Tuesday, 8 January 2013

Supa Nova

Info from circuit designer J. Nagy: The Supa Nova is a very low to pretty high gain, tube-ish, distortion pedal that relies on a MOSFET (BS170) to overdrive two JFETs (J201). The tone controls are designed to provide adjustment to the middle and upper frequencies. Voltage at the drains of Q2 and Q3 should be about 5.4 and 4.7, respectively, but make sure to tune by ear. Q4 can be a 2N5088 bipolar transistor or a JFET. The layout is meant to accommodate either. The JFET is smoother and mellower than the 2N5088, while the 2N5088 (my favorite) is clearer and has a bit more edge and attack. Silver-mica capacitors are recommended for the pF values, as these sound less smeared in this circuit than ceramic. All capacitors are in uF unless otherwise noted. Consider excluding D1 if a battery is your primary power source. You might notice that it sounds better this way. If you like to live dangerously, see if you can hear a slight increase in highs by removing D2.


18 comments:

  1. I'm presently building this one, as soon as my order for the few non-stocked parts arrives.
    Can't believe no one has even commented on it before....it's very interesting to me, especially given my disdain (tiredness) of opamp overdrives and love for anything MOSFET/JFET.
    So, hopefully this one will be able to be moved to the verified column soon. I'll update when complete.

    Geezer

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    1. I also just built this and I also LOVE it. Like you said, the sleeper hit of the year (only 10 comments, maybe 2 builders here).

      Anyway - tons of gain but cleeeeeen and excellent sustain. Really pushes the tube pre-amp with just the right harmonics, and no grit or wooly.

      I am going to try to post a tone sample.

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  3. Alrighty, you can mark this one as verified!

    But good gracious.....this thing is PURE GAIN! I'm going to try a 1meg pot in place of the 470k/470k voltage divider between Q2 & Q3 to see if it can be tamed a bit. The drive control sounds great when it's just cracked a little bit open, But anything past that is fuzz city!

    I used 2SK170BL's instead of the J201’s (twisted leads for correct pinout and subbed 1k's on the source, ala the Fetto)....running 12v, so biased the drains of Q2/Q3 at 6v and 7v respectively

    Sounds very comparable to the Fetto, maybe even a bit sweeter, if that's possible!

    I'll update after trying the pot tamer.......

    Geezer

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    1. Wow....wow....wow!
      I had high hopes for this pedal, but it has more than surpassed all of them. Right now, it looks like this one will kick the Fetto(s) off the board, it's THAT good!

      The fix for the super high gain problem was fairly simple. I replaced the 500k linear drive pot with an audio taper 500k, and since I had already socketed the bottom 470k resistor of the voltage divider, I replaced it with a lower value.... I went all the way down to 33k and that seems about right to my ears. So that's like a 500k pot turned almost all the way down. Even with the gain attenuated that much, the pedal is still very loud, much more volume on tap than unity. With the drive and volume pots at around 50%/12 o'clock, it's pretty much perfect unity gain.

      This is the most amp-like pedal I've ever played. On the clean channel, it sounds like a great tube OD channel, responding to the guitar volume pot for clean to mean.
      On the amp OD channel, it gives a sweet vocal quality and will sustain into feedback on almost every note.
      If I didn't build it myself, I'd never know this was a solid state device....simply beautiful tone.

      I'm building another!

      Geezer

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    2. I'm tellin' ya folks.....this ones a sleeper and a keeper!

      If anyone's interested in the mods let me know and I'll post them

      Here's a rough sample recorded on my iPhone

      http://snd.sc/1a52qBM

      Geezer

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  5. hmmm. I just built this one today based on your comments, and I don't care for it at all. IMO, it's muddy (lacking real top end) and too middy for my tatse. I don't think it holds a candle to my Fetto (which I really dig). I downloaded J Nagy's pdf of it and i'm going to try some of his recommended mods, but to be honest, i'm not all that optimistic about it.

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  6. I found the problem that made it sound muddy and it's a great sounding pedal now! Miro's vero has a 10n across the second trimmer (near the top right), but after looking at the schematic, it's supposed to be a 1n (big difference in top end!) hopefully he'll correct that cuz it's a great sounding OD/distortion pedal now.

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    1. John is once again correct about my copy/paste error on that cap. :)

      Layout updated accordingly. Thanks John!
      +m

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  7. Based on the comments I am going to build this. I am wondering if there is a sub for bs170 as I don't have any at the moment. Also, how much give do you have with the trimmer? I have 2,10,100k trimmers. What would be the best for a sub and what is the trimmer doing? Thnx! I would love to see the mods people did and hear a sample! Thnx again!

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    1. 2N7000 should work fine in place of BS170s. 100K trimmers will also work fine. Although, the sweet spot in the trimmer turn will be harder to find.
      +m

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  8. Greetings! Wondering if using 22nf instead of 18 and 47nf instead of 50 is going to do anything unwanted to the circuit? Thnx!

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    1. Those subs will be ok. I don't think either will affect the tone in any audible way.
      +m

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  9. Thnx!
    Want to say to you guys, and you here it a lot, that I and probably many here are really really grateful of your guys work. I've made some amazing effects and have gained insight into something that has otherwise been a mystery. Ciao...

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  10. FYI - This one just earned the spot as my top overdrive after trying out maybe 10 different ones including Wampler plexi, Pinnacle and Ecstasy, plus some ROG and other drives. Into my clean Marshall this does sound just like my old Marshall on high gain. Put a compressor and EQ in front of it and it soars.

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