Lovepedal - Karl Fuzz

The Lovepedal Karl, it's actually a pretty cool sounding fuzz box - it sounds sweet at low gain and with a higher gain there's octave and ring mod tones too, it's really fun to play with. This is the older "two knob" version (there is a newer 3 knob variant that includes a tone knob). Here are a couple of great sounding demos of the Lovepedal Karl in action:

And here is a Google Videos link: http://video.google.com/videoplay?docid=-1428391728523134427

And another:

Well, there's a schematic for the Lovepedal Karl and it's thanks to Greg at Freestompboxes for this one, here's an internal gutshot and a photo of the de-gooped PCB:

[errrrrr, plastic pots??]

Here's the Karl schematic diagram:

Firstly there are a few strange things going on with the circuit - the 1M pulldown resistor is not needed - it's in parallel with the 5Kb "Intensity" pot, the two filtering caps are also unneeded - you can get rid of the 47uF cap. Looking at the circuit structure you can see it's an adaptation of Tim Escobedo's "Tripple Fuzz" circuit basing it's sound around that "non-selective frequency tripler" (the PNP/NPN transistor network):

The Tripple Fuzz is a really nice sounding circuit - build one up and see for yourself. Incidentally the Lovepedal Karl isn't the only commercial pedal that has used this "non-selective frequency tripler" structure; the Zvex Machine also employs it to great effect too!

Here's another non-selective frequency tripler design from the Tone God:

This one's using the 386 chip to generate the boost into the frequency tripler, the bias control is interesting here, it controls which portion of the wave gets tripled!

Here's a vero layout for the Lovepedal Karl drawn by roseblood11:

Ok, so some people have asked me about the newer "3 knob" Karl, the added control is just a treble roll off control (as far as I believe) - I would perform this mod by adding a 10n - 22n cap to ground via a 47kB pot just after the last output cap, pre master volume control. It may also be a low loss Big Muff type control, I'd think a big muff tone control would actually work a lot nicer than a simple treble roll off control. Download the Duncan Tonestack Calculator and start playing about with responses!

Here's the freestompboxes forum thread for reference: http://www.freestompboxes.org/viewtopic.php?f=7&t=12873