# Meet R2-D2 & C3-PO



## Chuck D. Bones (Apr 20, 2020)

I got a bug up my ass to build some stuff in handy-boxes and this is the result.  total parts cost for each was under 20 USD.





C3-PO is a parametric filter.  Big knob is FREAK, little knob is QUEUE.  The stubby toggle switch selects between low-pass, band-pass & high-pass.  Tuning range is 70Hz to 7KHz, almost 7 octaves!  This does the cocked-wah sound really well.  In LP mode with the Q control in the middle, it sounds a lot like a Cry-Baby.  In HP mode with the Q dialed down it can do a serious treble boost. This is not a booster per se, it is just a filter.  Average gain is more-or-less unity, so no volume control req'd.





The resistors are mostly NOS mil-spec parts from Electronic Goldmine.  The yellow LEDs and most of the caps came from there too.






R2-D2 is a bizarre version of a Fuzz-Face.  The 1st stage transistor is part of a 4N35 opto-isolator.  The 2nd stage transistor is a Russian ?? germanium.  The LED in the 4N35 is part of the feedback path.  Talk about a technology mash-up!  This is one of those cases where I had an oddball part and was looking for something to do with it.  I have a bunch of 4N35's, so I breadboarded this just to see what would happen and I liked the result.  Max gain is about 56dB.  Much to my surprise, the transistor in the 4N35 is very quiet.  Like any good FF, it makes a lot of even-order harmonics and responds well to the guitar's volume control.  Aluminum knob is FUZZ, clear knob is VOLUME, blue knob is TONE.  For the TONE control, I first tried the Fatness control from a Roger Mayer Page-1. The Page-1 control is similar to a BMP tone control.  It was too bright for my taste, so I retuned it a bit.  At zero, it's brown and smooth, near noon the response is flat and at 10 it sizzles, but not too much.  No mid scoop here.  Plenty of volume available, unity is around 9:00 or 10:00.  One of the things I like about Vero is it allows me to use oversized components like that turquoise 47nF film cap and the humongous 470uF electrolytic.  I stamped "R2-D2" on the big washer around the stomp switch, but the paint mostly filled it in.  I'm open to suggestions on how to improve the contrast on the lettering.


----------



## cooder (Apr 20, 2020)

Genius and very faaaawnkeeee! Love it!


----------



## Barry (Apr 20, 2020)

Is that a blank cover plate screwed on backwards for the base? They Look awesome


----------



## Barry (Apr 20, 2020)

A sharpie Paint Pen might help with the lettering, they have a silvery gray that might do the trick


----------



## Chuck D. Bones (Apr 20, 2020)

Barry said:


> Is that a blank cover plate screwed on backwards for the base?



It most certainly is.  I thought about making a bottom plate, but grabbed some blank plates for a temporary cover.  Tried installing it the right way, but it didn't look good.  Flipped it over and used panhead screws, viola!


----------



## HamishR (Apr 21, 2020)

So cool!  You could try sanding just the ring around the stomp switch on R2D2 which would reveal the metal but leave the paint in the type.

Is C3PO from the United Arab Emirates?


----------



## Chuck D. Bones (Apr 21, 2020)

Ha ha ha ha ha ha.  Home Depot stamps ID codes on their fasteners since most of them have no place for barcode.  But you probably knew that.  I should have glued that washer in face down like I did with R2-D2.  I like your idea about sanding the washer.  Then I could clear-coat the exposed metal.


----------



## MightySmallElectrons (Apr 21, 2020)

So cool and unique!!

A Sharpie and a wet paper towel. Color in the color you’d like, count to 10 and then wipe the surface with the wet paper towel.


----------



## zgrav (Apr 21, 2020)

I like the way you mounted the bases for the boxes.  Did you include the foam insulater pads on the back of them to give you a grippy base?


----------



## music6000 (Apr 21, 2020)

Cool Builds!


----------



## Chuck D. Bones (Apr 21, 2020)

zgrav said:


> I like the way you mounted the bases for the boxes.  Did you include the foam insulator pads on the back of them to give you a grippy base?



I did not.  I put clear neoprene feet on the bottom.


----------



## geekmacdaddy (Apr 22, 2020)

killer. love them both.


----------



## Mourguitars (Apr 22, 2020)

Awesome CDB !

Mike


----------



## dawson (Apr 22, 2020)

How incredibly cool- this build report made my day!

Thanks for the detailed explanation of the circuits and your design process.


----------

