Friday, 31 July 2020

Fuzzhead Fx Box of Germanium Mk. II

An updated version of a project I was tinkering with a couple of years ago. The idea was basically to find some use for some low leak USSR germaniums other than in Fuzz faces, Rangemasters and Tonebenders, And to do a germanium version of Zvex Box of Rock. Some biasing tweaks was necessary since BJT Ge's is a completely different animal to MOSFETs but the cap values in the signal path is more or less identical. Couldn't resist to add Boost switch so you can use it as a fuzz as well...and decrease the value of the low pass filter cap in the tonestack to 12nF since I found it a bit muddy with 22nF.

First version was positive ground but I used normal power supply for this version since I have to many unused MP38A transistors but other fairly low gain and low leak NPN germaniums should work as well.


 



26 comments:

  1. I'm ashamed to ask (kind of a challeng): can you think of doing this someday?:
    https://imgbb.com/Nns6nLR

    I promise I'll build it next minute.

    ReplyDelete
    Replies
    1. I guess it is doable once we find a suitable socket board for the Spin FV-1....

      Delete
    2. Ahem...

      'https://www.pedalpcb.com/product/fv1-adapter/

      Delete
    3. i made from there https://the7line.clan.su/publ/diystompbox/fv_1_reverb/2-1-0-46

      Delete
    4. should be doable. u still need a loaded EPROM

      Delete
  2. Great, man! Hope, old hope, it's the last thing to die. :o)

    ReplyDelete
  3. And here to, by the way:
    https://www.musikding.de/FV-1-adaptor-pcb

    ReplyDelete
  4. Any suggestions for gain ranges?

    ReplyDelete
    Replies
    1. Hfe 60-80 sounds good, you can probably go higher. More important is the leakage which should be really low otherwise you might experience some serious hissing.

      Delete
  5. This comment has been removed by the author.

    ReplyDelete
  6. This comment has been removed by the author.

    ReplyDelete
  7. Never mind my previous comments...forgot to add the 100n MLCC in the top row. Sounds awesome - only thing is that I might experiment with a Rev Log for the gain pot, see if the sweep is smoother.

    ReplyDelete
  8. Question: What would be the easiest way to take the toggle switch to a separate footswitch for the boost? Wire one side of a DPDT, pins one and 2?

    ReplyDelete
    Replies
    1. Thats exactly how to do it and if you want a LED indicator you can connect pin 5 to ground and pin 4 to a current limiting resistor that connects to the cathode of the LED. Anode leg goes to 9v.

      Delete
  9. Built PCB for this one, Great Fuzz, used mp 38a hfe=60-70, added some mode like TB mk3- ge diod between base Q3 & earth. Use DPDT to flick mode.
    Thanks for the scheme!

    ReplyDelete
    Replies
    1. Very cool! Glad you like it. Would love to see your PCB layout!
      And how does your diode mod affect the overall sound?

      Delete
    2. diode add some smooth & compression.

      Delete
  10. This comment has been removed by the author.

    ReplyDelete
  11. This comment has been removed by the author.

    ReplyDelete
  12. This comment has been removed by the author.

    ReplyDelete
  13. https://imgur.com/4lIouSX
    https://imgur.com/MBsOyfW

    ReplyDelete
  14. This fuzz has a lot of harmonics, sustaine, dirty, so this is my favorite last month!!! Thank you, Fuzzhead!

    ReplyDelete