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Old 24th April 2013, 12:16 AM   #11
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What I would do is establish another star ground, isolated from chassis, that will be your "Main Audio Ground". Ground from each power supply board to this ground (fat wires). Ground from each amp board to this ground (fat wires). Ground from negative speaker posts to this ground (fat wires). All RCA's and binding post's definitely isolated from chassis. Twisted pair from each RCA to amp board (small wires). Single CL-60 from "Main Audio Ground" to your already established "Earth Ground". No other grounds. And I always do my earth ground the way it's shown at figure 3 with the star washers and everything: Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
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Old 24th April 2013, 12:21 AM   #12
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Hi,
Just so you can have an idea of the star ground attached it is drawing showing it. Also I used a ground breaker.
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Old 24th April 2013, 10:17 AM   #13
AndrewT is offline AndrewT  Scotland
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With ONE dual secondary transformer, you should not have TWO dual polarity supplies.
Each amplifier requires it's own Main Audio Ground. One pair of dual secondaries cannot have two Main Audio Grounds. It can only have ONE.
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Old 24th April 2013, 10:22 AM   #14
AndrewT is offline AndrewT  Scotland
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in diagram post1 you have shown STAR ground.
It is not.
The mains PE wire should be bolted to the chassis where it enters the chassis.
The transformer screen should be bolted to the chassis at the transformer using the shortest possible screen leadout wire.
The Two NTCs can be bolted to any part of the chassis. They do not need to meet up with any of the other chassis connected wires.

The Star Ground is an Audio Ground that all parts of the Audio circuit can take a reference. Since you have a two channel amplifier running from ONE pair of secondaries, you MUST create a common Main Audio Ground for the two channels. This is the thick wire that Zen is referring to. For best performance this wire should have zero length. This is an impossible target. Make it as short as possible.
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Last edited by AndrewT; 24th April 2013 at 10:36 AM.
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Old 8th May 2013, 05:25 PM   #15
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Hello,
Sorry for the delay on the response to your suggestions. I have ordered a few new parts and some wire. I have received everything and my amp is on the bench ready for a new grounding scheme. There are some conflicting suggestions written above..

This is what I would like to do:
Quote:
What I would do is establish another star ground, isolated from chassis, that will be your "Main Audio Ground". Ground from each power supply board to this ground (fat wires). Ground from each amp board to this ground (fat wires). Ground from negative speaker posts to this ground (fat wires). All RCA's and binding post's definitely isolated from chassis. Twisted pair from each RCA to amp board (small wires). Single CL-60 from "Main Audio Ground" to your already established "Earth Ground". No other grounds. And I always do my earth ground the way it's shown at figure 3 with the star washers and everything: Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
I have read this article as well as a few others that are highly regarded. Here are my last remaining questions..
1. Does "Main Audio Ground" need to be fully isolated from chassis? How would you recommend doing this?
2. Is a single CL-60 between "Main Audio Ground" and Safety Earth a good replacement for a "ground loop breaker".
3. Should my transformer shield wire go to "Main Audio Ground" or to its own independent place on the chassis?

Here are my tentative connections:

MAIN AUDIO GROUND: PSU Boards, AMP Boards, NEG Speaker Posts (Six Wires).

Twisted Pair from RCA input to AMP board.

Main Audio Ground connected to Safety Earth via CL-60 Thermistor.

I would be forever grateful for clarification. I have the day off today so I would like to get started. Thanks so much in advance

-Madison
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Old 8th May 2013, 06:01 PM   #16
basi is offline basi  Croatia
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This is Star Grounding.P.S Remove your black and blue wire between amp boards.

Click the image to open in full size.
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Old 8th May 2013, 06:20 PM   #17
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OK great, thanks so much.. This is almost exactly what I had in mind.

Is it necessary to have two wires from each AMP board to Main Audio Ground (GND and INgnd).

Should I leave the two CL-60's in place? Connect them both the Main Audio Ground?

Should main audio ground be isolated from chassis?

Thanks so so much
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Old 8th May 2013, 06:20 PM   #18
6L6 is offline 6L6  United States
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Main audio ground must be isolated through a ground loop breaker - in this case the CL-60.

Safety earth NEVER is connected through the CL-60, it must be on chassis metal (the PSU ground, and therefore the main audio ground) is what's isolated from the chassis, through the CL-60)

Transformer shield should connect to the chassis, as AndrewT explained.


Hopefully your efforts will make things quieter!
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Old 8th May 2013, 06:29 PM   #19
basi is offline basi  Croatia
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Quote:
Originally Posted by madisonroberts View Post
OK great, thanks so much.. This is almost exactly what I had in mind.

Is it necessary to have two wires from each AMP board to Main Audio Ground (GND and INgnd).



Thanks so so much
No if they are connected on amp board.
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Old 8th May 2013, 06:39 PM   #20
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1. Main Audio Ground definitely isolated from chassis. I have attached a picture of what I used in my monoblocks. I have this mounted a short distance from the big filter caps.
2. CL-60 is OK as a ground loop breaker
3. I agree with 6L6, follow Andrew's suggestion

Safety Earth should really be very near your AC inlet, connected very securely to the chassis as shown in that article if possible.
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