This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Thursday, June 14, 2018

Jon Patton Cardinal Tremolo V2

The Cardinal Trem is a harmonic tremolo designed by Jon Patton and meant to emulate the tremolo effect built into several Fender amps from the early 60s (Twin, Super, Pro, Showman, etc). What makes it harmonic? The audio signal is amplified by the first JFET stage, then split into a high-pass path and a low-pass path. Each path is modulated optically with the vactrols, then amplified and mixed into the output. The LFO is designed around a quad opamp (in the original it's a quad, I had to divide it into 2, dual opamps to make it fit) and pulses the LEDs in the vactrols. Schematic and full circuit explanation can be found here.

The L pad will need to be grounded in some fashion for the LEDs to pulse. LED1 can be used as an external rate indicator, either on all the time or as the on/off indicator as well. Jon recommends using optical bypass for this effect (hence doing the Optical Bypass layout on Tuesday 😁), so to use LED1 as the indicator LED, connect it to both pads for the LED on the Optical Bypass board and ground the L pad. If using a 3PDT, just connect the L pad to lug 4 and lug 5 to ground as outlined in the General Layout Notes page.


11 comments:

  1. Note: Q2 & Q2 must be matched.
    Interesting proyecto, awesome layout! Thanks

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  2. hi everybody!
    i finished my build last night and........ it works!
    funny to see how the two ledś are working, but i have a light distorted sound!
    maby the problem is that i didńt used matched fets!!
    but i think the pcb layout itself is correrct!
    another great "artwork"

    maby you can mark it as verified, i,m going to build a jfet-matcher for the correct values.

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    Replies
    1. Wich type of LEDs have you used with the LDRs?

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  3. a few more notes :
    cant bias Q1 to 6V, with the trimmer all the way down i got 6.9V!
    bout the distorted sound, with the guitar vol half down i get a clean signal.
    maby i,m going to install a input trim-pot, and change the Q1 trimmer to 10K!

    greetings from Austria

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    Replies
    1. Yeah, definitely increase that trimmer value. Sounds like 10k should do the trick. Will probably help with the distortion too. Thanks for verifying!

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  4. Another great job. I have been looking forward to building this. One tip, if you etch your own board do a continuity check on the traces. I couldn't figure out why I couldn't balance the vactrols. A hairline trace grounding the center of the 100k trim. DOH!

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  5. I built it!! Sounds awesome!!!
    But there is a little distortion when I play loud. Any idea to solve this?

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    Replies
    1. I suggest going through Jon's original build doc linked above. I think he talks about how to resolve that.

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    2. Mmm... I read it, But if adjust the voltaje to V/2 the sound gets noisier. I simply adjust the Trimmers to the lowest gain point

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