Dunlop Rockman ACE  [schematic]

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

I really like the rockman sound. This sounds like a nice build idea. Your description sounds a lot like the Mockman actually.
I have built the mockman and i say it plays nicer with single coils than the Sustainer.
This circuit probably will too. Strat + Sustainer = ear fatigue in a very short time. Even with all compressors up and all trebles down. I use the Mockman for gigs and rehearsals. The The Distortion/Sustainer is far too fragile (broken plastic case when I found it 15 years ago) to leave my home musical environs.

Thanks for your reply Darth.

My first life as a teenage songwriter: all songs sounded like more kickass Boston-y sound...in my head. Sustained leads, reverbed octotracked choruses. I thought derivative BS was awesome. Today, my derivative BS is far more refined. Progress.
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estragon
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Post by estragon »

It seems the schematics are gone, only the thumbnails.

Could someone repost please? or were the schems removed upon request?

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darthoverdrive
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Post by darthoverdrive »

Not sure what happened to the images but here they are again.
I've attempted a couple of times to trace out the Sustainor but always seem to give up. Its just that complex of a circuit. It sounds so much better than these stripped down headphone amps.
Attachments
PCB image
PCB image
Schematic of Rockman headphone amp
Schematic of Rockman headphone amp

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DSV
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Post by DSV »

This is a schematic of the Sustainor I found a whle ago on the net:
http://www.4shared.com/zip/vuTn0kWO/roc ... ainor.html

Quite complex circuitry, though the main idea (compression -> distortion -> cab sim) was already found in the headphones amps.

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darthoverdrive
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Post by darthoverdrive »

Complex indeed. I find the patents to contain a wealth of information too. The headphone amp is described in patent 4584700, the compressor in 4627094, the smart gate in 4809337, the auto clean in 4752960, the chorus and reverb in 4489439.

Plus there are the Nobels schematics and their knock off products of the X100 and XPR.

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shickapooka800
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Post by shickapooka800 »

Thanks to the darthoverdrive for the trace. I used it to modify my guitar ace to sound more full and sparkly.

I was in a hurry (always) so I tried to come up with mods that only parallel additional components, that way I could quickly tack on components and test.
mods:
R20 to 500k (by parallel 1Mohm add-on) -- lowers gain and gives me crunch rather than distortion, works well with my pickups allowing me to clean up with vol knob
D2 clipped and another 1n4148 added in series (for asymmetrical clipping -- personal preference, would have tried LED if I had some)
C21 REMOVED
C22 increased to 6nF (by parallel addition of .0047uF I had laying around)
C13 increased to 3nF (by parallel addition of .002uF )

Comparison of modeled response (comparison because I may not have the original right anyway...) attached.
I'm very happy with how it turned out, very full bottom, with some sparkle. I was shooting for a Jensen 10" in response, but with minimal effort, so the 2.5kHz peak is a bit high-q for my taste, but it works. There is a bit of harshness with a high output tele bridge pickup, but I can make it work -- I have convinced myself it sounds very similar to speaker cone breakup. All around transformed the thing into something useful. I only use the 'dist' channel, no heavy, no clean. also, I DO NOT use the compressor section (pull Jumper TJ1). It is too invasive for my taste, so I will next turn to taming it a bit (or not, I'm happy with it as is).
Image

edit: just some backstory, I did all of this because the first thing I did when I got the Rockman Guitar Ace was put it on clean (sounded really promising), then running some fuzz pedals into it --- big mistake. Upon looking at the old Soloist and X100 schematics I noticed it was common for one clean channel to bypass the "complex filter". Sounded like a herd of bees. I initially wanted to just re-route the clean into the eq section, but I thought it sounded a bit thin. Now I can have a semi-dirty amp sim that can take fuzz and overdrive pedals convincingly. Since I lowered the gain to be on the verge of clipping, it also responds to boost pedals well. I use an MXR 6-band to boost the mid bands and push the Guitar Ace into full distortion. Alternatively, I ran this setup without clipping diodes for a bit the other day, and it does well as a clean amp pushed hard with the original 1M feedback resistor R20. I imagine with R20 to 500k and no clipping diodes, it should be clean.

Oh and now I can run it into my full range stereo (some ls3/5 diy clones and subwoofers) and in a small room I get that tactile low frequency picking action you get from a half stack. I don't care what the EQ is, 4 12" speakers in close quarters has a 'feel' that goes low.

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Carvindc125
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Post by Carvindc125 »

What does R38 do??
I understand everything but R38

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CheapPedalCollector
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Post by CheapPedalCollector »

Can someone reupload the sustainor, 4shared is broken

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Carvindc125
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Post by Carvindc125 »

CheapPedalCollector wrote: 07 Feb 2021, 22:10 Can someone reupload the sustainor, 4shared is broken
I have it and will upload it for you shortly.
Would you happen to know my question above as to what R38 is doing on the Ace compressor?

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george giblet
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Post by george giblet »

Carvindc125 » 07 Feb 2021, 02:18
What does R38 do??
I understand everything but R38
This question came up on the other forum. Some photos of the pcb point to a possible later version of the board and/or there could be some tracing issues around the JFET on the schematic in this thread.

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JTEX
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Post by JTEX »

I was studying darthoverdrive's Rockman ACE schematic and I ended up completely redrawing it to make it easier to read (hopefully). Here's my version. Hopefully it will help someone. Let me know if you find any issues with it.
ACE.pdf
Rockman Guitar Ace / Metal Ace
(73 KiB) Downloaded 60 times

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Carvindc125
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Post by Carvindc125 »

JTEX wrote: 08 Jun 2021, 00:14 I was studying darthoverdrive's Rockman ACE schematic and I ended up completely redrawing it to make it easier to read (hopefully). Here's my version. Hopefully it will help someone. Let me know if you find any issues with it.

ACE.pdf
Wow! That is Amazing! Great work!
george giblet wrote: 21 Feb 2021, 07:25
Carvindc125 » 07 Feb 2021, 02:18
What does R38 do??
I understand everything but R38
This question came up on the other forum. Some photos of the pcb point to a possible later version of the board and/or there could be some tracing issues around the JFET on the schematic in this thread.
I have since discovered there are different versions of the board.
It looks like when SR&D made the Guitar ACE it used the same compressor that the Rockman, II, IIB, Soloist, X100 used.
When Dunlop took over they redesigned the compressor so that it would work a higher VGSoff range. IE they redesigned the compressor so they could use cheaper fets.

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Carvindc125
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Post by Carvindc125 »

george giblet wrote: 21 Feb 2021, 07:25
Carvindc125 » 07 Feb 2021, 02:18
What does R38 do??
I understand everything but R38
This question came up on the other forum. Some photos of the pcb point to a possible later version of the board and/or there could be some tracing issues around the JFET on the schematic in this thread.
As you can see in this pic.
There are differences in Dunlop Guitar ACE and SR&D Guitar Ace.
Dunlop is on the left. it uses an extra opamp and a trim pot to allow a much higher range of FETs to be used on the compressor this comes at a price though. More noise.
The one on the right is SR&D Guitar Ace. Notice one less opamp and no trimpot. It appears to be using the same compressor from all the other headphone amps SR&D produced and appears at first glance to be the exactly the same as the soloist compressor in particular.
Attachments
ACE VS ACE.png

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JTEX
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Post by JTEX »

I guess that the schematic I redrew (see above) is of the Dunlop version. I figured that the extra, low power/noisy op amp would make the whole thing extra noisy. Clever trick, but not well implemented.

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george giblet
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Post by george giblet »

Great work Carvindc125 and JTEX. I guess that answers the question.
Clever trick, but not well implemented.
Yes, it's not quite there. Kind of wrong as drawn (not the schematic but the original design).

The Rockman boards are dated on the bottom, I saw 1990 on one unit, and have SCHOLZ R&D on the bottom. Markings in copper.
The Dunlop boards are dated on the top but they have Rockman text on the top silkscreen. Carvindc12's pic looks like 1995.

The tell-tale sign for the Scholz-Rockman is the LED near the corner of the PCB.

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Post by JTEX »

Carvindc125 wrote: 08 Jun 2021, 14:03
As you can see in this pic.
There are differences in Dunlop Guitar ACE and SR&D Guitar Ace.
Dunlop is on the left.
Did you take the picture? If so, could you elucidate the R38/R36 mystery once and for all? Thanks.

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