Silicon "Mindbender" with Tone Control (Verified)

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Silicon "Mindbender" with Tone Control (Verified)

Tom F
I'd been wanting to build a tonebender, specifically Mirosol's Mindbender, for a while. However, since we all know decent germanium transistors are either hard to come by or quite expensive (especially for me here in Canada, where I have to add ridiculous shipping fees to the cost just to get them to me), I kept putting it off. I eventually decided to have a look at silicon designs, but even though a few of them were posted a couple months ago, I also wanted to see how hard it would be to simply adapt the Mindbender for use with silicon trannies. Thanks to a schematic from general guitar gadgets, I'm happy to say I succeeded.


Obviously, all credit goes to Mirosol for the original. However, I rearranged the layout so that emitter resistors could be connected to each of the transistors. I also added the 470k resistor across Q1's collector and base, as per the GGG schematic. I then chose 2N3904s for Q1 and Q2, and a 2N5088 for Q3. Obviously your own personal preferences may make you choose differently and measure gains, but I liked the ones I put in enough to keep them in without even measuring. I also changed the Attack pot from 2k linear to 1k reverse log (although I used linear in my build as I didn't have any at the time, this just seems like an improvement in the sweep). Finally, to compensate for the harsh highs silicon is known for, and to increase overall versatility, I put in a Stupidly Wonderful Tone Control at the end of the circuit.

I only just finished a little while ago, and haven't tested at louder volumes as it's quite late, but it seems to work perfectly. Tomorrow I may fine-tune the trimmer, but I'm quite satisfied with the sound. Needless to say, consider this verified. The best part is, if you remove the 470k resistor, and replace the emitter resistors (2.7k, 100r, and 220r) with jumpers or even lower values, you can use this with germanium trannies and have more or less the original Mindbender, but with the convenience of a tone control. Hope this layout ends up being useful to you guys!
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Re: Silicon "Mindbender" with Tone Control (Verified)

Tom F
Update: After getting a chance to play around at greater volume, I decided to swap the 2N5088 for a 2N5089 at Q3. This gave a better volume level. I may also play around with the emitter resistor values, but only out of curiosity - I like the intense sound this gives off now, I just want to see what effect going to slightly higher values would have. For those of you who like tinkering with things, I would suggest socketing those resistors to find the perfect value for you.
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Re: Silicon "Mindbender" with Tone Control (Verified)

Tom F
Another update, I did end up changing the emitter resistors on Q1 and Q2. I chose 1.8k as the new value, and it sounds perfect. Completely usable throughout the whole range of the attack pot, and the tone control helps keep the higher frequencies from getting too congested if desired. Here's the final layout: