SSL patchbay extension, parts used and techniques Part 2

[jimlfixit]

In my last post on this subject, I described how I rewired an SSL patchbay using existing Brand-rex cabling and also mentioned some of the parts and techniques used by SSL.

This post deals with an SSL extension patchbay I built for a job that got cancelled and has been left lying around … any offers? I will mention the details and cable lengths in a future advert!. Some of the parts and methods are different from those mentioned in part 1 but I thought you may be interested to find out how I did this. If not, do something else now as it could get quite boring as I describe the details!

As in all my posts, feel free to disagree, correct me if I have got something incorrect or suggest alternatives (I'll add them in later and give you a credit!). I'll add any changes in red so you can see the difference from my original post.

This 112 way G series grey patchbay was part of an 8 way extension to an SSL console and contains all the relevant channel I/O functions wired on a standard SSL patchbay as follows:

1   A/B: Mic sources fully normalled to mic inputs.
2   C/D: Multitrack returns. 1/2 normalled to line inputs.
3   E/F: Channel inserts (1/2 normalled).
4   G/H: Group outputs 1/2 normalled to multitrack sends and also group monitors back into the console.
5   J/K: Multitrack returns (linked from row C) 1/2 normalled to tape monitor inputs.

All these functions take up 40 jacks top and bottom. The track remotes never appear on the patch (as there is no need and they are not analog signals). SSL internal console cables going to the channels are not screened at the patch as they are linked to one of the two 3/4 x 1/4" ground copper bars near the upper buscard instead (more on grounding in another subject).

The DL studio installation cables such as mics and multicore sends (record) and returns (replay) along with the centre section DL's (31, 32, 33 and even 34) are screened at the patch and also connected at the DL's like all the wiring in and out of an SSL console apart from the odd bit of timecode and some centre section switching functions.

I have temporarily labelled this patchbay for the purposes of this post so you can refer to the wiring.



A/B: Looking from the front (unlike the picture which is the rear view), there are mic sources fully normalled down to mic inputs (normally rows A and B). Notice the green screen drain wires are connected so the console (via it's OBA connector panel earth stud to an external ground point) provides an earth for the mic cables via the patchbay which is part of the console grounding system. This is important so some form of earthing is provided for the mic inputs especially if a singer grabs hold of the mic and there is a fault … possible death as a result! Don't just ground the audio and console earths via the console power supply. Use a star earth system whereby the console, computer rack and other studio equipment are grounded close to the end final ground point regardless of any piece of gear taken out of the loop. Again, more on this earthing stuff in another subject.

A useful feature: As this A/B patchbay is fully normalled, you can plug a jack into the top A row to send a signal back to the live area which won't also be sent to the mic input due to the fully normalled wiring which breaks the link between A and B rows. This is a handy function as it could act as a tie line between the Control Room and live areas. Therefore, row A could act as a two way feed in AND out of the studio live areas (perhaps for extra cue feeds for unused mic source cables during a recording session).

C/D: The next 8 jacks are rows C/D which are multi returns 1/2 normalled to line inputs. Again, the screens are connected from the DL. C links to J as the multi returns feed both the line and tape monitor inputs (normally rows D and K respectively).

E/F: Near the middle of the picture are the channel inserts (E/F) with no screens connected at the patchbay as detailed above.

G/H: The Group sends are 1/2 normalled to Multitrack sends and Group monitor inputs. There are two cables from each jack on row H, which you can't see very well in this picture and only the multitrack sends on row H is screened at the jack. The group monitors are screened at the channel end as mentioned before.

J/K: These are multi returns (again), normalled to the console tape monitor inputs. Notice the lack of wires on the top row on the left of the picture. This is because I have cross linked the circuits from the multitrack returns C, to J further along the patchbay without using Brand-rex twin screened cable, just SSL type kynar wire in twisted pairs instead as they are very close together on the same patchbay. On normal SSL patchbays, row C would link to row J via Brand-Rex cables but they are only grounded at row C, not J as this would mean they are grounded at two different points even though they are very close together. This also avoids extra and unnecessary wiring. Remember that the patch screens are shorted to the patch fronts which, in turn are screwed into the rack strip which also forms part of the console frame (have you fallen asleep yet?).

On this 112 way patch, there are 16 jack positions top and bottom free for other use such as outboard, parallels and other useful functions like phase reversals whereby the hot and cold circuits are swopped. This is especially useful for mics and balanced outboard equipment as the USA normally defaults to pin 3 hot on an XLR and the UK, Europe plus Japan usually use pin 2. Phase reversals could be used whilst recording a snare drum for instance with different makes from different countries (AKG and Shure as examples) of mics on top and underneath to get them in phase with each other.

Nerd warning: The following may only be of interest to wiring people!

Anyway, I'll explain the different wiring methods I've used, some of which are non SSL standard in this case. First of all, I used Hellermann green TH10 x 25mm drain wire sleeves as opposed to black which SSL uses. Green coloured versions make more sense in my mind as Brand-Rex has a black cold wire which could be a bit confusing especially if you are in a hurry to rewire something (and get all the black coloured wires and sleeves muddled up). Also, note the H20 sleeves are 2/3 on the cable and 1/3 on the core wires coming out to the patch which I commented on in part 1. They are more likely to slip off the outer cable insulation if only fitted half way on the insulation and the emerging core wires plus screen although, over time, they do stay in place when the sleeve lubricant dries off.

On this patch, I used a round nylon lacing cord (not the usual SSL flat waxed lacing twine). I got this idea whilst completely rewiring an old console for Shep Associates in Meldrith, near where Neve were based in the UK many years ago. Looking at the old Neve ways of looming plus learning from other ex Neve wiremen while working at the, then new, Metropolis studios in London about 1989 enlightened me with different techniques that could be used. This is a non continuous knot and takes more time but it looks quite groovy and retro.

Lacing cord is actually great for custom projects, especially on panels, where you may need to add or change things later on but is not so good if the loom is subject to flexing as the knot could come loose therefore, secure the loom with cable ties on a tiebar before it heads off somewhere else and gets moved about. The advantage is that this cord can be cut off without affecting the rest of the loom lacing so that you can add more wires in if required, redo the knot and no one would know the difference! This is a well known shipping knot also used in Scouting and is based on the clove hitch. A lot of people use cable ties for this purpose which are much more expensive but, if you add one more wire to the loom, lacing cord could be the way to go otherwise, you have to cut a load of ties off and buy some more to do the re-looming!

I'll try and draw some examples of this cord technique plus the SSL continuous lacing using twine in a later subject but, meanwhile, here are some rough buying specs for both the SSL waxed twine and the Hellermann type cord which are both useful for different purposes.

1   SSL large waxed twine (patchbays and console interior looms): Hellermann MW/090 2.3 mm width, black.
2   SSL smaller waxed twine (mostly 5K Pot looms): Hellermann MW/062 1.5mm width, black.
3   Neve and prototype wiring lacing cord about 1.1mm in diameter with nylon inner core: Hellermann PNF 1012, black.
4   Smaller prototype lacing cord (about 0.9mm from memory): RS used to do this but check out multi comp versions from Farnell. I'll update this when I find a suitable part.

Notice the cable ties on this patch (they are the Hellermann type used by SSL). To make the job neater, turn the knotted part inwards towards the patch and use fully flush (not semi flush) cutters so that there is not a sharp bit sticking out to scar your fingers when you are digging in the patchbay to fix something in a hurry (it can hurt!).

Also, note that I haven't labelled each wire to the patch but have laced each circuit individually. This saves time and money. The loom is laced with cord and held on the patch with cable ties. As this patch deals with channel functions, there should be no need to rewire or add cables to it, hence my decision on this. Centre section patchbays, if remade from scratch, should be individually labelled in my view as they go to and from a multitude of places.

For part 3 of patchbay wiring techniques, I'll deal with wiring a multicore to a patch rather than individual wires starting at the patch which is easier. I've seen some examples of doing this on other websites but I think I have something to add as an alternative! More on this later.

Finally, I have spent some time compiling this and have tried to check my information to make it accurate and informative. I don't own an SSL anymore and haven't worked with the company for over 10 years. I hope this post proves useful and apologise for the lengthy message (is this the longest post so far?). I have about 5 more posts in connection with SSL wiring in draft form which I intend to post when I have the time and can check the details. If anyone needs an SSL patchbay built, get in contact (www.profcon.co.uk) as I have most of the SSL parts here. Regards from Jim Lassen, based in the UK.

[sintech]

Stunning post Jim, thanks for sharing this information.. you are the original SSL wireman, and we bow to you. 

[jimlfixit]

Thanks for the comments Andy but, heck, can any other wire people add to the mix as I'm surrounded by Techies here. There is a difference as Techies fix things (plus do wiring). All I do is muck with cables without the fixing bit. I may have been at SSL (Cecil as I sometimes call them) since the early days, but I never worked on a console frame until I left in 1987. All I did in my years there was to build the stuff that goes in them or connects everything together plus a lot of interfacing between the designers, production, test and service!

Lots of other people who were there near the beginning have left but, surely, there must be other wiring people out there who have some knowledge and ideas. Come and join in the forum, whoever you are and wherever you are based (there are loads of SSL's in the US and Japan for instance) otherwise, it just seems down to me at the present time.

[jimlfixit]

Following on from my post about lacing twine and cord here is a picture to go with the descriptions.

1   SSL large waxed twine (patchbays and console interior looms): Hellermann MW/090 2.3 mm width, black.
2   SSL smaller waxed twine (mostly 5K Pot looms): Hellermann MW/062 1.5mm width, black.
3   Neve and prototype wiring lacing cord about 1.1mm in diameter with nylon inner core: Hellermann PNF 1012, black.
4   Smaller prototype lacing cord (about 0.9mm from memory): RS used to do this but check out multi comp versions from Farnell.
The second picture is an example of me using the item 3 (Neve type 1.1mm cord) for an Edac panel (not finished) for Toerag studios (one of 4 panels wired to 7 x GPO 1/4" patchbays). Notice the individual knots for the looms with cable ties used to secure them to the panel tiebar, which I made up.