Boss OC-2 octave: mods and tracking improvements?

[stm]

A friend lend me a Boss OC-2 octaver.  Great sound, but octaves are unstable and from time to time you hear the octaves are not dividing properly.  Rolling down the guitar tone knob helps marginally to stabilize this.  The neck pickup is slighlty better than the bridge one, but not that much.

Looking at the schematic there are some low-pass filters which could improve situation if cutoof frequency is lowered, but at the cost of reducing oparation at higher frequencies.

Does any one knows of a mod to make octaves on this unit more stable? Or maybe a better octaver to build?

I love the way this octaver generates almost clean tones!  Around 1992 I made an octaver based on a fuzz and had the same tracking problem.  Besides that, it sounded very thick, especially when you threw in a small amount of the 2nd octave and a moderate amount of the first octave.

[Russ]

About the best route I've found is to run a compressor in front of my OC-2. This really helps to stabilize it's tracking. I think Boss even suggests this.

Russ

[StephenGiles]

Believe me, you are wasting your time. You need to extract the fundamental first, in other words create a sinewave at the frequency of the note you are playing. In order to do that, I suggest you have a look at the input section of the EH Guitar Synthesiser (not the micro synth) over at Mark Hammer's site. Yes, you need a compressor but then an adaptive filter which does all the fundamental extraction, square up the sinewave then divide. Even that will not give 100% performance, but a great improvement on the Boss offering.
Stephen

[StephenGiles]

Try this for size:

Now that.......is an octave divider!

[KarbonHed]

Rolling down the guitar tone knob helps marginally to stabilize this.  The neck pickup is slighlty better than the bridge one, but not that much.

You're on the right track there I think.

What you'd have to do is alter the cut off point of the low pass filter. You would probably gain better tracking at lower frets and strings but probably at the expense of highter notes whose fundementals would be attenuated below the point at which the rest of the circuit can process them.

It's something I've been meaning to try for a long while, I might try and get a second oc-2 on ebay so I can try it. My guess would be that if you altered the LPFilter you would also improve the tracking for bass guitars as well.