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Monday, March 9, 2015

D*A*M GB-80 GreaseBox

Here's the germanium version of D*A*M's GreaseBox fuzz. It's based on the Tone Bender Mk. III but without the tone control. Q1 and 2 form a darlington pair to amplify the signal, and Q3 provides the fuzziness. The original units are positive ground effects and use PNP germanium transistors. That is reflected in the perf side of the image below, but for the PCB, I laid it out for negative ground for those of you who (like me) have a bunch of NPN germaniums.



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3 comments:

  1. CristianoOctober 25, 2016 at 8:49 AM

    Any advice for transistors hfe?

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    Replies
    1. Effects LayoutsOctober 25, 2016 at 9:02 AM

      Pretty low for Q1-2 as they form a darlington pair, and then around 100 for Q3. It's much like a Tone Bender Mk III without the tone control.

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  2. JDTNovember 7, 2022 at 12:37 AM

    Verified on perfboard. I used NPN GE transistors and had the polarized components oriented as on the etched layout. The transistors were 2N1304 with hfe's in the low 60's for Q1 and Q2, and about 110 for Q3. I did not have to tinker with the bias at all. The fuzz is smooth, warm, and a bit mellow, matching what I have read about the Tone Bender Mk. III. I have not tried a straight, Mk III clone, but the treble on this one is smooth enough that I do not feel the need to add a tone control. Putting a bigger input cap on a switch could be a useful mod to get a fuller sound, but the circuit sounds nice and balanced in its stock configuration.

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