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DIY Stompboxes => Building your own stompbox => Topic started by: Big Monk on February 08, 2021, 08:01:47 AM

Title: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 08:01:47 AM
My late night researches have been focused on grounding for the past few nights. I have been looking for ways that provide a more idealized (from a technical standpoint) grounding scheme than what I am used to (Star Ground at input jack). What I came across was a post from R.G. that has intrigue (and confused) me:

So how it should be done is:

1. The input jack sleeve should be connected to the enclosure right where it punches through the enclosure. This can be done by just the screws holding it into the box, but as noted paint, and eventually just dirt and time will make this not so reliable. This ought to be done with a star/toothed lockwasher under the fixing nut to bite into the enclosure metal for long term reliability. This makes the input ground a solid RF/shield ground to bleed incoming RF from the wires into the surrounding enclosure and keep it out of the circuits. This can also be done with a small ceramic cap of maybe 0.001 from the input sleeve right to the chassis if for some other reason you don't want to - or can't! - DC-ground the input sleeve right there. The cap leads have to be as short as you can possibly make them to be effective.

In the ideal case, this connection to the chassis at the input jack should be the **only** conductive connection to the chassis.

2. The incoming DC adapter jack and battery leads, etc. grounded sides should not connect to the chassis where they come in or elsewhere. They should run directly to a point on the circuit board where traces split out to power the circuit.

3. The input ground should connect to the circuit board ground right at the input circuitry.

4. The output jack should be isolated from the chassis, and a signal ground wire run from its sleeve back to the ground common point on the PCB. This way, only output signal currents run through that ground wire. Hooking its ground to the input jack ground terminal forces both input signal currents and output signal currents to flow in the same wire resistance. This makes an explicit shunt feedback loop around the whole pedal. As long as gain and impedance are low enough, it doesn't matter, but when you get enough, it oscillates from the feedback.

5. The input jack should not be wired for the input-power switching trick by using a stereo jack and running power negative to the ring terminal. This forces 100% of the power supply current for the whole pedal down the input signal ground wire, and the currents used by the circuit are fed back into the input. When current, gain, and/or impedance get high enough, this can make it oscillate. The output jack is a better place for this, as the currents are higher and it's not automatically a feedback issue. But it does risk putting signal out  on the output line for the next pedal. The best way to do jack-based power switching if you want to do it is to use a bipolar transistor to switch power and a resistor from its base to the stereo jack ring terminal. This can only contribute a DC offset, and a very small one, instead of a signal.

6. LED ground returns should go either to the place power is brought onto the board from the power jack or back to the power jack. This keeps the large-ish current changes off the signal reference ground wires.

Most of this makes perfect sense to me from an implementation standpoint but my brain is stuck on what I am used to and what i am used to is tying all grounds to the input jack sleeve.

In the scheme shown above in R.G.'s quote, where are the rest of the grounds connected to provide independence from the enclosure ground provided by the input jack sleeve?
Title: Re: Clarification on Pedal Grounding
Post by: anotherjim on February 08, 2021, 08:37:53 AM
Sometimes, I use mixed jacks. A plastic body pcb mount that also plays a role securing the board, and a metal one to ground the case. Only suits small projects as the board is L shape to clear the metal jack and the plastic one should be mounted at a slight tilt on the board so it remains level due to the enclosure sides being angled.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 03:12:51 PM
I guess my main concern would be, in the absence of the Input jack functioning as the global "star" ground point for the circuit, where do the other circuit grounds make their connection?
Title: Re: Clarification on Pedal Grounding
Post by: GibsonGM on February 08, 2021, 03:21:51 PM
Monk, open the .pdf here where it says "Click Here" to download.  This shows the standard ways of wiring up stompboxes...all work fine, most of us use the 3pdt option but there are exceptions.    Each shows how the grounds work!  They all DO connect together...


http://www.tonepad.com/getFileInfo.asp?id=76 (http://www.tonepad.com/getFileInfo.asp?id=76)
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 03:34:10 PM
I'm looking more for clarification on R.G.'s quote above and how it is applied practically.

I'm comfortable with traditional offboard wiring. I guess I am just wondering how R.G's grounding methods above are incorporated with normal offboard wiring.
Title: Re: Clarification on Pedal Grounding
Post by: EBK on February 08, 2021, 03:57:35 PM
I do something in my builds that is similar (I believe) to what R.G. proposed, but I use the output jack sleeve terminal instead of the input jack sleeve terminal as my enclosure shield ground connection.  Essentially, treat your enclosure as a shield, not a ground current conductor. Connect only one spot on the enclosure to ground.  For me, this means I use insulating shoulder washers on my input jack so the sleeve terminal doesn't contact the enclosure.  The output jack is mounted as usual, and it's sleeve provides the shield ground connection.  It doesn't much matter (usually) where you decide to connect your circuit grounds together, but I try to make a star ground connected as close as possible to the DC jack (my input jack, output jack, stomp switch LED, and circuit board each get their own ground wire; this does mean I'm not keeping my input ground "with" the input signal technically).
I will never tell you that my method is "necessary", "proper", or "better" though.  There are plenty of noises from plenty of sources in guitar signal chains.  You'll often hardly notice any difference between sloppy builds that work and super neat by-the-book wiring.  It is more a pride in craftsmanship issue, I believe.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 04:22:40 PM
I do something in my builds that is similar (I believe) to what R.G. proposed, but I use the output jack sleeve terminal instead of the input jack sleeve terminal as my enclosure shield ground connection.  Essentially, treat your enclosure as a shield, not a ground current conductor. Connect only one spot on the enclosure to ground.  For me, this means I use insulating shoulder washers on my input jack so the sleeve terminal doesn't contact the enclosure.  The output jack is mounted as usual, and it's sleeve provides the shield ground connection.  It doesn't much matter (usually) where you decide to connect your circuit grounds together, but I try to make a star ground connected as close as possible to the DC jack (my input jack, output jack, stomp switch LED, and circuit board each get their own ground wire; this does mean I'm not keeping my input ground "with" the input signal technically).
I will never tell you that my method is "necessary", "proper", or "better" though.  There are plenty of noises from plenty of sources in guitar signal chains.  You'll often hardly notice any difference between sloppy builds that work and super neat by-the-book wiring.  It is more a pride in craftsmanship issue, I believe.

Maybe this is my hangup: If we use either one of the jacks as the shield ground connections, through it's sleeve connection, how do we then run a ground from it's sleeve terminal and not have issues?

As an FYI, i'm a pretty sharp guy, it's just that i am having a mental block here.
Title: Re: Clarification on Pedal Grounding
Post by: EBK on February 08, 2021, 04:32:35 PM
Maybe this is my hangup: If we use either one of the jacks as the shield ground connections, through it's sleeve connection, how do we then run a ground from it's sleeve terminal and not have issues?
You don't have "issues" because you only have one path for the ground current for that jack, i.e. the wire from the sleeve terminal to your circuit board ground connection (or wherever you choose to run that to).  The ground current won't flow over the enclosure itself because there isn't another electrical connection to the enclosure it can flow to/from.  If you ground both jacks and don't insulate one from the enclosure, then you would have two electrical connections to the enclosure, and current can flow between them.
Quote
As an FYI, i'm a pretty sharp guy...
I hope you didn't read my comment as implying otherwise.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 04:37:23 PM
Ok. I plan on using Cliff style jacks but with a raised tooth washer and also a 3/8" washer with a solder tab on the input jack.

I hope you didn't read my comment as implying otherwise.

Absolutely not. I was just trying to highlight the fact that this is me genuinely trying to sort this out on my own first rather than just pinging people to do it for me. You've been extremely helpful and I appreciate it.
Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on February 08, 2021, 05:43:34 PM
The wiring is about problem sources and counter-measures.

The problems are:
- External RF sources
- Ground loops on the signal wires  (from amps, pedals, or other external devices).
- Ground loops relating to power (possibly only at high frequencies)
- Ripple currents in the grounds due to unregulated power supplies putting charging filter caps on the effects PCB.
- Currents pulses on the grounds originating from devices on the effects boards (like charge pumps, DC converters, even LFO).
   Remember these currents will appear between the effects board and the DC power.
- RF originating from the pedals digital circuit getting out of the box. 

The worst wiring will work some of the time and the best wiring will work most of the time.  Most good wiring will be close to the best except for a few specific problem scenarios.

The normal way of using the input socket as the star point and grounding the output socket is one good way and is probably the most economical way of getting good performance    RG's is another way and EBK's is also a good way.   All have small cracks in the armor.   Peter Cornish's method is probably the most evolved in the sense of trying to remove the problems.  However a non-isolated input socket might be better.  The output socket not grounded with the mounting bolt might not be as good for RF.   

Peter Cornish's methods is:
- Isolated input socket.
- Input switches input power.
- Input socket wired to chassis with short wire from the input socket ground to grounding lug on the enclosure.
- The input and output cables are shielded inside the enclosure.
   [clarification: the cable shields must connect at both ends.]
- The output socket is isolated.
- Output socket wired to chassis via a capacitor

The reason the input socket is used as the star ground in the normal case and in Peter Cornish's case is because the input socket is used to switch the battery and/or DC power in let.   The requirement for input socket to switch the both battery power and/or DC adaptor power is a constraint.   RG's solution for example doesn't lend itself to input socket switching as undermines some of the good intentions of having the star point on the PCB.

Some builders might fob-off some of the problems or say "I don't do that" but the truth is when a pedal will goes out into the world people will used them without considering any constraints.


EDIT:

Here's some picks of the Cornish method,
https://aionfx.com/news/tracing-journal-cornish-ss-3-soft-sustain/

Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 06:37:39 PM
The wiring is a about problem sources and counter-measures.

The problems are:
- External RF sources
- Ground loops on the signal wires  (from amps, pedals, or other external devices).
- Ground loops relating to power (possibly only at high frequencies)
- Ripple currents in the grounds due to unregulated power supplies putting charging filter caps on the effects PCB.
- Currents pulses on the grounds originating from devices on the effects boards (like charge pumps, DC converters, even LFO).
   Remember these currents will appear between the effects board and the DC power.
- RF originating from the pedals digital circuit getting out of the box. 

The worst wiring will work some of the time and the best wiring will work most of the time.  Most good wiring will be close to the best except for a few specific problem scenarios.

The normal way of using the input socket as the star point and grounding the output socket is one good way and is probably the most economical way of getting good performance    RG's is another way and EBK's is also a good way.   All have small cracks in the armor.   Peter Cornish's method is probably the most evolved in the sense of trying to remove the problems.  However a non-isolated input socket might be better.  The output socket not grounded with the mounting bolt might not be as good for RF.   

Peter Cornish's methods is:
- Isolated input socket.
- Input switches input power.
- Input socket wired to chassis with short wire from the input socket ground to grounding lug on the enclosure.
- The input and output cables are shielded inside the enclosure.
- The output socket is isolated.
- Output socket wired to chassis via a capacitor

The reason the input socket is used as the star ground in the normal case and in Peter Cornish's case is because the input socket is used to switch the battery and/or DC power in let.   The requirement for input socket to switch the both battery power and/or DC adaptor power is a constraint.   RG's solution for example doesn't lend itself to input socket switching as undermines some of the good intentions of having the star point on the PCB.

Some builders might fob-off some of the problems or say "I don't do that" but the truth is when a pedal will goes out into the world people will used them without considering any constraints.


EDIT:

Here's some picks of the Cornish method,
https://aionfx.com/news/tracing-journal-cornish-ss-3-soft-sustain/

Thank for this. I will read through it more thoroughly and internalize it but one thing that jumps out at me is the use of the PCB itself as the star ground point. I hadnít really thought of this.

So essentially Iíd pick a point for Chassis ground, likely the input jack, and then take all other grounds to the PCB? Obviously in a well thought out manner and not willy nilly.
Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on February 08, 2021, 06:46:21 PM
Quote
Thank for this. I will read through it more thoroughly and internalize it but one thing that jumps out at me is the use of the PCB itself as the star ground point. I hadnít really thought of this.

There's motivations behind the normal method and RG's method.  The biggest change in RG's method is the star ground on the PCB.

Quote
So essentially Iíd pick a point for Chassis ground, likely the input jack, and then take all other grounds to the PCB? Obviously in a well thought out manner and not willy nilly.
Yes that's pretty much it.   Boss pedals have this method nailed.    IIRC, some of the Boss schematics explicitly show the wiring - but it's not as clear as having a pic or actual unit showing where all the wires go.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 06:58:03 PM
Thank you to everyone who replied. This was one of those things where the pieces were floating around ready to click into place with some constructive advice.

Much appreciated.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 06:59:58 PM
Quote
Thank for this. I will read through it more thoroughly and internalize it but one thing that jumps out at me is the use of the PCB itself as the star ground point. I hadnít really thought of this.

There's motivations behind the normal method and RG's method.  The biggest change in RG's method is the star ground on the PCB.

Quote
So essentially Iíd pick a point for Chassis ground, likely the input jack, and then take all other grounds to the PCB? Obviously in a well thought out manner and not willy nilly.
Yes that's pretty much it.   Boss pedals have this method nailed.    IIRC, some of the Boss schematics explicitly show the wiring - but it's not as clear as having a pic or actual unit showing where all the wires go.

Just to put the fine point on this: letís say I choose the input jack to make my Chassis ground connection. I would bring a wire from the sleeve to Chassis in some way (many ways to skin this cat) but also bring in input ground (signal ground) from the sleeve to the star point?
Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on February 08, 2021, 07:39:45 PM
Quote
Just to put the fine point on this: letís say I choose the input jack to make my Chassis ground connection. I would bring a wire from the sleeve to Chassis in some way (many ways to skin this cat) but also bring in input ground (signal ground) from the sleeve to the star point?

In the simplest case you use the input socket sleeve terminal as the star-point.

A second configuration would be a to use a large ring terminal as the star-point, mounted on the socket itself.     In this case there's no harm wiring the sleeve terminal to the start-point.   The advantage is all the connections are soldered and not passing through the chassis.

A third configuration would be to use a separate grounding lug for the star-point.  It *must* be located as close as possible to the input socket.  In this case the reasoning follows the previous case.

To wire or not is (or should be) a minor point as you want the connections to the chassis to be good (by using star washers).    Also when you consider the output socket, soldering wiring the sleeve of the input socket is a little hypocritical because the output socket often uses the case connection to get the ground.   You probably don't want power running through the ground connection though, so that's a good motivation to solder the input socket sleeve to the star point. You can run a wire wire from the output socket sleeve back to the star point but then the output socket has two ground point which are not close to each other.    To avoid the output socket dilemma you would use an isolated output socket, then you go down the rabbit hole of needing to use shielded cable and have cap to ground like the Cornish method.   

You can debate all the fine points for hours but in practice the difference between the Boss method and the Cornish method is pretty small.     I'm with EBK in that  I'm not enforcing what I think on others.   For a small box like a pedal the differences are small.

I remembered this thread which went through all the same issues,

https://www.diystompboxes.com/smfforum/index.php?topic=123930.0
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 08, 2021, 08:55:12 PM
Maybe this is my hangup: If we use either one of the jacks as the shield ground connections, through it's sleeve connection, how do we then run a ground from it's sleeve terminal and not have issues?
You don't have "issues" because you only have one path for the ground current for that jack, i.e. the wire from the sleeve terminal to your circuit board ground connection (or wherever you choose to run that to).  The ground current won't flow over the enclosure itself because there isn't another electrical connection to the enclosure it can flow to/from.  If you ground both jacks and don't insulate one from the enclosure, then you would have two electrical connections to the enclosure, and current can flow between them.

So, if Iím processing this correctly, I can make a single connection from the input jack sleeve to the enclosure (in any suitable way) and also connect the sleeve to the star ground. In essence, one provides my shield ground for the whole circuit while the other provides the signal ground for the input jack.
Title: Re: Clarification on Pedal Grounding
Post by: Fancy Lime on February 09, 2021, 02:28:55 AM
Is there a reason to use the input as the star point rather than the output? I would not expect that to make a huge difference but if it does, wouldn't the output be closer to earth (assuming the effects chain ultimately goes to an amplifier with ground=earth)? The guitar end (input) is just floating with no real ground, no? Just curious why most people seem to star the input.

Andy
Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on February 09, 2021, 03:45:53 AM
Quote
Is there a reason to use the input as the star point rather than the output? I would not expect that to make a huge difference but if it does, wouldn't the output be closer to earth (assuming the effects chain ultimately goes to an amplifier with ground=earth)? The guitar end (input) is just floating with no real ground, no? Just curious why most people seem to star the input.
It starts from the fact most pedals switch the power using the input socket.   There's a slight advantage going with the input because the input circuits are more sensitive to junk and if you have a gain pedal it will boost that junk.

In many cases you could try hard as you like to create a bad set-up and it still works.  Then you get some crazy cases like the guy with the 1stop power supply issue a couple of weeks back.   He was getting buzz in *bypass* mode with a true bypass setup.  Worked fine of battery but acted weird with the PSU.   He had filters on the PSU rails  and a star ground at input.   A tough one and it was not resolved.

EDIT: FWIW, running the power through input socket isn't actually a good thing but it's what pedals do!
Title: Re: Clarification on Pedal Grounding
Post by: anotherjim on February 09, 2021, 05:30:51 AM
You can get jack sockets with isolated switching if you want to keep a power connection away from signal. Up to DPDT. Commonly used in rear panel patch connections on fancier guitar amps. They are nearly always PCB mounting. I'm not certain if the pin size/spacing is right for matrix board. I've got an open frame one that was used to switch resistor networks to run headphones off main speaker amplifiers. It looks quite a contraption.
https://www.tubeampdoctor.com/en/marshall-1/4/6.3mm-jack-pcb-with-dpdt-switch
Not really suitable for panel/case mounting though.
Title: Re: Clarification on Pedal Grounding
Post by: EBK on February 09, 2021, 06:33:23 AM
So, if Iím processing this correctly, I can make a single connection from the input jack sleeve to the enclosure (in any suitable way) and also connect the sleeve to the star ground. In essence, one provides my shield ground for the whole circuit while the other provides the signal ground for the input jack.
Yes.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 09, 2021, 07:53:50 AM
It starts from the fact most pedals switch the power using the input socket.

EDIT: FWIW, running the power through input socket isn't actually a good thing but it's what pedals do!

I wonder if switching power on the footswitch would be better. You could easily source a 4PDT stompswitch and dedicate 1/2 to true bypass switching while the other half switches the LED circuit and battery circuit. Or you could simply do what some of the major purveyors of vintage style PNP fuzzes do and put a small switch near the DC jack that allows the user, particularly one with the pedal integrated into a pedalboard, to manual switch the battery connection off.

That way you could just use a mono jack for input and output.

As I am now seeing pretty clearly the way forward here, now I need to visualize and draw up how all the connections route in my enclosure.
Title: Re: Clarification on Pedal Grounding
Post by: anotherjim on February 09, 2021, 08:02:34 AM
Power switching with bypass causes big thump noises. There are plenty of small chip amplifiers with soft power-on muting and any muting circuit could be added to an existing design, but we don't want the short silence during changeover either.
Everybody thinks of that idea at some point!  ;)
Title: Re: Clarification on Pedal Grounding
Post by: EBK on February 09, 2021, 08:16:46 AM
You could also choose to skip power switching entirely.  I haven't built a pedal with a battery option in many many years, so I build my pedals so they are always powered on when the power supply is present.  Much simpler. 
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 09, 2021, 09:39:17 AM
You could also choose to skip power switching entirely.  I haven't built a pedal with a battery option in many many years, so I build my pedals so they are always powered on when the power supply is present.  Much simpler.

Well, I am not a fan of batteries. Even for a PNP circuit, i'd prefer to just use a charge pump voltage inverter to get the required voltage for the PNP circuit as opposed to running a battery.

An easy option, of course, it to simply use a SPST switch to turn off power. I see this all the time on many of the boutique vintage fuzz clones. Doesn't have to be operated when the pedal is engaged and simpyl allows the user to remotely switch the battery off without unplugging anything from the pedal board.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 09, 2021, 12:26:43 PM
Well it's settled: The Tayda "Copper Hammer", pre-drilled enclosures i'm using don't have enough space for a battery so I don't have to worry about power switching!
Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on February 09, 2021, 05:50:41 PM
Quote
You could also choose to skip power switching entirely.  I haven't built a pedal with a battery option in many many years, so I build my pedals so they are always powered on when the power supply is present.  Much simpler. 
I've notice pedals which don't have batteries still switch the power.    If you think about it, it's not very useful and seems more like a tradition if anything else.   If you have a string of pedals powered from an adaptor/PSU you aren't going to be playing with the input sockets at all.   Once you get rid of the input socket switching RG's star point on the PCB is very appealing.
 
Quote
You can get jack sockets with isolated switching if you want to keep a power connection away from signal. Up to DPDT. Commonly used in rear panel patch connections on fancier guitar amps. They are nearly always PCB mounting. I'm not certain if the pin size/spacing is right for matrix board. I've got an open frame one that was used to switch resistor networks to run headphones off main speaker amplifiers. It looks quite a contraption.
https://www.tubeampdoctor.com/en/marshall-1/4/6.3mm-jack-pcb-with-dpdt-switch
Not really suitable for panel/case mounting though.

I had an Ibanez bass which switched the +rail with on of this *style* of jack, they were common back in the day.  They didn't last long.  I eventually gave up and put in a standard stereo Switchcraft socket (and switched the -rail).    I'm not sure about the style you posted or the complex isolated ones.  IIRC switch craft might have switched types.

(https://www.musikding.de/media/image/product/516/lg/63mm-stereo-jack-with-switch.jpg)

Another way to do the switching is to use a transistor/MOSFET to switch  one of the supply rails *on the PCB*.   The switching is done with a low current control signal wired to standard stereo input socket.   That way there's no real power going through the input jack.   A few pedals with charge-pumps and DC/DC converters do this to stop the DC input current pulses going through the input jack and causing noise/whine.
Title: Re: Clarification on Pedal Grounding
Post by: antonis on February 09, 2021, 05:58:29 PM
Everybody thinks of that idea at some point!  ;)

Some of us at more than one point.. :icon_lol:
Title: Re: Clarification on Pedal Grounding
Post by: duck_arse on February 10, 2021, 08:54:04 AM
you need to be careful using those ^ style jacks Rob shows ^ above, because the single throw type sometimes is N/C when you want it N/O contacts.
Title: Re: Clarification on Pedal Grounding
Post by: anotherjim on February 10, 2021, 11:01:22 AM
Some while ago I'm sure somebody here made a detection switch for the plastic Cliff/Re-an type sockets. The plastic covering the end over the plug tip was removed so a microswitch lever could be operated by the inserted plug. Clever, but I can't remember why it was necessary.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 10, 2021, 01:22:45 PM
By ruling out the use of a battery, and the subsequent removal of power switching from consideration, i'll be able to follow R.G.'s steps, with a few minor exceptions, to the letter. I just need to revise my board design to accept, in a logical and elegant manner, the concept of the star ground being the ground "rail" of the circuit board.

Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on February 10, 2021, 07:43:26 PM
Quote
Some while ago I'm sure somebody here made a detection switch for the plastic Cliff/Re-an type sockets. The plastic covering the end over the plug tip was removed so a microswitch lever could be operated by the inserted plug. Clever, but I can't remember why it was necessary.
Cool idea nonetheless.

Quote
you need to be careful using those ^ style jacks Rob shows ^ above, because the single throw type sometimes is N/C when you want it N/O contacts.
I got a feeling i saw some switchcraft ones which went the other way.   I think Peavey had some similar looking to what I posted but they had open backs like the Boss connectors.  Those had switches.   I suspect the Peavey ones are a hell of a lot more reliable.   The prong things like my pic are hopeless.

Quote
By ruling out the use of a battery, and the subsequent removal of power switching from consideration, i'll be able to follow R.G.'s steps, with a few minor exceptions, to the letter. I just need to revise my board design to accept, in a logical and elegant manner, the concept of the star ground being the ground "rail" of the circuit board.
RG's scheme is what's used in larger scale equipment (equipment where doing silly things like switching power never comes into it).  It's works well.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 11, 2021, 07:21:14 PM
So Iíve set up my PCB layout and done my enclosure planning based on the following:

1.) Input jack will be mono plastic Cliff style with tooth washer and washer with solder tab. Input sleeve will have a wire to the solder tab washer and wire to ground rail on board.

2.) Shielded wire will run, with shield grounded at input jack to the switch then another pieces of shielded wire from switch to board. Shield has a dedicated spot on board connected to ground rail.

3.) LED will connect in the normal fashion and a ground wire from the 3PDT will go to dedicated pad on ground rail. (This one Iím up in the air about, as LED transients seem to be an issue of concern and grounding at the board is something Iím not sure about).

4.) Non switching DC jack will run to dedicated +/- pads on board, with ground dead side running directly to the ground rail.

5.) Output will have same arrangement as input.

Sound alright? I believe this upholds what has been discussed here and besides some unknowns/misgivings surrounding my connection of the LED, I feel pretty good about it.
Title: Re: Clarification on Pedal Grounding
Post by: anotherjim on February 12, 2021, 04:09:06 AM
Reduce LED transients by using high-efficiency/high bright LED's so you can use a large series resistor.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 14, 2021, 08:50:56 AM
I finalized the PCB last night. I laid out the ground rail to accept connections from all the off board mechanical parts and positioned the pads in the logical places where they will make connection. Controls pads are measured to be directly in line the pots, input and output connections are on the side and can accept the shield wire ground at the point of entry, there are ground pads for the input and output jack sleeves and also a pad for the switch ground. Power input has its own ground pads as well and Iíll be taking the advice on high powered LEDs and large limiting resistors into account.

Iím using Neutrik unswitched mono jacks with ferrule and shoulder washer and have solder tab washers to make the Chassis connection at the input jack.

Thanks for all the help! I need to put eyes on the layout a few more times with an eye toward ensuring I didnít miss anything and then I think Iíll order a limited run.
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on February 16, 2021, 01:10:47 PM
Like a fool I never attached a photo:

(https://www.themodernbrewhouse.com/wp-content/uploads/2021/02/Grounding-Layout.png)
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on March 16, 2021, 07:49:25 AM
Maybe this is my hangup: If we use either one of the jacks as the shield ground connections, through it's sleeve connection, how do we then run a ground from it's sleeve terminal and not have issues?
You don't have "issues" because you only have one path for the ground current for that jack, i.e. the wire from the sleeve terminal to your circuit board ground connection (or wherever you choose to run that to).  The ground current won't flow over the enclosure itself because there isn't another electrical connection to the enclosure it can flow to/from.  If you ground both jacks and don't insulate one from the enclosure, then you would have two electrical connections to the enclosure, and current can flow between them.
Quote

Circling back on this after setting up my "Prototyper" breadboard environment for proper grounding: So even though there is continuity between the signal grounds and the enclosure, ground current won't flow through the enclosure? My concern is I have continuity from the ground rail on my breadboard to the enclosure.

I'm likely missing something elementary here but even as an EE, i've never been afraid to look stupid if it will help people out or help me learn something!
Title: Re: Clarification on Pedal Grounding
Post by: iainpunk on March 16, 2021, 08:26:19 AM
Quote
Circling back on this after setting up my "Prototyper" breadboard environment for proper grounding: So even though there is continuity between the signal grounds and the enclosure, ground current won't flow through the enclosure? My concern is I have continuity from the ground rail on my breadboard to the enclosure.

I'm likely missing something elementary here but even as an EE, i've never been afraid to look stupid if it will help people out or help me learn something!
its generally a good idea to use a real soldered wire connection to the ground lugs, since you can't trust the jack's connection to the enclosure.
i personally use one grounded jack and the rest are isolated ones, to avoid ground loops.

cheers
Title: Re: Clarification on Pedal Grounding
Post by: EBK on March 16, 2021, 08:47:15 AM
Quote
Circling back on this after setting up my "Prototyper" breadboard environment for proper grounding: So even though there is continuity between the signal grounds and the enclosure, ground current won't flow through the enclosure? My concern is I have continuity from the ground rail on my breadboard to the enclosure.

I'm likely missing something elementary here but even as an EE, i've never been afraid to look stupid if it will help people out or help me learn something!

I could make this explanation more complicated and complete, but let's think of it this way:

Imagine you have some wires connecting two points in your circuit A,B and you make a single connection to your enclosure at point C in the middle.  We can model your enclosure as if it is just a long wire connected at that one point, like this:

(https://i.imgur.com/zFntLQll.jpg)

The Xs indicate that there are no additional connections to the enclosure.  Thus, there are no current sources or current sinks anywhere along that enclosure "wire", except through point C.  Therefore, no current can flow to/from anywhere along the modeled enclosure.  You should have continuity between any point on the enclosure and point C because current could flow if you added a source, such as the test current provided by your multimeter probe.  Is that any clearer?
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on March 16, 2021, 09:15:11 AM
Quote
Circling back on this after setting up my "Prototyper" breadboard environment for proper grounding: So even though there is continuity between the signal grounds and the enclosure, ground current won't flow through the enclosure? My concern is I have continuity from the ground rail on my breadboard to the enclosure.

I'm likely missing something elementary here but even as an EE, i've never been afraid to look stupid if it will help people out or help me learn something!

I could make this explanation more complicated and complete, but let's think of it this way:

Imagine you have some wires connecting two points in your circuit A,B and you make a single connection to your enclosure at point C in the middle.  We can model your enclosure as if it is just a long wire connected at that one point, like this:

(https://i.imgur.com/zFntLQll.jpg)

The Xs indicate that there are no additional connections to the enclosure.  Thus, there are no current sources or current sinks anywhere along that enclosure "wire", except through point C.  Therefore, no current can flow to/from anywhere along the modeled enclosure.  You should have continuity between any point on the enclosure and point C because current could flow if you added a source, such as the test current provided by your multimeter probe.  Is that any clearer?

It is!

So in short, there is no issue with the sleeve being connected to the enclosure AND the sleeve going to signal ground on the PCB/Breadboard/Etc. since the enclosure only connects to the sleeve of the input jack and has no other path by which to "receive" (for lack of a better descriptor) current, i.e. a single connection to the enclosure is shunting rather than conducting current.

I don't believe I have any ground related noise anyway, but was mostly just trying to square this idea in my head.
Title: Re: Clarification on Pedal Grounding
Post by: EBK on March 16, 2021, 09:28:22 AM
...i.e. a single connection to the enclosure is shunting rather than conducting current.
I prefer to think of it as the enclosure does not "participate" in the basic operations of the circuit.  Shielding is a "bonus" that the enclosure provides in this configuration, which I like to simply enjoy and take for granted.  :icon_wink:
Title: Re: Clarification on Pedal Grounding
Post by: garcho on March 16, 2021, 09:57:46 AM
Great thread. It's important to walk through things step by step. I think part of what makes this issue confusing for so many people is:

ē often, when you do it "wrong", it works just fine
ē self-taught tinkerers like myself tend to focus only on voltage and forget that electricity is voltage AND current
ē ground vs earth vs shield vs reference vs... but it's all ground?!?!  ;D
Title: Re: Clarification on Pedal Grounding
Post by: Big Monk on March 16, 2021, 10:06:25 AM
...i.e. a single connection to the enclosure is shunting rather than conducting current.
I prefer to think of it as the enclosure does not "participate" in the basic operations of the circuit.  Shielding is a "bonus" that the enclosure provides in this configuration, which I like to simply enjoy and take for granted.  :icon_wink:

Well said.

Appreciate the input. Now let me go build that power supply filter I've been thinking about all morning... :)
Title: Re: Clarification on Pedal Grounding
Post by: amz-fx on March 16, 2021, 05:27:08 PM


regards, Jack
Title: Re: Clarification on Pedal Grounding
Post by: Rob Strand on March 18, 2021, 06:57:55 PM
Quote
regards, Jack
Quite a good video but the motive behind it it more about safety and stopping audio geeks doing stupid things.

The part from 17:40 (and some background for that back to 14:52) is probably more useful in terms of understanding mains related  "buzz".

With that in mind you can start to think a bit more about how mains borne noise couples in,
https://www.analog.com/media/en/technical-documentation/application-notes/41727248an_347.pdf

If you can explain why touching the guitar strings decreases the buzz you know you have got the idea.