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XLR input to amp module connections?

March Audio

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Great article by Bruno Putzeys here. Even has some audio humour thrown in.
https://www.edn.com/the-g-word-how-to-get-your-audio-off-the-ground/

When you get to section 4 there is a preamp to build which costs peanuts. Clever engineering by Bruno allows the use of a £6 car stereo potentiometer to produce results you would pay £ 00000 for.

As I see it the shield of the balanced cable is connected to metal shield around your audio components but not to the ground of the PCB where your delicate audio signals are.
It is a good article, linked in post #5. https://www.audiosciencereview.com/...t-to-amp-module-connections.15547/post-495454

However,

page 9

"At some point the problem became so prevalent that the AES had to enshrine the obvious into a standard. Called AES48, it patiently explains that the shield should be connected to the chassis via the shortest possible route and that connections between the PCB ground and the chassis should be made elsewhere. "

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restorer-john

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Although I tend to define myself as a Bruno fanboy, this design has a huge weakness: if the pot track breaks open, the op-amp will be open loop, which could have catastrophic consequences.
As a side note the DC removal circuit from this preamp is the same as the one used in the NAD M22.

I had noticed that too. It does beg the question of who actually designed the front end/most of the NAD M-22. It's got BP written all over it. In fact, the component choices are very, shall we say, Philips.
 
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prasanth.nath

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Edit: Updated with answers found elsewhere on the forum.

Hypex confirmed the same in an email.
In my current set up, I have connected this GND (from amp to XLR) directly to pin 1, on the amp side as well as the pre-amp (which is in a separate box).

A few things are not clear to me, and I would be grateful for an explanation:
* Where exactly should we connect this GND wire (ie, the shield form amp module to xlr chassis), and how? For egs, drill a hole an inch away from the XLR and screw it there? . Answered on page 14: https://www.audiosciencereview.com/...ore-nc252mp-its-all-amirs-fault.13195/page-14
* Why is this cable missing in the figure 24 below? Probably not relevant
* When the modules are attached directly to the metal chassis, the amp modules's PCB GND automatically gets connected to chassis because the heatsink is connected to PCB GND. DO we need to use GND-wire and connect it again to chassis? I realize now that this is a dumb question. The resistance of this path would be higher than the resistance of a direct connection, so a direct connection would be needed.
* Do we do the same procedure upstream kit - ie the source that feeds this amp box - as well? In other words should the cable shield form DLCP board to XLR should be terminated near the pin 1 (but not to pin1), just like the amps?


The module input cable screen should be connected to chassis elsewhere, not at pin 1.

see page 9 specifically but its all good info.

https://www.diyaudio.com/archive/bl...d1460406090-bruno-putzeys-micropre-g-word.pdf

"At some point the problem became so prevalent that the AES had to enshrine the obvious into a standard. Called AES48, it patiently explains that the shield should be connected to the chassis via the shortest possible route and that connections between the PCB ground and the chassis should be made elsewhere. "

View attachment 79776

View attachment 79777
 
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