Does this diagram look like a solid shielded cable scheme?

[guitylerham]

Hey guys,
I've got all my circuits up and running for my multi-FX board and now I'm going to start wiring them into the enclosure. I'm learning how to use shielded wire to protect from interference. How does this drawing look to you?



I will use braid pair wiring. The enclosure is bent aluminum sheeting. Since this will include 10 circuits and two ac transformers, I really want to do my best to quiet this thing. I know the transformers cause a separate problem with EM radiation and I'll work to address that as I need to. How does this look? Is it logical?

[therecordingart]

I'm not so sure it'll do any good on your pot wiring and in/out since only one side is attached to ground. I'm not an expert on the subject, but it almost seems like more hassle than it's worth unless you're currently having issues.

[guitylerham]

Thanks for chiming in. As far as I've learned to this point, when using shielded wire, you want to only ground one end of the shield otherwise you can create ground loops and add to the noise issue.

[deadastronaut]

ive only ever had to use sheilded wiring on high gain stuff,

and then i only take the shielded inner core wire from the 'switch' to  the pcb 'in', and just ground the outer shield onto the pcb....(one end)

[Ice-9]

Thanks for chiming in. As far as I've learned to this point, when using shielded wire, you want to only ground one end of the shield otherwise you can create ground loops and add to the noise issue.

Correct.

[therecordingart]

Thanks for chiming in. As far as I've learned to this point, when using shielded wire, you want to only ground one end of the shield otherwise you can create ground loops and add to the noise issue.

I can see that. So, in a sense, does the floating end act like an antenna passing noise to ground?

[seedlings]

Thanks for chiming in. As far as I've learned to this point, when using shielded wire, you want to only ground one end of the shield otherwise you can create ground loops and add to the noise issue.

I can see that. So, in a sense, does the floating end act like an antenna passing noise to ground?

Sort of.  The ground shield is... a shield.  Like the enclosure is a shield.  Like 'shielded speakers' are OK to use near tube televisions.  Grounding both ends of the shielding creates a 'resistance' between two ground points, and even though that resistance is very small it becomes a current path.  If foreign current flows through your ground path, it will be induced on your signal wire.

This is a good read, even though it is tube-heavy in content:
http://valvewizard2.webs.com/Grounding.pdf

CHAD

*edit: one other possible problem you can run into is transformer placement.  If at all possible place that item last.  Before you drill out for it, hook up some headphones to your signal wires, or connect your signal wires to a guitar amp.  Connect the transformer to power, but the other ends of the transformer don't need to be terminated.  Move the powered transformer around and listen.  Place the transformer in a spot where you don't hear any interference.  I learned this the hard way building two tube amps that 'hum' while on standby... boo.

[Paul Marossy]

ive only ever had to use sheilded wiring on high gain stuff,

and then i only take the shielded inner core wire from the 'switch' to  the pcb 'in', and just ground the outer shield onto the pcb....(one end)

That's the only time I've had to use shielded cable. It was on my Shaka Tube. Other than that, I've never needed to use shielded cable in any of my builds.

[guitylerham]

Yeah, the transformers will be troublesome and I do plan on leaving them loose until I get it all up and running. I'll try and place them in the best place. With ten circuits inside this 26 inch box, there won't be much room to move.

So my drawing doesn't look like it'd do harm though? Does high gain include boost pedals, tube screamer, distortion +, or tube sound fuzz?

[deadastronaut]

Does high gain include boost pedals, tube screamer, distortion +, or tube sound fuzz?

i' do the shielding on the tubescreamer, distortion, and fuzz, just to be sure i don't end up with a radio..........not sure on the boost!...

[guitylerham]

Ok, will do! Thanks guys.

[guitylerham]

Man, I just spent an hour wiring in the first circuit and it's becoming clear how much of a pain this will be twisting shielding around nearly every wire to and from pots and switches. Can I just wrap a single grounded wire around all three of the wires on a pot? This would cut down on the chaos a bit...

[deadastronaut]

twisting shielding?...

i use rca phono lead wire...chop one of those up, strip the ends, use inner core for connections...use one end of outer (shield) to pcb ground...and just heatshrink the other (shield) end

so it can't touch anything....

[Ice-9]

Man, I just spent an hour wiring in the first circuit and it's becoming clear how much of a pain this will be twisting shielding around nearly every wire to and from pots and switches. Can I just wrap a single grounded wire around all three of the wires on a pot? This would cut down on the chaos a bit...

Tell me your not making your own shielded cable by twisting the shield around a single wire ! That would really be a pain to do, use the single core shielded grey cable readily available (just like instrument cable, strip the outer cover to show the shield and the inner wire is signal)

[deadastronaut]

^

[guitylerham]

Yeah guys... I was twisting my own pair. It is hideous. I'll redo all of that using a better wire. I'll check out the RCA. I think the instrument cable kind might be a little thick for my tight quarters but that's a good idea too. Thanks guys.

[deadastronaut]

Yeah guys... It is hideous.

  i bet it is ...like most things in life, keep it simple is best!..  good luck man!..

[Seljer]

You could probably get away with using a cable with 3 conductors + shield for the pots instead of individual ones

[Morocotopo]

Shield first all the inputs, those are the most critical points, and the runs from input jack to the switches also.  After that, only add shielding if necessary. The most critical wire is the one between input jack>switch>FX input.

[guitylerham]

Seljer: that's a good idea!

Morocotopo: I agree with that procedure, however since I'll have noisey transformers within inches of a few of the effects, I'll just go ahead and shield EVERYTHING and hope for the best. I'm imagining that locating those xformers inside a box with sensitive circuits while keeping things quiet from EMF and such will be quite the chore. Hold onto your butts.