PNP FUZZ FACE - ADDING 9V Jack and LED - HELP!

[ammalato]

Hi All:

Sorry for this...I'm building a fuzz face clone using a replica circuit board (Arbiter Issue. 1 PNP design) and the layout below.  I've got it working as shown below, however I want to add two "upgrades" and I'm having a hard time finding the proper diagram.  

1) I'd like to add a 9v jack for a standard power supply:  center (-).  I know PNP circuits are grounded positively, so the power supply cannot be a daisy chain (it's not...it's a voodoo labs PP2+) however I've had PNP clones in the past that ran fine off a standard boss power supply (I believe the jack just has to be wired in reverse).

2) LED - I'd like an LED indicator as well.  

Can anyone tell or illustrate for me how to add the 9v jack and LED to an otherwise standard PNP Fuzz Face?  Again, currently everything is working and wired as shown below.  

[mcknib]

Add a small voltage inverter circuit on vero to allow you to daisy chain it with your negative ground pedals which is what your other PNP pedals would have had using a charge pump like a MAX1044.

I use this one

http://tagboardeffects.blogspot.co.uk/2012/05/negative-voltage-inverter.html


With your LED you'd just flip the orientation i.e put your anode to where you'd normally put the ground connections on your 3PDT switch, ground being positive in this case and your cathode to 0v obviously making sure you use a current limiting resistor as normal.

Positive ground is hard to get your head round I've build a few with LED indicators and still couldn't easily tell someone how I wired it but as far as I can remember I soldered my CLR to the anode soldered that to the switch and the cathode to 0v. With your LED not being positive ground you'd just wire it 'as normal' i.e power (positive ground +9v) going to the anode with your CLR and 0v to your cathode.

Hopefully you won't be as confused as I am trying to explain it!

[ammalato]

Thanks, I actually had a charge pump (the general guitar gadgets one) in there, but it was too freakin' confusing so I removed it.  I don't want one as I have no need to daisy chain effects (I have two voodoo labs PP2+...so 16 isolated channels). 

The unit i had previously I had built, but it was a slightly different circuit (and a million year ago)...there was no charge pump / inverter...just wired the jack in there in reverse...

Thanks,

[GibsonGM]

Hi Ammalato....Go here, follow the download links (2 pages, sorry I did not direct link) and get the OFFBOARD WIRING .pdf
http://www.tonepad.com/downloadWarning.asp?id=76
Save this document for future reference, it's great to have.  Might be what you need, if you reverse all the power connections!!


Much easier to either use the inverter mentioned above, IMHO.   If you play games, you will end up with "+" on the shield of your guitar cords and get noise and problems, even shorts.  Just my 2 cents.  It CAN be done - but SHOULD it?  That kind of thing.   But if you know what you're doing, have at it...I'm more worried about your cords... 

Anything that gets you back to grounded jack shield is the way to go!!  

[induction]

Much easier to either use the inverter mentioned above, IMHO.   If you play games, you will end up with "+" on the shield of your guitar cords and get noise and problems, even shorts.  Just my 2 cents.  It CAN be done - but SHOULD it?  That kind of thing.   But if you know what you're doing, have at it...I'm more worried about your cords... 

Anything that gets you back to grounded jack shield is the way to go!!  

This is incorrect. Power adapters have no ground reference. The output is isolated from mains voltage, and provides voltage differences, not absolute voltages. If you wire the positive lead to ground via the cable shield, then you get 0V and -9V. If you wire the negative lead to the shield, you get 0V and +9V. Either way, the shield is grounded.

[GibsonGM]

Good catch re. my poorly expressed reply, Induction; you are right in terms of what you just stated.    Ground is your reference, be it -10V or what have you.   AS LONG AS all the associated (following or previous) stuff is ALSO referenced to it...I was talking about the + ground and other pedals connected to it.

I don't do positive ground / PNP stuff and mix it with negative ground myself, just didn't want to see him short his power supply.    I'll keep my statement that "anything that gets you back to grounded jack shield is the way to go"...anything that doesn't cause a short in your power supply.  That would be a COMMON ground, no?

My concern, not very well explained,  is **What happens when you have a positive ground, then plug in the next effect that has a negative ground?**, and your shields are now connected to + AND - of the SAME supply .... which is what I was trying to get across in my reply.  They must be common to each other, or isolated, correct? (inverter would do that)

I'm well aware that you can use a positive ground, lol - even some cars do...making it play nice with a negative ground following is the point.   So, if you use both + and - as ground in your chain and run pedal to pedal, that's fine?   (scratching head)
("If you play games, you will end up with "+" on the shield of your guitar cords and get noise and problems, even shorts.")  << unisolated + ground mixed with -,  isn't that a dead short?
If this is not the case, what am I missing, and why is it so common a topic if it's not an issue?

[induction]

You're correct, positive ground circuits usually* cannot be daisy-chained with negative ground circuits or it will short the power supply. But the OP stated that he was aware of this, and has no intention of daisy-chaining his positive ground pedal with another pedal because he has 16 isolated PSU's to work with. So I took your statement to mean that having positive ground and negative ground pedals in the same signal chain will cause a short. That statement is incorrect, both because it is not true, and because apparently that's not what you intended to say. So I apologize for the confusion, but I thought it was important to clarify this for the OP or for anyone else who reads this and might get confused.

*This excludes circuits with charge-pumps included in them, and circuits like this one, which have the topology of a positive ground circuit, but connect the ground lug of the input and output jacks to the negative rail instead of the positive rail. Both of these examples are still negative ground to my mind, because the DC voltage inputs are 0V and +9V, but I include them here just for clarity.

[GibsonGM]

Yup, no worries on the confusion, man.  My 'caution' was intended to make it very clear to the OP that there's the possibility for trouble if this isn't understood - sort of a bad idea, IMO...5 years from now when the supply dies for some reason, and he uses one that isn't isolated - or loans the pedal to someone, etc. etc.   Positive and negative ground pedals in a chain *without consideration for what's happening* WILL cause a short if wired using "the conventional scheme", as you certainly know.  My statement wasn't "untrue" for this reason only.  The 'workarounds' are fine, again just stating the obvious.

I only felt like I should point that out because of the initial confusion on how to wire up the jack or add the LED made me think he might just pop it in and here comes the smoke.   But to each his own, everyone gets to wire up their own stuff any way they see fit! 

The examples you posted sure look negative ground to me, too