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Originally posted by zentropa

did about 4 hours worth of digging and didn't find any info on it aside from the clarity mods.

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http://music-electronics-forum.com/showthread.php?t=5052

I have no knowledge of what the "Twilight Zone" mod is or actually does. The boastful ad copy is no better or worse than just about any other. A quick trip to pedalgeek or Musictoyz will confirm that. I took a look at the manual for the mods over at Bob Keeley's site, and while there is more to it than I presume, I think I can suss out what the essentials are.

First off, the stock unit does its clipping with a pair of 1N4148 diodes. They set a limit on how hot the output signal can ultimately be. If they are added to with extra diodes, or replaced with diodes that have a higher forward voltage, you will achieve a noticeably greater overall maximum output level. This sort of change/outcome is common to every distortion circuit that uses diodes for clipping. It does not change the behaviour of the tone controls or anything else. It simply raises the ceiling so that if the signal wants to stand a little taller, it can.

If you add a diode to only ONE half of the clipping section, you get something that many folks (Keeley included) will refer to as asymmetrical clipping. I have publically expressed doubts about this before, since I feel that the asymmetry is a function of several other things being lined up at the same time, but it is clear and not a misrepresentation at all that such a change produces a slightly different quality of distortion and does permita slightly more dynamic feel, not to mention more output (though NOT more gain; those two things are different).

I have no idea where the cap and resistor substitutions are so we'll ignore them. In high-gain devices it IS useful to lower the noise floor on the input section, but if you can tolerate the current level of noise in your pedal, this to-be-suggested change will not make it any worse. To accomplish the essentials of the mod, locate a point on the board where you see two small glass diodes lying beside each other, end-to-end. That is one will have a stripe in one end, and the 2nd one will have a stripe at the opposite end. Unsolder one end of one of the diodes, and gently lift it up on the component side of the board so that it is standing at sort of a 45-degree angle. It doesn't really matter which diode or which end.

Find either a 1N418, or a 1N914, or perhaps even a 1N34 at Radio Shack or wherever. The 4148 or 914 will result in more change in level. Solder one end of the additional diode to where the lifted-up lead used to go. Make absolutely sure that the orientation is correct. What is "correct"? Well, if the original end you unsoldered had the stripe, then you should solder in the extra diode with the stripe at that end. If the original unsoldered end was non-stripe, then that's what goes there. With the extra diode added, snip the lead off, and solder the two free ends of the standing diodes together, making sure not to overheat the joint too much.

That's it. Package her up, and rock.

The Keeley way of doing this provides a toggle switch to select between stock and mod. That's part of the reason why the mod costs more than my simple description would suggest. They do the machining, and make sure they have a decent switch that will fit the available space without shorting out anything. In Boss pedals, such switch installation does require precision, and that's what you're paying for. Since the extra diode will provide a sound you won't dislike, and since you know how to reverse the mod, we'll leave it at that and ignore the switch. If you hate it you can always remove it.

One other thing you can do to make the unit a little more deadly is to add more gain. If you trace the path of the Gain control (a 200k pot), one end of it goes to a 1k resistor. Replace that 1k resistor with another resistor, anywhere from say 39k to 68k, whatever you have on hand. That will raise the gain of that stage from 202x to 270x (if you use a 68k resistor).

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Originally posted by jack

Also, Monte Allums has 3 different mod kits for the MT-2...the Keeley modded MT-2 contains a 3 way switch...so maybe their mods are similar? I haven't had any experience with any of Monte Allums pedals or mods, but I hear lots of good things about them.

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Originally posted by Laurie

Well... I put in a mod that I think similar to the "JCM Boogie" mod. LED + 1N4004 for the diodes plus increased C36 to 1�F. Also removed C25 and C35. Still not what i'm looking for.

Here is a question... One of the things I did to this pedal is replace all the 1�F electros with polyester, and the 10�F electros with tantalum. I read somewhere that leaving the old electros in keeps the pedal a bit dark and it actually sounds better? What do you think?

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