I need to wire a punchdown type patchbay between tape ins (balanced TRS) on my tape machine and direct tape outs outs on my console (unbalanced).
The shield on the patchbay is not carried through the patchbay when a cable is not inserted.
The normal path is going to be direct out 1-24 to tape in 1-24.
I'm guessing I need to jumper the shield permanently to get this to work?
There also 8 console subgroups where the outputs are balanced. I'd like to be able to patch these into the tape outs via a patch cord. This wiring is a snap too.
It all works in my head, but will me making the permanant shield connections cause me problems when patching from the subgroups and when repatching the 1-24 channels?
I need to wire a punchdown type patchbay between tape ins (balanced
TRS) on my tape machine and direct tape outs outs on my console
(unbalanced).
The shield on the patchbay is not carried through the patchbay when a
cable is not inserted.
Look at the patchbay closely. If the jacks are all individual and mounted on an insulated panel, then the sleeves are indeed not connected betwen a a jack pair. If the jacks are constructed as a pair, however, most of those have the sleeves of the pair on the same piece of metal so they're connected.
There also 8 console subgroups where the outputs are balanced. I'd
like to be able to patch these into the tape outs via a patch cord.
This wiring is a snap too.
You should wire the patchbay as if everything was balanced. On the console direct out end of the cable, connect the shield and ring wire to the sleeve/shield/ground on the connector. That will put the signal between the tip and ring at the tape deck, and that's what you want. If the shield is indeed not connected between the jacks unless there's a patch cable inserted, leave it that way for starters and see if it hums. If it does, then connect the jack pair sleeves. If it doesn't, then leave it alone.
Gareth Magennis 16 March 2006 19:04:44 [ permanent link ]
"leftofthedial" <robert@leftofthedial.com> wrote in message news:1142517363.642149.316930@p10g2000cwp.googlegroups.com...
I need to wire a punchdown type patchbay between tape ins (balanced
TRS) on my tape machine and direct tape outs outs on my console
(unbalanced).
The shield on the patchbay is not carried through the patchbay when a
cable is not inserted.
The normal path is going to be direct out 1-24 to tape in 1-24.
I'm guessing I need to jumper the shield permanently to get this to
work?
You shouldn't have to. The direct out shields will be connected to the desk ground, thus the cables from desk to patchbay are shielded to ground. If your tape machine is grounded properly too, the cables between tape machine and patchbay will also be properly shielded. Connecting the two shields at the patchbay shouldn't make any difference, but then ground loops and grounding problems are aften rather tricky and sometimes a bit illogical. Try it - if there are no hum problems you don't need to connect the patchbay shields.
You are in fact creating an earth loop by connecting them together: follow the loop from the desk mains power socket to desk chassis to direct out shield, to patchbay to tape machine input shield, to tape machine chassis to tape machine power socket, and back to the desk power socket via the mains wiring.
Gareth.
There also 8 console subgroups where the outputs are balanced. I'd
like to be able to patch these into the tape outs via a patch cord.
This wiring is a snap too.
It all works in my head, but will me making the permanant shield
connections cause me problems when patching from the subgroups and when
I need to wire a punchdown type patchbay between tape ins (balanced
TRS) on my tape machine and direct tape outs outs on my console
(unbalanced).
What grounding scheme do you use? Do you have a ground buss at the patchbay or not?
The shield on the patchbay is not carried through the patchbay when a
cable is not inserted.
Why does it matter what happens when thre is no cable?
The normal path is going to be direct out 1-24 to tape in 1-24.
I'm guessing I need to jumper the shield permanently to get this to
work?
Depends. The shield and hot on the unbalanced side go to cold and hot on the balanced side, respectively. Now, you can connect the ground on the unbalanced device to whatever your grounding system is.
There also 8 console subgroups where the outputs are balanced. I'd
like to be able to patch these into the tape outs via a patch cord.
This wiring is a snap too.
It all works in my head, but will me making the permanant shield
connections cause me problems when patching from the subgroups and when
repatching the 1-24 channels?
Your goal: there should be ONE AND ONLY ONE path on the ground lines from any piece of equipment to any other. There are dozens of different ways you can do this, including constructing star grounds, ground busses, etc. It doesn't matter which one you use, as long as everything has a proper ground and it never has two. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis."
Why does it matter what happens when thre is no cable?
If a pair of jacks is normalled to gether, there's a hole in the shield. This may or may not matter. But if he doesn't connect the shield on the unbalanced end to the ring of the jack, he may not have a signal path, or it may run all through the house to find its way back.
Thanks Mike, Looks like my console already does this for me. The jacks in the console are dual purpose (group outs or direct outs) and use TRS jacks. With the switch in group outs, it's TRS ground compensated. With the switch in direct outs, the TRS jack is Tip=hot, ring=gnd, sleeve=gnd.
My current cables are TRS to TRS. I'll just have to see if it still works when I wire in the patch bay, otherwise I may be replacing the TRS on the console side with the TS'.
