Negative ground vs Positive ground wiring - here we go again.

[markm]

I could be off base here but, many older U.S. and European automobiles used Positive ground electrical systems strange as it may seem.

[col]

I just built a neg ground tonebender with pnp trannies and have built several others including a FF and have only had problems with batteries which were failing slightly. No problems whatsoever with the power supply which is a regulated multi-point. When the batteries have fallen below arounf 8.5v the circuits tend to get noisy and oscillate. I need the neg ground as I use them alongside other pedals.

Col

[MikeH]

I need the neg ground as I use them alongside other pedals.

You can still use a positive ground effect in line with other traditional negative ground effects can't you?

[R.G.]

I need the neg ground as I use them alongside other pedals.

You can still use a positive ground effect in line with other traditional negative ground effects can't you?

Negative and positive ground pedals can be used together in any combination.

What you can't do is use one single-polarity power supply for positive and negative ground pedals. The positive ground pedals connect the positive side of any power supply that gets connected to them to signal ground internally. The negative ground pedals internally connect the negative side of any power supply that gets connected to them to signal ground. If you have a positive ground pedal and a negative ground pedal with a signal cable between them on a single power supply, then both the negative and positive sides of the power supply are connected to signal ground, and the power supply is shorted.

The answer is to use two different power supplies. One power supply can run as many negative ground pedals as you like, the other power supply can run all of the positive ground pedals. You just can't have the ground on a single power supply connected to both positive and negative sides.

This is a slippery concept to beginners - did everybody get that OK?

[choklitlove]

i might be mistaken, but i thought the 1 spot can run both.  it has those connectors.

here's what it says on the page:
"Reverse Polarity Converter for Yamaha (CYR):
* Allows the 1 SPOT and MC5 cable to power Yamaha keyboards, samplers, and drum machines, as well as certain reverse polarity effects pedals"

here:http://www.visualsound.net/1spot.htm

[Ronsonic]

Just to add to RG's, some power supplies have multiple isolated outputs so the same box can provide power to a mix of pedal.

You just need to be very sure that's what you have.

Ron

[R.G.]

i might be mistaken, but i thought the 1 spot can run both.  it has those connectors.

I do happen to know about the 1Spot.

It's a single power supply output with low noise and high output. So it can run any reasonable number of the same polarity effects at the same time. The reverse polarity converter does just that - it inverts the polarity on the plug. It doesn't (and can't!) make a new, isolated output.

So if you are running things from 1Spots, you will need one unit for all of your normal negative ground pedals, and one for all of your positive ground pedals. Fortunately, they cost little enough that two of them to do this is very reasonable.

[MikeH]

Despite many warnings about building a Neg ground circuit with PNP tranny's I decided to try it out anyway.  When I had it on the breadboard, it didn't oscillate at all, just gave me a nice fat fuzz.  Actually pretty damn quiet as well.  Sounded awesome. Well, I made my PCB using Tonepads layout and soldered it up.  When I hooked it up to my test rig, it started oscillating like friggin crazy; making all kinds of noise.  I messed with the controls and it stopped.  Didn't oscillate anymore, at any setting, no matter how hard I tried to get it to.  Wierd.  Before, I must have played with it for hours on the breadboard and it never oscillated once.  Wierd again.  The Fuzz face is a mysterious thing.  I'm going to try and put a gigantic Electrolytic cap across the + and - to try and make sure it doesn't oscillate, if that doesn't work, I guess it's pos ground time.

[R.G.]

Congratulations! You got away with it... probably.

[carrejans]

I need the neg ground as I use them alongside other pedals.

You can still use a positive ground effect in line with other traditional negative ground effects can't you?

Negative and positive ground pedals can be used together in any combination.

What you can't do is use one single-polarity power supply for positive and negative ground pedals.

Sorry for bumping this old thread.

It's very clear for me why you can't use a single-polarity power supply for positive and negative ground pedals.

But what's still strange to me, is the fact that you can put two effects after each other, one neg and the other pos ground.
Because like this, you are connecting pos ground and neg ground to each other with the patch cable, no?
So I don't get this.
Can anyone explain?
Thanks...

[MikeH]

"Positive Ground" is kind of a slang term.  Ground is always 0 volts.  A 'positive ground' pedal runs off -9v, the battery + is connected to ground, but it's still 0v.

[Hides-His-Eyes]

GROUND IS RELATIVE...

[Govmnt_Lacky]

But what's still strange to me, is the fact that you can put two effects after each other, one neg and the other pos ground.
Because like this, you are connecting pos ground and neg ground to each other with the patch cable, no?
So I don't get this.

Join the club my friend. I cant wrap my head around it either. By jacking a Positive ground pedal to a Negative one (i.e. a PNP Fuzz Face to a NPN Booster) you are essentially connecting the V+ from the PNP to the V- of the NPN. I have had people tell me that using 2 seperate power supplies (one for each effect) solves this problem but you are STILL shorting the two together via the Output jack of the PNP and the Input jack of the NPN or vice versa.

It baffles me even after the multiple explanations 

[Perrow]

GROUND IS RELATIVE...

Except when skydiving

[R.G.]

Join the club my friend. I cant wrap my head around it either. By jacking a Positive ground pedal to a Negative one (i.e. a PNP Fuzz Face to a NPN Booster) you are essentially connecting the V+ from the PNP to the V- of the NPN. I have had people tell me that using 2 seperate power supplies (one for each effect) solves this problem but you are STILL shorting the two together via the Output jack of the PNP and the Input jack of the NPN or vice versa.

It baffles me even after the multiple explanations 

Draw the schematic, using just a box for the effect circuit, but coloring in the jacks, signal, ground, and battery wiring for two effects.

The issue is not where the grounds go, as was noted. It's where the power supply leads must go to get the two kinds of ground.

Draw the picture.

[Govmnt_Lacky]

Draw the schematic, using just a box for the effect circuit, but coloring in the jacks, signal, ground, and battery wiring for two effects.

The issue is not where the grounds go, as was noted. It's where the power supply leads must go to get the two kinds of ground.

Draw the picture.

Ok... Lets go about this a different way.

Take 2 wall warts and cut the plugs off the end of the wire on each unit.

Now, wire the V+ from one of the wall warts to the V- of the second wall wart.

Now..... PLUG THEM BOTH INTO A WALL SOCKET!

WHAT HAPPENS? 

This is essentially what you are doing when you use two seperate wall warts. One to power the PNP and the other to power the NPN. The only difference is that you are doing this via a pedal to pedal jumper cable.

Am I wrong in thinking you will have a MAJOR problem with blown fuses by doing this?

[PRR]

> WHAT HAPPENS?

Draw the darn schemetic, the CIRCUIT.

Show the LOOP that your electrons run around.

Wall-warts introduce black-box mystery. Take two 9V batteries. Connect JUST the + of one to the - of the other (leaving two other terminals unconnected). What happens? Where are the electrons flowing?


> Except when skydiving

Conversely, if you are a fish, surface level is an UPPER limit not the lower limit as when air-breathers sky-dive.

[Perrow]

Ok... Lets go about this a different way.

Take 2 wall warts and cut the plugs off the end of the wire on each unit.

Now, wire the V+ from one of the wall warts to the V- of the second wall wart.

Now..... PLUG THEM BOTH INTO A WALL SOCKET!

WHAT HAPPENS? 

This is essentially what you are doing when you use two seperate wall warts. One to power the PNP and the other to power the NPN. The only difference is that you are doing this via a pedal to pedal jumper cable.

Am I wrong in thinking you will have a MAJOR problem with blown fuses by doing this?

Is this what you had in mind? (some details left out)



I say, count the loops. I see none. You can even omit the diodes.

Conversely, if you are a fish, surface level is an UPPER limit not the lower limit as when air-breathers sky-dive.

Sky is still up though But I see your analogy and amaze at how you incorporated my OT humorous remark to point at something relevant to this thread. *applause*

[Gurner]

"Positive Ground" is kind of a slang term.  Ground is always 0 volts.  A 'positive ground' pedal runs off -9v, the battery + is connected to ground, but it's still 0v.

That was always my take too....it'd be much less consuing to simply say negative supply (pos ground) or positive supply needed for a circuit!

[R.G.]

"Positive Ground" is kind of a slang term.  Ground is always 0 volts.  A 'positive ground' pedal runs off -9v, the battery + is connected to ground, but it's still 0v.

That was always my take too....it'd be much less consuing to simply say negative supply (pos ground) or positive supply needed for a circuit!

Remember Reinhold Niebuhr's serenity prayer?

God, grant me the serenity
To accept the things I cannot change;
Courage to change the things I can;
And wisdom to know the difference.

It would indeed be less confusing to say positive supply or negative supply.

It would also be less confusing if Benjamin Franklin had guessed correctly about what came eventually to be known as the polarity of charge carriers. Electricity is carried in metals and resistors as moving electrons, which are negatively charged. So we have the curious situation where electrical current is viewed as moving from more positive to more negative places while the current is carried by negatively charged electrons flowing from more negative places to more positive places. But we're stuck with it. It would be much simpler if he'd guessed the other way round. The math works both ways, but we have to keep two pictures in our heads at the same time.

Fortunately, we are capable of doing this if we try.