Tuesday, July 22, 2008

Passive True Bypass/Feedbacker pedal

After a series of drilling and spray painting mistakes forced me to abandon the aluminum case I was originally using for this project, I rehoused it in the black plastic Radio Shack job you see in the photos. To be honest, I think it looks a lot better this way, almost like something from the Shadow Hills line. Not bad for a $3 box!

In any event, this is a passive version of the True Bypass Looper/Feedbacker design I saw on the Beavis Audio Research site. Before getting underway, I found a wiring how-to on the Experimentalist Anonymous board which helped immeasurably. If you decide to build one of these, be sure to click both of those links and keep the pages open.

This is a twofer utility pedal that doesn't make a sound on its own. Instead, it acts as both a true bypass loop, to introduce one or a series of pedals into your signal, and as an overload feedbacker, sending an adjustable amount of the overall output back into its Send jack for chaotic noise effects.

It's also very simple to put together, only costs around $20 in parts and is entirely passive-- you'll never have to open it up to change a battery!

In the video below, I ran a clean guitar into the In jack (right, bottom) out to an amp via the Out jack (left, bottom), and from the Send jack (right, top) into a BYOC Analog Delay, then into a BYOC Mighty Mouse, and from there back into the pedal via the Return jack (left, top).

When the switch at the top of the pedal is in the down position, it acts as a simple true bypass loop; when it's in the up position, it's a feedbacker as well, with the dial in the middle controlling the amount of the signal being fed back into the circuit.

One thing worth mentioning-- it may have to do with the fact that I was using a plastic case instead of a metal one (though I doubt it), but I had to connect the grounding in a jack-to-jack cascade (like in the Beavis diagram), and not simply to the Output, as shown on the Experimentalist Anonymous page. Before I did this, the pedal gave me a wicked 60hz hum, which doubled in volume when it was engaged. Also, if you're following the EA guide (and you should-- it's really, really helpful), take note of the typo in their final photo-- the center row and the right-most row should swap their numbers (i.e. the top, from left to right, should read 1-4-7).

Speaking of errors, I apologize for the lighting in the video below. Also, it should stop at 1:30 or so, and not 2:30. I'll fix this soon enough. Enjoy!

"Buzzsaw" by The Turtles.

EDIT: The video problem has been solved.

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Blogger felix said...

Awesome Pete! Nice job, it does look really good.

I've had the stuff to make a dual FB looper for months now, and I keep spacing on printing out the graphics/drill template and just finishing it already.

I am the king of unfinished projects!

11:16 PM  
Blogger Pete Shambler said...

Thanks Felix!

The FB looper (at least this version of it) took a little less than an hour to whip together. Totally painless. Go for it!

I'd be excited to hear what it would sound like in the midst of a proper modular setup-- let me know if/when you've built yours!!

12:09 AM  
Anonymous BenT said...

OH...MY...GOD! I hope you didn't put an "off" switch on that thing, because I expect it to be "on" all the time.

The "sludge" factor is sooooo hiiiigh, man! DAMN!!!

8:26 PM  

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