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MXR x MadBeanPedals Setback Analog Delay

Started by SugarKeys, January 16, 2023, 10:47:02 PM

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So excited - completed my first build since college days 20 years ago!

Prompted by a retail experience. Bought a late 70s MXR Analog Delay from a local shop. A couple of days later I noticed a minor switching issue, which I probably could have fixed myself, but I thought "I just bought it, and their tech is surely more skilled than me."


Phone call from them: "I think we've destroyed the pedal." It seems their tech was probing around and shorted the 120V AC (it's a plug-in pedal that includes a transformer to 12V DC) to the signal ground, in the process frying every IC on the board. Including the unobtainable Retcon R5101 delay chip. A "Charge Coupled Device" - subtly different from a BBD, in terms of implementation. Bummer!

I am fortunate enough to own a couple of other pedals that use the Retcon R5101, and by swapping them around, confirmed that it was indeed fried.

The shop were super cool about it. Gave me my money back, and the fried pedal for free.

So now I have this sweet vintage 70s enclosure, and no hope of obtaining another Retcon R5101, without cannibalizing another pedal. I saw some posts about retrofitting these pedals using PT2399-based circuits (like here

But that approach felt so... 2010's. We have CoolAudio, Belling, and Xvive BBDs now! And the MadBeanPedals Setback promised about 300 ms and self-oscillation, so similar specs to the MXR original!

My skill level is closer to "Cowboy" than "Genius" but I dove in anyway...
So I ripped out the dead guts, set them aside in case someone makes a drop-in replacement for the R5101 (my money is on "not in my lifetime"), and built a Setback into this case. It rips!

Build notes:

  • It's true bypass now which is cool

  • I used the 12V value for R40 and am powering it at 12V with my Strymon Ojai R30
  • Soldered the bypass LED straight to the board for diagnostic testing but the finished pedal acts like the original, with no LED
    Didn't detect any clock noise even with the "Clock" trimmer cranked, so I'm getting about 380 ms max delay. Is that because I got a good compander? Or because the new Xvive chips are really clean? Makes me wonder If we can get even more delay out of that chip
  • Found a panel-mount DC jack that perfectly covers the hole that held the AC cable strain relief. Don't know why this makes me so happy
  • Didn't have an easy way to mount this tight little board into this giant enclosure, so I found some vintage MXR-style crappy foam to wrap it in. It definitely gives the tone that extra push off the cliff. As they say, "the toan is in the foam"
  • I "rocked before I boxed" and had only the dry signal coming through. I thought I'd screwed up somewhere; the clock circuit looked good on my scope, but the audio input and output around the BBD didn't sound right on the audio probe. It turned out both my compander and my MN3005 were sketchy because I got them from eBay. Noob mistake. Got replacements from Cabintech and now I'm stylin'. Very glad I socketed all ICs

Minor issue:

  • Noticing a slight volume drop with Mix at full dry

In any case, this was an awesome fun build.


How cool is that?  Bummer about the original though, there's just not that many Reticons in the wild to be killing them off like that...
Gordy Power
How loud is too loud?  What?


Bummer indeed..

Great work saving it though- this rules!
Criticism is encouraged: constructive, or otherwise.


Maaaaan, as far as the old pedal, that sucks man, sorry to hear that. I guess the tech is lucky he didn't get lit up. Cool build though.
Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.


Very cool build and great save 8)  I wonder why Xvive doesn't try and do a Recticon reissue?  Maybe a patent thing.  It would put some awesome flangers back into the wild if they did. 


Thanks all for the love. Imagine if they brought back a SAD1024 reissue. BBD Renaissance


Quote from: Bio77 on January 16, 2023, 11:57:25 PM
  I wonder why Xvive doesn't try and do a Recticon reissue?  Maybe a patent thing.  It would put some awesome flangers back into the wild if they did.

Aside from possible IP issues, from what I understand the major hurdle is that the Reticon chips were manufactured using an obsolete process for which production tooling no longer exists, thus making any attempt at recreating them prohibitively expensive due to the need to build a whole new production line.
Doomsday Devices


And I think to complicate matters Reticon is a military contractor so the IP situation likely becomes even more tangled.  I'd love to see a fresh 1024 though.
Gordy Power
How loud is too loud?  What?


The patents are long expired. I actually have a bunch of chips I would donate for delidding (dead) if someone would be interested in recreating them.
That which burns twice as bright, burns half as long.


Quick demo video, comparing my build to the MXR original that I have (which is a totally unrelated circuit built around a Reticon chip, but still an interesting comparison...)


really cool build to salvage a 3rd party's """""repair""""" job, dude.

Also I love your video demo—and I hate it, because it reminds me of the '77 Suitcase I had to sell 6 or 7 years ago ;___;