Octarock (FoxRox Octron 3)

[MichaelW]

Build Rating

5.00 star(s)

3rd build report for today. I didn't get a chance to do a demo for this one. Maybe I'll add one later.

I've never played with an octave pedal before, and I wasn't really planning on building one until @harmaes talked me into building this one
(I may have mentioned before how easily influenced I am)

This thing is pretty cool. Tracks very well and works in all positions on the neck. According to the manual it's supposed to work better on neck pickups but I'm finding that it works pretty well with any pickup position.

Also interesting is how the original uses Ge diodes to create the octave sounds but this build called for Bat46's. I wonder how it would sound with Ge's?

Lots of cool sounds in this pedal and the sub octave is really the star here. It can sound HUGE. And you can dial in as much or as subtle of an effect as you please.

I'm still toying with it and seeing how to use it and how I would use it in the context of a song.

I was inspired by @DGWVI 's awesome graphic style and aspired to copy him.

Super smooth build. I used MMBF5457's soldered to the board and everything else is stock according to the BOM.
(The BOM calls for BAT41's although the board silkscreen called for BAT46's. I followed the board.

 

[DGWVI]

Also interesting is how the original uses Ge diodes to create the octave sounds but this build called for Bat46's. I wonder how it would sound with Ge's?


I was inspired by @DGWVI 's awesome graphic style and aspired to copy him.

Super smooth build. I used MMBF5457's soldered to the board and everything else is stock according to the BOM.
(The BOM calls for BAT41's although the board silkscreen called for BAT46's. I followed the board.


View attachment 42569

View attachment 42570

The diodes for the octave up section are just for the wave rectifier. GE won't make a huge difference unless they're significantly lower forward voltage. I used 5817s in mine because they consistently measure lower than any GEs or or other Schottkys I have on hand. The lower vf lends itself well to a more piercing, and easily achievable octave up.

The BAT41/ 46 (GE in the OC-2 and Pearl Octave) in the octave down section just adds a DC offset when it switches phase, dependent on the fet switch. Silicon is probably better simply for stability.

Also, sir... There's no graphics on your stompydoo. I suggest you bust out some stamps and get to letterin'

 

[jeffwhitfield]

I have an original of this pedal. One of my favorites. I’m almost tempted to build one and, if it replicated it well, sell it.

 

[harmaes]

Super clean build Mike! Looking great! Tempting to build one…

 

[Robert]

Also interesting is how the original uses Ge diodes to create the octave sounds but this build called for Bat46's. I wonder how it would sound with Ge's?

The first version Octron used germaniums according to the Foxrox website, the Octron 3 used schottky diodes just like the Octarock. (No idea what the Octron 2 used)

I tried the prototype with BAT41, BAT46, 1N5817, and 1N4148. None seemed superior over the other.

I also tried a matched pair but can't say that it made a tremendous difference. The diodes in the original weren't very tightly matched.


It's a great circuit, by far the best analog octave up I've ever used. I'd have no problem buying an original if I wasn't interested in building one.

 

[DGWVI]

The first version Octron used germaniums according to the Foxrox website, the Octron 3 used schottky diodes just like the Octarock. (No idea what the Octron 2 used)

I tried the prototype with BAT41, BAT46, 1N5817, and 1N4148. None seemed superior over the other.

I also tried a matched pair but can't say that it made a tremendous difference. The diodes in the original weren't very tightly matched.


It's a great circuit, by far the best analog octave up I've ever used. I'd have no problem buying an original if I wasn't interested in building one.

It might be placebo on my part, but the lower the vf definitely seems to work better for octup tones.

I match mine out of habit from all the Green Ringers I've built. Granted this uses opamps instead of a transistor, it does still do the out-of-phase and rectified thing to achieve it's octave up

Agreed on it being (one of) the best analog octave ups out. For "cleaner" octup, I haven't heard one that does it better

 

[Robert]

It might be placebo on my part, but the lower the vf definitely seems to work better for octup tones.

Yep, logically you do want the lowest vf and closest matched pair you can get but it still sounds great if you don't take the time to bother.

Luckily diodes are cheap and you can measure vf with dang near any DMM, so it's a no brainer to do it.

 

[MichaelW]

It might be placebo on my part, but the lower the vf definitely seems to work better for octup tones.

I match mine out of habit from all the Green Ringers I've built. Granted this uses opamps instead of a transistor, it does still do the out-of-phase and rectified thing to achieve it's octave up

Agreed on it being (one of) the best analog octave ups out. For "cleaner" octup, I haven't heard one that does it better

What diodes/ Vf did you use? BAT46's are pretty low already right? I have some super low Ge diodes, like under .200mv. Wondering about giving that a try. The Octave Up is not quite as robust as the Octave down. But still I love being able to play all over the neck and get the effect.

 

[DGWVI]

What diodes/ Vf did you use? BAT46's are pretty low already right? I have some super low Ge diodes, like under .200mv. Wondering about giving that a try. The Octave Up is not quite as robust as the Octave down. But still I love being able to play all over the neck and get the effect.

I use a specific batch of 1N5817s I picked up from a surplus shop. They consistently measure between 0.213 - 0.219, with most sitting at 0.217.
The new stock I have from Tayda measures slightly higher, but still work well in this application

I have some GAZ51 germs that measure around 0.15, but they're kinda cumbersome to use, and super fragile.
All the D9* diodes I have on hand measure above 0.225

I did slightly modify mine after playing around with it a bit -

I increased R33 to 47k and C19 to 10n. Does darken the Octup a smidge, but gives a better range of flutey tones across the fretboard. I did this, because don't ever touch the tone controls on the guitars I have

 

[giovanni]

There was a troubleshooting thread about the JFETs, did you test them beforehand? I have a few JFET circuits in the pipeline and now I feel paranoid about them!

Anyways, great build! I also own an original and it sounds fantastic. Glad to hear that the dyi version sounds good!

 

[DGWVI]

There was a troubleshooting thread about the JFETs, did you test them beforehand? I have a few JFET circuits in the pipeline and now I feel paranoid about them!

Anyways, great build! I also own an original and it sounds fantastic. Glad to hear that the dyi version sounds good!

That was my thread. The JFets were just a bad batch that didn't work in this particular circuit. They we are from Tayda, but the other Tayda-sourced FETs I used work wonderfully

 

[MichaelW]

There was a troubleshooting thread about the JFETs, did you test them beforehand? I have a few JFET circuits in the pipeline and now I feel paranoid about them!

Anyways, great build! I also own an original and it sounds fantastic. Glad to hear that the dyi version sounds good!

I got these from Quest I think, they've been fine, I don't bother checking SMD values if they come from a reputable source. (meaning not Bangkok

 

[Locrian99]

I got these from Quest I think, they've been fine, I don't bother checking SMD values if they come from a reputable source. (meaning not Bangkok

I bought 10 57’s from stomp box parts thru holes a while back for a phase 90 build they all tested perfectly and very close. I ended up with 2 matches sets of 4 out of the 10. Not sure if they still have them but was a good source for sure.

 

[MichaelW]

I bought 10 57’s from stomp box parts thru holes a while back for a phase 90 build they all tested perfectly and very close. I ended up with 2 matches sets of 4 out of the 10. Not sure if they still have them but was a good source for sure.

That's pretty amazing that you got 2 matched sets out of 10.

 

[eh là bas ma]

the best analog octave up I've ever used.

For "cleaner" octup, I haven't heard one that does it better

I wonder if you tried this one ?

"Up, Down, Daddy!" PCB - delyk PCBs

My daughter melts my heart when she asks me to "Up, Down, Daddy!" when throwing her up into the air and catching her. I figured this was a perfect name for an octaver with 1 octave up and 1 and/or two octaves down.

www.delykpcb.com

Is it even better than Pearl OC-7 octaver, in your opinion ?

 

[Robert]

It is actually derived from the OC-7.

The octave down is virtually identical, octave up however is far cleaner (and more prominent) than any Green Ringer style octave up I've used.

 

[DGWVI]

I wonder if you tried this one ?

"Up, Down, Daddy!" PCB - delyk PCBs

My daughter melts my heart when she asks me to "Up, Down, Daddy!" when throwing her up into the air and catching her. I figured this was a perfect name for an octaver with 1 octave up and 1 and/or two octaves down.

www.delykpcb.com

Is it even better than Pearl OC-7 octaver, in your opinion ?

Yes, I built that one along side the two Octarocks. The Octup in the UDD is cleaner as in less grit, but the octave isn't nearly as prominent.

As @Robert states, the octave down is nearly identical, though I also prefer the OctaRock for that as well

I'll try to make a comparison vid in the next few days. Still working out a weird issue with the UDD

 

[eh là bas ma]

I d'like to mention the fact that the OC-7 octave up can sound very differently, according to the internal trimmer setting. Based on this answer, reply #2 :

"Balancing the rectifier is almost a lost cause with musical signals, you need a regular and symmetrical waveform to get to the "ideal". A sine wave gives the best chance of doing it. Even then, there's little chance of getting a result that sounds at all "sweet". The problem is the sharp transitions in the narrow pointy bits of the rectified waveform are harsh and not really harmonic which can't very well be filtered out. It's another flavour of nasty fuzz but you can find sweetspots if you're prepared to find its strengths."

Pearl OC7 octaver clone and Meridian : trimmer questions

Pearl OC7 octaver clone and Meridian : trimmer questions

www.diystompboxes.com

Using a cheap casio electric piano instead of a guitar, I've found a sweet spot around 11'. A narrow spot where the octave up starts to sing in a pleasant way. Perhaps "cleaner" as you would put it ? Edit : you can clearly hear some high freqs coming in, and quickly disappear if you turn the trimmer just a bit further...
I also came to realize that this octaver is well suited for piano too, you can really hear the full chord with much better tracking than with a guitar.

So I guess to make a fair comparison, the OC-7 has to be carefully calibrated ? ...and it's not so easy, in my experience.

 

[andare]

You've built dozens of pedals without graphics. How do you know which is which and what the knobs do

 

[MichaelW]

You've built dozens of pedals without graphics. How do you know which is which and what the knobs do

Generally it's easy to figure out. But I tweak until I find a good sound