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Old 15th June 2006, 01:23 AM   #1
taj is offline taj
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Default Need grounding advice

I'm almost ready to start wiring my AudioSector module chipamp but I'm a little (a lot) unclear on how best to ground everything for minimum hum/buzz.

Here's a drawing of what I've come up with based on my chassis layout. Am I close?

..Todd
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Old 15th June 2006, 05:51 AM   #2
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Three things:

1: The Star Ground should be the AC Ground Primary
2: (Correct me if I'm Wrong, but doesn't the ground output need to be connected to V-? You might have problems getting any sound...
EDIT: 3: Just the case should be AC Primary Ground. The rest of the stuff like the smoothing caps (if they're 2 in serial) and other "GND" things should be connected to the transformer's ground! Don't let those grounds get mixed up.
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Old 15th June 2006, 02:37 PM   #3
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Quote:
Originally posted by DJ Exprice
Three things:

1: The Star Ground should be the AC Ground Primary
Yes, and connected to the chassis, correct?

Quote:

2: (Correct me if I'm Wrong, but doesn't the ground output need to be connected to V-? You might have problems getting any sound...
You lost me here. Is your "ground output" the black speaker terminal? In most amplifier schematics I've looked at, it's tied to earth/AC/chassis ground. I don't think I understand what you're saying.


Quote:

EDIT: 3: Just the case should be AC Primary Ground. The rest of the stuff like the smoothing caps (if they're 2 in serial) and other "GND" things should be connected to the transformer's ground! Don't let those grounds get mixed up.
I think you're referring to 'signal ground' versus 'chassis/AC/earth ground' right? But I don't understand what you mean regarding transformer ground. Do you mean the center tap of the secondaries should NOT be tied to AC ground?

Thanks DJ.

..Todd
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Old 15th June 2006, 02:46 PM   #4
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Quote:
Yes, and connected to the chassis, correct?
Good.

Quote:
You lost me here. Is your "ground output" the black speaker terminal? In most amplifier schematics I've looked at, it's tied to earth/AC/chassis ground. I don't think I understand what you're saying.
Yes - I was talking about signal ground. I'm not sure about the black terminal needing to be what, but maybe somebody else knows...


Quote:
I think you're referring to 'signal ground' versus 'chassis/AC/earth ground' right? But I don't understand what you mean regarding transformer ground. Do you mean the center tap of the secondaries should NOT be tied to AC ground?

Center tap and AC Primary ground shouldn't touch unless the 0v one the transformer is PERFECTLY 0v. I wouldn't connect them.
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Old 15th June 2006, 03:15 PM   #5
kvholio is offline kvholio  Netherlands
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Taj, just some questions: do your transformers have 2 independent secondary`windings ?
Are you using the audiosector rectifier-pcb with all 8 diodes ?


with kind regards,

Klaas
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Old 15th June 2006, 03:25 PM   #6
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Quote:
Originally posted by kvholio
Taj, just some questions: do your transformers have 2 independent secondary`windings ?
Are you using the audiosector rectifier-pcb with all 8 diodes ?


with kind regards,

Klaas

Yes and Yes.

..Todd
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Old 15th June 2006, 03:38 PM   #7
kvholio is offline kvholio  Netherlands
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Thanks Todd. You can connect one secondary winding to rectifier-pcb at 2 points both marked "ac1", and the other secondary winding to points marked "ac2".(so you DONT connect the secondary windings to eachother).

Connect pg- from rectifier-board to pg- on amplifier-board, and of course pg+ from rectifier-board to pg+ on amplifier-board.It's also a good idea to twist those wires.
Please get back and tell if this makes sense to you - i know there's more connections to be made, like to take it one step at a time.

With kind regards,

Klaas
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Old 15th June 2006, 07:03 PM   #8
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Quote:
Originally posted by kvholio
Thanks Todd. You can connect one secondary winding to rectifier-pcb at 2 points both marked "ac1", and the other secondary winding to points marked "ac2".(so you DONT connect the secondary windings to eachother).

Connect pg- from rectifier-board to pg- on amplifier-board, and of course pg+ from rectifier-board to pg+ on amplifier-board.It's also a good idea to twist those wires.
Please get back and tell if this makes sense to you - i know there's more connections to be made, like to take it one step at a time.

With kind regards,

Klaas
Yes, of course you are right. I wasn't thinking properly when I drew that picture. I would have discovered that as soon as I began connecting it together. I'm more confused about which items need to be connected to the star ground. Especially regarding input and output jack grounds.

And Daniel mentioned using resistors between signal ground and AC ground. I assume this is done on the AMP board where it is marked CH gnd. From there to resistors to star?

..Todd
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Old 15th June 2006, 10:04 PM   #9
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I have noticed a lot of confusion on these forums as to how to ground the GainClone. Myself included.

I've seen plenty of different ways of doing it, none labeled as "correct". The PDF on chipamp.com for the LM3875 kit instructs the user to connect both CHG (chassis ground) wires from the amplifier boards to the AC earth ground pin on the IEC connector, and to the chassis. Physical details on this are vague.

Then I've seen all kinds of other configurations. Including using the chassis as ground for the negative binding post and negative signal input. Then there are people using 10R resistors to chassis ground. This doesn't make sense to me.

What we need is Peter Daniel or BrianGT to step up and explain the correct way to do it, WITHOUT options.

I also made the mistake of using ONE toroid and TWO rectifier boards, only to find out later that that is not true dual mono and will most likely introduce hum. If my right channel hadn't blown up I would be able to confirm that.
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Old 15th June 2006, 10:30 PM   #10
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Quote:
Originally posted by phorensic
I have noticed a lot of confusion on these forums as to how to ground the GainClone. Myself included.

I've seen plenty of different ways of doing it, none labeled as "correct". The PDF on chipamp.com for the LM3875 kit instructs the user to connect both CHG (chassis ground) wires from the amplifier boards to the AC earth ground pin on the IEC connector, and to the chassis. Physical details on this are vague.

Then I've seen all kinds of other configurations. Including using the chassis as ground for the negative binding post and negative signal input. Then there are people using 10R resistors to chassis ground. This doesn't make sense to me.

What we need is Peter Daniel or BrianGT to step up and explain the correct way to do it, WITHOUT options.

I also made the mistake of using ONE toroid and TWO rectifier boards, only to find out later that that is not true dual mono and will most likely introduce hum. If my right channel hadn't blown up I would be able to confirm that.
I'm sure you're right; there are plenty of ways to accomplish a good quiet ground system. "Correct" will probably have many variations.

I suspect the ChipAmp forum (if I am at all typical) is where amp builder's begin their hobby, rather than dive straight into a Nelson Pass design, for example. For that reason, I think it's normal to expect more confusion in this area.

You are also right that it would be nice to see Daniel or Brian chip in (no pun intended) with some advice. As Daniel well knows, I'll be happy to document/illustrate any schemes deemed "correct". They are not, however, the only ones able to offer advice in this area, and the other helpful souls that reside here can straighten us newbies out just as well methinks.

..Todd
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