Wednesday, 25 September 2019

Keeley Magnetic Echo

Original info:
"The Mag-Echo pedal simulates tube tape echo sounds by using the delay circuit and a little bit of modulation.  Tape echos have long been regarded as a warm and very guitar friendly form of delay.  The Mag-Echo achieves similar results by using a touch of Lo-Fi delay, a slightly filtered echo response to keep things warm, and some modulation.  Modulation, or “Wow and Flutter” in the tape world is a slight pitch shift or wavering that occurs as the tape is pulled across the heads.  The modulation we use is similar to what we use in our Seafoam Chorus, a slight wavering of pitch on the trails of the repeats.  With a simple set of controls for the delay – Time, Regen, and Level and with the “Wow and Flutter” controls – Depth and Rate you can create some very vintage or rather unique tones"
PedalPCB's schematic, info and pcb available here.




46 comments:

  1. Thanks Alex! Looks cool and sounds fun!

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  2. Gonna build this once verified!
    If I wanted to add a momentary infinite feedback stomp switch would I use a SPST and connect feedback 1+2 or 2+3? Basic question but I'm just getting into this stuff. Thanks in advance.

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  3. Replies
    1. It's to protect the LED, i'd use a 2.2k if you're using a 3mm LED :)

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  4. D1 and D2 are the incorrect way to do transient voltage suppression diodes.

    https://www.electronics-tutorials.ws/power/transient-suppression.html

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    1. https://www.allaboutcircuits.com/technical-articles/transient-voltage-suppressors-tvs-an-introduction/

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    2. I think the Zener diode D3 followed by the 100u Cap would do the transient voltage suppression.

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    3. Not for input voltage. They are using D1 and D2 for TVS to quiet the signal for the repeats at pin 2. I had done some research on this about reducing noise. I have been designing my own delays with TVS diodes at repeat/feedback pin 2. I believe I had some across Keeley using clipping diodes as a method for noise reduction.

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  5. I build it yesterday.Got only dry signal no effect.Any sugestion?

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    1. Check, double check and triple check that all components/wires are correct and in the right place on the vero - only takes one row out to silence the build! Then check for solder bridges on the underside - run a knife in between each vero track underneath..

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  6. Will this work with the UK Electronic PT2399 tap tempo board please? It mentions that that has particular requirements for pin 6 of the PT2399 chip, which I think is left unconnected here, if I'm reading it right? I am probably not, though.

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    1. This comment has been removed by the author.

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  7. Built this yesterday and it works.

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  8. Finished today,everything is working ok but i heave only one feedback.Is there anything special i can look for?Thanks in advance!

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    1. Hi there, I'm having the same problem, only one repeat. How did you fix this problem?

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  9. Alex, you can tag this verified. I am really enjoying this one. Thank you for the layout.

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  10. Hi Alex,got it working and i like it!Is there way to increase amount of the wet signal?Thanks!

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  11. Please, add a version of the modification with tails, as Zack did with EQD Disaster Transport Jr.

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    1. For tails, looking at the schematic and how tails were added to other PT2399-based builds, I believe that the easiest way to add this capability is to perform this surgery:

      1. Make a cut on the top row at position 11, so halfway between the 1u cap and the 10K resistor, leaving an open pad on either side.

      2. Add a wire from the top row, position 10, just to the right of the 1u cap, and attach it to pin 1 on your tails switch.

      3. Add a wire from the top row, position 12, just to the left of the 10K resistor, and attach it to pin 2 of your tails switch

      4. Connect pin 3 of the tails switch to ground.

      When "bypassed" the input to the PT2399's input buffer will be grounded and allow the tails to fade-out. Follow the stomp-switch wiring guidelines for the Deep Blue delay or the Disaster Transport Jr.

      The OPA 2134 will now be a unity gain buffer in your pedal chain, but it's a dead-quiet, high quality, op-amp, so a really good choice.

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  12. Just finished my build and everything works! I haven’t twiddled the “gain” trim pot yet - is it for input level? does it add distortion to the repeats?

    Anywhoodle, really digging this project and thank you for taking the time to make a layout!

    Cheers!

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    1. Did you find out what the 'gain' trimmer does? I'm curious.....

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  13. Gee thanks... I just built a delay and now you post this... after I run out of PT2399s... and have cannibliazed my crapfi delay as I didn't use it.. I suppose I need to buy more PT2399s

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  14. You clearly haven’t been taking this seriously... ;)

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  15. If someone knows how to increase amount of the wet signal it would be apprecieted greatly.Thanks:)

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    Replies
    1. Lower the 10K resistor at right side of the 47nF capacitor.

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  17. https://send.firefox.com/download/b0fc407556893dc7/#sSihG3JdLqVZ5YH5WBSbVg

    assembled a stereo option with the ability to enable two effects in series and added an inverter for the ping pong effect
    Everything works, thank you

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  18. So im getting delay, but lfo is not moving. If i move the deprh the modulation is there but its static.

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  19. Yup. Second one built and still having no modulation. I can hear it there when i move the depth pot, but other thwn than nothing. I have posted in the forum and posted pics of second build.

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  20. Haha! Got it working. I actually prefer c100 for depth and b100 for feedback. The tapers seem to be smoother.

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    Replies
    1. Great to see that you got it working!

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    2. Thanks man. Focusing on the resistors at the bottom i replaced the “120k” i had in there and boom working like a charm. X

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  21. This was my biggest build to date. Fired up and worked first go!

    This is my favorite delay out of all I've built so far
    (Deep Blue Delay
    Faux Analog Echo
    Disaster Transport Jr
    Cave Dweller 2015
    CutureJam Delay/Verb
    Rebote Delay
    CrapFi Delay)

    This one I used the exact IC's per layout/schematic I didn't want to mess about..

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    1. Is it much different than the Disaster Transport Jr ?

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    2. yes. It has some modulation to make it sound much more like a tape unit. lots of 'wow and flutter'

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  22. Can I add a regular PT2399 tap tempo kit to this schematic?

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  23. Can 2134 be substituted with a tl072?

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    1. Made it with 72 and works like a charm on the first go! Again big thanks for all these cool layouts!!

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  24. G'day Guys, I've finished this build and after finding a few silly mistakes, plus an odd situation where lug 3 of the speed pot was soldered to it's row but it wasn't making a connection with the rest of the row!??! It's fixed, up and running but I've got a couple of thing to ask about.
    Is the LFO LED brightness meant to go up and down with the Depth pot?
    I'm using TL082s as I don't have the 2134 or the LM358.
    With the B100k depth I was only all the modulation seemed to be bunched up at the end so I used a C10k and it is a lot better. I do have a C500k, would that be better or overkill? I don't have any C100k on hand.
    This is a nice delay and thanks for the layout!
    Cheers,
    Thommo.

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