Build Your Own Clone Message Board

Hi all,

First off I'll apologise for posting loads of posts in the 250+ forum over the last few days.

Anyway if you haven't seen my other threads, I have built 250+ to mxr dist+ spec with clipping mods. Its built as a thank you gift for a good friend of mine who loves hair metal, we're talking Ozzy (Randy Rhoads, Jake E Lee era), motley crue, twisted sister, etc. that kind of thing. I initially built it because he loves Randy Rhoads and apparently he used one (probably with a JCM 800 or similiar though).

Now I rather like the distortion this thing produces, but I like indie, classic rock and blues, not back-combed metal. So I think I want to make it have the option (ideally via dpdt switch) to crank it up one gear.

Ideally I would like:
- Smoother distortion, more fizzy and less brutal/rough (the opposite of the LED clipping I guess). The current setup I have which is on the way to acheiving this is Asymetrical 914 diodes 3 vs 1, but I think there might be better options out there.

- More gain! Is this possible via a any resistor/cap switches that I could toggle switch?

The other thing to consider is I have tested this pedal with my telecaster sith single coil pups he plays an ibanez rg and a charvel model 4, so they are going to give it a bit more oomph and a smoother sound anyway. We do have the same solid state marshall map though.

To me this pedal sounds more like an overdrive by todays standards. I can still get it to crunch and distort, but just not as much as my rat or big muff, but thats not really too surprising. (I will also double check my board as I think I may have put the odd 250 component in by mistake instead of a dist+!)

I think if I give it him in its current state, he'll still use the distortion produced on the dirty channel of his marshall instead of this, so I want to give him a reason to switch

Thanks in advance!

~ J

Ha, here we go again!

Ok, so I don't know exactly what you want here but I can explain how the gain works.

The Op-Amp is set up as a Non-Inverting Amplifier.

Without going into too much detail, the gain is 1 + Z2/Z1, were Z refers to a complex impedance, ie. Z = R + j*X, where R is resistance and X is reactance. The reactance of a capacitor is 1/2*pi*f*C.

So assume the section from pin 2 (- terminal) to ground that has the 0.047uF cap, the 4k7 or 47k resistor and the 500k pot, is Z1.

Z2 is the parallel combination of the 10pF cap with the 1M resistor.

So if gain = 1 + Z2/Z1, to get more gain, make Z2 bigger or Z1 smaller.

If you want less gain, you could add a resistor with a SPST switch in series between the "Easter Egg" holes, say a 1M resistor, you flip it on and the parallel combination gives you 500k, or half gain. This is kind of dumb, you could just turn the knob! Adding something in parallel will not allow you to get higher resistance.

So, if you want more gain, a good start would be to TAKE OUT the 1M resistor between pins 2 and 7, THEN from the "Easter Egg" hole add the 1M resistor in series with with a 1M pot wired as a variable resistor. That way R2 can go from stock gain with the pot at zero to double gain with the pot at full (2M total).

I haven't done so it may sound rough but it's a place to start....

FF, thanks for that. I went a bit crosseyed in the middle though. As for increasing the gain, I might have a crack at playing with that 1M resistor, as you say increasing the value and seeing how that turns out. Good idea with the 1M pot however I think I'd just like to keep it with the two knobs and hopefully two toggles, one for gain boost/stock and one for clipping. Is there any reason why you would move the 1M resistor to the easter egg holes rather than keeping it in its current position? I'm not sure I understood the reason for that?

Also I put in the germainium diodes from my other 250+ kit, they are awesome, definately the right direction I want to go with this pedal tonally. More smooth distortion than the rough distortion provided by the LEDs and to a lesser extent the 1N914s.

Can any one suggest any more diode clipping settings that I could use in place of the LEDs to get something similar to the germainium 1n34a diodes, but more so in that direction? Think METAL! \m/ Speaking of which does anyone know what clipping diode combination is in a boss MT2?

Cheers

~ J

Hey J,

Not really the clipping guru, but to answer the question about the resistor, no there is no need to move it. The cheapest way to do the mod is with a SPST switch, and two resistors. You would solder the big one where the 1M is now, this could be anywhere from 2M and up (could put a socket and experiment). Then accross that big resistor (or at the Easter Egg holes now) put a resistor with a SPST switch in series, this will result in the big resistor in parallel with another one that would effectively give you 1M. Depending on the values you choose you'll have to calculate the right resistances.

The easiest one is 2M, if you switch in 2M in parallel, the combination will be half of that, or 1M, the stock value.

Otherwise use the formula for parallel resistance:

1/Reffective = 1/R1 + 1/R2


Good luck,

Nathan

Awesome thanks.

This is going to sound very silly. I've used a black DPDT toggle switch for the clipping. It was about 6X the price of a standard 3 way, but it looks so cool, they (banzai) don't do similiar SPST ones! But they do have some black DPDT on/on toggles so I think I'll have a go at using one of those to switch between the 1M and the 2M resistor.

I've been looking at the YJM 308 I might get some of the diodes used on that but I think thats more of an overdrive pedal.

Thanks for your help!

Not silly at all, do what feels right! I hate doing extra wiring so I'd keep it simple.

You might want to try bigger resistors too. 4.7M / 10M, might get pretty crazy though...

I'm currently fooling around iwth a 250 to get more gain and different clipping modes out of it. I built the kit as a 250-spec and swapped out the 250-spec R4 resistor (47k) with a 4.7k (Dist+ spec)- easy way to get more gain and a bit more output. With the 4.7k in there, you have to back off the gain knob to about 2:00 to get stock 250-level of gain.

Check this out:

http://73guitars.blogspot.com/2008/08/o ... otype.html

I made the resistors footswitchable, so you could have stock and high-gain modes. I'm trying to figure out how to switch the diodes with the remaining lugs on the 3PDT switch.

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Oh yeah - almost forgot. I found that keeping the stock IN914 diodes and adding a IN4001 in the third spot mad e anoticeable difference - smoother, a bit less raspy. I guess that's asymm vs. symm clipping for you...

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The metal zone is using 2 1n4148 type diodes in a symmetrical fashion. With that said, you aren't going to get anywhere near the gain of the metal zone with a single opamp gain stage and diode clipper type of circuit. The metal zone is several gain stages with the diodes adding extra clipping.
bw

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