amp grounding schemes - Page 4

AndrewT · 14th April 2006, 09:21 AM

Hi Bensen,
Re layout in post25; just as you said, the signal ground from output board to signal ground needs to be omitted because you have a combined ground on the output board.

The other signal grounds (three from input and two low level stages) come together at the signal ground. The layout shows this signal ground running to the short ground leg feeding the 15V supply. Try this but also try connecting Signal-GNDs direct to Power-GNDs. As a third alternative try connecting Signal-GNDs via 10r to Power-GNDs.

Finally there are too many power grounds running to the output board; the thick green lines should go from 48V ground to Power-GNDs. Then the choice is take it from the PSU common or take the thick green from the short link running to the 15V PSU.

Re post26 earthing layout; there are safety grounds connected to the mains earthing system. These MUST be connected as shown.

There are also connections inside the gear from safety ground to either signal or power ground. These must be broken and the signal/power grounds left floating with respect to the chassis/safety ground. Now there is no hum/earth loop. This is where you can now fit the disconnecting network using that range of components including a ground lift switch but this lift switch must only be closed on ONE component. Experiment to find which component or none gives the quietest result.

Bensen · 15th April 2006, 03:12 PM

The humm is gone

I've put the wires as in the attachment of post #22.
Thanks Cortez for your clear drawings.

Greetz
Ben

Cortez · 15th April 2006, 04:21 PM

Cool, I'am happy for the silance!

Cortez · 17th April 2006, 02:39 PM

What about this one ?
The point: the high current GND wire from the speaker goes
directly to the main filter caps as near to their legs as possible.
And the signal GND goes to the wire that connects to two caps.

Cortez · 17th April 2006, 02:52 PM

Or the GND should be right on the rectifier ?
Because now the large charging current impulses
are shared with the speaker current on these wires ?

Bensen · 18th April 2006, 03:41 PM

Quote:

Originally posted by Cortez
What about this one ?
The point: the high current GND wire from the speaker goes
directly to the main filter caps as near to their legs as possible.
And the signal GND goes to the wire that connects to two caps.

Yes Cortez,

I do that always in my amps, except for this one, this is a bridged amp.

Greetz

14th April 2006, 09:21 AM	#31
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi Bensen, Re layout in post25; just as you said, the signal ground from output board to signal ground needs to be omitted because you have a combined ground on the output board. The other signal grounds (three from input and two low level stages) come together at the signal ground. The layout shows this signal ground running to the short ground leg feeding the 15V supply. Try this but also try connecting Signal-GNDs direct to Power-GNDs. As a third alternative try connecting Signal-GNDs via 10r to Power-GNDs. Finally there are too many power grounds running to the output board; the thick green lines should go from 48V ground to Power-GNDs. Then the choice is take it from the PSU common or take the thick green from the short link running to the 15V PSU. Re post26 earthing layout; there are safety grounds connected to the mains earthing system. These MUST be connected as shown. There are also connections inside the gear from safety ground to either signal or power ground. These must be broken and the signal/power grounds left floating with respect to the chassis/safety ground. Now there is no hum/earth loop. This is where you can now fit the disconnecting network using that range of components including a ground lift switch but this lift switch must only be closed on ONE component. Experiment to find which component or none gives the quietest result. __________________ regards Andrew T.

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15th April 2006, 03:12 PM	#32
Bensen diyAudio Member Join Date: May 2003 Location: Belgium, Limburg, Bree	The humm is gone I've put the wires as in the attachment of post #22. Thanks Cortez for your clear drawings. Greetz Ben

15th April 2006, 04:21 PM	#33
Cortez diyAudio Member Join Date: Dec 2002 Location: Hungary	Cool, I'am happy for the silance!

17th April 2006, 02:52 PM	#35
Cortez diyAudio Member Join Date: Dec 2002 Location: Hungary	Or the GND should be right on the rectifier ? Because now the large charging current impulses are shared with the speaker current on these wires ?

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