# Tone Bender MkII build



## vadsy (Dec 2, 2010)

I found this stuff while cleaning up last week and would like to build it over the Christmas break. I think I have all the necessary materials and components but would love some advice on how to avoid possible headaches come test time. I have some reading to do on the board layout or possible using something completely different than the little pictured below. Any advice to give on layout or components or whatever else?

Thanks in advance.


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## mhammer (Nov 30, 2007)

1) You'll want to include a pull-down resistor on the input in order to avoid switch-popping. Something around 1meg, between the input capacitor and ground, is sufficient.

2) The TB MKII is essentially a Fuzz Face with an added input buffer stage. This is why the transistor with the lowest hfe is placed there: because hfe doesn't matter for a buffer. I gather the trannies came from Small Bear. I recognize Steve's schematic style.

3) Worth using sockets so that the socket pins take all the heat and you reduce risk of damage to the trannies. Besides, it lets you experiment with other transistors, like silicon ones.

4) The ZVex Wooly Mammoth is also a Fuzz Face derivative, and one of the things it includes is variable resistance where R4 is. Consider subbing a 250k pot and 82k-100k fixed resistor, to get a broader range of R4 values. I've done this on a few FF-derived pedals and it's a worthwhile addition for different flavours, while still being ableto nail the stock sound.

5) Again, noting the FF-ness of the pedal, the FF used a variety of values for the cap coming off the R7 wiper to ground. The schematic shows 4u7 but both smaller and larger values can be used. The cap value sets the bass rolloff point where max gain is applied. Larger cap values (e.g., 22uf or 33uf) allow for more bass, and lesser values roll off bass. Absolutely nothing wrong with using a toggle to select between several different cap values. Just note thatthere will be pop when switching caps so do your toggling in bypass mode.


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## vadsy (Dec 2, 2010)

Thank you for the rundown, I will take note and give some of this a try.
Yes, I got this stuff from Small Bear, some from Mammoth and a forum member made me the board but I have no idea what the layout is supposed to be so I think I'm going to try and use this...


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## mhammer (Nov 30, 2007)

Forgive me if I am underestimating your chops, but given this is a positive ground circuit wire it up for battery-only if you don't know how to wire up your external power jack for use with a supply. The circuit is not a current hog, so you'll get decent mileage out of a 9v.


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## vadsy (Dec 2, 2010)

My chops are pretty limited for most of this stuff so no worries. I was planning to make this a battery only for now, just for simplicity.


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## mhammer (Nov 30, 2007)

In which case, score yourself some heat shrink tubing to insulate things like put lugs, any toggle or stompswitch lugs, and even jack lugs.

You'd be surprised how many of the IWBIBIU (It worked before I boxed it up) posts over on the stompbox forum are the result of solder lugs getting shorted out aganst other things. Most of these result from the mis-spacing of holes in the chassis so that some things are a tight squeeze, as well as components getting twisted around when tightening outside hex nuts. The heat shrink allows them to butt up against each other without risk of metal-on-metal contact.


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## epis (Feb 25, 2012)

Here is layout for your PCB (NPN Mind Bender), just keep in mind polarity is opposite for your transistors. Switch positive and negative on power supply and all electrolytic caps.
http://fuzzcentral.ssguitar.com/mkII/mindbenderlayout.gif

P.S.

Reverse 1N4001 diode polarity as well


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## sambonee (Dec 20, 2007)

Mhammer

You're alwwys quite articulate in your posts. This explanation is excellent. 

Pedals are your thing too?


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## greco (Jul 15, 2007)

dumb post on my part....deleted


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## vadsy (Dec 2, 2010)

epis said:


> Here is layout for your PCB (NPN Mind Bender), just keep in mind polarity is opposite for your transistors. Switch positive and negative on power supply and all electrolytic caps.
> http://fuzzcentral.ssguitar.com/mkII/mindbenderlayout.gif
> 
> P.S.
> ...


Thanks for the link, it seems to check out and match up with what I have. I was going to abandon it for vero board but this should look nice.


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## knight_yyz (Mar 14, 2015)

you can add a charge pump to change polarity


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## mhammer (Nov 30, 2007)

sambonee said:


> Mhammer
> 
> You're alwwys quite articulate in your posts. This explanation is excellent.
> 
> Pedals are your thing too?


Thanks for the nod. Between here, the former alt.guitar and alt.rec.music.makers newslists, AMPAGE in its various incarnations, and the DIY Stompbox forum in its various incarnations (both have reset the count several times), I probably have some 40,000 posts since 1991. After a while, you get skilled in explaining (though my 14 years of teaching university and CEGEP also helped hone that). Like any of us old farts, I was raised on Craig Anderton, John Simonton, and Robert Penfold, so I learned from the best. It also helps that I have about 30 binders of schematics and manuals and some 8 gig of schematics on the tablet I'm writing on at the moment. Spend your days and nights flipping through all of that, and looking at 300 versions of the same basic circuit, and you get a good bird's-eye view of how these things work, and what matters. I also build and mod a lot, so I get to learn experientially too.

Pointless to have spent all that money on books and photocopies and components unless you can spread the insights.


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## mhammer (Nov 30, 2007)

knight_yyz said:


> you can add a charge pump to change polarity


You can, but I don't know that it sidesteps the grounding issue. Whether your -9V comes from a battery, or from inverting an external PS, the fact remains that +9v is ground.


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## knight_yyz (Mar 14, 2015)

Sorry, I used the wrong terminology, Look for the negative voltage inverter its a rally small daughter board you add to the circuit. 
http://tagboardeffects.blogspot.ca/2012/05/negative-voltage-inverter.html


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## sambonee (Dec 20, 2007)

Mhammer. I nominate you most sincerely as "famous for the week".
The other post was asking who's famous on here. Well now we have one week covered. Hope you don't spiral downward when you title leaves you in a week's time. 

All joviality aside, you're an excelent addition to GC. We're fortunate to have so many generous people in the know. 

Sorry to steal the thunder.  As you were.


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## mhammer (Nov 30, 2007)

Much appreciated. You've been pretty helpful since joining, yourself. So right back at ya.

A week of fame? Sure, I can handle that. It takes _at least_ 8 days for it to go to my head.


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## sambonee (Dec 20, 2007)

Haha. Good one. Like a welcome hangover?


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## knight_yyz (Mar 14, 2015)




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