Saturday, 13 November 2010

Fuzz Face PNP negative ground with simple bipolar power supply

This one will let you continue to use the more consistent PNP germanium transistors, but the charge pump will provide a -9V supply, so the ground at 0V can be daisy chained with all your negative ground effects.  The same structure could be used with any circuit that is usually PNP like the Rangemaster or Tonebender.





36 comments:

  1. I recently built this layout and I love it, but I have to turn the volume pot up all the way to get a unity gain. Is there anything I can try to get more volume out o this pedal?

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  2. If you increase the 470 ohm resistor to something like 1K or 1.5K then that will give you a volume boost.

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  3. Do you wire this like a normal negative ground circuit (grounds go to sleeves of jacks)? I built this but cannot seem to get it working properly.

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    1. Yes it should just wire up as a normal negative ground. The IC converts 9V to -9V meaning you can use PNP transistors with a conventional (0 volt) ground. If you've got a multimeter check you're getting -9V on the top rail. The top of the link at column 5 or pin 5 of the IC would be a good test point if you're facing the component side of the board.

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  4. Pretty awesome. I have some MAX1044s lying around and thinking it'd work great with a PNP Tonebender. Thanks!

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  5. Can the bias pot be left out for a fixed resistor? I ask because I have a matched transistor set from small bear with the proper resistors included and I want to put this into a box with only two knobs. The resistor I have to replace the pot is 9.1k. Is it just simple as connecting the resistor to the board where the leads for the pot come off or am I missing something?

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    1. Yes that's no problem, the resistor as you say just goes between the two Bias pot wires. You may want to move the 470R and cut 2 columns to the left to give you more room for the resistor. Maybe try and get it in between the 22u and 10n caps.

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  6. Hello, this is not exactly related to this layout but I thought is close enough so I'll post it here. I had a NPN Fuzz Face built and then I decided to give a go to the PNP version. Besides changing to positive ground from the DC supply and reversing the polarity of the LED (both of them I did) I was supposed to change the polarity of the electrolytic capacitors on the board. That I forgot. I had the circuit with 9V supply from a battery for some minutes testing what was wrong until I realized and then reverse them. Now I have a functioning PNP Fuzz Face which sounds good in my opinion, in the ballpark of the previous NPN version. But I am still worrying if I may have damaged the electrolytic caps in some way I am not noticing since I don't hava a multimeter able to measure caps. Everything sounds good to me and I get reasonable votage meterings in the legs of both transistors. Should I worry about this? Is there any way to know if the caps went bad?
    thanks

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    1. If it sounds good then you haven't damaged the caps. If they were damaged you wouldn't hear anything so don't worry about it

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  7. can a 7660S be used instead with no modifications? Tnx :D

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    1. Yes, that's the one I'd prefer to use anyway

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  8. awesome fuzz, i used IT308v q1 56hfe and q2 65hfe and it sounds good however i didnt have the right bias pot so i am waiting on that to get it dialed in properly as it sounds a little gated, cant wait to get it nailed! cheers

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    1. hey guys hold that! i was just playing with this one and i noticed that even when the effect is bypassed the volume control still works? i cant see any obvious offboard wiring mistakes...any ideas on where i should be looking ?

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    2. I am going to use this layout and change the 2u2 cap to a 1uF and vol to 250k Log ala sunbender... and toss it inside a 1590bb along with an octavia for 2/3's of a captain coconut in a sense =)
      Thanks for the great layout IvIark !

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  9. Hi mates!

    I have to say that I wouldn't recommend this build. Fuzz faces and many other fuzzes cannot use a filtering cap from -9 to Ground as they get totally tamed. Here we have the final cap of the inverter... that acts too as a filtering one for the effect, so the effect gets tamed and mild.

    Sadly, this cap is mandatory for the pump, as if not present, the -9v rail gets inconsistent and tuns at about -6volts.

    So, while in some pedals, like the Tonebender, that originally has a filtering cap, and works pretty well with the inverter, the Fuzz Face is not one to use with inverter pump.

    BR

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    1. Wish I knew about this earlier. I removed the filter cap I had in my fuzz face build just to find it sounds much more ballsy, present - "better" - without the cap. It's like all the effect really comes much more forward. I could hear just a tad bit more of noise being added, pretty much an insignificant change. Thanks for the tip!

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  10. what is the function of the bias pot?

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    1. It biases the second transistor. The usual recommended voltage is 4.5v on q2 collector, but you can get some interesting sounds when misbiased and so it's a worthwhile addition

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    2. http://www.muzique.com/lab/fuzzface7.gif
      What do you think about this negative ground method for germanium fuzz face?

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    3. Yes I've seen that before and it's a perfectly good way of doing it. Using 0 to 9V with connections the opposite to what you would expect is exactly the same as using -9V to 0V. I traced the Lovepedal Silicon Fuzzmaster which did it exactly this way.

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    4. I did it with russian germanium transistors, and there are too many oscilations and unstable sound, but I didn't have much time to adjust it. will try to put the trimmer instead of 33k and to obtain the 4.5v on the Q2's collector.So it mean that the problem is not in the negative ground. Thanks

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    5. or I should put the trimmer instead of 8.2k?

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  11. The 33K is biasing Q1

    The bias resistor for Q2 is usually 8K2

    I like to use a 10K pot in place of the 8K2 but 8K2 should at least get you in the right ballpark to where if your transistors are good it will sound OK

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    1. OK, thanks a lot. I will try to get the sound from that circuit. :D

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  12. I used a 10K trimmer instead the Pot and I can not get the 4.5V on q2 collector. The voltage varies between 8.0 to 9.5 V

    What I need to do to decrease the voltage ??

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  13. Hello ,

    a 50k pot or trimmer is better ( 47k if you use a trimmer is the closest one) , to fix the voltage at 4.5v. This is the value of bias pot used by Zvex in his Fuzz Factory.

    Cheers,

    David.

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  14. Hi, I've had a look at the comments on here as well as your offboard wiring guide but I'm still not sure how to wire this up. Any chance you could please explain it to me? Cheers

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  15. Hi, hope this doesn't class as spamming as I've posted this question in another thread. Just wondered if anyone can explain 4 pin germanium transistors to me, can I still use them? Does S get clipped off or linked to one of the other pins?
    Thanks for any info that might help this beginner.

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    1. Pin 4 is usually for grounding the case itself. Try leaving it unconnected to anything. If noisy try running a wire from it to ground. I suspect that will be unnecessary tho.

      Good luck

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  16. Superb many thanks for the swift reply!

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  17. If I wanted to build this as a regular PNP FF, I could wire power straight to the top row, correct? Then be careful to not daisy chain the effect.

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    1. yep. just remove the power inverter and the line of cuts separating it from the fuzzface section.

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  18. Hello @LvLark, thanks for the layout (and all of them btw), I built my 2nd fuzzface using this layout but I get a weird noise, a high pitch warble. Previously, I built one for a friend with a ne555 inverter daughter board and with a fixed resistor instead of the Bias pot. My question is if this noise can come from the voltage inverter circuit or has something to do with the bias. Do you have some advice?

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    1. Never mind, I switched the 7660s for a Maxx1044 and problem solved.
      Thanks again

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