Simple power supply grounding questions

[Winston OBoogie]

... I do not own any of the original german studio / broadcast cassettes of the late tube technology phase like V72 etc. with the Tuchel connectors. But it seems to me, that most of the schematics have zero Volt lines not connected to the earth/case ground. Maybe I'm wrong, I've never seen the racks either, but if not, what was the reason for this seemingly strict separation of Zero and case/earth ?
edited: case not chassis - chassis might have been on 0V.

In a multi amplifier environment such as a desk, the zero volt lines from the V72's were taken back to a bus, and this bus made one connection to the desk chassis and earth at the rear of the desk.
At the amplifiers, although the metalwork of each amplifier would be in contact with the rack and frame metalwork once inserted into the rack, it was also usual to bond the chassis connection on the amplifier's tuchel connector to the rack chassis.
The only other connection to the individual amplifier's chassis were cable screens, both inside the amplifier, and on the cable forms running to/from the rear connector. Only one end of the cable screens on the cabling was connected to a chassis point.

 

[abbey road d enfer]

In a multi amplifier environment such as a desk, the zero volt lines from the V72's were taken back to a bus, and this bus made one connection to the desk chassis and earth at the rear of the desk.
At the amplifiers, although the metalwork of each amplifier would be in contact with the rack and frame metalwork once inserted into the rack, it was also usual to bond the chassis connection on the amplifier's tuchel connector to the rack chassis.
The only other connection to the individual amplifier's chassis were cable screens, both inside the amplifier, and on the cable forms running to/from the rear connector. Only one end of the cable screens on the cabling was connected to a chassis point.

This example is not typical anymore of a "modern" mixer. Since every inlet/outlet is balanced/floating, the multiple 0V do not strictly need to be interconnected.
I think the way these are interconnected, mesh or star, is indifferent.
In most modern miwers, power distribution is of utmost consideration, and I maintain that ground follows signal is what gives the best results in terms of noise.

 

[Bo Deadly]

This example is not typical anymore of a "modern" mixer. Since every inlet/outlet is balanced/floating, the multiple 0V do not strictly need to be interconnected.
I think the way these are interconnected, mesh or star, is indifferent.

I'm not sure that's what Winston said. He said 0V is connected to the chassis and earth at one place in the back. That's entirely consistent with modern gear. The metalwork was a "mesh" which is of little interest as it's all just shielding and not carrying signal.

Although modern mixers are known to use ground cancelling summing but that only works if the channels are fairly isolated from each other such as because they're so simple that they don't have direct outs or inserts (like a small format Mackie) or the extra channel IO is balanced. Not sure if impedance balanced would be ok with ground cancelling summing. I suppose you would just loose a little of the ground cancelling benefit but the channel would still work ok.

 

[Winston OBoogie]

Yep, correct. One connection only between the OV lines from the individual amplifiers and chassis/earth. I was specifically answering member Sc's question regarding how the old German valve equipment amplifier cassettes were configured in the racks.

For the record, those valve amplifiers/gain blocks each contained their own internal power supply - power transformer, rectifier, smoothing/flitering etc., which may have been why SC was asking how a multi module setup was handled.

 

[abbey road d enfer]

For the record, those valve amplifiers/gain blocks each contained their own internal power supply - power transformer, rectifier, smoothing/flitering etc.,

A clever way of eschewing the pitfalls of noiseless grounding. But quite costly.

 

[Sc]

Yep got it now - thank you. Amazing gear, still priceless.

 

[Yash]

If you get the right SMPS and you use it properly, it will definitely out perform a linear supply in every way. No question. But again, there are rules and if you don't follow them, you can easily get noise:

Rules for Using SMPS for Audio

That's a lot of 'IFs'...

Been there, done that, took measurements, and they're all on the audiophilestyle large 'AC Filter, Grounding...' thread.