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, July 23, 2015

DOD FX25 Envelope Filter

The FX25 was initially produced by DOD in the early 80s and is an OTA-based envelope filter/auto-wah. It's a fairly tweakable and you can find various mods on other sites, but this is for the stock layout. The original switching circuitry has been removed, so you can use true-bypass. An LM1458 is listed in the layout below, but just about any dual op-amp should work there (TL072, NE5532, JRC4558, etc.), so if you get a little distortion, try a different op-amp.



Update Aug. 10, 2016:

I've fixed the layout as per NapAlpha and Eduardo's comments below. Thanks for catching that guys. Sorry it took me so long to make the fix.

24 comments:

  1. On the PCB there is no connection between C7 and R12-R13. The resistors R12 and R13 are 10K and not by 1K

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  2. Hello layot ​​this work? There I gotta change ?
    Thanks

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  3. i did this layout but no sound at all.. helpless!

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  4. is there someone verified this layout here?

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  5. nap_alfa55 was right. change 2x 1k resistors (COORDINATE H/V C-P/S and D-P/S, up 13600)by 10k and connect C-S to K-J. WORK FINE. VERIFIED!
    any mod or change for bass?

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  6. Replies
    1. Yes, work fine. Remember to connect R12/R13 with C7 and change it with 10k

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  7. Sorry about the error in the original board, guys. Thanks for catching that missing connection. I've corrected it and it's good to go.

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  8. Build this one with 47r ( did not found 51r). Worked for few seconds then burned de 47r twice! Any help? Thanks!

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  9. Could be your power supply. Maybe use a high wattage resistor there?

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    1. Bad 1n4007 diode...short the 47r to ground. Replace it and no more resistor burn. But the effect still don't work as should be. I turn it on and it works well til' 30 to 40 secs of play then it's down. Any help???

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    2. i had this problem but i double check and had a short on my traces check your connections

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  10. Put as VERIFIED! I just finished and it works very good! I made it with a LM13700 and MC1458.

    Greetings from Corrientes, Argentina!

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  11. can i request for a dodo fx25 in a 1590A without the footswitch? thanks and more power..

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  12. Im into audio probing the circuit. From input to pin3 of ic 1458 the audio seems to be ok even for pins 1,2 and 7. For pins 5 and 6 the audio volume drops. I need to max the amps volume to hear the audio output. I tried to test the directly at the output and theres the slightest volume of audio that I can hear with amps volume maxed. The voltage for me are normal for both ic. I will try to get the exact voltage later when im free to get my hands on it again. I use LM13700.
    And can you point out the connectivity of the audio path circuit from input to output?
    Thank you

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    1. Pin 7 is the output of the 2nd half of the opamp, so if the volume is ok out of there I would think it's ok. I'd guess the issue you're having is later in the circuit. Here's the schematic for reference:

      https://images.talkbass.com/attachments/dodfx25_sch-png.2309823/

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  13. Are the potentiometers log or lin? I've also seen a picture of an original fx25 with one of the pots reading: C500K?

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    1. The B prefix means lin. Those are what were specified in the schematic I believe. Rev. log pots may improve the sweep of the controls. YMMV.

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