Saturday, 19 January 2013

Runoffgroove Mockman

From ROG: This project has returned from beyond the grave for a tune-up. Compressed, harsh, and '80s sounding are fitting descriptions of its sonic character. Yes, it is a niche sound which is quite the opposite of some JFET-based distortions developed by the 'groove, however we feel it is a great time capsule of an era fondly remembered by many. Whether you are looking for a simple weekend project or willing to play a cover of an '80s hard rock anthem, the Mockman will suit your needs.

During the '80s, countless artists recorded directly to console using a Rockman amp. The Mockman sounds uncannily reminiscent of this sound as it is based on the Scholz Rockman's distortion section. Distortion is created by overdriving the op-amps, similar to the Sansamp units, but with strong equalization in each stage: a high-frequency emphasis combined with an aggressive low-frequency cut.

In this revision, the optional LEDs were completely removed, the high-end has been tamed to reduce hiss and some harshness, and gain was increased for additional sustain. Also, switch at the output sets the amount of bass for a biting '80s sound (Classic) or a heavier '90s sound (Modern).

The original op-amp was an RC1458, however you are encouraged to audition any dual opamp, as this component is an integral part of the sound. The JRC4558 opamp works quite well. Some faster/better op-amps like TL072 and NE5532 produce a slightly brighter sound. Modern rail-to-rail opamps like TLC2262 and TLC2272 sound a bit louder and better defined. In particular, our favorite op-amps were the JRC4558 and TLC2262.

The output filter capacitor can be set initially to 470pF, then tuned according to your preference and the op-amp in use.



20 comments:

  1. Hell yes you can tag this! It's a full on 'hair metal' style distortion, high gain with a nice EQ balance. It's times like this a wish I still had long hair so I could put a power headband on or shave it into a mullet and rock the f*ck out!

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    1. OK, no mullet but you get the idea.

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    2. Excellent, thanks for verifying mate

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    3. It really is a pleasure mate. This won't be everyone's cup of tea but this is exactly what I want from a distortion as opposed to a Fuzz. It's badass!

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    5. No, it seems an understanding problem, not a grounding one :) You can't find any path to ground on the lower row, because is not connected to ground.

      The only pin of the IC that is connected to ground is Pin 4. Your voltages are a real mess, and have no sense at all, so you have something really wrong on your board. In the schematics that you tell, the volume lug connected to ground is 1, as in all volume knobs, unles you want a volume knob that works counter clock wise.

      If that's your first vero, check the cuts, component location, solder bridges between rows.

      Voltages should be something like

      4-5v
      4-5v
      4-5v
      0v
      4-5v
      4-5v
      4-5v
      9v

      J.

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    6. THank You. I figured that out and found a bad cut in row 3 (ground) at the top, I now have new voltages I will post now.

      000
      000
      4.68
      000
      4.68
      000
      000
      9.47

      Now, I get a sound, but it start out way distorted and then fades out, I tried reducing the pot - no help. It sounds like a capacitor problem since it fades out the more I play it, and within about 20 seconds have no more sound.

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    7. I had a similar problem with the Univox Superfuzz, and finally happened to be a resistor from emitter to ground, that should be 1k8...but I soldered 1M8 instead :P

      If you find no dodgy caps, check resistor values, just to be sure.

      Anyway, 0 volts on Pin 1, 2, 6 and 7 is not normal, so check this area first, as there's something wrong there.

      J.

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    8. By the way, there are no cuts on row 3 (ground)

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    10. Darn .... I rebuilt this thing from scratch and it still has the same problems. I don't seem to get voltage to the IC. I am thinking maybe I have the outside grounding wrong (on the guitar in & effects out) - any tips there?

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    11. Maybe it is the switch I don't get. I have a STDP (single pole double throw) - so it has two positions, but three lug on the bottom. I assume it goes in pairs, so I would wire up 1 & 3 for sw 1 and sw 2 --- but I am not sure. Any help here?

      Also - should I ground everything to the board? Sorry but this is the first project I have done here - and not having any joy.

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    12. I JUST got this working. I should have known when the voltages were not right that it was related to the input voltage. It turned out I had a 22k resisitor where I should have had a 100 ohm.

      So - two things when you start to build these - it is probably a good idea to set out all your parts ahead of time so you have them accounted for. Then, print out a copy of the schematic and check off each part as you add it to the circuit.

      To troubleshoot it, it is easy to check caps (the value is printed on them), resistors, for us newbies, are a little harder. The "Electronics Asst App" is invaluable. It shows you all the right codes for caps & res. for any value.

      To trouble shoot, it is also easy to see the circuit, but I fixed my build when I opened up that app and started checking all my resistor values.

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  2. Damn, 10 minutes from my second tag of the day. Well done mate! I had a rock man in the 80's, used to plug it into my portastudio and I thought I was George Martin. Very nice indeed, Miro!

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  3. Guys! That means that we are 4 tags away from the fact that Mark has to write another notification! How cool is that!
    +m

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  4. I built this one and it sounds ok. Would help if it had a tone stack of some sort. Any suggestions and how to put it with this circuit?

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  5. Forgive the newb-style comment, but I assume the SPST switch will be a normally-open switch, correct?

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    1. No. It is latching on-on or on-off switch. Something like this will work fine:
      http://www.taydaelectronics.com/electromechanical/switches-key-pad/toggle-switch/mini-toggle-switch-spdt-on-on.html
      Just leave the pin 3 unconnected.

      Normally-open usually refers to momentary switch.
      +m

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  6. Needed a break from building Fuzzes so built this and DeArmond square wave today. This is an excellent sounding pedal. Built today using a TL072 and its a loud pedal with a great heavy sound with an added brightness. Definitely recommend this one.

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