Building a new patchbay, need a little advice on cabling

lo.fi.love

lo.fi.love

Functionally obsessed.
The monster RCA patchbay has bitten the dust and I'm replacing it with a TT patchbay, true normaling (instead of my homemade normaling system using toggle switches!) and a MUCH smaller form factor. I'm really excited.

I'll be soldering these patchbays. And I'm wondering about what kind of cabling to use. Specifically, there's high impedance coax cable that looks really good for unbalanced runs, and low impedance balanced line cable, and I'm not sure which to use because I'm building this for my unbalanced -10dB setup and I don't know if either cable is appropriate for this.

Can anyone lend some insight into this?

Thanks!!
 
The standard is 22AWG stranded pair with drain and foil shield...been the standard for a long long time. Redco has the Gepco variant in many colors in per foot quanitities for $0.14/ft. I believe you'll not find a better price and the Gepco product is good. Its what I'll be using to build up the wiring harness for my MCI console...I'll be getting 100's of feet of it.

Did you find your patchbays already? I have those really, really nice Switchcraft 96pt bays for cheep.
 
Hey Cory!

Good to hear from you!

I found the patchbays already, from Mister Patchbay, about $500 for three 96 point patchbays by ADC. I'm a real Scrooge with money and this seemed like the best deal. Plus I think it's cool that this guy makes a living from refurbishing patchbays and I want to support that :)

I guess the basis of my question is that coaxial cable has a gigantic copper shield around the "hot" lead, and I suspect that it may be better than a foil shield with a drain for unbalanced systems. I'm basing this off of a hint of knowledge and an ounce of speculation. What do you think about this specifically?

By the way, I'm still working out the problem with the 48. I just haven't had a lot of time for music lately and I'm getting caught up on the most nagging issues, the priority being this patchbay. I can't tell you how many times I've punched my fist in the air and screamed because a channel dropped out!!
 
I guess I'm wondering, too, what makes a cable better for high or low impedance signals, and how this relates to a studio that's basically running RCA input and output on everything.
 
I got the 4 new condition Switchcraft 96pt bays for $20 total. [duck]

Wait...just looked at the pictures again and they are 144pt...basically 48 3-jack sets, one normalled pair and one non-normalled (I think)

They look like this:

IMG_2985_2_1.JPG



Silliest part is I don't need them but for $20??

I have all the ADC bays I need and more to build up the patchfield on my MCI console so these are just surplus. I'll put them on eBay and see what I get.

Foil shield provides for 100% coverage. Braided shield typically doesn't get much better than about 90%.

Be careful with the coaxial stuff because some of that stuff is designed for 75ohm video and you don't want to use it on audio.

The other thing about coax that I don't really like is that the center conductor is solid core. Electrons don't travel through a metal conductor, they travel on the surface, so stranded cable is better because it provides more surface area.

Shielding is the same for balanced vs. unbalanced, so what's good for unbalanced is good for balanced and vice-versa. What's MORE important is how the shield is tied to the system at each end and how each device deals with audio grounding...can of worms and I'm putting my can opener away unless you have questions or more importantly problems to resolve.

Cable that's good for high impedance is good for low impedance and vice-versa. You want good quality stranded conductors, good shielding...one factor to look at is the capacitance of the cable but pretty much any decent cable is going to be acceptable in that area and the Gepco cable is no exception. I just keep pushing the Gepco stuff because it is very reasonably priced and though it doesn't have the same name as a couple snobbish brands it is perfectly good cable...even great cable and the price is right.

It doesn't matter what kind of connector is terminating the cable...the same demands apply to the cable regardless of the ends. 24AWG is fine, 22AWG is better. Most of my multi-channel snake cable is the Gepco GepFlex stuff which is 24AWG and I'm not worried because all of my snakes are 16' or less. I have some longer snakes for remote work that have 22AWG conductors but inside the sound room its mostly 24AWG. I'm going with 22AWG with the MCI harness because that's what MCI used and what the MCI guys say I should use. Fortunately the Gepco stuff is priced well and comes in all the colors that MCI originally spec'ed for their harness so I'll be able to recreate it visually and according to the original cable spec.
 
Ive done all my snakes, patches and all backplane with Beldon 24 gauge teflon jacket, teflon conductor insulation, 100% braided tinned copper shield. Its Mil-spec and not cheap but I really like it. I have no time for anything with PVC insulation or jackets (then again I work in the cable/connector industry). If everything you are interfacing is using RCA pin-plugs, you might consider a roll of consumer grade audio coax? Why bother with pairs?
 
I used all Beldon 9451 for my stuff, balanced and unbalanced. Personally I'd just get a couple of boxes of wire and make what's needed.
 
Don't worry over it too much, get some Gepco single pair install or snake cable (I like it better than Belden et. al. far as tinned copper cond/foil shield cable goes, good price and strips better/cleaner) or if you have more coin to spend, check out the Gotham Audio GAC-2/1 install cable, high purity bare copper conductors with a copper double shield, nice stuff. Either of these should be fine for your purposes, 2-conductor is fine for unbalanced runs and I presume you'll want it for your balanced runs such as mic input patches or any balanced i/o you might have on outboard gear.

Other advice I would have is don't be too stingy on connectors, get solid quality ones that make a reasonably firm connection. I like gold plated better than nickel, they tend to stay cleaner but your mileage and budget may vary. Either way what you want is a good clean reliable connection.

Keep the unbalanced runs as short as is reasonable to keep noise down.

And...get twice as many zip ties as you think you'll need. LOL.
 
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Ditto on the gold plating...I don't tend to spring for it but I always feel like I should...with all the old stuff I deal with its always the Gold plated pins that are still lookin' great 3, 4, 4+ decades later.
 
briank said:
And...get twice as many zip ties as you think you'll need. LOL.
Click to expand...
+1000

I also agree that the cable isn't worth worrying about so much. The quality of your soldering and the care you put into planning the wire runs will probably mean a lot more in the end.
I was in the same boat last month, upgrading from RCA to TT bays (at the same time, I upgraded to a pair of Studer 169 consoles that can be linked together). I scrounged a lot of surplus Mogami and Canare and it was certainly more of a pleasure to work with than Gepco, but it all worked equally well once hooked up.
Here's how I organized the bays:
http://dl.dropbox.com/u/9818263/Studio%20Stuff%20for%20website/BottleGardenPatchbayUpdated.xls
It was a pretty time consuming affair. I think I would have lost it if I hadn't sprung for one of these guys: Paladin Tools
 
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