Saturday 6 February 2016

Montarbo Sinfhoton Highly Modified

Well I said that I would post a layout with a bunch of modifications to the Montarbo Sinfhoton based on what I've read people have already done. So without further a due.

  1. Removing the 100k resistor that's in series with D1 & D2 will increase the amount of fuzz, so you can lower it for more fuzz, raise it for less fuzz, or put it on a switch for 2 different settings. Hell, you can take and have 3 different settings using different combo of resistors.
  2. The "Focus" switch, by putting a cap to ground at the input increases the compression of the fuzz and can provide a subtle boost in output.
  3. The gain control I explained previously, but apparently putting a pot in series with the 22k or 47k resistor to ground gives a fuzz control. Johnk had used a 25k Linear pot, and raised the resistors value to 180k.
  4. Notice I used the "Later Version" to make the modified layout, this is because from reading a lot of people preferred the 2uF caps being raised to 10uF like the later version. BTW, you can use 2.2uF I just wrote 2uF because that was in the original schematic.
  5. As noted earlier, you may want to play with the 10k resistors to the transistor Collectors to set the bias right,
  6. As far as transistors go it seems higher gain transistors, >500hfe, people seemed to prefer, but I didn't read a lot about how lower transistors sounded. To me this looks like a really stripped down and modified Big Muff, essentially just the clipping stages, I would think some of the transistor tricks for the Big Muff may work out here, but no idea.


  1. Zach, this was even faster than light!

    1. haha. i actually did it when i did the normal layouts, just figured i would wait a day before posting this one.

    2. hey shane, you're right. thanks for the catch. i must have forgotten to change that in the build notes. just fixed and re-uploaded.

  2. The 1M reistor in the bottom right is not connected to anything on the top side.

    1. oop i accidentally took out the link that connects it to the Collector of Q1. fixed and updated.

  3. You can tag it.Just got done rocking it on my test box.
    Definitely one that I will box up!
    Didn't play w/transistors or diodes though.Have MPSA18 and 1N914 in it and sounds great to me.Might mess with it tomorrow,but I need some sleep.

    1. Hi Shane, did you see my build notes (at the bottom of the page)on the two knob version?
      It's worth trying an orange LED if you have one, for D3 only (the north facing diode). It had a huge effect on my build, but might have less of an effect on the highly modified version. Worth a try though.

    2. Hi Beaker,I had not seen the build notes.But I will try that out when I get a chance.Thanks for mentioning it.

    3. Awesome. Glad to hear all the mods work, and work well for that matter. Btw, how does the switch on the input sound? And how does the gain pot work? Does it give a good control of the gain and the taper right?

    4. I don't have any orange LEDs :/

  4. Now that I've boxed it,it's very quiet.
    I'll report back once I get a chance to mess with it more.

  5. Dammit!rookie!while playing w/transistors I put them back in backwards!
    Focus switch seems to do as described,a subtle difference,but it's noticeable.
    Fuzz switch is interesting,when in the resistor position I get a cool little warble,kinda like its on the verge of oscillation.
    The gain knob completely cuts all volume at full ccw.
    The bass and treble are noticeable,but not extreme.

  6. I still don't get much volume out of it.What changes do you recommend?

    1. By that I mean that I don't even get to unity w/the volume knob maxed

    2. Shane, that's the issue I had with the two knob version - very quiet, very polite. Try the mod I suggested above - swap D3 for a LED, orange if you have one. Make sure you swap the NORTH facing one of the pair, and see if that helps. It made a big difference on mine - loads more volume, and a much better sound IMO.

    3. i was thinking, if we up the volume pot it should up the max volume by preventing as much signal going to ground.

    4. Whoa!
      Thanks for that reminder Beaker!
      Don't have orange,but I tried red and green.I really liked the sound I got with green.But when I come across an orange one I'll try that too.
      LEDs really bring this pedal to life!All my switches and knobs are way more responsive now.And volume?Yeah,there's plenty on tap now :)

    5. If anybody tries to up the volume pot,please post your results.I was about to try that later this evening until Beaker reminded me of the LED mod in D3.
      Since I had it boxed already,the D3 mod was obviously the easiest solution for me.

    6. I increased the volume pot from 25k to 50k on mine. Gives it some extra welly.
      I tried a few different LEDs:
      Red sounded good but a little "mushy".
      Green started to gate on some notes.
      Orange sounded best - no mush, no gating.
      I did not try yellow as I don't have any.
      Of course, your results may vary.

      It now does that magic "sounds like two guitars instead of one" thing, with stinging clear driven notes over a wash of Muff like fuzz. Perfect for Husker Du riffs!

  7. Damn Zack! : P
    All the time you reported "serie" this is actually a parallel component!

    Anyway, jokes apart, thanks like always for your huge contribution and for making this community wider.
    So, I have an original Sismetone by Montarbo in my hands, I've traced it back to the "Early Version" layout and seems to be quite the same.
    When I'll have some relax days I will try to add the gain controls.
    I think it will need some effort to tackle the good combination between the potentiometer and the 20 / 47k resistor (suggested 180k)

    I don't think I will modify the rest of the original circuit because I already like it a lot as is but also because the orignal board is quite messy and too old-stylish to tweak on it.
    May I'll give a try to the "fuzz switch" for its easy of integration.

    I'll Keep you posted :)