Non-Isolated Power Jacks - I just dont get it.

[niggez]

I dont get how to use them. I always end up putting isolation tape around them...Is there a way to use them that lets me mount them on metal chassis without having to isolate them?
I could just buy isolated jacks, but they dont look as good.

Edit: I assume my way of doing it is the only way, since the shaft of my plugs is always 9V+ i have to somehow isolate it from the chassis.

[Mark Hammer]

For safety reasons, barrel jacks are great.  You can make the outside/shaft the (negative) ground connection so that no one will ever find themselves holding a ground connection with one hand and accidentally pinching the hot connection of the barrel plug between the thumb and index of the other hand.  If it was a phone plug, where the tip is positive, a person very well could accidentally be touching the tip and a ground connection somewhere else and get to see "the magic blue lights".

"But wait", you say, all those Boss and other adaptors use the shaft for V+ and not for ground.  Correctamundo, my friend, that they do.  Why?  Because when the insertion of a plug is supposed to lift the connection to an internal battery source, and make a connection to an external source, something has to get bumped out of the way, and something has to do the bumping.  With a phone plug/jack, you have the tip to do the bumping.  In the case of a barrel plug, there IS no tip, and the only thing that can do the bumping is the shaft of the plug.  So.....whenever you're displacing an internal battery by inserting a barrel plug, the outside will virtually always be positive, because it needs to be.

Of course, when there is no internal battery supply, and nothing needs to be bumped out of the way, it becomes the manufacturer's choice as to whether they want the  shaft to be positive, or the inside pin connection to be positive.  As noted earlier, from a safety standpoint, it's better if the most likely part of the plug that a user touches is the ground.  And if outside is ground, then that makes it a breeze to use a jack that provides automatic connection of the plug ground to chassis ground, exactly the same way it typically happens with mini (1/8") phone jacks/plugs on all those old EHX pedals.  In fact, though I may remember it wrong, I do believe my two old Boss BF-1 flangers (which do not use batteries) use an outside-neg jack/plug.

The fact that "manufacturer's choice" exists for non-battery-powered devices is is also the reason why many companies like Boss and DOD will insist that you use their wallwarts.  Really and truly, there is likely no difference between the 9v/300ma wallwart you can buy locally for $5 and a Boss PSU as far as whether it can power your pedals.  HOWEVER, Boss has no idea if YOU understand the difference between outside pos and outside neg (and let's be honest, a great many users don't, present company excepted).  So, to assure that you will not accidentally blow up one of their pedals with the wrong polarity and blame them for "producing such a crappy product", and in order to alleviate them of the burden of teaching all their customers about polarity and the basics of electricity, they simply say "Use our PSU".

So, the short answer is that outside-ground power jacks exist because they can be safely used, and outside-pos power jacks exist because sometimes they NEED to be used.

[slacker]

If the shaft of your plugs is 9 volts then the only way to use these sort of DC sockets is to isolate them from the chassis. If you are only ever going to use DIY pedals, that have this sort of socket you could reverse the polarity of your plugs so the shaft was negative and reverse the connections on the socket. That works fine, but you can't then use the socket to switch the battery. Just mark the plugs in some way so you don't accidentally use them with centre negative pedals.

[Elektrojänis]

If you are only ever going to use DIY pedals, that have this sort of socket you could reverse the polarity of your plugs so the shaft was negative and reverse the connections on the socket. That works fine, but you can't then use the socket to switch the battery.

Why couldn't you just switch the battery from it's negative side? Many people allready do it when using a stereo jack for the input to turn pedals off when there is nothing plugged in to the input. Is there something I did not understand?

I've used this method on some builds:

Wire goes from negative battery terminal to the "switching pin" (the one that connects to the shaft contact when there is nothin plugged to the socket) of the power socket. The shaft contact is connected to the ring terminal of the input jack.

Positive battery terminal is connected to the center pin of the power socket (it could connect to the positive power input of the circuit board too if that is more simple to wire) and the center pin is connected to positive power input of the circuitboard.

Rest of the wiring is just the standard stuff.

[slacker]

Yeah that would never thought of that 

[niggez]

thats what i thought, switching inside/outside of my power supply, but that would mean opening up 5 or so pedals and resoldering the wires...
ill just keep the jacks isolated with the isolation tape method!
Maybe i can make myself someething more lasting, like modified isolation washers or something...more permanent. I will see. Thanks for your help.

[drewl]

Boss  set their pedals up that way so you'd have to use thier power supplies.....i

[aron]

They do this so we have to purchase adapters for our one spots. :-)

[Jered]

  Or you could use non-conductive boxes. Wood, plastic, whatever...
  Jered

[Mark Hammer]

Boss  set their pedals up that way so you'd have to use thier power supplies.....i

Read my post above.  Boss would probably prefer not to HAVE to make or sell power supplies.  The markup and revenue is minimal, relative to the nuisance, and there is no guarantee whatsoever that you will ever buy even one of their pedals to use it with.  What it does guarantee is that they can simply say in the product manuals "Use THIS supply" and no one, out of millions, will ever return a busted pedal to the company because they used an incompatible PSU that Roland didn't warn them about.

If it was the case that all wallwarts using barrel plugs observed the same polarity and were always regulated DC, then Roland and every other company could simply say "Get yourself a 9v adaptor that provides at least this much current", and be done with it.  They are forced into providing PSUs because of the nonstandardization "out there".

[jakenold]

That BOSS-standard is a tricky one!

Anywho, you can drill a hole that is larger than the plug itself, then fill it up with JB Weld, and drill a new hole after the epoxy has cured for an extended period of time (I can't remember how many days). I think it was Steve Daniels that proposed this on his website. I've done it a couple of times, and it works great. Just be sure to get the epoxy on the inside of the chassis as well, so it has something to hold on to, in case the users is rough inserting the plug.

Jake

[Michael Weidenauer]

My method of isolating jacks (in fact my girlfriends had the idea) is using plastic washers and isolating the rest with a short piece of shrink-tube.  Works very well!
If you have high volotages, maybe better use two layers of shrink tube!

[numpty]

Use a rubber grommet for isolation, you may have to remove a bit of rubber each side with a stanley knife to clear the thread

[Mark Hammer]

The other approach is to use a mini phone-jack.  They are cheaper, smaller, and a whole lot easier to install.  Many companies (e.g., EHX) used them for years before peer pressure forced them to "go barrel".

"But I spent $$$ on a decent wallwart to power my pedals.  I'm not about to change, or butcher that sucker, now!"

You do not have to.  Said it before and I'll say it again.  Make yourself a power distribution box.  That is, a little plastic box that sits on your pedalboard.  The wallwart (as is) plugs into that, and the power is distributed via a bunch of jacks on the box.  The wallwart doesn't have to be butchered at all, and you can run cables with the plugs/jacks/length of your choosing to each of your pedals in the neatest and most convenient manner possible.  You could make yourself a daisy-chain cable with barrel plugs for your Boss pedals or EHX Nano pedals, another with phone plugs for your DIY pedals, and yet another for that bloody wah whose side-mounted jack always manages to screw up your cabling plans.

The chief concern over mini phone jacks is that there is a momentary risk of shorting hot and ground if one inserts a "live" plug.  Barrel plugs, by comparison, hold no such risk.  If the power-distribution box remains on the pedal board, with all power-cabling in place, then nothing is "live" until you insert the wallwart's barrel plug into the barrel jack in the distribution box.  Problem solved.  The fact that the distribution box is plastic is also a nice safety feature.

The other thing you can do with the box is install a power status LED to let you know that the unit is powered up and ready.  A "deluxe" version accepts a higher voltage (e.g., 18vdc) and regulates that down to 12 and/or 9v, so that you have several possible output voltages for pedals with different requirements.

[gez]

"But wait", you say, all those Boss and other adaptors use the shaft for V+ and not for ground.  Correctamundo, my friend, that they do.  Why?  Because when the insertion of a plug is supposed to lift the connection to an internal battery source, and make a connection to an external source, something has to get bumped out of the way, and something has to do the bumping.  With a phone plug/jack, you have the tip to do the bumping.  In the case of a barrel plug, there IS no tip, and the only thing that can do the bumping is the shaft of the plug.  So.....whenever you're displacing an internal battery by inserting a barrel plug, the outside will virtually always be positive, because it needs to be.

Hadn't thought of that, but if the barrel was negative and you bumped the negative lead of the battery instead of positive, there wouldn't be any problem.  Unless I'm missing something?

[aron]

Another cool choice is to simply purchase the 1-5 outlet extender cord for the One Spot. You can use this cord with any adapter - positive or negative barrel based.

[Processaurus]

Yes, you could run the battery plus directly to the circuit, and negative to the jack and have it be disconnected when the plug was inserted just as easily.  The weird reason for the tip negative standard:
http://www.diystompboxes.com/smfforum/index.php?topic=57641.msg448260#msg448260

For the nice metal DC jacks, Steve at small bear recommends making a big hole and bondo-ing it, and then drilling a small hole in the bondo "plug" for the jack.

[earthtonesaudio]

I say rebel against the convention.  Start using barrel jacks with tip/center as positive.  It makes more sense.  Then you chop the cords on all your wall warts, and reverse the wires...

And pretty soon the whole world will follow your lead.  This is true because humans are rational actors, and will quickly change their set-in ways once they see a more sensible alternative. 

...On second thought, maybe that's just the way people behave in my own twisted mind.  Or in France.

[gez]

The weird reason for the tip negative standard:
http://www.diystompboxes.com/smfforum/index.php?topic=57641.msg448260#msg448260

Was this arrangement used on early pedals, then?  I don't recal seeing it on any of the Boss schematics I've seen, so I'm a little confused; unless I've misunderstood your post.  Could you link to a schematic? (didn't quite follow your explanation, sorry.)

[Processaurus]

The weird reason for the tip negative standard:
http://www.diystompboxes.com/smfforum/index.php?topic=57641.msg448260#msg448260

Was this arrangement used on early pedals, then?  I don't recal seeing it on any of the Boss schematics I've seen, so I'm a little confused; unless I've misunderstood your post.  Could you link to a schematic? (didn't quite follow your explanation, sorry.)

Yeah, I think it's just for ACA adapter (earlier boss) bedals.  I thought it was for all of them, but you got me to try beeping out a couple current (PSA adapter) boss pedals and the tip is connected directly to the chassis ground.  My experience was with an older CS-3, I was trying to figure out why it sounded distorted & yucky with the adapter putting out a good 9v, but normal with a 9v battery.  The series resistor from circuit ground to power supply ground was dropping the voltage too much.  Maybe it wasn't for ground loops, but to drop the voltage of their unregulated ACA adapters?