Rockman X100 or Sustainor Circuit…

[Caldo71]

Reposting from the older, now-archived wishlist…

Rockman X100 in pedal format?

Would be an interesting project. Originals are getting pretty expensive.

forum.pedalpcb.com

Where it seemed for a while there was some forward movement (a “Goat” was purchased) and then things seemed to sadly fizzle.

Also really want to re-iterate that although there is always constant hype around that hilariously cheezy trademark Rockman distortion sound, it’s the “CLEAN 1” tone that truly shines and remains über useable to this day. Would be a shame to leave that part of the circuit forgotten.

 

[Cybercow]

The X100 used a clever technique. The switch was a slide switch with a small lever that moved another internal slide switch when slid to one extreme. Scholz is a brilliant designer.

You can see it on the right in this picture.
View attachment 28488

It depends on which 'Rev x' it is. Rev 10s don't seem to have that hidden switch. My Rev 8 X100 does.

And agreed. Tom is a brilliant designer. If one carefully examines his X100 compressor circuit, amazement awaits those whose eyes don't permanently cross trying to sort it out.

 

[Cybercow]

Something to think about for sure. There’s a few spots in the circuit I’d like to play with for some tone control. There’s one trimmer in the distortion circuit. Could be a gain pot.

That trimmer is in the pre-gain stages - well before the distortion circuit. Changing it out a B100K allows for more volume, futzes with the tone and gets ya pretty close to that 'brown' sound'.

 

[Scruffie]

It is. Oddly enough some versions use soft clipping in that same location. (or maybe it's the Sustainor or Distortion Generator?)

I built the distortion + EQ standalone and put a gain pot in there. I never investigated why, but it just sounded really off unless the pot was near dimed, defeating the whole purpose. The breakup crackled and just sounded broken.

From prior experience, LED clipping can just sound like that sometimes if it's not being punished by signal, the clipping dips in and out too much to sound pleasing.

But, I wouldn't countenance less gain

In reference to Cybercow's comments though, why not make the input buffer a gain stage

 

[jeffwhitfield]

I won't say it is an improvement on the original, but I will say that it would take advantage of the different form factor for a pedal. Looking up Tom Scholz's patents quickly lets you see that his MIT engineering degree has been put to a lot of use.

Something tells me that Tom likely made more money off his degree than anything. Rockman likely made him more money than even Boston. Granted, he's sold a shit ton of albums by now plus royalties out the ass.

 

[Cybercow]

In reference to Cybercow's comments though, why not make the input buffer a gain stage

We tried that. It creates unwanted distortion further into the circuit when that input buffer is more than unity-gain. And there are damping (signal diminishing) resistors distributed throughout the circuit for balancing the volume of the four different MODEs.

 

[Scruffie]

We tried that. It creates unwanted distortion further into the circuit when that input buffer is more than unity-gain. And there are damping (signal diminishing) resistors distributed throughout the circuit for balancing the volume of the four different MODEs.

Fair enough! Is that just in the compression and or chorus section or do the EQ's run out of headroom? I should probably stick it in a simulator rather than keep speculating.

 

[Cybercow]

Fair enough! Is that just in the compression and or chorus section or do the EQ's run out of headroom? I should probably stick it in a simulator rather than keep speculating.

Everything gets wonky IMO. Just too dirty. I dunno if it's a headroom issue or what. It just didn't sound right.

 

[Cybercow]

Meanwhile, been testing out this monstrosity of a test jig. Using ONLY the preamp, (DIST/EDGE/CLN1/CLN2), portion of an X100, (no effects), I injected my FV-1 Development test bed board into the mixing section where the FX would normally be injected, and am working up the SpinCAD patches in stereo to nail the original FX100 FX. It's using the sequential switching circuit we developed and a couple of BC modules to provide the ±6v supply to all circuits except the FV-1 dev board. Used trimpots in place of the mixing resistors to find the correct mixing balances for the all signal paths coming into the mixer section. That other small daughterboard with the two trimpots is just a stereo boost to bring the entire X100 portion of the circuit up to unity gain. (The X100 is notoriously below unity gain when simply bypassed.)

Getting the chorus sound was easy. Nailing just the Echo wasn't too much of a struggle. But nailing the "BOTH" (Chorus & Echo) effect is a bit tougher because the limited number of lines SpinASM allows for a single patch. Pretty sure it's going end up using two FV-1s to achieve a good sounding "BOTH" effect in stereo. But then that also opens up the potential to use the other 5 patch slots in the EEPROM for different verbs and such.

 

[Cybercow]

Meanwhile . . . . we got in our first batch of finished enclosures for the V2 stage of the project.

 

[VivekMEHTA]

Post in thread 'Rockman X100 or Sustainor Circuit…' https://forum.pedalpcb.com/threads/rockman-x100-or-sustainor-circuit….10202/post-124973


Hello, I'm the Vivek mentioned in post above.

I'm the Chief Designer for that Rockman inspired project.

Looking forward to lots of Rockman discussions here !

 

[VivekMEHTA]

Here's what I got so far. Now, the only thing I'm unsure about is the power requirements. It looks like the original ran at 6v? I don't see any reason why this circuit couldn't run higher than that. Surely 9v will still work. Gonna breadboard this and go from there.

Hmm...might need to migrate this convo to a different thread other than the Wishlist.

Good stuff !

Original X100 ran on +6/0/-6

 

[Cybercow]

Here's what I got so far. Now, the only thing I'm unsure about is the power requirements. It looks like the original ran at 6v? I don't see any reason why this circuit couldn't run higher than that. Surely 9v will still work. Gonna breadboard this and go from there.

Hmm...might need to migrate this convo to a different thread other than the Wishlist.

The schematic you shared looks lacking in several ways. Doubtful it would sound anything like an X100.

And the X100 power supply is actually a ±6v dual-rail supply. When measured, it comes in around +6.2vb and -5.7v. We used a couple of Buck Converter modules tied together (in a wholly unintuitive manner) to achieve a nice solid ±6v dual-rail supply.

 

[JTEX]

Hello world

 

[JTEX]

I'd be happy to contribute what I have learned about the X100 and a whole bunch of other Rockmodules during the development of my "Shockman". It was (and still is..) the longest development time of any electronics project I've ever worked on.

Here's a recent epiphany I had, just as an example of the many little details to be found in the X100 and its various iterations:

In Rev10, the compressor gain control element (the JFET) is basically turned off in DIST and EDGE. To compensate for the resulting lower gain before Dist, the distortion feedback resistor is increased to 4.7M, from about 1M in previous revisions.

Why did they do this? To reduce hiss in DIST/EDGE modes.

 

[Robert]

I've seen the Shockman, excellent work!

 

[Scruffie]

I can't enlarge the schematic but I think that trimmer is related to the input compressor. It looks like the distortion stage itself is the hard clipped LED portion, which could easily accommodate a gain pot, as for tone control, the two twin-t's could be made adjustable with a bit o-simulatin' but I think I'd look at adding something like an output tilt EQ.

For funsies I whipped up a fully variable version of the EQ, not sure how usable it'd be from the simulated pot positions but if anyone fancies playing with it.

 

[Robert]

That's interesting, I might have to give this a go just to play around with.

I won't use it in any commercials.

 

[benny_profane]

My Scholz X-100 Rockman has tripled in price.

I don’t see any tubes, how does it sound? Like Def Leppard's Hysteria album.

www.rig-talk.com

 

[Robert]

For a minute I thought TGP had updated their theme.

 

[JTEX]

Here's what I got so far. Now, the only thing I'm unsure about is the power requirements. It looks like the original ran at 6v? I don't see any reason why this circuit couldn't run higher than that. Surely 9v will still work. Gonna breadboard this and go from there.

I discovered a very consequential error in the original X100 rev10 schematic, which found its way into your drawing, too. Having just traced a couple of rev10 X100's, I guarantee that there is no actual connection between pin 7 of U1 and the cathode of D1 (I'm using the references from your drawing). This makes a major difference in the operation of the circuit. Once you correct this, you'll see that in DIST/EDGE, the R17/R19 divider puts approx. -1.6V on the JFET gate, turning it off (it disables the compresor, turning it into a fixed gain stage).

It took me a year to notice this. There are other differences between the X100 R10 schematic and what I traced from actual production units, but it's mostly just component values that will voice it a bit differently, no big deal. But this one error is MASSIVE.

If you find it hard to believe, trace it yourself. Also, if you look at older Rev10 drawings (hand-drawn, from the same original X100 pdf that everybody seems to have), you'll see that the error is not present.

This ought to save a lot of grief to whoever tries to make an exact X100 clone.