Tuesday 22 March 2022

Interfax HP-1 Harmonic Percolator - Early silicon version

 The earliest version of the infamous HP was actually a dual silicon transistor circuit. It also had a few addons and a few big cap fifferncies compared to the later Ge/Si version. Not sure how it sounds but I guess some of might be interested to to try this one out.

The 2N3565 transistors had a quite wide gain range between 100-600 hfe so socketing might be a wise idea. I would start out withs 2N3904 or 2N5088s, just mind the pinout.

Schematic is avaiable HERE.




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8 comments:

  1. Tyler Lafferty22 March 2022 at 18:30

    Wondering if you could put together a layout for the Fuzzy Balls from this link? It's a modified version of the EHX Bassballs which has a CV in for the filter, plus a few other changes from the original.

    https://urekarm.tripod.com/synth/fuzzyballs.html

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    1. fuzzhead23 March 2022 at 04:34

      Hey guys!
      Right now I simply don't have the time to draw as many layouts as I would like to. :-/ Right now I just upload layouts from my backlog. But both of your schematics is saved so hopefully they will eventually be transcribed into layouts at some point.

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  2. Guilherme22 March 2022 at 21:48

    Hey man, can you do a layout for the PEDALPCB Pendulum Harmonic Tremolo?

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  3. Shane30 April 2022 at 22:18

    Hey Fuzzhead, I *think* you can tag this verified. Built it and it seems to work, but it's not very loud. However, could be my choice of transistors which are currently two KSP06s arounde 100hFE each. I socketed them so I'll try various ones.

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    1. fuzzhead30 April 2022 at 22:29

      Nice! Yeah it is worth socketing and try other transistors since old stock 2N3565s had a very wide range of Hfe, I think it was between 100 up to 600!
      Is it above unity ATM?

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    2. Shane1 May 2022 at 03:51

      I have it maxed and it seems right at unity or maybe just a hair above but not by much.

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    3. fuzzhead1 May 2022 at 13:43

      I think you you nailed it since generally, "Percs" reaches just abouve unity. There are exceptions since its part values varied during its lifespan.

      If you want a bit more ouput you can sub D2 for a silicon diode.

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    4. Shane1 May 2022 at 18:22

      Oh nice! Good to know....I think the KSP06s didnt have quite the sonic qualities I was looking for...swapper them for some old 2N3439 switching tranaistors I had laying around (similar hFE of 100 or so), and it sounds great now.

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