OT: mixing unblanced gear in a balanced patch bay

[jmh]

Yes, I was specifically suggesting doing the custom wiring at the individual device patch bay solder lugs but could also be on the individual device connectors.

Yes, all patch cables will be TRS.

Ha. I suggested the exact opposite, with all wiring in the back of the patch bay being wired for balanced, you can achieve every one of the configurations in those diagrams with a couple of custom patch cable variations. I'll admit that you'd have to do some thinking when repatching - but in reality, you are always in that situation when you re-patch balanced <-> un. You could throw in a couple of isolation transformers to minimize those concerns.

I have another life in telecom. The wiring engineer of one of my buildings thought he was designing the ultimate in flexibility having the phones wired on cat 5. Unfortunately the 100 pair that ran between closets only supported 25 channels (when punching to rj45s) so the installers had to hand make custom patch cables to utilize any of the 3 unused pairs per rj45 - what a disaster, if you just touched anything, you were sure to knock out a phone. I spent the next 10 years troubleshooting problems. It turned out that design was not a very good idea - but in the engineers defense, it turned out to be quite handy when we switched to VoIP. Anyway it takes a few minutes to crimp a cable and I've used this kind of patching to do all kinds of tricks, and you can go in and out of the same jack and create a loopback to change your wiring configuration by plugging in different loopbacks.

I don't have any nice tt patchbays hanging around - but a bunch of rj45 patchbays that I could uses as a reconfiguration bay with a handful of loopback ends I could cut a few trs cables in half and punch them. I think I'm going to set up one channel worth to see if this is more trouble than it is worth.

Dave how do the the patchbays terminate the wires? They might have a 66 - or more likely a 110 punchdown block. If they do I recommend getting a good tool rather than improvising. If they are used, inspect the wire slots carefully for any wire fragments because if an old piece of wire is underneath, it can interfere with a good connection. And also read the patchby documentation to make sure you are getting compatible wire type and gauge - because depending on the termination method, this can impact the longevity and reliability.

Finally, I'm a big fan of minimizing connections. The likelihood of noise and other issues goes up exponentially (or at least non linear) with the the number of connectors switches and splices in a path wiring a patchbay is cost and time consuming and you don't initially notice when you need to break out the contact cleaner. The point is you don't need flexibility for a wire you change every couple of years - do the ones where it is beneficial. Getting reliability in exchange for flexibility is a good trade.

Take my suggestions with a grain of salt. I confess I have limited experience with audio patchbays - but a great deal with network and telecom...

[jmh]

After thinking about it I kind of remembered that 110 block may be for solid core conductors (but haven't found good documentation to confirm) - in which case stranded and braided shielded conductors would use something else. Nevertheless, splurging for good punchdown tools is inexpensive upgrade.

[Dave Labrecque]

Yes, I was specifically suggesting doing the custom wiring at the individual device patch bay solder lugs but could also be on the individual device connectors.

Yes, all patch cables will be TRS.

Slick. Thanks.

[Dave Labrecque]

After thinking about it I kind of remembered that 110 block may be for solid core conductors (but haven't found good documentation to confirm) - in which case stranded and braided shielded conductors would use something else. Nevertheless, splurging for good punchdown tools is inexpensive upgrade.

Both 110 and 66 block (all my experience is with the latter) are all designed for solid-core wire. After all, this tech came to the pro audio community from the telco folks. That said, although it's not quite as reliable, stranded wire has been used this way by recording and broadcast studios for decades. My Tucson studio back in the oughts had three 96-point TT bays all brought out to punch-down blocks, and I only occasionally had a connection go flakey that I can remember. A quick re-punch with the punch-down tool usually fixed it. Best to pull the wire out and repunch it a few millimeters farther along the wire, if possible, I think. IIRC, multiple-wire punch downs (two or more wires on a single punch-down point) were more likely to be problematic, but still usable.

My go-to studio wire has always been Belden 8451 (or 9451 where the shield foil is bonded to the outer jacket; makes stripping hundreds of wires go quicker). But I have to wonder if there's cost-effective, shielded, 22AWG, solid-wire cable out there. It'd make the punch-downs even more robust and reliable.

[Dave Labrecque]

JMH, you just gave me an idea. In the past I've normalled my studio mic lines right into my mic pres and/or console channel strip inputs directly on the TT bays. But I've now read in a couple places how that's a bad idea because of short-circuit voltage transients that can happen while hot patching with phantom power on, possibly blowing up sensitive electronics. That never happened to me before (although I do have a story about frying a nice Beyer ribbon mic by straight-up hitting it with phantom power; d'oh!), but even so I'm considering putting those connections on an XLR jack field instead of TT. But now I wonder if RJ45s would be a more fun way to handle that. Little shielded CAT6 patch cables would handle the "normalling" as well as re-route patching as needed. Hmmmm. I dunno. Just a thought.

Dave how do the the patchbays terminate the wires? They might have a 66 - or more likely a 110 punchdown block.

Each 96-point bay comes out to two 66 blocks (from solder lugs on the back). One for the top row of jacks, one for the bottom row.

If they do I recommend getting a good tool rather than improvising. If they are used, inspect the wire slots carefully for any wire fragments because if an old piece of wire is underneath, it can interfere with a good connection. And also read the patchby documentation to make sure you are getting compatible wire type and gauge - because depending on the termination method, this can impact the longevity and reliability.

I hear ya. I've been down this road before. I bought the first three bays from a guy shutting down his studio (friend of a friend). They were used, but worked fine. There was a little clean-up needed. No biggie. They worked for me for twelve years. A few years later I bought two or three more from him, but have yet to put them into service. That was maybe 15 years ago. Wish me luck!

Finally, I'm a big fan of minimizing connections. The likelihood of noise and other issues goes up exponentially (or at least non linear) with the the number of connectors switches and splices in a path wiring a patchbay is cost and time consuming and you don't initially notice when you need to break out the contact cleaner. The point is you don't need flexibility for a wire you change every couple of years - do the ones where it is beneficial. Getting reliability in exchange for flexibility is a good trade.

I know what you're saying is true. My challenge is to set aside my GAS and be smart about optimizing this balance. However, the GAS is strong with this one.

Take my suggestions with a grain of salt. I confess I have limited experience with audio patchbays - but a great deal with network and telecom...

Don't be so modest. You sound like a wise man. I know I'll end up spending more time than I need to wiring all this up. However, I'm not too worried about reliability, based on past experience. Plus--you've seen the big studios with those huge 10U patch bays. Of course, they had maintenance engineers on staff to fix things, so there's that...

Have I said wish me luck, yet?

[jmh]

In the past I've normalled my studio mic lines right into my mic pres and/or console channel strip inputs directly on the TT bays. But I've now read in a couple places how that's a bad idea because of short-circuit voltage transients that can happen while hot patching with phantom power on, possibly blowing up sensitive electronics. That never happened to me before (although I do have a story about frying a nice Beyer ribbon mic by straight-up hitting it with phantom power; d'oh!), but even so I'm considering putting those connections on an XLR jack field instead of TT.

I'm not sure about the details, but I think that the intention of the skinny tip to prevent closing the circuit to the wrong contact with switching to prevent connection until full insertion (if I tell this to a woman, will she buy it? ...or perhaps this is the reason why there is no truth in advertising).

I don't know if tts were designed specifically for balanced audio, or for telephone switchboard designs - in which case only the tip and ring might be used for connection and the sleeve may have been a mechanical guide so the tip did not contact the sleeve wipe. Although I think some systems may have had functions like sending ring voltage with partial or full insertion, then you would adjust the position to provide battery for conversation.

Anyway the horror stories of blown circuits and ribbons we have heard from may stem from the use of 1/4" trs bays, or 1/4 to tt cables. I have a feeling that tt bays intended for audio are less likely to have these effects than other solutions.

The mechanics of connectors is pretty cool and a lot of thought has gone into them. (on re-read I have to add, am I a ****ing nerd or what?) Even something as simple and ubiquitous as an rj45 with the fangs that pierce the insulation then impale the conductors - and then everything gets held in place by the elasticity of the deformed plastics. If you look at some of the females, the geometry of the contacts make or break circuits on specific orders (and there are different varieties of these for various telephone, network and other uses). You can see this in all kinds of connectors like flash and usb. It often looks like inconsistent manufacture - but the irregularity of the contact strips is intentional and part of the spec.

Going back to tt patchbays, it would be great to talk to a design engineer - it would give youtube purpose - instead of the 100000 patchbay videos by those who know some - or less...

[jmh]

I thought of something else. Since they used 66 style punch blocks, the pinouts may be arranged so you can do the normalization with bridging clips - as well as yield several of the wire variations that have been discussed.

Also if you have some punches where you intend to have more wires connected most 66 punch tools have non-cutting tips so you can let the wire continue and punch it down again elsewhere.

Also there are various couplings available that you can slide on the 66 posts to breakout the connections. I have 2 conductor that breakout an RJ11 - but I bet you can get screw terminal ones too. Just an idea to throw in the mix.

Anyway now that you've said you are using 66 blocks, I can see how you may want to just punch a particular configuration for a certain in or out...

[Dave Labrecque]

I dunno, man. 48 volts on the tip is going to jump to any metal it touches with an attractive path behind it (like a sleeve or a ring contact). Those are always "on." Any switched open doesn't happen till after such contact is made (by virtue of that contact, in fact). Even on TT bays (which are really just miniaturized 1/4-inch jacks). I'm not optimistic.

But an intriguing concept, for sure. You'd think they'd have invented such a beast by now.