Wiring to Krone Block - Single vs multistrand

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morls

Well-known member
Joined
Jul 15, 2013
Messages
257
Location
Australia
Hi,
Looking into Krone blocks, and the recommendation is single-strand 0.5mm wire. Is there any reason NOT to go single-strand for audio from patchbays to Krone block?
Cheers
Stephen
 
Single stranded wire is more fragile and susceptible to cracking, so it is not recommended for use in installations where cables move or are affected by vibrations. Krone connectors preferred single stranded cables in order to achieve better contact in the contact blades, which can be problematic with multistranded cables. So, for example, Mogami installation cables are not at all good for connection to Krone connectors because they have too soft insulation and a lot of strands, while for example some stiffer cables such as Klotz and Draka can be used. That's my experience, maybe it will be useful for you.
 
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Krone blocks were made for telco's. Multi stranded wire will simply not attach too well. That's why Krone advises single stranded. It's amazing how much pull these can withstand.

Ever saw the inside of an old-fashioned phone xchange? The wires in the bay are being pulled on on a daily basis, by techs pulling new connections and removing old ones. And even if the bay is mounted on solid concrete, there's often something to cause vibrations. From ventilations fans to test equipment mounted in or next to the bay. That's what the connections on a Krone block are designed for. It's also why you really need the appropriate Krone punchdown tool.

With our national telco, using stranded wire is ground for immediate dismissal. At least in theory. I've never known a tech to be foolish enough to try it.
 
I ’m assuming Krone blocks are punch blocks. I’ve always got them second hand and reused them in the past. Always tin or solder the multi strand pigtail wire end before pressing into the punch block.

Back in the 80s. Studios would actually change boards with request for different consoles for a track ing or mixing session (like at the village recorders). Punchblocks would be used for the interconnect. Also I remember aN MCI 400 series with punch blocks for Interface. Just solder the multi strand wire striped end before inserting into the block. Mogami Would not be my first choice as mentioned for punch blocks. Back in the day belden 8451 would be pretty standard. It’s much stiffer and uses Teflon coating. It’s high capacitance but with transformer 600 ohm, it had good bandwidth. For more modern gear or unbalanced, it could roll off. My later consoles used Cannon DL or Edac. I got away from Punchblocks after the 80s. My 2cents
 
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Soldering wires before putting them in compression type connections is a really bad idea. If you have the right cable it's not necesaary to do this with Krone blocks. You get a phenomenom called cold flow, which makes the solder go soft & powdery when it is under comprssion which makes the connection loose in the long run. When I used to run PA systems we had to redo any plugs that had the cables soldered before screwing them in the terminals because the connections went bad. The extra resistance could cause arcing in mains connectors in bad examples & ground loops in the Earth connections.

The current oxygen free wire is not really suitable for these types of connections. It is too soft. The multi core cable that was used back in the day was much stiffer than what is available today.
 
More on 'cold flow' from a marine electronics article:
Soldering the ends stiff is often suggested as a way of increasing durability with many of these connector types, perhaps even making the push-in, spring loaded type safe. This is not true. Under high mechanical load the solder will deform, loosening the connection and allowing strands to cut. If the connection is overheated (and this does not need to be to the solder melting point) only enough to soften it ever so slightly-the wire will deform and the joint will come loose. Cycled a few times, they can literally fall apart. Tinned wire is OK, but do not prep the wire ends in any way other than twisting. Crimping a pin onto the wire end should be a last resort, and we've never seen the need for it on a boat.
 
You get a phenomenom called cold flow, which makes the solder go soft & powdery when it is under comprssion which makes the connection loose in the long run.
I did not know this. I stand corrected. Thanks for the info Rob. It’s good to keep in mind for screw down termination as well.
 
Technicians for our local telco get a one month introductory course on wiring before the can start work. The part on wiring reads as "do not ever use stranded wire", "don't use solder anywhere".

In fact there are teams known as "welders" that use a kind of solder. But they don't do anything else but repair cut wires (usually bundles of 400 or multiples of that). They use something we might call "solder", but it's nothing like the solder we all know.

What is widely in use for fast fixes, are "Scotch locks". That's a plastic thing with some paste and a blade inside. It has two holes to insert wires. Once inserted, you just use pliers to close the knife. It's a fantastic tool, but not cheap and it's considered a temporary fix. They're made by 3M. Works in the wet, in dirt... A bit like WD40. Wonder if it's developed for military use too.
 
Soldering the ends stiff is often suggested as a way of increasing durability ... This is not true
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Interesting and helpful thread. I see similar discussions in other areas. For example, ham radio operators love to solder every wire in the shack, thinking it makes better electrical and mechanical contact/continuity. In fact, the heat weakens the wire and makes it brittle, along with all the other problems with soldering wire listed earlier in the thread. I was told by a feller who specializes in one-off circuit boards for NASA and Defense Department that a really good, solid, clean and firm crimp connection can be electrically better and less prone to failure from mechanical stress than a soldered connection. Hams rarely accept this advice. There is, of course, a point to soldering some connections and not soldering other types of connection.

Again, interesting thread. James
 
I've managed to get my hand on 30 Krone disconnect blocks, a frame and punch tool so I'm going to go ahead and do this.

At the moment I'm using ADC patchbays, cutting DB25 snakes in half and stripping the wires so I can use the punch block on the back of the patchbay. This is still unreliable though, so I've opened up one of the patchbays to check out the options. It's all single-core copper, beautifully wired to the longframe sockets, so I don't want to mess with that. My plan is to remove the rear punchblock and connect this wiring directly to the Krone block. From the other side I'm going to run multicore (10 x single stranded twisted pair 24AWG) telephone cables to my gear. I've attached a data sheet for the cable.

I'm not at all sure how to go about wiring these multicores for Tascam DB25, which has 3 pins per channel. As I understand it, the twisted pair should take care of interference and crosstalk for each channel's hot and cold, but how do I handle the grounding pin? Here's one idea I had, but it seems to me this might introduce interference and/or crosstalk:

Pair 1 ch1 +/-
Pair 2
ch1 shield/ch2 shield
Pair 3 ch2 +/-
Pair 4 ch3 shield/ch4 shield
etc

Another solution might be to have some sort of bussed ground system for each DB25?

I'm going to try a couple of things out once the cable arrives, but if anyone here has experience with this type of thing any advice would be most welcome :)

Cheers
Stephen

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After some more reading, including some good posts here, I've learnt a bit more terminology, and am putting together a wiring scheme.

The cable in my previous post is unavailable, it is discontinued. From what I can gather 20 core, 10 twisted pair solid core cable is pretty much redundant, but I've managed to track down what looks to be great cable here. I've also learnt to call each unshielded twisted pair UTP.

So, my patchbay/outboard gear/Krone blocks will be wired using UTP cabling. Pin 2 hot, Pin 3 cold, pin 1 N/C. From what I've read this will work, and the use of 10-pair Krone blocks now make a whole lot more sense.

Cheers
Stephen
 
Yep, good point Bri. I'll be crimping DB-25 pins onto the solid-core and making my own Tascam DB-25 connectors. By not using pin 1 for each channel that gives me 16 pins per 8 channels, so each 10-pair cable and Krone block will carry 10 channels. I'll have to be very clear with my documentation, and labelling on the Krone frame, but it'll give me much more reliable wiring. I'll also be able to use twisted-pair jumper leads to hard-wire connections like DAC-out to console-in. Any configuration changes will be done at the Krone frame.

Hopefully...
 
Here’s the Tascam wiring for insert send and returns…

8D309823-A242-40BC-AF9B-8E4B3901B555.png

And the pins used for 8 channel, UTP cabling

C13F6D18-E18F-4B54-99BD-B41897EA82AA.jpeg
 
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