Patchbay & grounding

[tlmaen]

Hi guys,
I am getting my first 4k console this week.
I am planning the patchbay right now, as I have to do it completely from scratch (except for the standard SSL Patch-rows).
My former Neumann Console used a different grounding scheme than SSL.
Its not a star ground its a meshed Ground. So every Module, Cable, Multicore, etc is grounded everywhere and as often as possible.
Also all of the multicores are grounded at both sides.
This worked very well for that console, but I have read that a proper star grounding is crucial with an SSL.
I can't remember where, but I read somewhere that you have to lift the ground pin on one end of the multicores...

I have to rewire all of my multicores from all of the outboard and Converters, Mic-lines, etc.
The Neumann Console has a Lemo Patchbay. I have to resolder everything to the new TT patchbay.
So I would like to do it right (and only one time)!

How is it done right?

Thank you!
T

[Pinebox]

The grounding scheme stuff is why I strongly suggest clients move onto modern dsub bays with switching normals and grounds these days. They make installation so much more simple. Mosses and Mitchell makes some really nice ones if you want to keep with the original manufacture. The materials cost of a new bay might be intimidating but if you might end up saving money then if you try to reuse a solder jack bay and have to clean the old wires off the jacks and such. Absolute nightmare. For console connections the solder jacks are fine, nothing ever moves really, but if you decide to change anything up for the outboard, being able to configure the order on the dsub bays is huge. The only drawback with this is sometimes you need to make a descrambler cable/panel if your layout doesnt all fall into groups of 8pair.

[tlmaen]

I forgot to say that the patchbay is a remote patchbay.
I do not have to change anything between the console and the existing SSL patchbay (hopefully)
I bought a few used M&M patchstrips for my outboard gear with solder lugs (My assistant will desolder it and make it nice and shiny ).
I don't have to deal with DL Connectors, only multicores to the extra patchbay strips...
I am not a big fan of D-Sub connectors, prefer the soldered connection.
All of my Outboard/Converter Multicores are in Banks of 8/16/24.
I am moving things around with patchcad for some days, getting slowly to a good layout.
But I need some light in this grounding thing!

T

[waltzingbear]

its been a long time since I installed a SSL, perhaps Jix will chime in too.

My recollection is that most all if not all I/O on an SSL is balanced, If that is the case, then a mesh ground system is desirable as no ground is ever used for audio transmission, only for noise immunity. Integrating unbalanced equipment into the system is where you can get into trouble. Best to convert external to balanced to make ground paths irrelevant.

[tlmaen]

That would be great because its dead quiet right now. Would like to keep it that way.
I have almost no unbalanced equipment, except for a few reverbs, but I have some balancing equipment for this case.

Can anybody confirm that the SSL is completely balanced?
Does anyone else is using a meshed grounding scheme?

T

[Dave Dicson]

The Mic lines have to have grounds on both ends, or you won't get phantom power, if you need it.
Some SSL DL connectors are wired 1 - 24 or 1 - 32. We had both and I had to wire them so they are all 1 - 24. This is to the "outside world". The DL connectors between the  SSL the Patchbay can be wired either way.

[amillar]

Channel inserts aren't balanced. Sorry. And 651 inserts aren't properly balanced.

[jimlfixit]

Just seen this post and hope this helps.

1   With ANYTHING coming in or out of the SSL patchbay, the SSL Tech ground should be the main studio tech ground which is a 0BA (or M6) Brass screw hanging out of the connector panel which may link to your 661 SSL supply or your main tech ground directly to your fusebox or tech ground stake in the ground. Keep it clean and direct.
2   SSL DL 96 way connectors from the studio always have ALL the screens connected and ALL the screen wires soldered to the patchbay.
3   NONE of the internal SSL console wiring has the technical ground connected at the patchbay to avoid ground loops.
4   The patchbay screens are shorted to the frame which is the main tech ground as mentioned.
5   The SSL has two copper bars running through the console. One is more logic stuff and the other is more analog stuff (upper buscard with the 6 way Bicc connectors on) but they join together at the end at that point under the patchbay.
6   As I understand it, all the mic, line and multitrack track inputs are fully balanced BUT, maybe the inserts are not fully balanced as Andy Miller has mentioned.
7   There are more complicated issues with the SSL tech ground system so, please contact me directly if you wish to discuss this.
6   All this is complicated, depending on your studio or house wiring layout (ie: different circuits, fridges or dimmer lights on the same circuit etc).
Hope this helps in a way and regards from Jim L

[tlmaen]

Channel inserts aren't balanced. Sorry. And 651 inserts aren't properly balanced.

That sounds funny :-) 'not properly' means just impedance balanced?

I hoped you would chime in, Jim!

1   With ANYTHING coming in or out of the SSL patchbay, the SSL Tech ground should be the main studio tech ground which is a 0BA (or M6) Brass screw hanging out of the connector panel which may link to your 661 SSL supply or your main tech ground directly to your fusebox or tech ground stake in the ground. Keep it clean and direct.
2   SSL DL 96 way connectors from the studio always have ALL the screens connected and ALL the screen wires soldered to the patchbay.

Does this also refers to an external patchbay?
So this means that all of my Outboard Gear Multicores needs to be connected with the screen to the Patchbay...

I don't have a dedicated star Gnd connection in my Studio, it was just not needed with my Neumann Console.
The Fusebox is directly beside my control Room, wich is kind of a star gnd point, as all of my power cables go directly to the Fusebox.
Its in the same room as the Console PSU

4   The patchbay screens are shorted to the frame which is the main tech ground as mentioned.

Ok, but that would create a gnd loop if the screen is also connected to the gnd at the outboard gear?
(I think that's what I read. can't remember where. It says 'do not connect the screen at both ends...')

7   There are more complicated issues with the SSL tech ground system so, please contact me directly if you wish to discuss this.

What kind of issues? I am sure its also helpful for other people...

Thank You!

Best,
Tilmann

[jimlfixit]

Hi Tilmann
Remote patchbays are a different matter and depends on if you have a wooden rack or a metal one as the SSL metal patch tech screens could be become the SAME as any unbalanced gear case AC earths. This could be important as well as mic source grounds and a singer who touches the mic could get a shock and even die if the studio tech and normal ground wiring is not done correctly and something goes wrong.

Hardly anyone deals with this but it could be important of course.

Screening both ends could also be a problem but, if the console and effects etc are on the same circuit, it may not be. When I wire Pro Tools to/from an SSL I do NOT screen at the PT end as the SSL does that anyway.

Connect me directly so I can answer as I am not quick with all this writing stuff.

Hope this helps from Jim Lassen

[tlmaen]

Just figured out that all of the Remote patchbay Connectors are Siemens/Tuchel Brand. They are 30Pin connectors.
I guess it was first installed in a broadcast Station/Truck.
I have to look at all the paperwork wich comes with the Console tomorrow.

The Rack for the patch will be a wooden Rack, but I had great success covering the inside with Alufoil and ground it if necessary.

Floating everything wich is connected to the ADDA is probably a good idea...

Everything in my control Room is connected to the same Powerline.
Anything special to consider with the switch mode PSU? (I may ask Malcom Toft if he have some advice)

Thanks,
T

[Richealey]

The old console at Le Studio also had Tuchels. I guess that’s what they used back then.
You will need a big ground wire from the console lug Jim talks about to an external grounding point.
That is usually at the least a copper stake in the ground outside the building. At Le Studio our ground was a copper grid that was in the lake. Tom Hidley used to route the air conditioning condensation drips onto the ground stake soil to keep it as conductive as possible when it was hot and dry. Smart.
The idea of having a tech ground separate from the power ground is to eliminate the crap that travels
down the power ground from getting into your console audio. If tying into the power ground worked for you before it my still work but don’t think the 3rd pin on the power supply cord is going to be enough. Look at the size of those ground bars under the console. You’ll still need a heavy gauge wire connecting to a ground point. Consider a metal cold water pipe if there is one you can get too.

There are rules for audio grounding and there are various ways to achieve the same results.
Basically, the shields should only be connected at only one end of the wire (except mic lines). I discovered at some of the studios that were wired before I was employed that they had connected the audio shields at both ends of the wires to everything. It still worked great. Grounding is a bit Voodoo. I’m pretty sure since the console patchbay section is coming pre-wired it should be fine.
My suggestion is once the console is installed connect only the console related patchrows.
Connect up some monitors so you can listen for ground issues as you proceed with connecting the rest of the stuff. By connecting your gear in steps, you can find issues as they happen and deal with them before proceeding to the next piece of gear. The worst thing you can do is connect everything up, find out you have hum, and them try to trouble shoot it. For the outboard gear if you think about it once you plug in the patch cord to a line in or insert, you’re now connecting the console ground via the patch cord to that wire. I never bus the grounds at patch rows, but others may.
I’d probably connect the shields for the outboard gear to the patch point and the gear and see what happens. You’ll certainly have to do this with external mic pres or you won’t get phantom power getting to the mic. Again, try each piece individually to listen for hum. With unbalanced gear like a Yamaha SPX90 I’ve always had to isolate the metal chassis of the unit from the metal rack rails.
I use Gaff tape on the back of the rack ears and heat shrink on the rack screws (with plastic washers) where they could touch the chassis. If you have metal rack rails the chassis of all the rack gear is connecting through the rack rails. The chassis is usually tied to ground. Oh no another potential ground loop. Good luck. I hope your install goes flawlessly. 

[tlmaen]

Thanks for your explanation!
I got the 'Console' yesterday. its in a lot of boxes and the two halfs of the Frame.
Happy that its in my place right now, was a nightmare with that Brexit sht.
I just read quickly through the documentation. It was first installed in a danish broadcast station.
That's probably why it is all Tuchel.
Not one shield is connected to the Patchbay, only hot & cold. Even the mic lines (they must be grounded at the other end...)
Each Patchbay has only one separate tiny Gnd wire going to the console.
But I couldn't fire out the other end, its big spaghetti right now...
I can start putting it all together in January have to finish a few mixing projects.
I think I will first install the Console in the same manner as my Neumann Console, and then take it from there if there are any issues.
The Neumann Console has six PSUs, all connected with only one normal IEC Power Cable.
But I will prepare a big copper Gnd Wire to my Fusebox, the internal Copper bar left some impression on me...

thanks,
T

[tlmaen]

Found a very interesting and detailed white paper about grounding and shielding. worth reading.
He is also explaining why it not makes sense to have a separate Gnd Rod (wich is dangerous and not allowed).

https://www.jensen-transformers.com/wp-content/uploads/2014/08/generic-seminar.pdf

My patchbay are made of solid metal, so every connection shares the same ground.
Its not possible to add or lift gnd from/to certain connections.
So my options are very limited. But I guess it worked for the last 40 years...

T

[waltzingbear]

that is a very good paper, you can also see the paper at the Rane website
https://www.ranecommercial.com/kb_article.php?article=2107
https://www.ranecommercial.com/kb_article.php?article=2127

Cheers