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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.


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16 comments:

  1. BerkicauFebruary 22, 2017 at 12:23 PM

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

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    Replies
    1. H.A.February 23, 2017 at 6:45 AM

      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. H.A.February 23, 2017 at 6:49 AM

      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. BerkicauFebruary 23, 2017 at 10:14 AM

      omg it's too complicating....

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    4. IvMMarch 20, 2017 at 8:02 PM

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

      Delete
  2. IvMMarch 20, 2017 at 8:07 PM

    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.

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    Replies
    1. Effects LayoutsMarch 21, 2017 at 9:26 AM

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

      Delete
    2. IvMMarch 21, 2017 at 10:37 AM

      Me neither.. another EHX eccentricity
      Thanks David!

      Delete
  3. AnjangMarch 22, 2017 at 8:31 AM

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

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    Replies
    1. Effects LayoutsMarch 22, 2017 at 10:29 AM

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

      Delete
  4. MonjeMay 1, 2017 at 2:53 PM

    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!!!

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  5. damdam51November 1, 2019 at 12:30 PM

    This comment has been removed by the author.

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  6. UnknownFebruary 15, 2021 at 2:14 PM

    Hello all.

    Is there a schematic available also?

    Best Regards
    Oren Pildus

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    Replies
    1. Ricco SeixasMarch 11, 2021 at 3:07 PM

      https://www.google.com/search?q=ehx+hot+tubes+schematic&client=ms-android-motorola&prmd=sivn&sxsrf=ALeKk03U-d9pvdCoZzJ_hNobbnV7ZnGQgQ:1615493100280&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjf2IPjhKnvAhVNHLkGHftTC_QQ_AUoAnoECAsQAg&biw=360&bih=512&dpr=3#imgrc=zWFXLFebK-_nOM

      Delete
  7. Dennis KriggerSeptember 10, 2021 at 4:22 AM

    Hi, i can't find the schematic for this version (9v) anywhere. Do you have it ?

    ReplyDelete