Monday, 16 January 2017

Wren and Cuff Phat Phuk B

From the Source:


Here’s what the Phat Phuk is:
A germanium/JFET booster. A unique sounding pedal which adds a beautiful sheen to your bass’ top end and a bit of grit to the overall tone. It’s a fantastic pedal for situations where you want a lift in your overall level, during a chorus or bridge for example, with a bit of bawdy bump via the germanium transistor.

One nice feature is also the more modern JFET transistor at the input which keeps the pedal impedance-friendly when it comes to active bass pickups. This helps the Phat Phuk to remain consistent whether you put a P-Bass in front of it, or a Warwick Thumb.
Another recommended use: As a simple preamp when going direct into your DAW. Helps to de-sterilize your bass’s direct tone and add a little life before the signal is converted to ones and zeros.


Something else that was considered when creating the Phat Phuk B. Many clean-boosts offer way too much boost in my opinion. In any normal playing situation, including intentionally slamming the front end of a tube amp to induce the amp’s natural overdrive, one really only needs a hefty thump to get the job done. There’s nothing wrong with having a large amount of volume on tap, but a problem that can sometimes occur is a lack of ability to fine tune the amount of boost you want. When the sweep of the knob goes from zero to melt-down with one turn of the knob, it gets tough to really dial in a precise amount of boost. Also a slight bump of the boost knob (with a foot or nervous “live show” jitters) can send things out of control. I know because its happened to me. Went for the big chorus during a song, hit the clean boost (not mine, this was long before Wren and Cuff existed) and tore the heads off the people in the front, pissed off the sound man, and pretty much ruined that song. Therefore, the volume sweep was reduced with the Phatty. You still get a big gob of gain, and probably won’t ever need to run the pedal “at 11″, but the trade -off is worth the extra control. Just an example of what Wren and Cuff prides itself on: pedals that sound superior, look beautiful, can take a beating, and are made with the “real world” player in mind.
In other words: A meticulous attention to detail.


A few notes:

1 - I posted the trace, board pictures, and schematic in the request section, here so everyone can take a look and check the trace.

2 - the Germanium Transistor in Q2 is a Chinese Transistor with the markings removed, but what can be made out is AX9. This is PNP, but the hfe is unknown, but the good news is the schematic has been verified by JohnK, big thanks, with a PNP Germanium with 91hfe. So for now, as I put in the layout notes use a PNP Germanium with at least 90hfe, but by all means test it with other values. Don't forget that if you're using Russians that many times transistors with lower hfe seem to act similar to others of higher hfe.





Layout 1:



Layout 2:


Tweaked the layout to make the bias trimmer an external pot. I chose a linear taper as it's common to use linear taper pots for bias adjusting and the trimmer should act linearly. JohnK used a 1k reverse log pot, but I think you won't get the full range you do with the trimmer by lowering the value.

45 comments:

  1. Hi! Just built this, only boosts to under unity. On the schematic, there is a 4u7. Is this important to the circuit?

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    1. Yea. There's an error, and that cap is miss labeled as a 10uF, must have forgot to change it when I copied and pasted a cap. It's the 10uF cap going to the base of Q2 that's connected to a 10uF cap. Try changing it and seeing if that corrects the issue.

      What transistor did you use for Q2?

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    2. I mistakingly used a npn (it was unlabled, thought it was a AC 127.)
      Going to try to find a suitable transistor.

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    3. It may be NPN in the original. I'm not certain since I didn't remove it and test it. For some reason I have a feeling it's PNP. Hopefully with changing that cap and trying a PNP Ge transistor it comes to life.

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    4. crazy idea. can you try to connect the emitter to ground. travis and i were talking and we both think that it makes sense that it would be give more common circuit designs.

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  2. Thanks Zach for posting this! I literally went looking on here for the original Phat Phuk the other day. Imagine it's pretty similar. Is it just me or the 1000uF seems like a bit overkill for powersupply? I might just shove a 47uF in there since it'll make zero sound diff. Thanks again!

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    1. according to the video demo he claims it's to tame the hiss. i think it's way high too, but it could be due to the Chinese transistors he uses aren't the best.

      try it the way i have it in the layout and try an NPN and PNP Ge transistor. if it doesn't seem to work right try connecting the emitter to ground and see if that makes it work correctly as i mentioned above. can't wait to hear if it works out.

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  3. Hi! Thanks for the layout btw. The only germanium I have on hand is a tesla 102NU70 npn at a hfe of 44, so I don't think it has enough juice for this. Going to have to order more germs for testing.
    I do see that the schematic has a total of 4 10uf, one being tantalum + the 4u7.
    When I tied the emitter to ground, there wasn't a effect on the signal.

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    1. Hi Don, are you from Maine by any chance?

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    2. Hello Highsmith, I'm from Quebec

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    3. Very nice, I knew some Arsenault's in Maine. Quebec is pretty close though! Cheers!

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  4. ive got a few got shots of the super phat phuk but i sold it before i started building so it wont be enough to trace from as i didn't get the trace side or pot values i'll post it asap for the curious tho

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  5. just an FYI. the germanium transistor is definitely a PNP. i just drew up, etched, built and tested a PCB for it and it sounds awesome. (my germ has an hfe of 91).

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    1. Great. I'll add that to the layout. Did you use the schematic I posted?

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  6. yes. i used your schematic. i posted a pic of it in the forum on your Phat Phuck thread.

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    1. fantastic. beautiful build, btw.

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  7. Any recommendations as to specific germanium pnps to use for this one? I was going to pick up a couple of AC 128s with 100-110hfe, but I wanted to see if anyone had any other recommendations.

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    1. i've tried several different ones and they all sound pretty much identical.
      i tried SFT308's, SFT352's, an AC128 (large cylinder can), AC128's (narrow can), OC75's and OC44's.

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  8. Another question: if I wanted to move the 'Bias' pot to the outside, I would need to use a 2k Linear pot, correct?

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    1. i actually just did this to the layout. i believe linear would be the taper of choice. try it out and if you don't like how it behaves try changing it to log. can't wait to hear how it turns out.

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    2. actually, a 1K reverse audio works best for an external bias pot.

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    3. and with the 1K reverse audio you still get the full range

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    4. really? that's good to know. i would not have expected that using a lower value would work like a higher value trimmer based on what i've experienced in the past when changing trimmers to pots. i'll make the change to the layout notes.

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    6. If you are putting an external bias on the PPB, which lead (1,2,3) goes to which hole on the board?

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    7. the bias is adjusted by the trimmer, and it's shown in the 2nd layout with a pot as gain. follow the notes under layout 2.

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  9. AWESOME. Thank you so much. I can't wait for the Mercy Phuk layout to do a killer 2 in 1.

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    1. Just wanted to come back and say I knocked this out last night and it is EXCELLENT. Used an AC125 with an hfe around 117 and it is perfect. Slight fur and excellent boost. I would recommend definitely putting the bias outside, you can go from the slight fur to a pretty mean fuzzy OD. Righteous!

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  10. What is everyone using for the 1000uF? Would 330uF or 470uF work just as well?

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    1. i used a 100uf and it's fine. 1000uf is overkill.

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  11. Just built the one with external gain/bias. Sounds great. I used AC125 and 100uF instead of 1000uF

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  13. Hey, just noticed this, but...on layout #2 - where does the External Bias pot connect to the board?

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    1. the gain pot is the bias trimmer.

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    3. Gah, sorry. I was looking for 'bias' and got fixated on that. Thanks for clarifying.

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  14. Know this is quite old now but just built it up and had problems with DC whine, faint but annoying. Noticed that 1 and 2 of the trimmer/gain pot connect to the raw DC rather than the smoothed DC that feeds the JFET, which seemed a bit weird (and not how it is on the schematic). Changed it around and it's quiet as a mouse now. Probably not worth a correction, as it probably depends what transistor you use, but I wanted to put the information up here in case anyone else has the same issue.

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    1. Wouldn't expect that to make that much of a difference. But, I can easily make that change to the layout. Its just additional power filtering, so it could also be that the power source you're using isn't filtered.

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    2. I was surprised too, my PSU is filtered pretty well so I don't think it was that. At a guess I'd say it was maybe to do with the 100R creating a resistance/potential between the emitter of the BJT and the drain of the JFET? Hard to say without tinkering though, and it's boxed up now.

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    3. that's actually probably it. i went back to my trace and schematic and the trimmer should be connected to the 100r, and cap/resistor to ground. most likely the noise was due to the added since the trimmer wasn't connected to the cap/resistor to ground which helps filters out the unwanted noise. btw, good catch buddy. surprised no one noticed it before when it was verified.

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    4. Will you be updating the layouts, for those of us that are schematically-challenged?

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    5. Already taken care of man.

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  15. Finally got around to building this with the external bias and 100uf in place of the 1000u, and it's awesome. Thanks for this!

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  16. Built with the external bias pot. Used an AC125 and it sounds great on both bass and guitar!

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