Ibanez SML/MS10/SM9 mods

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Ibanez SML/MS10/SM9 mods

Postby miketbass » 20 Jan 2018, 10:56

Hello all

I figured I would share some of my mods for the "Super Metal" Ibanez series pedals. I have worked from the schematic posted here:
http://www.freeinfosociety.com/electron ... php?id=588
I had an Ibanez SM 9 many moons ago which was sadly stolen, and recently revived an Ibanez SML that made it's way into my hands DOA. I played it in stock configuration for a bit and it was about how I remembered: lower output, sort of a thicker and fuzzier distortion character, and very mid focused. The stock tone shaping controls offer a wide and flexible range, but the lows are voiced in the lower mids and the high range is voiced rather high and piercing for my taste. I guess the designers were going for the voicing of a Marshall stack, and with this in mind it does approach that sort of sound. After looking at some available documented mods it seemed that most of them revolved around playing with the clipping diodes and and fixing the inherent low volume. This is all well and good, and while it allows you to shape the distortion character I was interested in changing the voicing of the pedal.
It seems that many of these Japanese "Metal" pedals shared some basic design similarites: soft clipping stage, hard clipping diodes to ground, and a gyrator with the "mids" and "highs" tied to the same pot to control those respective tones. Well, it just so happens that one of my all time favorite stompboxes is the Boss HM-2 for it's signature midrange grind. If you compare schematics there is much similarity between the topography of these designs. So... why not do a "Super HM-2"? Well that's exactly what I did. On to the mods.

R58 - 100 ohm - this fixes the low output and allows for a volume boost in the last quarter turn of the knob
R11 - 1K ohm - this allows more distortion and gives the stompbox more than enough gain
C1 - 1uf - this is likely a much larger value than necessary, but allows the full bass range of the instrument through (helps with bass guitar)
C15 - .027uf - I paralleled a .015uf cap here, you may try .01uf or so too - this shifts the bass frequency down, removing "mud" and adding thickness
C19 - .033uf - rebuild the "Edge" control to HM-2 spec
C20 - .0056 - rebuild the "Edge" control to HM-2 spec
C26 - .0047uf - rebuild the "Edge" control to HM-2 spec
R26 - 710 ohm - rebuild the "Edge" control to HM-2 spec (I placed a 1k ohm trimpot here for variable gyrator frequency, and marked the 710 ohm spot)
D1 - 2x 1n4148 in series - this allows for asymmetrical clipping in the first clipping stage, and allows a little more signal through to push everything harder
D3 - 2x 1n4148 in series - this replaces an LED originally here, this is likely not necessary but simply copies the first soft clipping stage

I socketed the opamps and played with some different combos, I have JRC4559 in there right now I think. I also placed NTE458 in TR1 (which is incorrectly marked as a BJT transistor and is actually a FET) which is likely lower noise and slightly higher gain than stock, I'm not sure this adds much value tbh. Change all of the 1uf electrolytics to cheap box film, the power filter cap for a fresh one, and the ouput cap to either a fresh aluminum or tantalum electrolytic. The results are more than impressive. With the edge control dimed, low at 1 o'clock, attack at 1 o'clock, distortion at 9 o'clock, and level just past noon I get all of the aggressive frequency response of the HM-2 with a much thicker, saturated sound. The pedal now achieves beyond unity gain, the low end is very powerful, there is plenty of gain on tap. It is absolutely amazing! A much more modern sound that for better or worse barely resembles the stock sound. Compared to the HM-2 or DOD FX-56B it seems to be less harsh and buzzy, much more full and actually has more gain and saturation than either (likely because of the second soft clipping stage). I have been using the "swedish chainsaw" sound for a project lately and I will likely use this as either my main sound or as an alternate guitar track. I have not played it through a proper bass rig but the huge low end response seems to work much better on bass guitar than the HM-2.

You can still grab the SML models for reasonably cheap, say $50-60 or so. Quite frankly if you were to buy one and do these mods, buy a DOD FX-56B and change .0068uf cap in the gyrator to .0056uf you would have everything the HM-2 does but better. I have all three, and while there is some magic in the stock Boss HM-2 sound I find myself using these "clones" much more often as they simply sound better. Cheers and happy modding all!!
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