[ProAudio] Muncy Revisited: Pin 1 to chassis through a capacitor?

[Richard L. Hess]

John,

I agree with you, but I think the Pin 1 of the input connector should be 
connected directly to chassis, preferably using a purpose designed XLR 
connector if you're going to be in very high RF. I think Neutrik has an 
XLR connector with Pin 1 bonded to the connector housing which is then 
bonded to the chassis. The power supply should be grounded to the 
chassis via a short lead -- remember ohms-per-square? The chassis is a 
lower impedance than any wire (as long as it's metal.

I agree with the twisted triplet from PS to amplifier board. I'm not so 
certain the chassis connection needs to come from that triplet, but 
rather a shorter jumper.

The output, while not shown, should be a floating jack with a capacitor 
directly to ground for RF bypass with the common signal lead coming from 
the amp module. If there are two amp modules (one per channel), that 
requires additional wiring.

I defer to Bill Whitlock in this. I think I'm accurately portraying his 
suggestions, but there is a lot of stuff on the Jensen Transformers 
website (or at least there was before it was bought by Radial Engineering).

Cheers,

Richard

On 2023-12-02 1:08 p.m., John Chester via ProAudio wrote:
> On 12/2/23 12:21 PM, Bob Katz via ProAudio wrote:
>
>> Naturally, I started a firestorm on facebook asking a question about 
>> grounding in a headphone amplifier I'm building. 
>
>
> A ground loop running through both the headphone amp and the power 
> supply board doesn't seem like a good idea to me.  Here's my revision 
> of your diagram:
>
> https://photos.app.goo.gl/gWfABiqTc82mKZLV9
>
> I wouldn't opine on whether the ground loop will upset the power 
> supply without seeing both the power supply schematic and the PC board 
> layout -- assuming it's not a potted blob.  Best to just get rid of 
> the ground loop.  Zero volts to chassis ground should be on the DC 
> side of the power supply, never on the AC side.
>
> Zero volts to chassis should occur before the zero volt line gets to 
> the headphone amp, not after.  IMO the most cautious approach to power 
> supply wiring would be to run 3 twisted wires from the power supply to 
> the chassis ground point, where the zero volt line gets connected to 
> chassis, and then continue with 3 twisted wires to the headphone amp 
> board.
>
> -- John Chester
>
>
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-- 
Richard L. Hess                           AES Life Fellow
Aurora, Ontario, Canadarichard at richardhess.com
http://www.richardhess.com/tape               647 479 2800
http://www.richardhess.com/notes    Quality tape transfers
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