I'd like to modify my Rocktron Rampage Stompbox

[Breogan]

Hi there!

I'm a newby here and I don't know if this is the right place to ask this question... Anyway, hello to everybody!

I have a Rocktron Rampage pedal and it's too much gain and metal but with some settings you can get a very nice warm distortion out of it. I thought that may me posible to mod it and make it a medium gain pedal. Do you know if there is any schematic avaliable?

I also would like to know if there are any kind of mods that could be apply to this pedal. I've read on Harmony-Central that some people had replaced the "sustain" knob (from 500K to 250K) to get less gain from the pedal.

Thanks a lot!

Breo

[Mark Hammer]

Sounds to me like the mod you read about is for a gain-setting pot.

Though not the ONLY way to adjust the gain in an op-amp/IC-based distortion, one of the most often-used methods is to vary the feedback resistance between the output pin of the chip, and one of the input pins.  As the feedback increases, it's a bit like loosening the reins on a a horse that wants to just bust out.  The looser the reins, the faster it runs.  In the case of gain, the higher the resistance, the "faster it runs" (i.e., more gain and distortion).

If a 500k gain pot is replaced with a 250k gain pot, AND if the design is close to what I'm imagining, then the 500k pot will also be able to dialin subtler grind, but it will be trickier to do so since all those sounds will be located in a small portion of the pot's rotation.  Switching to another value pot will have the effect of pushing out the hot tones in favour of stretching out the subtler zone - a bit like moving the girlfriend's clothers out of the closet so the boyfirend can finally find that shirt he's looking for  .

Of course, you don't have to change the pot to do that.  What you CAN do is simply wire up a switch to engage a parallel resistor.  In this case, a SPST toggle would connect a 470k or 560k resistor in parallel with the pot, so that it becomes LIKE a 250k pot.  The taper of the pot will not be exactly the same, but it won't matter so much when you can select ranges.  If you want to experiment without needing to drill holes or bugger anything up, just solder the parallel resistor onto the pot leads directly and see if you like what it does, first.

One other thing I'm going to guess about.  It is often the case that a small capacitor is placed in parallel with the feedback resistance to keep unwanted high-end in check.  This is useful in some configurations because as the gain is cranked you generate tons of harmonic content, a lot of it undesirable.  Since the amount of treble-trimming is a joint function of the capacitor AND feedback resistance, one of the neat things about this arrangement is that you trim off MORE treble as the gain is cranked.  Because the cranked gain adds harmonic content as a result of clipping,reducing the treble content as gain goes up tends to keep "fizz" in check and produces a more consistent and satisfying distortion.

The cap that is in there may be selected to produce a certain amount of treble trimming to suit max gain with a 500k pot but not produce the same degree of treble-trimming when the max resistance is only 250k or thereabouts.  That may or may not be a problem but I guess you'll know when you hear it.

[DDD]

Hi guys:
Could you please give a link to the Rampage schematic diagram? They say there is a couple interesting tricks there. To my surprise I cannot get the schematic on the Net.
Thanks in advance.

[Breogan]

Mark

Thanks a lot!!! That was a great explanation! I allways wanted to start messing with pedals, I think can be a great starting point. I am very used to wire my guitar so It won't be a proble to sold a resistance to a pot. I am interested in the effect I'll make.

Thanks!

[Breogan]

By the way... Is there any way to get an schematic?

Thanks again!

[Mark Hammer]

None seems to be posted around.  Many, though not all, manufacturers will send you a factory schem for a fee.  Yes it may be expensive for a simple sheet of paper, but if 10 or 20 dollars gets you a "new" pedal, doesn't that make you happy?

[Breogan]

Hi Mark!

I've tried reducing the resistance of the sustain (gain) pot setting a resistance in parallel. I didn't sold anything, I just stock a resistance in the pot's holes to see the effect on the pedal's output. The original pot is 340K and, with the resistance in parallel, It changed to 140K.

With the lower pot value it happened just as you stated. The gain resduced a lot and  now I it's posible to set differents types of low/medium gain output. I liked much more the low gain settings. The sustain at max doesn't even get a compressed tone with endless sustain. I see it as a much more ussefull pedal, I want to try it to drive my tube amp!

I am very happy with the change so i think i am going to leave it that way.

I should say that the pedal changes a lot the tone of the guitar if you set a flat eq. But if you set the bass to almost max and the treble to almost min (and scoop to min) you get a more natural tone. With this setting the tone of the pedal's output is very similar to the tone of the pedal switched off. This fact makes me think that may be the flat setting (Bass and treble to 12 and scoop to minimun) it isn't as flat as the manual states.

Rocktron states that the pedal has a +-15db treble and bass eq. This means active control, but could it be passive? Could it be possible that the bass and treble pots are a -30db eq pot with -15db centered in the 12 o'clock?

Now I would like to see If I can change the eq section a bit to center the setting I preffer.

[Breogan]

bu-hump!

[kupervaser]

I have the schematic.

Write me an email and I will send it to you.
angar666hotmail.com

[clintrubber]

Hello,

Interested in the schematic. I've tried contacting kupervaser as well but since it's an old thread who knows if it's still available ?

Thanks!