Older vero layout for the ProCo Rat with a few mods:

Vero layout for the ProCo Rat with a few more mods based on a schematic from beavisaudio. A few errors in the schematic was corrected, and the mods have been modified to accommodate a 5-way rotary switch.

Update (11.11.2010): Finished my second ProCo Rat build. This one comes with a lot of options, courtesy of beavisaudio.com. You can choose between stock, LED and Mosfet clipping in the feedback stage, and there’s a rotary switch with 5 clipping options following the IC (stock diodes, no diodes, asymmetrical diodes, LEDs and Mosfets). And there’s a Ruetz mod (extra potmeter) that can be bypassed with a switch.

Not sure if I’ll ever use all these options, but they were fun to build. If I could change one thing I’d remove the Ruetz pot bypass switch altogether.

Update (28.11.2010): The rotary switch shaft was sticking out a fair bit more than the other pot shafts, so I added a couple of washers to the rotary on the inside of the enclosure. Looks better now.

Update (20.10.2011): Fixed dead layout link.

Related Posts

40 thoughts on “ProCo Rat

  1. Thanks for the earlier help! Unfortunately I have to ask another thing, since the switch sent earlier has only one pole, what should OFF be wired to? Or should I get another switch?


  2. Leave out the ruetz switch (and the associated wires on the board) along with R2 (47ohm). Wire the ruetz pot lug #3 directly to “drive #1” or to where it says “ruetz SW 2” on the board.

  3. Should work fine, I think. Adjust the notch/washer thing on the rotary switch to where it stops at the requisite number of positions, then wire according to the layout (ignoring the remaining unused switch positions).

  4. Also how would I go about removing the switch to the Ruetz mod so that the mod is always on?

  5. Hi Veit,
    Yes, LEDs are polar components. On the layout one side of the LED will be somewhat flattened compared to the other side.
    On this particular layout the LEDs are used for symmetrical clipping, so as long as you orient them opposite of each other the order doesn’t matter.

  6. Hello Harald,

    my last post and question from 24.08.14 is obsolete, i now understand the layout and the symbols. But LEDs normaly have a special polarity, doesn`t this matter in the case of the clipping diodes (D4 and D5 in the layouts with the few mods)?

    Thanks for answering.

  7. Hello Harald,

    i`m new in building pedals. Can you please explain when to use metalfilm-caps and when ceramic-caps? And why? What´s the difference between? It is possible to read this out of the layout? I think the symbols in the layout – for example C6 and C7 – are a litle different, C7 with some grey in the midle of the symbol for ceramic?

    Thanks for your help, and the great work at your site!

  8. To be honest I can’t remember what those fixes were, and I’ve been looking through my files and can’t locate the schematic either. Sorry. The one up there now looks OK.

  9. Hi Harald,
    Can you please clarify “A few errors in the schematic was corrected”? Do you mean that the schematic at beavisaudio is incorrect?
    Many thanks

  10. Such a long time ago! I guess I’m trying to say “not connected”, meaning the “Off” setting on the 5T rotary should have an unused/open lug.

  11. It depends on what color LEDs you chose and also how hard you drive them. I think red LEDs are typically easier to light up because they only need approx. 1.5V across.

  12. Hi Harold,
    I just finished the full mod Rat built with all the pots and switches , it works great! too many kinds of dist and drive.My question is : I s there any case that one of the led will be lighting? Mine are all off and i got some voltages on them?
    Any help is more than appreciated.
    Thx much for the layout!

  13. Well, my bad..I wasn’t very careful when I put the 100u capacitor…sorry
    The thing is that know I have squealing broblems and I am trying to find if by adjusting C5 and C3 will fix it…maybe I damaged something with my mistake
    Thanks you for your response

  14. Hey Harald! I am having some trouble with this one. The problem appears on the fet. I used an audio probe and saw that the signal arrives fine till the gate of the fet but never leaves the gate correctly(what I mean is that I can barely hear the effect only with the amp cranked). I tried a few 5458s and 5457s with no luck…do you have anything to suggest?
    Thanx anyway

  15. Just finished my rat clone and I’m very pleased with sound of it. Very versatile dist. For Ruetz mode just placed dpdt switch with jumper instead of 47R resistor and thats it. 🙂 Difference in sound of the LM308n(one od the best IC’s for beautiest dist) depending of the manufacturers. It’ definitely not all the same…Tnx very much, Harald! Awesome layouts.

  16. Hi Harald, I think i’ve found a way to add one more pot which works on r7. In this way you can control both 47 and 560 ohm resistors.
    -Cut under R8 (f7)
    -Wire Ruetz SW 1 and 2 (e1 and f1) to Ruetz SW first lug
    -Wire pots third lugs to Ruetz SW third lug
    -Wire D3 Led (f8)to Ruetz SW second lug
    -Wire 1k pot #1first and second lugs to Ruetz 1, 2 (d1)
    -Wire 1k pot #2 first and second lugs to d7, just before Capacitor 9.
    The additional ruetz pot is a 1k linear pot.
    Obiouvsly you can wire 1 and 2 of each pot lugs with a jumper.
    I’m not sure if it works and i can’t verify it now because i’m not building a rat clone, but it should work.

  17. Hi Harald, What resistence should I replace with the potentiometer for the Ruetz mod in the few mods version (without bypass switch)? Thank you and Merry Christmas!

  18. You run one wire from the board to lug #2 and then you optionally connect the other lug (either 1 or 3) to lug #2 as well.
    For the ruetz mod you need an SPDT on-on switch.

  19. where there are two numbers by the pot name ( e.g filter 2,3 ) does one separate wire go from that point on the board to both the 2nd and 3rd lug on the pot or is the 2nd and 3rd soldered together at the pot? also what type of switch is used for the ruetz mod? 🙂

  20. I maybe want to add a momentary footswitch for feedback loop. I’ve read about one where the loop was between IC1 out and the input of the effect and another one where there was a loop between the output and the input of the effect. Does anyone have experience with feedback loops in a pedal? What would be the difference? Thanks.

  21. Yes, you’re right. And the easiest, at least if you’ve got solder lug pots, is to run one wire from the board to the drive pot and then daisy-chain from there to the feedback switch.

  22. Okay I’m looking at the More Mods version yet again, and can’t figure out how to wire this bad boy!

    Do I wire Drive 2,3 to the board, then run a separate wire back to Feedback SW 2?
    If that would work, do I likewise wire Filter 2,3 to the board, then back to clip SW common?

  23. I completely understand, it’s not exactly intuitive. If you look at my vero layout for the OKKO Dominator I’ve described how to wire an identical switch (called the Mid SW in that layout). Hope that helps.

  24. I’m new in building pedals and want to build the ProCo Rat with a few mods but I don’t understand how to wire the mod SW from filter 1 to DPDT and back to the board (SW out 1,2,3). Can someone help me? Thanks

  25. Kind of, but if youdo this approach I’d at least get a pair of on-off-on switches. With the 5T rotary switch you’ll always have -one- clipping option enabled (there’s also an option for no clipping at all). With a pair of on-on switches you’d always have two clipping options on at any one time. By changing them for on-off-on variants you’ll have the option of no clipping (both switches at off), any single clipping option (the other switch at off), and two clipping options at once (both switches engages). Now, I don’t know how having two clipping options at once sounds.

  26. Instead of using a 5T rotary for the clipping part, would it work to use 2x SPDT on-on switches instead and use the middle lug on them as the “common” and then have two modes on each switch since there are 4 clipping options with the rotary?

  27. I built the “less mods” version and it sounds great, better than my 1985 original. I plan to build the 4 knob version with all the extra mods once my parts order comes in… thanks for providing such cool layouts!

  28. Remove R2 (47ohm) and connect “Ruetz pot 3” where “Ruetz SW 2” is on the vero board. Ignore any reference to “Ruetz SW”. That should do it

  29. If I want to omit the Ruetz switch, as you suggested, what change do I make on the vero?

    Can’t wait to build this! Love it!

    Keep up the great work.

Leave a Reply

Your email address will not be published. Required fields are marked *

Time limit is exhausted. Please reload CAPTCHA.