[ProAudio] Muncy Revisited: Pin 1 to chassis through a capacitor?
Richard L. Hess
lists at richardhess.com
Sat Dec 2 12:02:20 PST 2023
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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