This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Wednesday, February 22, 2017

EHX Hot Tubes

Here's the Hot Tubes overdrive from Electro Harmonix. It's based around a 4049 hex inverter chip (like a Red Llama) with a dual op amp pushing it. Original units from the 70s had buffered bypass and a direct out jack. I guess they needed something to fill up those massive enclosures EHX used back in the day. I've laid this out for a 125B enclosure with top mounted jacks and your favorite method of true bypass switching.


12 comments:

  1. Is it possible to replace the IC with 4069?
    B2M would be hard to find I guess..

    ReplyDelete
    Replies
    1. It is possible but considering the effort and the costs it's imho not worth it since a 4049 will cost you only ~20Cents. Anyway, if you still want to do it with a 4069 have a look here: http://www.runoffgroove.com/6949.html

      Delete
    2. Me personally love cmos inverter based overdrive pedal designs but imho there are a lot better designs out there. E.g. the Emma Reezafratzitz, Blackstone Appliances Mosfet Overdrive, Mad Prof Stone Grey and many other DIY projects.

      Delete
    3. omg it's too complicating....

      Delete
    4. I'm in the same situation... very hard to find.

      Delete
  2. Is there any alternative or tweak to use other Drive pot, instead the B2M?
    Maybe B1M?
    I can't figure out how it works really..more than a variable resistor.
    It's the only component left to finish it.

    ReplyDelete
    Replies
    1. Definitely try the 1M. I don't think I've seen a 2M pot before quite honestly.

      Delete
    2. Me neither.. another EHX eccentricity
      Thanks David!

      Delete
  3. i watch the schematic.. you forgot C6= 4.7uF and R8=47K
    This is deliberate ??

    ReplyDelete
    Replies
    1. Not deliberate. Just missed them. I've updated the layout. Thanks for pointing that out.

      Delete
  4. You can mark this layout as verified, because everything works perfectly, the volume button does its job, the tone is very wide, and the overdrive starts by giving a small heat of valves until the complete saturation (I used a Pot of 2.5M was the only one I could manage).
    I was finally at peace with my soul, I was curious to hear the sound of a pedal with an IC of this type, I had already done Reezafratzitz twice, before and after the bug was corrected, the Stone Gray, always with bad results and a Background noise above acceptable. This one worked first, with no background noise.
    Thank you!!!

    ReplyDelete