This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Saturday, November 15, 2014

SolaSound Tone Bender Mk. III

Smoother sounding than the Mk. II Professional, the Tone Bender Mk. III not only added a tone control, but the circuit was a deviation from earlier Tone Benders. Q1 and 2 create a Darlington pair that amplify the signal, while Q3 is what creates the fuzz. I've laid this out for negative ground operation, so make sure to use NPN transistors. Q1 and 2 can be low gain silicon if you don't want to use germaniums. Q3 could also be silicon, but a germanium is most likely going to sound best. You can also reduce the value of the 220k resistor (or just replace with a jumper) between Tone 2 and Volume 3 for more output.

Here's a compact layout:



The original TB3 had a cool way of mounting the pots to the circuit board (see pic below). This approach was later emulated by Ross with their Distortion, Compressor, and Phaser pedals, and ProCo with the RAT. 



Since I'm a sucker for eliminated offboard wiring, I created another layout (PCB only, sorry) inspired by the original, but updated for more modern components (like radial electrolytic caps and 16mm pots) and to fit in a 1590B or 125B.



And a shot with the components not in "outline" mode.


This has an optional 1M resistor between the base and collector of Q3 if using silicon transistors.

This layout can also be used for the Vox ToneBender Mk. III and the 3-knob Park Fuzz. See Fuzz Central for component changes.



22 comments:

  1. That old-school-looking layout is bonkers! Just beautiful...

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  2. Just a question for the old school layout:
    if i want to use npn transistor and -9v power supply, i only need to put polarized components (in this case diodes and electros) upside down, right?
    Hope to verify this soon, it will be my first etch!

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    1. pardon, i was meaning PNP trannies, sorry for the typo

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    2. Yeah if using PNP trannies, just rotate any polarized components. Good luck!

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  3. Hi! nice old-school layout! Can i use two AC187 for Darlington pair and one AC188 for the fuzz?

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    1. The AC187 is a NPN while the 188 is a PNP. So to answer your question no, not without some modification. Better to use another NPN for Q3. Sockets are your friends here.

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  4. Why is there an extra diode added to the circuit? I think it wasn't in the original tone benders. Also the 2M and 1M resistors, what are they for? Just curious :) Great job

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    1. The extra diode is for polarity protection, the 2M resistor is a pull down resistor so you don't get switch pops when activated, and the 1M resistor there if you're using silicon transistors.

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    2. If I wanna use pnp germanium should I use the extra diode anyway? I know every polarized component and the power wires must be inverted, right?

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    3. I would use the diode. Always good to have polarity protection. And yes, if using PNP, flip the polarized caps, diodes, and power wires.

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    4. Hello I think the 1n34 Diode can't be inverted in any case becouse it put the base of q3 to the ground......

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  5. I'll use 2n3904/bc548 for darlington formation, and germanium for Q3.
    This last one, and the diode, are the "must be"

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    1. The reason Q1-2 are in a darlington is because they didn't have transistors with a high enough hFE to just use one back then. Combining 2 modern silicon transistors will likely provide way too high a hFE and won't work. If you don't want to use low hFE germaniums for Q1-2, I suggest not trying to build this layout. Look at something like the DAM GB-83 or EQD Hoof Reaper.

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    2. This comment has been removed by the author.

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    3. Sorry if I insist on silicon transistors on all projects.
      It's not that I do not want to use them: where I live, germanium transistors are very hard to find and expensive (avoiding purchase on ebay, pay customs).
      Thanks again!

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    4. No worries. I get that. Germaniums can be a pain to work with in the first place and often substituting silicon transistors makes it a bigger pain.

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  6. What's the correct size to print it? Do you have an image file with the correct size?

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    1. https://www.dropbox.com/sh/iaegm30zvqgcvp1/AAD0x_GB3EZqRwcwSxW7QBlFa?dl=0
      All the files are in .pdf with correct size.

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  7. can you give a recommendation on what trannies to use? cheapest and easily obtained if possible. I get confused with all the different combos and names. Also is this a negative ground(boss style) or positive ground powered effect. I think i got that right. Id like to be able to use with my visual sound 1 spot, i know there are adapters but id rather avoid that if possible. Im a sucker as well for elimination of offboard wiring as much as possible. Also old school style layouts. Too bad the inverted pin type pots arent anywhere close to accessable as the 16mm right angle ones. i know small bear has them. havent checked the cost , but havent seen any layouts that would even accomidate them. Thanks if you can give tranny recommendations.

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    1. Cheapest are probably Russian old stock germaniums like MP38s. That's what I'd start with for this build. I also cannot recommend enough getting something to test transistor gain (hFE). A lot of digital multimeters have them. Ideally you want the first 2 transistors to be pretty low (80 or lower) as they form a darlington transistor pair. The 3rd transistor should be around 100-120. Really, it's more about the hFE of the transistors than the actual type. Surf ebay and find some cheap options and measure. Or order from someplace like Small Bear that sells measure sets of transistors for various old germanium circuits. Best of luck!

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  8. Which is the difference on the cap from Q2's emitter to ground? Lower value = more gain/highs?

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