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Mine has toobz and sounds ten times better.

So I think a 3n3 across the output (to ground) worked well to my ears on my home rig.  I'll have to solder it in over the next couple days and try it more in a couple rigs to see if that helps.  I think that may have saved the pedal.


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Thanks Jon.  I'll take a look at those parts of the circuit.  Strapping the cap would be really easy (if it works and sounds good) - wouldn't even need to take the board out of the box.

I've built a Tweedy Bird drive that is a lot of fun to play.  My only problem is that the treble is a little much.  The J201's are Fairchilds and biased to around 4.5-5V.  I'm looking for ideas where I can cut some treble from the circuit without changing the character too much.  Playing with the Tone Stack calculator doesn't seem like there is much flexibility in the treble side (at least beyond what is already in there).  Between Q4/Q5 and Q6, it looks like there is some additional filtering where R13, C13, and R15 form a low pass filter (based on my limited electronics knowledge).  I think if I lower R15, that should drop the treble across the board.  Am I right?

Very cool idea and incredible execution!


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I'm probably in the $40-$50 range per month.  Haven't sold anything (except two pedals to a close friend).  Tayda does help keep the costs down while I figure out what works and what doesn't for me.

If one of the pins goes to ground, I would leave it connected all the time.  You could then use the 3rd row for an LED to let you know which pot is active...

Pictures - I'm still confused...  No audio on the output of either the IC1 or IC2 paths.  Soldering is a little sloppy (the tip on my Radio Shack iron was almost blunt nosed).  I did lift traces in a couple spots, but I either used a bit of resistor leg wire or just solder bridged across and checked for continuity at all spots.

Yup - the regulator is putting out 5v.  The voltages around the BC550s are (c/b/e):
Q2 - 4.9/1.1/2
Q3 - 4.95/4.3/3.4

I was expecting the base of Q3 to be the same as the emitter of Q2, which it wasn't...

I also verified all caps and resistors.  No substitutions for transistors.  J201 is passing signal as expected and the voltages look reasonable.  Diodes are all correct per schematic and facing the right way.

So I populated an Autobahn board and fired it up...  Nothing.  Reflow all of the joints and clean up what appeared to be a couple unintentional bridges.  I did lift the traces in a couple spots, but I "fixed" that by using bits of resistor legs to connect the lifted area to the places it was supposed to go and everything checked out by continuity. 

OK, break out the multimeter.

IC1 (LM324) - Pin 4 is at 8.7V, Pin 11 at 0, everything else is at about 4.3V except pin 7 which I've measured at 7v and I've measured at about 80 mV.  Strange thing #1...

IC2 (LM13700) -
1 1.49V     16 1.49V
2 0.44V     15 0.97V
3 1.49V     14 4.3V
4 4.28V     13 4.2V
5 4.3V       12 7.6V
6 0            11 8.7V
7 0.68V      10 7.6V
8 1.7V        9 6.4V

Ground and +V are OK.  Don't know what to make of the rest...

Audio probe -
I have signal up to the C6/R17 junction and nothing on the other side, but I have audio on pin 14 of the LM324 (if the sense pot is wide open, with it "closed" there is nothing at 14).  No audio on pin 13.  Take the IC out (wondering if it is fried), and there is audio on the trace between R17 and the sense pot.  Put a TL074 (don't have another LM324) in its place and I get the same - no audio at pin 13.  With the LM324 in the circuit, the audio is really weak and heavily distorted later in that path (around R20) with a very weak signal feeding Q2.

On the LM13700 side, I have audio to the C2/R5 junction, but nothing past it anywhere on the LM13700.  Haven't tried taking that IC out, because at that point I was a fine mix of confused, frustrated and tired.

Any thoughts?

I built my first pedal about a year ago - Mudbunny.  Then a second and a third...  #2 (a yellow shark) has something kinda wrong with it (Nature control doesn't quite work), but I like the way it sounds so much I'm afraid to mess it up by "fixing" it!  I just boxed up #14 this weekend, which is a crazy 4 board, multi-effect in a big enclosure.  I've learned a bunch, but still have a lot to go and have a board full of cool pedals that I wouldn't otherwise have.

My box-o-not-quite-there only has one board in it right now, which I have to trouble shoot over the next couple days.

Thanks for the input!  I guess it sounds like the input/output impedance would have to be tweaked.  My idea came from seeing the ad for the new TC Helicon vocal harmonizer (which I told a friend could let me be out of key 3 times on the same note).  I thought that I could build a singer buddy a cool little board (he's using the crappy effects on a Behringer PA now) with a delay, pick up that harmonizer, and be good to go.

I can see the Sea Urchin being too dark.

Single malt - I tend to bounce between Glenlivet 12 (or 15 or 18 when I'm feeling rich) and Balvenie Double Wood.

Bourbon - 4 Roses Small Batch is a great bourbon for about $30/bottle - not quite as "rude" as other cheap bouborns.  High West makes some very refined boubons and ryes for about the same price as a lower end single malt.  I plowed through a bottle of the double rye that I think I will have to replace.

I know the PT2399 is designed as a delay for vocals.  I've built a couple delays for guitar (sea urchin and echo base) and was wondering whether there were any interesting DIY concepts out there for a vocal stomp box delay.  Any suggestions?