Rockman X100 - Make it a DIY Pedal

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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phatt
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Post by phatt »

Carvindc125 wrote: 29 Nov 2020, 13:20
phatt wrote: 29 Nov 2020, 10:37
Carvindc125 wrote: 29 Nov 2020, 05:12 Am I correct here? Is this how the circuit looks on Clean 1 before it hits EQ-1?
Looks good to me, nothing like a highlight colour to follow the signal path.
Good on you :thumbsup
Phil.
So basically Clean 1 before it hits the cab sim is just a Compressor with an input Buffer right? Its basically relying on the cab sim to filter the overall tone right?
Adding R11 and C107 (HPF) are also inserted in the signal path forming part of the tone shape as well as cab for clean 1&2.
Phil.

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Post by Carvindc125 »

I saw in an earlier post in this thread someone was wondering what the Diodes were doing in the Compressor.
Here is the answer.
This makes me think that the Diodes and the Jfet pretty much have to be what's listed. Different diodes will lead to different compression and perhaps could be a good thing but likely not a good thing.
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Compressor.png

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Post by Carvindc125 »

Alright guys! I got some AMAZING news late last night.
Fermusicman was able to trace the EQ-1 and EQ-2 components on his Rockman X100. Below is the redrawn schematic with the corrected values. This is a HUGE one for us because as we know EQ-1 and EQ-2 are the heart of the rockmans tone.
As suspected some values have changed . Its interesting how the schematics overall circuit layout is correct but a lot of the component values are wrong.
I haven't had a chance to test the new values but this is the same person who helped with the Edge and DST values so im sure they will bring dramatic improvements.
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Eq1 y 2.png

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Post by Carvindc125 »

Alright! Here is the verified and corrected Stereo Chorus components. You will notice a very important component change R166 is now 620K instead of 560K. I believe R166 and R165 help determine the frequency of the 555 output. If im right then this change will make the chorus brighter.
It should be noted Fermusicman has looked at a couple different Rockman X100s and though they have the exact same components and values one has the Diode Jumped and the other doesn't.. They sound identical. There is no explanation on why it needs to be jumped in some units but not in others.
With this one Fermusicman may be done. He is having some issues verifying the Echo Trigger and Echo sections as well as the Amp Out Sections. The Echo section may can be replicated with a fast decay reverb circuit and the amp out section isnt that important if your just making a pedal version of the Rockman. HOWEVER Stay tuned and I will see if I can get anything else verified.
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Post by Yazoo55 »

Great project!

I saw the reference to my posts from 2017. Just to clarify, I used a 2N4339 transistor, as specified in the schematic. Using the trimpot, I was able to dial in the compression. Before that I had way too much compression.

To keep myself busy during the Covid lockdown, I went back and did the full echo board as well. I’ve got it all in a 1U rack. I also replaced the slide switch controls with push button controls and these work much better.

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Post by jarrodthebobo »

Yazoo55 wrote: 03 Dec 2020, 13:01 Great project!

I saw the reference to my posts from 2017. Just to clarify, I used a 2N4339 transistor, as specified in the schematic. Using the trimpot, I was able to dial in the compression. Before that I had way too much compression.

To keep myself busy during the Covid lockdown, I went back and did the full echo board as well. I’ve got it all in a 1U rack. I also replaced the slide switch controls with push button controls and these work much better.
How's the echo unit on its own? Isn't it just some sort of quick slapback delay/reverb? I feel like having a whole 1u unit for that part of the circuit is a bit of alot of space for such a small circuit... you gotta add the chorus to that unit too :secret: :mrgreen:

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Post by Yazoo55 »

I added the echo board to the main board so that the whole thing is in a 1u rack, basically a Rockman X100 in a rack unit. This works well with the push button panels I used. The only other thought I had today was maybe to make the trimpot accessible from the outside to be able to adjust the compression. I might come back to that.

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Post by Carvindc125 »

Yazoo55 wrote: 03 Dec 2020, 22:39 I added the echo board to the main board so that the whole thing is in a 1u rack, basically a Rockman X100 in a rack unit. This works well with the push button panels I used. The only other thought I had today was maybe to make the trimpot accessible from the outside to be able to adjust the compression. I might come back to that.
Man I am really torn on what to do for the chorus and echo. On one hand I really like the idea of a 555 cd4013b and mn3007 but the prices of an mn3007 have went way up! I wonder if I can swap a mn3207 in the place of the 3007?
Also thought about going with a digital reverb circuit, the equinox II sounds identical to the echo in a rockman. A Belton definitely log will work too for the echo which any of those will significantly cut down on parts count.
How did you set the pot up? Did you just delete the two resistors and use lugs 1 and 3 in there place and run the wiper to the Jfet?

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Post by Yazoo55 »

Yes, I removed the 2 resistors. The 2N4339 gate connects to the trimpot wiper, pin2. I can’t remember the other pin numbers but either way will work. Trimpot 1 or 3 is connected to the 2 1N914 diodes. Trimpot 3 (or 1) connects to the 2N4339 source pin and the capacitor C104.

You are right about the MN3007s. Genuine ones are getting hard to find. An MN3207 works from a positive supply with a maximum of 10v. The MN3007 works from a negative supply of up to 15v, so it would require a lot of work to re-design the circuit.

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Post by Carvindc125 »

Yazoo55 wrote: 04 Dec 2020, 01:03 Yes, I removed the 2 resistors. The 2N4339 gate connects to the trimpot wiper, pin2. I can’t remember the other pin numbers but either way will work. Trimpot 1 or 3 is connected to the 2 1N914 diodes. Trimpot 3 (or 1) connects to the 2N4339 source pin and the capacitor C104.

You are right about the MN3007s. Genuine ones are getting hard to find. An MN3207 works from a positive supply with a maximum of 10v. The MN3007 works from a negative supply of up to 15v, so it would require a lot of work to re-design the circuit.
Oh Your right! I forgot about that. with the +/- 6V 0grnd supply it would require a different chorus circuit and a separate power tap from the PSU...Probably cost the same in the end really.

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Post by Carvindc125 »

Alright I think this is correct? I plugged in the corrected values along with values from the schematic we have been using. This is with the 10M trimmer/pot on the compressor as outlined above.
Can someone verify this is what the clean section looks like. I swear To Scholz is like "having a hard time reading the schematic? Made it into a maze for you. :troll:

*Edit: Updating schematic with easier to read layout.
Would one of you guys care to validate this is what clean 1&2 looks like before it hits the EQ section?

EDIT EDIT Adding second schematic with pull down resistor and typical pin 3 biasing resistor. Both are not included in original schematic.
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Rockman_Clean1_2-1.png
Rockman_Clean1_2.png
Last edited by Carvindc125 on 04 Dec 2020, 15:05, edited 1 time in total.

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Post by phatt »

I Just noted that the above schematic (as well as the original) has no ground reference? :scratch:
As I understand it pin 3 needs a path to Common to work,, but I could be wrong [smilie=a_whyme.gif]
I don't know about the Rockman circuit but my old Nobels unit which is similar to this one had a 68k to ground at +input pin3.
Phil.

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Post by Carvindc125 »

phatt wrote: 04 Dec 2020, 13:23 I Just noted that the above schematic (as well as the original) has no ground reference? :scratch:
As I understand it pin 3 needs a path to Common to work,, but I could be wrong [smilie=a_whyme.gif]
I don't know about the Rockman circuit but my old Nobels unit which is similar to this one had a 68k to ground at +input pin3.
Phil.
Yup! Your right! I can't find a single reference showing a circuit for guitar that doesn't have one. This is probably one of the many "mistakes" that has been found on the official schematics. Also on the schematic there isn't a resistor from pin one to input cap of pin 5 which I always heard you HAVE to have a resistor when connecting output to input on opamps otherwise the impedance is off and the noise floor raises dramatically.
EDIT: Never mind that last part. First op amp is a buffer so no need for resistor from pin 1 to 5.

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Post by Carvindc125 »

phatt wrote: 04 Dec 2020, 13:23 I Just noted that the above schematic (as well as the original) has no ground reference? :scratch:
As I understand it pin 3 needs a path to Common to work,, but I could be wrong [smilie=a_whyme.gif]
I don't know about the Rockman circuit but my old Nobels unit which is similar to this one had a 68k to ground at +input pin3.
Phil.
Is the 68K going to ground or -6V
EDIT: Never mind. Took a look at the Nobels Schematic and it is going to ground.

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Post by jarrodthebobo »

http://www.stagecue.com/rockman.html

Found this cool little webpage here with some schems and mods... I see quite a few errors in the posted 'modded' schematic however but, may be something cool to look at!

Also, I'm not 100% if this circuit DOES need a reference resistor to pin 3 of the input buffer; I've yet to find a schematic that utilizes one (including the patent images) EXCEPT for a soloist schematic (but the resistor appears like it may be just to give an impedance to ground for the guitar input instead...). My circuit is working fine without it, and up until a few days ago I didn't even have a reference to ground on the input (which was causing squealies without plugging in a jack), but I added a 1meg resistor and havn't exactly noticed any tonal changes.

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Post by Carvindc125 »

jarrodthebobo wrote: 04 Dec 2020, 16:44 http://www.stagecue.com/rockman.html

Found this cool little webpage here with some schems and mods... I see quite a few errors in the posted 'modded' schematic however but, may be something cool to look at!

Also, I'm not 100% if this circuit DOES need a reference resistor to pin 3 of the input buffer; I've yet to find a schematic that utilizes one (including the patent images) EXCEPT for a soloist schematic (but the resistor appears like it may be just to give an impedance to ground for the guitar input instead...). My circuit is working fine without it, and up until a few days ago I didn't even have a reference to ground on the input (which was causing squealies without plugging in a jack), but I added a 1meg resistor and havn't exactly noticed any tonal changes.
Maybe it has something to do with there is an actual -V on pin 4 instead of +1/2V Given that scenario a pull down resistor from input to ground would affectively provide the Grnd reference pin three needs as well as prevent pop if you are using a switch.

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Post by Carvindc125 »

phatt wrote: 04 Dec 2020, 13:23 I Just noted that the above schematic (as well as the original) has no ground reference? :scratch:
As I understand it pin 3 needs a path to Common to work,, but I could be wrong [smilie=a_whyme.gif]
I don't know about the Rockman circuit but my old Nobels unit which is similar to this one had a 68k to ground at +input pin3.
Phil.
It looks like because it uses a bipolar power supply a bias resistor is not needed. Check out this page about half way down it explains how op amps work with bipolar and unipolar PSUs
http://www.generalguitargadgets.com/how ... istortion/

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Post by jarrodthebobo »

Just a heads up;

100% do not try and sub the 2n4339 in this circuit for other fets; I finally caved and purchased a couple and the difference in performance is rather dramatic (and much easier to bias now). I had 100% confidence that a j201 would be a suitable replacment for the 2n4339 since their data specs are quite close in terms of cutoff voltage and such but, save yourself the frustrations of trying to throw something. Upon plopping this tranny in, even without rebiasing it initially, the compression circuit works a hell of a lot better, the distortion 'feels' better under the fingers, less pumping artifacts, more natural decay, and for some reason, more highend (no idea why but a blanket has been lifted so to speak), although I'm not sure if the high end being reintroduced has something to do with the clipping circuit perhaps seeing a more appropriate signal, or the jfet itself having some sort of odd effect.

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Post by Carvindc125 »

jarrodthebobo wrote: 04 Dec 2020, 23:48 Just a heads up;

100% do not try and sub the 2n4339 in this circuit for other fets; I finally caved and purchased a couple and the difference in performance is rather dramatic (and much easier to bias now). I had 100% confidence that a j201 would be a suitable replacment for the 2n4339 since their data specs are quite close in terms of cutoff voltage and such but, save yourself the frustrations of trying to throw something. Upon plopping this tranny in, even without rebiasing it initially, the compression circuit works a hell of a lot better, the distortion 'feels' better under the fingers, less pumping artifacts, more natural decay, and for some reason, more highend (no idea why but a blanket has been lifted so to speak), although I'm not sure if the high end being reintroduced has something to do with the clipping circuit perhaps seeing a more appropriate signal, or the jfet itself having some sort of odd effect.
Nice! Thanks for the heads up.
Did you use a 10M trim/pot to bias?

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Post by jarrodthebobo »

Carvindc125 wrote: 05 Dec 2020, 05:34
jarrodthebobo wrote: 04 Dec 2020, 23:48 Just a heads up;

100% do not try and sub the 2n4339 in this circuit for other fets; I finally caved and purchased a couple and the difference in performance is rather dramatic (and much easier to bias now). I had 100% confidence that a j201 would be a suitable replacment for the 2n4339 since their data specs are quite close in terms of cutoff voltage and such but, save yourself the frustrations of trying to throw something. Upon plopping this tranny in, even without rebiasing it initially, the compression circuit works a hell of a lot better, the distortion 'feels' better under the fingers, less pumping artifacts, more natural decay, and for some reason, more highend (no idea why but a blanket has been lifted so to speak), although I'm not sure if the high end being reintroduced has something to do with the clipping circuit perhaps seeing a more appropriate signal, or the jfet itself having some sort of odd effect.
Nice! Thanks for the heads up.
Did you use a 10M trim/pot to bias?
I had used a combo of 2meg trimpots and 5.6m resistors in series with them in replacement of the two biasing resistors that go to the transistors in order to have a finer level of control over the bias selection. I also tacked on some 2meg resistors in parallel to try and see if dropping the overall values of the bias resistors made a change for the better for alternative jfets but it didn't for the most part.

The other bias method should be sufficient, but two trimpots just gives you the ability to drop pretty much anything in the circuit and get it 'working' at least :mrgreen:

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