Is there a simple octave up and octave down in one pedal?

[Ben Lyman]

Octave-up fuzz? Foxx Tone Machine.
Nothing can beat this great machine... :-)

YES! Love that thing but it's a bit complex for what I'm trying to do here. The Green Ringer is great if it has a fuzz to help it so that's why I'm going with it for now. It sounds great with a good ol Fuzz Face and so does the Shocktave so it seems simple enough to combine all three. I finished the layout, gotta play music tomorrow, then sometime soon I will start building this thing and find out how it works.

[Ben Lyman]

Still not perfect but it's getting there. I'm not giving up yet. The breadboard noise is gone but the actual pedal is not behaving like it did on the breadboard. I may have goofed up in my translation from board to box, I don't know why it's so different. I had to perform about 4 different mods to the pedal since completing it 2 days ago. It has too much fuzz for one thing. Also the low octave is not as good as my earlier experiments. The thing that is cool is that when the mix is balanced in the middle I can have low and high octave with the guitar knob up, then when I get the guitar knob down in just the right spot I can have just the upper octave effect.

[EBK]

Could the "too much fuzz" and apparent gating on the lower octave be related?  Bad bias voltage in your octave-down?

[Ben Lyman]

Could the "too much fuzz" and apparent gating on the lower octave be related?  Bad bias voltage in your octave-down?

Could be, I wish I understood it better. Can you look at the Shocktave schematic and tell me how I would go about adjusting it? Is it as simple as using a 25k trimmer on Q2c?

I say Shocktave because that is what I have gone back to on the breadboard today. I'm kinda starting over from square one again with Joe's Shocktave exactly as he has it because I want to try and get it to sound it's best before I go forward.

I also think I should leave out the Fuzz Face portion and just plan on stacking it, same as I do with my Greeen Ringer.

Another thing I noticed is that the buffer is kinda important because without it I get AM radio when I turn my guitar down to off, either vol or tone.

[EBK]

Another thing I noticed is that the buffer is kinda important because without it I get AM radio when I turn my guitar down to off, either vol or tone.

Not when it is boxed up, I hope.

[Ben Lyman]

Another thing I noticed is that the buffer is kinda important because without it I get AM radio when I turn my guitar down to off, either vol or tone.

Not when it is boxed up, I hope.

Yep, even boxed up. But that's ok, I got the box assembled and that's the hard part, it's easy to make a new board (w/buffer) and swap it out.

Also, I have a buffer on my pedal board anyway so it solves that problem as long as I use the pedal on my board.

[EBK]

Yep, even boxed up. But that's ok, I got the box assembled and that's the hard part, it's easy to make a new board (w/buffer) and swap it out.

That has got to be a shielding problem....

[Ben Lyman]

Yep, even boxed up. But that's ok, I got the box assembled and that's the hard part, it's easy to make a new board (w/buffer) and swap it out.

That has got to be a shielding problem....

Like unshielded guitar or cheap guitar cable?
Or maybe unshielded wire from pedal input jack to 3PDT switch and to out jack?
Why might it not have a problem when I put a buffer in front of it?

[EBK]

Ungrounded enclosure is most likely.  Buffer might either filter out the frequency or change the resonance of the circuit.

At any rate, while your buffer might work for the radio signal, there are a lot of other, more broadband noise sources out there.

[Ben Lyman]

Ungrounded enclosure is most likely. 

Ah, yes. Now that you mention it, I do recall thinking it was odd that my pre-painted enclosure was also painted on the inside, I don't remember ever seeing that before in the past. I guess my jacks and pots may not be making contact with the enclosure, I would think they would make contact where I drilled the hole but maybe not. I'll scrape some paint off and see what happens.

Now about that Shocktave schematic.. any pointers for biasing to get the best octave down?
Link: http://www.diystompboxes.com/analogalchemy/sch/shocktave.html

[EBK]

Now about that Shocktave schematic.. any pointers for biasing to get the best octave down?
Link: http://www.diystompboxes.com/analogalchemy/sch/shocktave.html

My first piece of advice is, because it worked on the breadboard, but not in the box, to check that no resistors got swapped, take a close look at every solder joint, and measure some voltages, for starters.  Any number of things can happen when you build something.

Incorrect part or incorrect/missing connection can easily mess up things.  It's hard to offer any more specific advice without more data.

I might be able to tell you more looking at pics of your actual build than looking at the schematic. 

[DeusM]

Check this out. Even has a vero layout, or order a PCB.

http://www.parasitstudio.se/guitarsynth.html

Dude! That thing sounds awesome! And also it seem pretty easy to build. Gonna try it.

[Ben Lyman]

^^^Ya, it would be awesomer if the price number had a $ instead of that weird symbol 
I guess I could order and just wait for it but I hate waiting that long. Plus I don't have any of those weird IC chips so I'd have to order those too.

I filed the box around the input jack and screwholes to connect the back. It's certainly fully shielded now but it still picks up RF. Only when I turn the guitar knob(s) off and touch the guitar (strings, knobs, bridge, etc)

[Ben Lyman]

[PRR]

> awesomer if the price number had a $ instead of that weird symbol

€8.00 is about 9 bucks US. (Copy to Google, it usually tells you.)

Credit card or PayPal usually does €/$ conversions automatically (at a cost somewhat higher than a professional money-changer could get most days).

[EBK]

I filed the box around the input jack and screwholes to connect the back. It's certainly fully shielded now but it still picks up RF. Only when I turn the guitar knob(s) off and touch the guitar (strings, knobs, bridge, etc)

I'm guessing you didn't file around the screw holes enough for the lid to make electrical contact (that is a very thick coat of paint), but I could be wrong.  Try wedging a piece of foil in that area to see if it makes a difference.  I'm assuming you checked for continuity with the bushings on the jacks, pots, and switches, but if you haven't, you should do so.

And, why is that one resistor shorted out?

[Ben Lyman]

€8.00 is about 9 bucks US. (Copy to Google, it usually tells you.)

Credit card or PayPal usually does €/$ conversions automatically (at a cost somewhat higher than a professional money-changer could get most days).

Cool, thanks Paul. I figured 22 thing-a-ma-jigs was probably a great price but I just don't want to bother ordering it and those giant centipede IC chips. I'm gonna keep working on my own with a breadboard and a pile of transistors for now. Perhaps I will eventually get fed up and order one of those PCB's but not just yet.

I'm guessing you didn't file around the screw holes enough for the lid to make electrical contact (that is a very thick coat of paint), but I could be wrong.  Try wedging a piece of foil in that area to see if it makes a difference.  I'm assuming you checked for continuity with the bushings on the jacks, pots, and switches, but if you haven't, you should do so.

And, why is that one resistor shorted out?

Full continuity on the enclosure. Jacks and Pots are all connected via ground wire to the necessary lugs but perhaps I should sand the paint off so their bodies make good contact with the box. I've never had to do that before and in the past the only time I've ever noticed the RF w/guitar knob interaction has been on the breadboard. I'm not too concerned with this particular pedal right now, it sounds really good when dialed in just right, I want to work on the next version and include Joe's buffer (which I shouldn't have omitted)

The 5 mods I have done to this box included jumping my R21 470k to bring more sub octave into the mix and adding a 10uF from Q2e to ground to bring more gain to the upper octave. You will also see (in the box photo) a 560pF added in a funky spot, there is a hidden 100k trim pot attached to the Fuzz pot, dialed to about 39k to stop some motor boating.

[Ben Lyman]

Since I had a better idea of what to go for, I was able to "tidy" up the breadboard... ahem!
Anyway, ground noise all taken care of, circuit simplified to include Joe's Shocktave exactly as he intended except that within the "Dry Mix" path I have a modified Green Ringer. Two mods: a LPF on Q1b and a 10k gain pot with 47uF bypass cap on Q1e.

So now it has a separate gain pot for each octave and a mix pot followed by volume pot. The problem is the Mix pot is B1M and in the middle there is significant volume loss. I suppose I could try a different mix pot next.

Panning mix to Green Ringer sounds like a Green Ringer with a variable gain pot, panning mix to Shocktave is loud but jumpy, in the middle sounds good but too quiet. Still, there's some good sounds in there if I tweak the knobs enough.

[Ben Lyman]

I just realized that I have been taking the Green Ringer signal from the input and not from where the Shocktave takes the dry signal. Now I wonder if I should move it to come after the buffer just to avoid that RF problem. I will try that later tonight and see how it goes.

If we look at the B1M Mix pot (r22) and I am thinking the best sounds come from right around the middle of it, should I reduce it to about 100k in order to preserve the volume level?

Also, making the Shocktave have a steadier low octave, maybe I should be playing around with Q3, what's up withR9 and C12?

EDIT: C12 is supposed to be 1uF
EDIT: C13 is supposed to say 47u

[robthequiet]

Mentally trying to calculate whether or not your outputs are in phase but the architecture is a bit beyond my analyticals -- phasing in the middle of a blend might drop some volume. Maybe someone with more engineering can weigh in, but is it possible you need to reference each of the two signals to ground before sending them to the mixer, as in output resistors to ground before C10 and C11?