True Bypass Loop Strip

[Mcentee2]

Tried search and got close to an answer, and also learnt a lot of other things!

I am planning a Tue Bypass Loop switch with multiple loops/switches. I've found various wiring schemes in diagrams and think I have head around the connections required for power/LED, switch wiring and jack wiring and am looking to follow the scheme here:

http://1.bp.blogspot.com/-SzM32SDZGdM/UX_DmZFl5aI/AAAAAAAAFhg/Bp3b9omf8Ds/s1600/TB+Looper+5+with+buffer+and+tuner.png

One thing that is never clear in any of these diagrams, nor can I find obvious info from bypass loops out there in the wild, is if *all* the jacks are insulted or uninsulated or if it is assumed they all make ground connection with the enclosure ?

If the above is "ok" and the enclosure offer the common ground path, then do I still need to connect up all the ground lugs via wire as well ?

Is this "good" ? or do I need to insulate all but the input or output jack ?

[duck_arse]

you need and want all grounds connected to ground. how you do it is up to you. using the box-as-connection will bite you when one jack-nut works loose. connecting all your sleeves via wire to a common point will help prevent that, but you might decide it's too many wires.

what are you insulating? you can use plastic jacks to isolate the jack from the case if you need them, but you still need to connect grounds to grounds.

[Mcentee2]

Not sure "what" i am insulating, just i have seen other posts that were similar about board patchboxes (Guitar IN, FX Send/Ret, Amp Out) that had ground loop issues because all the jacks were connected to the box and was keen to avoid anything similar.

Not even sure if should be separating the LED power ground from anything the jacks grounds touch....unlike the diagram I referenced which shows them all effectively joined together via the input jack.

[duck_arse]

(how rude of me, I didn't look yr dia.) the audio ground can be completely seperate to the led ground. if you use a battery, there is no need for it to connect with the audio. there are real-life cases that may disprove this rule.

[Mcentee2]

No worries - not rude at all!

So I should be ok with all the jacks' ground lugs using the case, and also wired as a backup I'll keep the power ground separate as this will be from a DC adapter.


Many thanks.

[duck_arse]

as someone said in another thread I just read, "yes".

[moid]

I'm going to ask a daft question (because I'm good at them, as Duck knows) but when you're talking about the jacks' ground lugs using the case, do you mean connecting a cable from the ground lug of the jack to the metal enclosure itself? If so, what benefit does that provide? I usually use a star ground where all grounds in the circuit and jacks connect via separate cables to the ground lug of the power jack, but if I don't have to do that I could could simplify the wiring in my builds a lot (there's usually 3 -5 wires going to the ground lug of the power jack).

[Mcentee2]

I'm going to ask a daft question (because I'm good at them, as Duck knows) but when you're talking about the jacks' ground lugs using the case, do you mean connecting a cable from the ground lug of the jack to the metal enclosure itself? If so, what benefit does that provide? I usually use a star ground where all grounds in the circuit and jacks connect via separate cables to the ground lug of the power jack, but if I don't have to do that I could could simplify the wiring in my builds a lot (there's usually 3 -5 wires going to the ground lug of the power jack).

If all the jacks are "uninsulated" - like your standard switchcraft metal skeleton jacks, and your enclosure is bare metal then all the jack's sleeve/ring connectors are connected through the enclosure.

I was questioning if that is a good thing or whether, in a TB strip, this could cause ground loop problems. Seems like the answer is "no worries, it will be fine" form the replies above.

Given this is a discrete enclosure and the whole case is at the same "ground level" as long as somewhere one of the connected-together jacks touch it then you should be fine and do not need star grounding for the signal grounds.

You could have the power ground and signal ground all touching the case or a single point but that assumes both are at the same "level".

.. If so, what benefit does that provide?

the benefit (sure you  know this) is that you need at least one connection between either signal or power ground to the case to earth all the em etc (faraday cage).

If you have all insulated jacks apart from one that touches the case, and then all jacks' grounds connect together via wires in a chain to the output jack ground, then that to me seems to avoid any of the ground loop scenarios.

My question was based on not seeing many (if any) TB strips that vendors sell wired like this with insulated jacks....

[Mcentee2]

Ok - I have been doing some more reading and research about this and have come across another aspect that I haven't got my head around yet.

A lot of vendors and DIY boards offer instructions or products for pedal-board patch bays.

These boxes nearly always seem to have isolated pairs of jacks - Guitar IN and Board Send is one pair; Board Return and Amp Send is the other - one of those pairs will be grounded to the case for RF purposes somewhere.

In terms of grounding, the patch bay only grounds at one point to prevent a loop between the In ground potential and the eventual Out ground potential.

I can see that with lots of pedals, more than one PSU etc this could potentially build up a difference in ground levels from start to finish, and isolating them avoids a loop.

However, if this is reducted down to a simple Out-FX-Return logical flow it seems to be the same as a single TB loop re signal flow (without the switch!) with the potential for a ground level variance from the input therefore will have a ground loop.

(I suppose a test of guitar lead sleeve connected to FX out lead sleeve would show any potnetial differnces - if your DMM was accurate enough).

With a single pedal you would expect the input/output grounds to be the same so no issue really with one pedal - however if you then have more TB loops for more pedals presumably at some point in your chain one of those will have a "different" output ground level.

So with a chain of "lots" of pedals I still don't get why then Patch boards standard is "isolated pairs", and TB strips are all non-isolated/ground/sharing ..

One assumes you will have a ground loop problem, the other assumes you won't.....



Pretty sure I am missing something ?

[Processaurus]

I think you may trying to solve potential problems, that can easily not be an issue. Why don't you build it, and see if there are problems? You can always make a special, ground lift 1/4" cable, by snipping the sleeve/shield connection at one end. There's no point in using insulated jacks, if you are just going to connect all the grounds together in the pedal.  The only reason to use insulated jacks, is if you know you are going to lift the ground (more likely to cause noise problems, in most scenarios), or are going to make a ground lift switch for every insulated jack.

The only ground loop problems I've had, is having old school pedals with AC power cords, that are 3 prong, they will make a ground loop to the amp, which has a 3rd prong ground as well. Also using two amps, each with a 3 prong plug. Especially if they are plugged into different outlets, then there is a hum, because the building's wiring can have different voltage potentials at ground at each outlet, so when they get connected together, by the signal cable, that difference in voltage potential causes current to flow down your cable, and the small resistance of the cable, causes the voltage, which should be zero, to wiggle around a little. That wiggle gets into your audio.

The only localized, pedalboard grounding issues I've seen, with pedals that used regular DC adapter power, are noise from one pedal's power usage getting passed to another pedal, from using a daisy chained power connector for the pedals. Some digital pedals are bad for that, they will make a whine, or little robot noises, when daisy chained. It's a case of power ground, contaminating signal ground. The solution is to use a separate power supply for the problem pedal, or a multi-output transformer power supply, like the voodoo labs pedal power, or similar clones.

I would see if you have problems, before worrying. If you do, you can do something like use a 1:1 isolation transformer for an output, or RG's opamp based, isolated A/B/Y switcher (designed for eliminating ground loops using two amps).

[pinkjimiphoton]

ground is ground. that said, you could keep the ac ground separate from the dc one. or more aptly, the audio and the power separate, but in my humble opinion you're far more likely to pick up noise.

mount all the jacks in the box. connect some busswire to all the grounds, and then connect this to your star ground, which would be the - post of your power supply jack. ground is ground, and that should keep everything at the same potential.

just + power to the CLR/led's, and ground the - of the battery. that way no surprises, no loops, less noise. even better if you add a buffer in there somewhere.

you may find you need to run a big resistor to ground from each switch if you're getting any pops due to dc potential differences (hey, it happens)

cool lookin' project. add a PIC and you could probably make it all programmable