SSL studio technical grounding and AC earthing

[jimlfixit]

I want to start a new topic about technical grounding here. I don't have an SSL console any more (I worked there for 7 years, left, bought one, broke it up and sold it ... sorry) so I have no up to date experience regarding this issue hence needing your help even though I have been involved in recording studio installations since 1987 whether the console was SSL, Neve or others.

Before I go into details about the SSL console technical grounding and possibly suggest some ideas regarding the overall studio tech grounding system, I have the following points to raise and questions to ask directly related to the SSL setup.

The 19 way Bicc power supply lead has various power grounds connected together and I think some of these link to the grounding block. Also, the centre cable (V on the Bicc I think) gets connected directly to the SSL frame on the connector panel (or not). At the other end in the 661 power supply, does it directly short to the mains ground (ie the metal case)? I have heard that this wire is used as a test wire and may get disconnected from the power supply once the console is up and running unless I have got something wrong.

Also, how is the SSL 665 computer supply technically grounded? I can't find any info on this. The console tech ground connects to the computer (691 11u rack) via the standard SSL supplied cable 25/0.25 wire and that must have some connection to the computer supply as well. Are both the 661 and 665 supplies sharing the same tech and or AC ground and how are they linked up? From memory, I think at least one of these power supplies had a tech ground terminal on the rear panel but I may be wrong.

Can any of you confirm any of these details please as I'd be interested to know so I, or someone else can draw up some proposal for an overall workable studio earthing scheme, get some ideas from other tech chaps and then post it? Eric in Germany was helpful and Mata, Andy and others can be as well. This isn't rocket science but depends on loads of factors and I encounter this problem and lots of questions to do with tech grounding in every installation. I know what to do with a general installation but need some of these SSL details confirming please so I and others know all the exact grounding and earthing signal paths involved.

Impedance checks between tech grounds and safety grounds would be handy to know. I believe that an impedance of something like 10 Ohms or more between a chassis earth and a signal ground may be enough to treat them as NOT the same thing. Correct or not?

Hope this makes sense and give me your feedback tech people so I can conjure up a cunning tech grounding plan.!

Regards from Jim Lassen (www.profcon.co.uk). Also on FACEBOOK

[sintech]

Hey Jim,

 I don't know much about the earthing scheme, apart from the info from you and photos, plus drawings from the service manual.

The console end of the 19way BiCC all earths are tied (including V) this then goes to the chassis ground.

Sure I tied the chassis ground with the output of both copper bars.

Mine is non-standard, but is 100% working with an amazingly low noise floor. :-)

I'd be interested to know exactly how SSL did it… just 10 minutes with a console, i could tell you! hehehehe

I noted that GG, ties his ribbon drains to the Chassis, and not to the Copper, and would love to know the correct approach.

[jimlfixit]

Hi Andy and others

Whilst doing a recent SSL install I intended to figure out the SSL AC and signal grounding signal paths but, I ran out of time in the end.

I'm surprised that the ribbons (meaning 651 ribbon screening with green wires?) get linked to the chassis frame and not the copper bar tech earth which is isolated from the console (big difference). Maybe that is standard but I can't remember. Other techs with SSL's out there ... please carefully clarify this and the 19 way Bicc centre pin V connections at either end (console and PSU chassis and/or tech ground).

I too could spend a few minutes sussing this out but don't have a console. Can anyone help please as it would benefit you all?

Regards Jim Lassen

[Artur D'Assumpção]

Hi guys,

From what I'm aware from the SSL Installation Manual the only system ground aspects that SSL mention are:

1) ground cable between console and rack (connects to the chassis ground pin)
2) ground 3rd pin on the SSL PSU power sockets (these should be provided directly from your main AC installation)
3) all your gear should also be grounded in the 3rd power socket pin (pretty standard)

And then you have to avoid ground loops at all costs the recommendation is:

1) to always use a STAR topology approach and connect any gear that has a 0V lift into a central technical grounds bar in the CR.
2) Always disconnect 1 side of the shield of cables, being the standard/recommended approach to lift the INPUT side of the cable.

This way you will assure that every gear is properly grounded and that there aren't any ground loops.

If you need this section I can provide it.

Cheers,

Artur