Question about connecting grounds

user68 · 12th August 2010, 08:53 PM

I'm unsure how the grounds should be connected in this circuit, not having the PCB. I have the IEC earthed to chassis but all other grounds are connected together but not to chassis.

However, whether the grounds are connected to the chassis or not, I have a problem with hum being fed into my amplifier.

- Should the left channel ground circuit be connected on the board to the right channel ground or should they be separately run to the chassis?

- Should the ground from C1 and C2 negative be connected to the ground from C5 positive or should they be separately run to the chassis?

- V1 pin 4 is shown as "GND" (not an earth ground symbol like the others - is this different?). Where would this be connected?

Can anyone please advise me on the correct procedure to connect the grounds in this circuit?

Globulator · 12th August 2010, 09:03 PM

Keep signal ground away from the chassis - they are different signals and should only meet once.

The signal grounds should be connected as in the schematic 2b.
Both channels ground can run together.
Ground the chassis to the signal ground at one point only, I'd choose near the outputs.

user68 · 12th August 2010, 09:13 PM

Thanks Globulator, but what about the three tube supply grounds in schematic 2A? Should they be kept separate from the signal grounds in 2B or can they all be connected together then connected to the chassis near the outputs?

aardvarkash10 · 12th August 2010, 09:17 PM

valvewizard's EXCELLENT article on grounding schemes...

DF96 · 12th August 2010, 09:18 PM

Keep the heater ground (C5 positive) separate, apart from a single connection to the chassis which could be at the same place as the signal ground connection.

C1 negative should have two connections: one to the transformer centre-tap (which should not have its own ground connection), and the other to C2 negative. Then C2 negative should have a connection to the signal ground. This arrangement keeps the charging pulses away from the rest of the circuit.

The aim is to keep each set of currents in their own loop so they don't interact, but then have a single connection to ground which just establishes a common potential.

Globulator · 12th August 2010, 09:19 PM

Quote:

Originally Posted by user68

Thanks Globulator, but what about the three tube supply grounds in schematic 2A? Should they be kept separate from the signal grounds in 2B or can they all be connected together then connected to the chassis near the outputs?

The PSU grounds are signal grounds too, so connect them at one point to the circuit signal ground near the output.

12th August 2010, 09:17 PM	#4
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	valvewizard's EXCELLENT article on grounding schemes... __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

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12th August 2010, 09:03 PM	#2
Globulator diyAudio Member Join Date: Aug 2004 Location: Cambridge, England.	Keep signal ground away from the chassis - they are different signals and should only meet once. The signal grounds should be connected as in the schematic 2b. Both channels ground can run together. Ground the chassis to the signal ground at one point only, I'd choose near the outputs.

12th August 2010, 09:13 PM	#3
user68 diyAudio Member Join Date: Jul 2010	Thanks Globulator, but what about the three tube supply grounds in schematic 2A? Should they be kept separate from the signal grounds in 2B or can they all be connected together then connected to the chassis near the outputs?

12th August 2010, 09:18 PM	#5
DF96 diyAudio Member Join Date: May 2007	Keep the heater ground (C5 positive) separate, apart from a single connection to the chassis which could be at the same place as the signal ground connection. C1 negative should have two connections: one to the transformer centre-tap (which should not have its own ground connection), and the other to C2 negative. Then C2 negative should have a connection to the signal ground. This arrangement keeps the charging pulses away from the rest of the circuit. The aim is to keep each set of currents in their own loop so they don't interact, but then have a single connection to ground which just establishes a common potential.

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