Thursday, 10 January 2013

Runoffgroove Big Daddy

Continuing Grace Overdrive article at ROG: During the testing of this circuit design (meaning the Grace Overdrive), the thought occurred to try a Jfet gain stage before the 386, instead of the buffer. The impedance would still be high and the 386 would see more signal and clip harder. The result is a pleasing grind and responsive big amp-like distortion. The gain control functions in the same way, but the range is higher in gain. Pretty effective, considering that if you want to use a gain stage, you probably don't want the semi-clean settings of the buffered version.

So here's the Big Daddy. Basically, Grace with a gain stage instead of buffer at the input.

And a little clip with gain maxed:





6 comments:

  1. There was a discussion about this on the TechXchange forum the other day: http://www.digikey.com/techxchange/message/6310. Your circuit design would be a perfect addition to the conversation. Thank you for sharing!

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  2. I'm not sure if verified or not. I've uilt it but i just get a small boost controlled by both pots, maybe it is because i used a mpf102. I´ll try it with other jfets.

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    1. It should be loud... And i'm not aware if anyone else has built this, but the changes between this and Grace are pretty minor. I just checked the schematic, and i'm pretty confident that the layout is correct..
      +m

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  3. Built it. And it is Loud with a captial L. And not bad little circuit. I'd still recommend the switchable "Big Grace" to get the best of both versions in one box.
    +m

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  4. What Diode do you use in D1?

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    1. That's series polarity protection, so any will do. But for low voltage drop you'd want 1N5817.
      +m

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