This is negative ground pnp? Right? 3-knob tonebender

[dstahl]

I am planning to build this from the GGG site http://www.generalguitargadgets.com/diagrams/tb3bb_sc.gif. and wanted to double check that it is negative ground pnp. It doesn't say anything funky about it being straight up pnp, and I did order the germanium pnp transistors from small bear, so I just wanted to make sure that I am not going to be unpleasantly surprised later on.
Thanks
D

[GREEN FUZ]

I believe it`s positive ground.

[dxm1]

I am planning to build this from the GGG site http://www.generalguitargadgets.com/diagrams/tb3bb_sc.gif. and wanted to double check that it is negative ground pnp.

Looking at the schematic, you can see that the positive terminal of the battery is connected to the ring terminal of the input jack. This will be connected to the sleeve (ground) when a cable is plugged in. Also, the negative terminal of the battery is feeding the collectors of the transistors - so it's positive ground.

It doesn't say anything funky about it being straight up pnp, and I did order the germanium pnp transistors from small bear, so I just wanted to make sure that I am not going to be unpleasantly surprised later on.

Why would that be an unpleasant surprise?

[dstahl]

so is there anything special I will have to keep in mind if I wanted to add a standard boss style dc jack? (I feel kind of like an idiot for not knowing this already)

[sfx1999]

Yes, do NOT share the power supply with negative ground effects.

[dstahl]

so there is no way I could have it so I could power this pedal with my daisy chain power supply (one shot)?

[slacker]

you'd have to convert it to negative ground to use it with other pedals on the same power supply.

[GREEN FUZ]

It`s usually around now that R G KEEN steps in to patiently explain probably for the millionth time the pitfalls of negative grounding PNP circuits. Or is that just the Fuzzface?

I know it`s been referenced before. Try a search in the archives. I also noticed some of the Tonebender variations at GGG have PNP negative ground layouts with a DC jack. Perhaps you could adapt one of them.

Check this out also. http://www.muzique.com/lab/fuzzface.htm

[dstahl]

Ok. Would a reverse polarity adapter work ala this http://www.visualsound.net/1spot.htm (at the bottom)? or if not that battery clip converter?
and if these would work could I still keep the effect on my daisy chain?

[GREEN FUZ]

It`s not so much the daisy-chaining as sharing the same power supply that`s the problem. So yes as long as the positively ground circuit is isolated using it`s own power supply or a battery it should work fine.

[slacker]

no that won't work, you can't run negative and positive ground pedals on the same wallwart. Doing this shorts out the power supply, because some pedals are using the negative side of the powersupply as ground and some are using the positive side of the powersupply as ground. When you connect 2 pedals together their grounds get connected together by the cable connecting them and this means you're connecting + an - on the powersupply together which shorts it out.
The only way round it is to use a separate powersupply for positive ground pedals use a battery for positive ground pedals or convert them to negative ground.

[dstahl]

Ok. last question, I swear(hope). if I put a MAX1044 in will that work and I can do the daisy chain thing?http://www.diystompboxes.com/smfforum/index.php?topic=53791.msg409536#msg409536 If not I will just bite the bullet and go the battery route. I know a fuzz won't kill a battery that fast, I just hate the idea of having to unplug that one input cable every time so it won't drain the battery when I'm not playing.
  I already ordered all my parts for the pnp build so I am kind of stuck there. and I hear you can get mixed results just switching elec. caps.
 

[dxm1]

Ok. last question, I swear(hope). if I put a MAX1044 in will that work and I can do the daisy chain thing?http://www.diystompboxes.com/smfforum/index.php?topic=53791.msg409536#msg409536 If not I will just bite the bullet and go the battery route. I know a fuzz won't kill a battery that fast, I just hate the idea of having to unplug that one input cable every time so it won't drain the battery when I'm not playing.
  I already ordered all my parts for the pnp build so I am kind of stuck there. and I hear you can get mixed results just switching elec. caps.

Yes, you can add a charge pump converter and then use your daisy chain ps. I've done this with most positive ground circuits that I've built. Here is the circuit I usually use. It also has RG's 'Cheap Polarity Protection' added. The negative voltage is taken off pin 5 of the 1044. You can skip the polarity protection by feeding +9V to the C1/pin 1 and 8 junction.

[col]

Some while ago someone did a stripboard layout for a -ve ground Tonebender Mk2 using PNP transistors (do a search, here or in the galleries) and I built it to see how it worked. It worked perfectly and sounded awesome. You should be able to mod that to have the tone control or just leave it off. Alternatively get hold of some NPN Ge transistors and use them.
I have never had any trouble with -ve ground PNP circuits despite the warnings unless the battery has been a bit low when I have had 'motorboating'.

[col]

You might be in luck! I was just tidying up and found this;

http://s159.photobucket.com/albums/t159/col07768/?action=view&current=3ktb.jpg

a layout I did for the 3K tonebander with neg earth and pnp transistors. I've not built it but it should work. The layout I mentioned for the Tonebender Mk2 Pro was by Andy Harrison.