Wednesday, 19 March 2014

Soulsonic Crackle Not OK

Requested compact layout as an alternative to the compact SHO.

Martin wrote when sharing the original schematic at Freestompboxes:

Alright, I got it finally figured out... an SHO-style MOSFET boost with NO CRACKLE!!!

I came up with a new gain control for it that allows for the same range of gain adjustment without having to adjust the Source. Since the Source stays fixed, there is no crackling.


While thinking about how to solve this problem, I realized I could treat the basic gain stage as an inverting opamp. So, I set a fixed max gain and tried a variable resistance in series with the input and voila, works perfectly.


Check it out and give it a try; it's a great improvement over the SHO and it's easy to tweak the sound to taste.




15 comments:

  1. This is not an improvement on the SHO because even on the minimum setting the amount of boost is too much for some people, even for me, and I play LOUD. Of course if the purpose is to punish an amp and everybody in the room then okay. But for just doing a simple boost in a dense mix of musical instruments on a rehearsal or live, it will be to loud, even with the pot on it's start position. Just so you guys know. That being said, it sounds great to me.
    But nothing is quite like a SHO with a Zetex brand BS170.

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    1. It may be worth expanding on it to get the best of both worlds, separate the source from ground and add an additional 5K reverse log gain control. Then you can use the new pot to alter the gain of the stage, and the original 1M pot to alter the signal level going into the stage. Personally the crackle never bothered me anyway, I've never altered the level in the middle of a song.

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    2. Hi guys.
      About the 1n5242B. I looked at the datasheet for a 1n5817 and it looks like it will handle (even overkill) the work. Can I use the 5817 or is there a better sub for the 5242 12v'r?
      jeff

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    3. The 1N5242 is a zener, the 1N5817 is a schottky

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    4. I was just about to say the same thing. That diode is basically there to protect the MOSFET, so any diode should work. I have no clue if it will, or how it will, affect the operation of BS170.
      +m

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    5. Thanks.
      That little detail got by me totally! I guess that's like the difference between a weeping willow and a pine....both are trees but very unsimilar!
      I don't have bs170 or 1n5242...can you you suggest sub's for these??

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    6. The 2N7000 will work in there (rotated 180 degrees), and any zener from 5 to 20V will work fine.

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  2. I didn't realise this wasn't tagged as verified yet. Tag it, I've built and used 3 or four of them. I've got a few built lying around waiting to be used..

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    Replies
    1. Awesome! Did you use all of the components in the layout, or did you modify?

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    2. Also, the first comment on here says that it is too much of a boost even on the lowest gain setting...Did you find this to be true?

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  3. Hello guys, is this project considered as verified?

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    Replies
    1. as i see, Willy verified it, so yes. i guess admins have missed that but it happens!
      anyway... it should be good to go

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    2. Yup. Has slipped by. Consider it tagged now.
      +m

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    3. Excellent! Cheers guys

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