Power switching with TRS jack socket

[rob.reido]

Hey guys,

I'm aware that some pedal manufacturers use a switched TRS socket for their input jack, so that they can wire the 9VDC supply up to the ring terminal, and the circuit power input to the sleeve terminal (I think!), thus shorting the two together and powering the circuit when a standard TS jack is connected to the pedal's input (as explained at about 1:10 in this That Pedal Show vid: https://www.youtube.com/watch?v=B5yJEQGSHZE).
This sounds like a great idea, as it avoids switching the circuit's power on/off every time the pedal is bypassed (as would happen if the 9VDC into the circuit was switched using the 3PDT footswitch), but I can't figure out specifically how this would be wired up, or if this would mess with the grounding of the input jack's sleeve.
If anyone could help me out with specifically how this is all wired up, then that would be awesome - a quick schematic would be ideal, as I'm quite a visual person, but any help would be greatly appreciated.
Thanks,

Rob

[GibsonGM]

Here you go, Rob!  http://www.generalguitargadgets.com/how-to-build-it/technical-help/switching-and-wiring/bypass-sw-options/

Usually it's the GROUND that is switched in/out, by the insertion of a plug into the input jack...enjoy.  Welcome to the forum 

[antonis]

Usually it's the GROUND that is switched in/out, by the insertion of a plug into the input jack...

Could your Highness define the term "GROUND", Sir..?? 

[GibsonGM]

Usually it's the GROUND that is switched in/out, by the insertion of a plug into the input jack...

Could your Highness define the term "GROUND", Sir..?? 

"Ground"  or "DC ground" is a common reference point of a circuit that each of the components or circuit blocks return to.  Although there certainly are positive ground systems, and grounds made at seemingly arbitrary voltage levels, in MOST stompbox and amp topologies, "ground" will refer to the negative side of a battery or power supply. 

Good, Antonis?

[antonis]

 

More than good, Sir..!!!
(always beholden to your Highness..)

[kraal]

This sounds like a great idea, as it avoids switching the circuit's power on/off every time the pedal is bypassed (as would happen if the 9VDC into the circuit was switched using the 3PDT footswitch).

Hello,

I don't really get what you mean with this sentence.
This trick is not related with bypassing your pedal. It simply disconnects your pedal from DC (battery) when you unplug the input jack (i.e. unplugging the jack breaks the DC circuit).
Note that it only works when using jacks with Make contact switch on the ring (and not Break contact switch)
If what you want to achieve is turning off the pedal when bypassing it, this can be done with a 3PDT switch (if you're not using a led) or a 4PDT (if you plan to usea LED indicator).

But maybe I misunderstood your sentence.

Regards,

[GibsonGM]

I think the OP just didn't know how the power is typically done, Kraal.  The GGG offboard wiring info should fix that! 

Maybe we should mention that the sleeve (also called the shield) of your guitar cord is grounded..and this pattern continues on down the line, from guitar, thru the pedals and into your amp.  So doing the jack switching shouldn't be done this way if you have a POSITIVE ground (like many fuzz faces) - you can't mix and match, the scheme is all negative ground....

[anotherjim]

The jack switching was really meant to save the battery. I think many who build without batteries in mind don't bother and have the DC input power permanently wired through.

Nobody switches power with the stomp switch - unless they like thumps in their speakers.

[willienillie]

So doing the jack switching shouldn't be done this way if you have a POSITIVE ground (like many fuzz faces) - you can't mix and match, the scheme is all negative ground....

No, it's fine as long as you aren't daisy chaining external power between positive ground and negative ground pedals.

Unless I'm misunderstanding you.

[niektb]

So doing the jack switching shouldn't be done this way if you have a POSITIVE ground (like many fuzz faces) - you can't mix and match, the scheme is all negative ground....

No, it's fine as long as you aren't daisy chaining external power between positive ground and negative ground pedals.

Unless I'm misunderstanding you.

Hmm, I don't think you should cause you would put a lot of DC on the signal ground (which the next/previous pedal may or may not like)

[GibsonGM]

So doing the jack switching shouldn't be done this way if you have a POSITIVE ground (like many fuzz faces) - you can't mix and match, the scheme is all negative ground....

No, it's fine as long as you aren't daisy chaining external power between positive ground and negative ground pedals.

Unless I'm misunderstanding you.

Yes, I meant if you are daisy chaining...

[willienillie]

So doing the jack switching shouldn't be done this way if you have a POSITIVE ground (like many fuzz faces) - you can't mix and match, the scheme is all negative ground....

No, it's fine as long as you aren't daisy chaining external power between positive ground and negative ground pedals.

Unless I'm misunderstanding you.

Hmm, I don't think you should cause you would put a lot of DC on the signal ground (which the next/previous pedal may or may not like)

No...

[Ben N]

So doing the jack switching shouldn't be done this way if you have a POSITIVE ground (like many fuzz faces) - you can't mix and match, the scheme is all negative ground....

No, it's fine as long as you aren't daisy chaining external power between positive ground and negative ground pedals.

Unless I'm misunderstanding you.

Hmm, I don't think you should cause you would put a lot of DC on the signal ground (which the next/previous pedal may or may not like)

This is why God made coupling caps. If Jimi in his wisdom could feed his neg ground Vox wah into his pos ground Fuzzface (or was it the other way around?) then we can too. Just no daisy chaining, at least not without a magic reversing power cable. (Jimi didn't have a wall wart.)

[bartimaeus]

Do any pedals actually switch power on/off using the 3PDT? I think you'd get undesirable noises if you did that, since you'd hear it starting up every time you switched to it.

I think every manufacturer who allows for batteries in their pedals does the TRS trick. I think the only time where it's not used are pedals with only a DC jack, and those pedals never switch off the power. But maybe there are some outliers I'm unaware of?

[willienillie]

But maybe there are some outliers I'm unaware of?

Some have power switches.  Early Big Muffs, Mosrite Fuzzrite, and a few others back before "disconnect input" was a standard.  Now some have power switches so that a battery can be used, for fuzz mojo or whatever, without users having to disturb their pedalboard arrangements by unplugging a cable.

I doubt any switch power with the bypass though, terrible noise.

[kraal]

I doubt any switch power with the bypass though, terrible noise.

Has anybody experimented / tried implementing a "standby mode" for pedals ? The return on investment may not be worth it, but I don't see why it would not be possible to achieve this for pedals.

Would the noise really be that high if using a footswitch that first "makes" the connection to the power (when pressing the switch) then "breaks" the bypass (when releasing pressure) ?

"They didn't know it was impossible, so they did it." Mark Twain

[rob.reido]

Hey again guys,
Thanks GibsonGM, kraal et al for all your help, this has really cleared things up for me. I'll definitely make sure to avoid switching circuit power with the 3PDT, seems like I've dodged a bullet there!

[Ben N]

I think every manufacturer who allows for batteries in their pedals does the TRS trick. I think the only time where it's not used are pedals with only a DC jack, and those pedals never switch off the power. But maybe there are some outliers I'm unaware of?

I'm no manufacturer, but I generally do it (out of habit, I guess) in my builds, and I rarely put in a battery clip. Just yesterday, I think I completed my first build ever with two mono jacks, thinki9ng, what do I need the extra wiring for?.