Saturday, 8 February 2014

Monolith Fuzz Oracle

This is a nice aggressive sounding fuzz.  The switch on the original is a push pull on the Color pot and so you can either do the same and get a 250K switched pot, or alternatively just use a DPDT 2 position toggle.

Info from Monolith Fuzz about the original:

The Oracle Fuzz is my original twist on the fuzztone "in my head"... Imagine an Italian made Vox Tonebender (2 transistor MK 1.5 circuit) with all of it's lovely midrange-heavy goodness mixed with the throaty low "huumphh" of an early Big Muff, and you're getting warm. 






36 comments:

  1. An OC76 usually have the Hfe from 30 to 70/80, the Hfe is a little high for OC75 too

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    1. They were measured from an original

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    2. Not that you have to get exactly that level of gain of course, and you could try any other type of germanium transistor too. I have some Russian GT402's and whilst they don't get up to 300hfe, there were some around 200 which may still be good in this.

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  2. can I use some ac128 or oc44 on this?

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    1. You can try any PNP germanium transistor. I'd recommend socketing them so you can audition a few different ones so you can choose your favourite combination

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  3. Tag it, Mark :P Sounds great with a 2N404 110hfe as q1 and a 2BS187-7 205 hfe as q2. Will have to check with different hfe's as I think that I have some very high gain germaniums (about 350) at any place.

    Colour is not very sensitive, Density is a great control, lots of different sounds as you turn the knob.

    Surely this one will get boxed (1590A, of course)

    J.

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    1. Awesome, thanks Javi! :o)

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    2. Just to note, that Q1 is fliped 180 degrees, collector shoud be up :)

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    3. It shouldn't mate. They're PNP so its emitter to supply

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    4. Sorry, I was reading wrong the schemtics, it's Ok as it appears

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    5. Yeah, I still have problems when dealing with PNP :P I still remember my PNP trannies exploding on the Soul Bender :P

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    6. I've tried the highest hfe germanium that I have, an AC184, rated 295. The result is even better than before.

      Sadly, I'm afraid that so high gain trannies are not common at all. Have never seen an OC75 over 120hfe, so don't know where the builder could find a lot to build this model.

      Well, now we know were we can use this rare high gain germaniums. Truly is a great fuzz, you won't regret if you build it!

      J.

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    7. Thanks for the info, I'll have to keep a look out for something high gain

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  4. Great little circuit. Looks very interesting.

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  5. This seems cool to me for two reasons.

    It gives me something to do with some really high gain germs I have, and I like the was the PNPs are flipped in a positive ground circuit like the Fuzz Factory

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  6. IME, the gain works better with reverse log 1 meg pot.

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  7. Hi John.
    Sorry for the unrelated question but would it be possible to get a layout for you Fat-Tone Junior?
    Thanks

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  8. a silly quetion, what is the 3rd pot on the pedal at the video?

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    1. There's 3 pots, Density, Color and Output (volume pot)

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  9. Thank you Mark now i understand that!

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  10. This comment has been removed by the author.

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  11. hi, i built it & it sounds fine. Vol & Color work ok. But DENSITY only works at the last quarter of the 1M-Pot. Had same problem with Meathead de luxe. Anyone got an idea how to fix it?

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    1. The taper of a reverse log pot would increase the resistance much sooner in the pot's rotation so I'd suggest trying that instead

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  12. Could someone explain the pot wiring?
    I don't get the "density" and "color" explanation on the left, while I cant figure what's "color 2".

    Seems like a sick pedal.

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  13. I just built this pedal in a 1590B enclosure. Cramped, but everything fit. I used a pair of TK3055 germanium PNPs, measuring around 300hfe each.

    When I plug the pedal in using my 1 Spot, there is a LOUD annoying hiss. At the lowest output setting, the hiss is unbearable. There's plenty of nice fuzz when I play, but this hiss makes the pedal unusable...

    Now, seeing as I built it in a 1590B, I had no room to put a battery. But, on a whim, I clipped a battery into the circuit with the bottom off, and voila! No hiss. Just fuzz. Plug the 1 Spot back in, hiss city. I'm gonna wire up a 9V snap to a 2.1mm barrel connector so I can run an external battery for now, but I'd like a more permanent solution and be able to run this off my power supply (I really hate batteries).

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    1. you might try adding a 10R resistor in series to the 9V with a 100uf like this to see if it helps:

      http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Monolith/9V_filter.png

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    2. Thanks! I'll try that out. I gotta wait till tomorrow to hit the parts store so I can grab a 100uf cap. I'm also gonna try out the pedal with a bunch of other power supplies tomorrow at the music shop I work at, see if anything sounds better. I also noticed that my 1 Spot started humming (used to be whisper quiet).

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  14. It's a bit silly to ask but is this one wired as a positive ground effect like a PNP fuzzface for example?

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  15. Built it with OC1075 trannys and worked like a charm, great sounding Fuzz.

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  16. Built this using OC602s and its really good but sound fizzles out pretty fast on the higher strings i presume its because these only have an hfe of 20 to 30. These were my only Ge PNPs i had left. However, could be that i had no B250ks so used a B220k instead. Will buy some others Ge PNPs and buy the appropriate pot and check the difference. May post back soonish with results.

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    1. those gains are way too low for this. i'm not sure about anyone else's build, but i found that as long as you've got at least 80hfe it should sound good. currently both q1 & q2 have gains of approx 100hfe. i've also had them a set in there that was about 100hfe for q1 and about 300hfe for q2 like the original. that sounded good, but the lower gain set is a little darker and warmer, which is more of what i like.

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  17. What does the 47pF capacitor at the Density Pot? More Noise? ;)

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