Mixing Console Ground Configurations-Layout

[boji]

Thanks Ian for the link about grounding!

"Outside the modules, power and ground were distributed using large copper or  brass bus bars. Each module was locally decoupled with 1000uF. Buses were carried in a special extrusion that consisted of a number of U shaped channels, one for each bus. Each module was hand wired to the bus via a bus resistor inserted in a feed through in the extrusion. "

"The only way to minimise interaction between modules is to make sure the power and ground conductors are as close to zero resistance as possible."

I'm not sure I understand the reason for the bus bar resistors. Wouldn't omitting them achieve the least resistance?  Are the resistors a necessary evil for channel isolation?

Edit: Now that I think of it this is a B+ issue, isn't it.

 

[abbey road d enfer]

Thanks Ian for the link about grounding!

"Outside the modules, power and ground were distributed using large copper or  brass bus bars. Each module was locally decoupled with 1000uF. Buses were carried in a special extrusion that consisted of a number of U shaped channels, one for each bus. Each module was hand wired to the bus via a bus resistor inserted in a feed through in the extrusion. "

"The only way to minimise interaction between modules is to make sure the power and ground conductors are as close to zero resistance as possible."

I'm not sure I understand the reason for the bus bar resistors. Wouldn't omitting them achieve the least resistance?  Are the resistors a necessary evil for channel isolation?

Edit: Now that I think of it this is a B+ issue, isn't it.

Ian was referring to mix bus, not power or ground bus. Mix bus need injection resistors, don't they?

 

[boji]

Oh man, the mix bus got that much metal too?  Woah.

No capacitance issues using that much metal on audio signal? My backplane is quickly becoming paltry in comparison...

 

[ruffrecords]

Oh man, the mix bus got that much metal too?  Woah.

No capacitance issues using that much metal on audio signal? My backplane is quickly becoming paltry in comparison...

My fault for using bus in two different contexts.

The power buses were big copper/brass  bars.

The signal (mix) buses were not. You may not believe it but each signal mix bus was a long strip of one hole wide veroboard. These fitted in the channels of the extrusion I mentioned. Holes drilled in the top of the extrusion were used to feed mix bus resistors to the veroboard.

Cheers

Ian

 

[abbey road d enfer]

My fault for using bus in two different contexts.

The power buses were big copper/brass  bars.

The signal (mix) buses were not. You may not believe it but each signal mix bus was a long strip of one hole wide veroboard. These fitted in the channels of the extrusion I mentioned. Holes drilled in the top of the extrusion were used to feed mix bus resistors to the veroboard.

Cheers

Ian

And I know from experience that if you had one of the veroboard strips fractured, one had to do a speleological expedition under the console and find with an ohmmeter were the cut was.

 

[ruffrecords]

And I know from experience that if you had one of the veroboard strips fractured, one had to do a speleological expedition under the console and find with an ohmmeter were the cut was.

Indeed. Definitely an Achilles heel on older Neve consoles.

Cheers

Ian

 

[boji]

Ah.. well that makes more sense now. Interesting  idea to encapsulate a single bus in a 'u' extrusion.  The more I listen to you folks explain console architecture, the more I wish I had volunteered in some professional studios before setting to work on my own...

 

[abbey road d enfer]

Ah.. well that makes more sense now. Interesting  idea to encapsulate a single bus in a 'u' extrusion.  The more I listen to you folks explain console architecture, the more I wish I had volunteered in some professional studios before setting to work on my own...

You would have needed to do that 30 years ago, when there were actual mixers in studios. Now there are only computers and control surfaces...

 

[boji]

I have a question not directly about general ground, but the PFL/AFL/SIP  relays I've added that tie to the bus:  Should I treat them like I have the Aux and Groups switches, in that when deselected, the bus resistors tie to ACOM?  I don't see why I should treat them any differently. Thanks for your input!
-Boji

 

[abbey road d enfer]

I have a question not directly about general ground, but the PFL/AFL/SIP  relays I've added that tie to the bus:  Should I treat them like I have the Aux and Groups switches, in that when deselected, the bus resistors tie to ACOM?  I don't see why I should treat them any differently. Thanks for your input!
-Boji

Since the only purpose of doing that is decreasing x-talk, you have to ask the question; is it a good point or not decreasing x-talk on the AFL/PFL bus?
I would think it is, although not as important as it is for main bus, since the PFL bus will never end up in the final mix. In practice, it's not a serious issue. Do you know there was one mixer where the mix could be reinjected into the PFL bus via a potentiometer, so a PFL'd signal could be heard in attenuated context instead of full isolation? Very clever feature that never really caught on.

 

[boji]

"...mix could be reinjected into the PFL bus via a potentiometer, so a PFL'd signal could be heard in attenuated context instead of full isolation."

That is cool, and seems easy to do. Yeah, why didn't that catch on?  Especially in the days of not having a computer monitor to see where you exactly were in a mix...  What's one more relay and pot in the monitor interface sect at this point? =P

 

[fazer]

The noise floor was minus 90 dB on the Neve 8036 (in the studio) measured with a soundtech distortion  test set.  We had 1064 and 1081 input modules in the console.  When you inserted eq on the 1081’s, the noise would go up to minus 65 due to extra circuitry in the 1081 .  The Consoles of the day we’re  minus 70 or so.  Neve did set a standard for others to follow.

 

[abbey road d enfer]

The noise floor was minus 90 dB on the Neve 8036 (in the studio) measured with a soundtech distortion  test set. 

I surmise it's for the channel alone, from mic in to direct out. At what gain was it measured? Output noise is directly dependant on the preamp's gain.

We had 1064 and 1081 input modules in the console.  When you inserted eq on the 1081’s, the noise would go up to minus 65 due to extra circuitry in the 1081 .

Wow! That's a serious degradation of performance. I've never done a thorough analysis of Neve EQ's, but I would have thought they were capable of achieving much better performance.