signal voltage is where you should tie the ground lines to the chassis. That happens to be at the input jack.
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Old 20th December 2002, 08:50 PM   #6
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Default I SEE.

Hi,

What I think you are confusing is the use of a smal cap between powercord ground and chassis.

Joel,

No,not necessarilly.
And how many grounding points are you going to have then on say a preamp with multiple inputs?
Or a stereo amp for that matter?

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Old 20th December 2002, 08:56 PM   #7
Joel is offline Joel  United States
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Default Re: I SEE.

Quote:
Originally posted by fdegrove
Joel,
No,not necessarilly.
And how many grounding points are you going to have then on say a preamp with multiple inputs?
Or a stereo amp for that matter?
DO you have to complicate everything? Is it compulsive? I really think you need help.
The 1/2" between the jacks is IRRELEVANT. If you don't like that idea - fine! - float your jacks, and put a chassis lug inbetween them. Tie your ground bus there. Done. End of story.
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Old 20th December 2002, 08:58 PM   #8
Joel is offline Joel  United States
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Frank, you really must evaluate your preferences. Go back and look over all your posts in the past. Have you EVER opted for the simplest measure??? I don't think so. The more complicated, the more you like it.
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Old 20th December 2002, 08:59 PM   #9
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Default LIFE SUX

Joel,

The point of joining a forum is to communicate,no?

Cheers,
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Old 20th December 2002, 09:25 PM   #10
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Default THE ART OF GROUNDING

Hi,

Quote:
Also I plan on soldering a chassis ground wire to the approximate center of my chassis and to the star ground point of my amplifier. Is the spot that I choose for the chassis ground connection crucial when using the star grounding method?
The center isn't what you need to use.although it can be a good poit to ground.
Basically you need a place where ground current activity is lowest.

Some experimenting may be called for and a scope is certainly helpful.
If you dont have one choos a place inside the chassis away from xformers and psu filtering and try it out.

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