Alex's Octave-Up Rabbit Hole

[Feral Feline]

Since you guys are octave up enthusiasts, I thought you might appreciate this. I recently built a couple double-analog-octave up pedals. Basically it’s just 2 green ringers in series, with a toggle to select one or both and of course the footswitch to bypass the whole thing.

The second circuit brings in a whole new sound. You can just barely hear the 2nd octave on certain notes, but mainly it just makes it more pinchy / nasty / aggressive (awesome with fuzz after it). It behaves similarly to the regular green ringer in that it works best with neck pickup playing up the neck.

Once I get around to making a little recording I’ll post a build report. You could of course use the concept with the other octave up circuits.

I attached a graph of what I think is approximately happening with the signal when the 2nd octave circuit is engaged. I did change the input capacitor of the 2nd circuit from 47n to 10n to help that high pass filter (DC coupling cap) work a little faster in theory. The difference is subtle but I think it’s there.

I can’t say if I like it better than the single octave, they’re both cool in their own way, which is why it's great to have the toggle. I have couple more boards I could send if anyone is interested!

+1 for a Demo!




For several years, I've wanted to build an effect with a toggle switch, and this might be the perfect effect for that idea.
Was to be an OD with a toggled fuzz-boost, but this lends itself even better as there'd be no knobs.

Plan is to build the following into it:

Except I'll have to add a 555-timer that ramps up slowly.

1st push, 30 seconds before it turns itself off.
2nd push, 15 seconds before it turns itself off.
3rd push, 3 seconds before it turns itself off.
4th push, 0.5 seconds before it turns itself off.

Have a 3D-printed skeleton hand that comes out from under a "VU-Meter"
Build it, then gift it to a friend that doesn't know what it does.

"Hey, where'd the sound go?"

 

[phi1]

It sounds roughly 2x as bad as the green ringer with chords haha! I’ll try to record something soon

 

[finebyfine]

It sounds roughly 2x as bad as the green ringer with chords haha! I’ll try to record something soon

Lol you’re talking to someone who basically started down this rabbit hole because of how much I love how chords sound through a green ringer! My curiosity is piqued now lmao

 

[DGWVI]

I'm for sure gonna try something like this. I'm interested in how a blend on the second octave would sound, or hell, maybe feeding the output of a ringer back into itself a bit. The Carlin Ring Modulator can kind of do that if I'm remembering correctly.

The Green Ringer works well with a feedback loop. Gets super 8-bit sounding. If you try it out, make the bias on the first stage adjustable for more intense fuzz tones

 

[DGWVI]

Had to whip a couple Ringers up because I was disgusted with myself for not having one on hand. Built one stock, and the other to updated Parentheses specs- I prefer the latter

Anyway, the feedback mod- I can't find my build notes or video from the one I'd made, but I'm guessing it had other circuitry to make the feedback loop more stable. I'll keep tinkering and report back

Also, if you have some sort of resonant low pass filter (I used the Micro V clone set for no sweep), drive it into the Ringer. Delightfully disgusting

 

[Feral Feline]

A demo of the resonant filter with Green Ringer would be fantastic. *hint hint*

 

[DGWVI]

A demo of the resonant filter with Green Ringer would be fantastic. *hint hint*

Didn't see this until now, but I'll try to whip up a demo in the next few days

 

[phi1]

Here's some phone clips playing through the Double Analog Octave pedal I made. Hope it's enough to give the flavor of the concept. The higher octave isn't always apparent but, that mode always gets nastier.

First clip (all Les Paul Neck pup):
Clean
Clean + 1 Octave
Clean + 2 Octave

Second clip (all Les Paul Neck pup):
Fuzz
Fuzz + 1 Octave
Fuzz + 2 Octave

then at the end I was just toggling between single / double octave.

The second clip is some chords per finebyfine's request!
Clean
Clean + 1 Octave
Clean + 2 Octave

 

[Feral Feline]

Sounds fantastic!

It's the sort of sound Reeves Gabrels would dig.

It's harsh in a good way, somehow avoiding ice-pick pain while still being a brutal sonic onslaught.

I know it's adding all sorts of harmonics, but the feel is one of deconstructionism.

Thanks for the demos!

 

[finebyfine]

@phi1 oh my god I'm loving the chords one, thank you so much for that demo. Some great sort of nastier-fuzz on the single notes too in a really interesting way. Definitely on the short list to do this myself

 

[Chuck D. Bones]

Your problem with the LM13700 circuit is you're driving it too hard. Either the 10K need to be bigger or the 33K needs to be smaller. You're powering it with ±9V, right?

 

[finebyfine]

Your problem with the LM13700 circuit is you're driving it too hard. Either the 10K need to be bigger or the 33K needs to be smaller. You're powering it with ±9V, right?

I was doing that one was just from a single 9V supply I think, with the inputs biased to 4.5v. Been a while since I played with it

 

[Chuck D. Bones]

So the schematic you showed is not what you built?

 

[finebyfine]

So the schematic you showed is not what you built?

Just checked some photos I took and I actually didn’t bias it - I built it as posted

 

[Chuck D. Bones]

That would explain why it sounded bad.

 

[finebyfine]

This is my take on JC Maillet's Super Full Wave Octaver that I posted about earlier. The main thing I dislike about his circuit is that the "Second" control (the amount of rectification) has a huge impact on the output volume. I liked being able to go from full to half wave but wanted the volume more stable, for if nothing else to hear the difference better.

This is the LTSpice output of JCMs with each color being a different step on the rectification



This is what I landed on, which is just cribbed from another op-amp cookbook type precision rectifier, but controls the rectification differently.



Here's the LTSpice output for similar steps of this method of rectification control. While there's some volume difference it's much less pronounced. Red is full wave, green is half wave.



I want to add some sort of treble roll off to the circuit to simulate switching to a neck pickup and rolling off a guitar's tone knob, but other than that am pretty happy with this spin on it. It has unity gain at noon on the volume which is another thing I didn't like about JCM's SFWO.

I also have a halfway decent AD633 octave up nearly fine tuned if you want to build the most expensive octave up ever

 

[Chuck D. Bones]

Instead of using IC1.2 as a Vref buffer (which you don't need), use it to make a variable low-pass filter and put it right after IC1.1.

You don't need R3 or R8.

IC2 can also be a TL072 if you like.

 

[Feral Feline]

@Chuck D. Bones — if IC2 can be a TL072, is there any advantage or disadvantage to just using one TL074?

Also, re R3 and R8 — jumper them to VR or to pins 1 and 7 respectively?

 

[Chuck D. Bones]

if IC2 can be a TL072, is there any advantage or disadvantage to just using one TL074?

Advantage of a quad over two duals is you only need one, disadvantage is PC board layout is usually easier with two duals than it is with one quad. This circuit is not layout-critical and there are plenty of talented folks here that can lay this out no problem.

Also, re R3 and R8 — jumper them to VR or to pins 1 and 7 respectively?

Correct. I can guess why the original designer thought it was necessary to put those in, but trust me, it isn't.

 

[MBFX]

I just finished breadboarding a Ge Fuzz Face and a Green Ringer with Ge diodes. I got lucky, and of the 4 I ordered two were almost identical. Even with my tone knob rolled up I get a strong octave effect! I had to stick the octave after the fuzz for good results. I'm going to wire it all up on a single perfboard and stick it in a big enclosure for fun