Reducing hum, noise and ground loops?

[thor.zmt]

Yes you can. But, assuming some sort of balanced input, "we" don't do that because it's not the correct way to optimise the interconnection.
Pin 1 should go straight chassis. There is an AES paper / standard on this since IIRC more than 20 years

If you do this it is vital to not use Pin 1 as audio ground.

And no, Pin 1 to chassis is not a standard, nor is it a formal AES recommendation.

Correction, there does appears to be an AES recommendation, AES48-2005.

I still consider that ideally screen and audio ground are connected separately, HOWEVER, if the majority of equipment follows AES48-2005 and uses shielded single pair WITHOUT separate ground connection, following AES48-2005 is expedient.

Both AES48 and my own recommendation agree that the shield should be terminated directly to the chassis under all conditions and the connection between audio circuit (ground) and chassis should be at the star point.

Back to my original point and post.

I feel that while what is written in that paper is technically correct, given that XLR is actually a 4-pin system (Pin 1, Pin 2, Pin 3 and Shell - Pin 4) I hold the opinion that it is preferable to treat Pin 1 as audio ground and Pin 4 as screen.

If such a device is interconnected using a cable and second device following "pin 1 to chassis" (or with a cable that follows the "4-Wire system" but a second Pin 1 to chassis device) it remains fully compatible and will perform as well as possible in the context.

But improved performance (reduced noise sensitivity, improved resistance to EMI/RFI) is possible in a system that is completely build on the separation between signal ground and screen / chassis.

If there is any need to debate this (there really should not be any), I suggest we do in the thread I split off, to preserve SNR here:

Are there things that can be addressed in older circuits to modify them to deal better with the wireless routers and such?

Thor

 

[scott2000]

Yes and no. The whole electrical behaviour must be considered. Generally, if you have an older piece of equipment, that has unacceptable power supply noise (Tube and transistors) replacing all electrolytic capacitors will usually lower noise, if the device is >> 10 Years old.

Weird that I just saw a video last night showing this (increasing main filter cap value) on an old kenwood amplifier. Settled some oscillations near peak output and actually improved low frequency response too.

So, as far as today's noisy environment, rf.... this is obviously a separate issue and capacitors in a circuit don't need to be included or rethought in this discussion?

 

[thor.zmt]

Weird that I just saw a video last night showing this (increasing main filter cap value) on an old kenwood amplifier. Settled some oscillations near peak output and actually improved low frequency response too.

Quite possible. Electrochemical capacitors age poorly. Even 10 years on the shelf means at least re-forming is needed.

So, as far as today's noisy environment, rf.... this is obviously a separate issue and capacitors in a circuit don't need to be included or rethought in this discussion?

Capacitors are crucial, but this thread about the OP's Hum and Noise problem. Which may (or may may not) turn out to be old power supply capacitors, not RFI/EMI etc. So it is better off in my new thread I think.

Thor

 

[Cqwet Dbdfte]

Tubes were made with plugs for sockets, maybe the liquid caps should have had the same.
I have no longterm experience with OSCON's, other than one that shorted out on a videocard, damaging not only the video card, but also the motherboard and the stuff plugged in to it.
Paper in oil has better long term prospects.