BOSS OC-2 synth mod with sound clips

[gastric]

11/04/11 LAST EDITED

The thread that exposed me to this: Boss OC-2 "Synth Mod"?

The video that started it all and has good illustrations on how to do the mod: HOW TO: Boss OC-2 Synth Mod - YouTube

A video done by one of our fellow TB members demonstrating it with bass: http://www.youtube.com/watch?v=SLwTW54cg-c&sns=em

What the mod does: pulls the raw octave signal from the IC and sends it directly to the output, bypassing all of the additional processing and specifically the low pass filter which gives it that dull, bassy sound. What you end up with is a more or less pure and well defined square wave. This works for OCT1 and OCT2. With that new tone a lot more high end is pushed, you also get a lot more note definition which makes playing way down the E string actually usable, and makes OCT2 genuinely useful on bass. Also, downstream effects respond much differently to the original and "synth mod" signal, often to better results, other times worse.

If you do this wire from R47 for OCT1 and R50 for OCT2, that'll provide a slightly higher volume output based on my testing. These are clearly labeled on the Tiawan PCB, you'll need to use one of the Japanese layouts linked below to figure out what's what as there's no screening on the PCB for the individual components.

Scroll to the bottom of this page to hear all of my clips here: Various bass and guitar effects sound clips - cgraham.com

NOTES:

* At full input volume you're likely to get residual noise on the attack and release of your playing. Roll your volume down until those noises go away. Since we've bypassed the envelope control over the octave output you'll note the audible octave tone and volume output does not change in relation to your instrument volume, you're just dropping input to the "synth mod" OC-2 below some internal gate. It'd be great if we could modify the pedal to work better at full input volume.
* OCT1 and OCT2 sound identical in their raw output tone. I mean, playing 12th fret A in OCT1 sounds identical to playing 14th fret G in OCT2.

Here's the schematic referenced in the YouTube video. The Free Information Society - Boss OC2 Electronic Circuit Schematic He verbally describes the two signal paths 4013 for OCT1, 4027 for OCT2, then blocks out the various components that control the envelope and separately the filter. There's not a lot of components in either section.

Here's another schematic from DIYStompboxes.net BOSS OC-2

Here's a different page from Hobby-Hour.com that appears to detail the Japanese board. I'm basing that on the smaller in-the-pedal diagram which matches my board and control knob sub-board layout. Boss OC-2 Dual Octave Down Guitar Pedal Schematic Diagram

Finally, here's my notes based on the YouTube video. Japanese OC-2 PCB notes I just transposed what he drew out in the video so I had a hard copy to look at. Ignore the red arrow at the top, that's bleed through from notes on the back regarding the DPDT switch.

Image of my alligator clips testing the raw signal being sent to OCT1 and OCT2.



Discuss.

[finalrequiem]

Subbed, so I can find this thread when I finally buy one of these.

[wolffman]

Thanks! That glitch out at 0:45 is rad- what's going on there? Also how's it track fast playing? Does it have the same gating as the regular OC-2?

[Dazonbass]

Cool, I love modding boss pedals.

[avvie]

Should stick this in the "hey how do I get that Muse bass sound? kthxbai" thread.

[gastric]

Originally Posted by wolffman

Thanks! That glitch out at 0:45 is rad- what's going on there?

You can do that right now with your current octavers. By turning them off before the loop ends. I didn't leave a ton of space at the end of the loop to be able to turn effect knobs and bypass two pedals before the loop starts again.

Originally Posted by wolffman

Also how's it track fast playing? Does it have the same gating as the regular OC-2?

Performance is the same, all you've done is strip the output filter and envelope section. Maybe the noise at the end of the octave when you stop playing a note is a little louder since it's not attenuated by the envelope follower. But you'll never hear it unless you're listening for in your solo/bedroom/office playing.

I've always wanted to add a hard gate to my OC-2 output. I wish I knew enough about electronics to figure out how to do that. There's an envelope follower section in the pedal already, has to be easy to leverage it.

[gastric]

Added a quick clip with fast playing so you can compare tracking speed, and some staccato playing so you can hear left over note-muting noise between the two pedals. Scroll toward the bottom: Various bass and guitar effects sound clips - cgraham.com

I contend the tracking and speed is identical. It's just that the "synth mod" signal doesn't have the slight envelope following the normal box does, plus it's so much more clear and harsh that any glitches or noises are more obvious than the comparatively softer / pillowy sound of the normal OC-2 filtered signal.

Really I think this mod would potentially negate the need for a gated fuzz box after the OC-2. Though the volume output is slightly less than a normal OC-2 into fuzz.

I'll see if I can figure out where to move the solder point on the PCB to put the signal pull after the envelope follower but before the filter section which might help attenuate some of the note/string-mute noise. Like I said, I always wanted a tight output gate on my normal OC-2. Any electronics gurus care to propose a fairly easy mod to add a quality gate control to the OC-2 circuit? I'd be happy to remove my OCT-2 functionality to put a gate knob there.

[Bryan R. Tyler]

Originally Posted by gastric

Somewhere there's at least one thread referencing this YouTube video: HOW TO: Boss OC-2 Synth Mod - YouTube which is where I first learned of this. But good luck searching for it, there's only one BILLION threads on OC-2 and synth. Heh. So here's a new one.

I remember that thread- it was started by a really handsome guy IIRC:
Boss OC-2 "Synth Mod"?


Your clips sound great. I'd still love another OC-2 with this mod done to it (still can't solder though).

[gastric]

Bingo! I actually thought I bookmarked or subscribed it, but searching for it was futile. Though I didn't think to search on the YouTube video link.

I'm certainly not a professional solderer. I just watched some YouTube videos and learned as I went. But I can tell you it's not as mysterious or difficult as you think it is. It's been an extremely valuable skill to learn, like installing and fixing drywall. I use it often.

I'm assuming some skilled electronics guy could make all sorts of fun mods to this pedal. There's a filter there that could be modified for different sounds. In fact, there's TWO envelope and TWO filter signal paths on the PCB. Since us bass players are usually only interested in OCT1 we could break the OCT2 path, install all sorts of controls to toggle OCT1 between the two signal paths. So you modify one filter to sound different, however that would be, have a 3 way toggle to switch between NO FILTER (synth mod) \ STOCK FILTER \ MOD FILTER. Now you have three different OCT1 tones out of the same OC-2 box.

[Bryan R. Tyler]

I mean I can't solder because of my eyesight. Yeah, I don't think anyone uses the OCT2 option. You could become the Robert Keeley of the OC-2....get to work!

[wolffman]

Originally Posted by gastric

You can do that right now with your current octavers. By turning them off before the loop ends. I didn't leave a ton of space at the end of the loop to be able to turn effect knobs and bypass two pedals before the loop starts again.




Performance is the same, all you've done is strip the output filter and envelope section. Maybe the noise at the end of the octave when you stop playing a note is a little louder since it's not attenuated by the envelope follower. But you'll never hear it unless you're listening for in your solo/bedroom/office playing.

I've always wanted to add a hard gate to my OC-2 output. I wish I knew enough about electronics to figure out how to do that. There's an envelope follower section in the pedal already, has to be easy to leverage it.

ahh i see. I'm going to have to try that! Yeah I've always wanted a slight volume boost rather than a slight decrease and a hard gate. Someone will figure it out eventually and make some money with it. I’m also interested in the 6 switch version he talks about…

[gastric]

Talor talks about adding a gate. Maybe someone can coax him into spilling the beans on how to implement that.

I'm pretty sure the "six switch" version was just the YouTube guy proposing different switches to toggle between the various OCT1 / OCT2 signal path options. Envelope \ No Envelope, Filter \ No Filter, and the various permutations.

I'd think a gate, boost of volume, and the ability to toggle between the filtered \ unfiltered signal would be adequate.'

Brian, didn't know about your eyesight. Sorry to hear about that. And I wouldn't have guessed.

[evilgabe]

Have you tried running the modded OC-2 through your Korg G5 yet? I'm curious how that will sound.

[gastric]

Originally Posted by evilgabe

Have you tried running the modded OC-2 through your Korg G5 yet? I'm curious how that will sound.

My Korg G5 is currently packed up in its box, unused. I've been using my Roland GR-55 for all synth needs.

[kevteop]

Originally Posted by gastric

Basically the "synth mod" removes the output filter from the octave generators so you get a more pure square wave out of the unit.

I've been meaning to do this mod, but I had an idea that it would be nice if you could have an adjustable filter rather than just off/on - if you could wire the LPF to a pot (say the OCT-2 that nobody uses!) and decide how much of the treble content you want to let through.

Having done the mod do you think this would be at all feasible?

Great clips by the way.

[gastric]

Originally Posted by kevteop

I've been meaning to do this mod, but I had an idea that it would be nice if you could have an adjustable filter rather than just off/on - if you could wire the LPF to a pot (say the OCT-2 that nobody uses!) and decide how much of the treble content you want to let through.

Having done the mod do you think this would be at all feasible?

Great clips by the way.

Everything is possible. I just don't know exactly how to do it. My electronics skills mostly end at following someone else's directions.


Here's the schematic referenced in the YouTube video. The Free Information Society - Boss OC2 Electronic Circuit Schematic He verbally describes the two signal paths 4013 for OCT1, 4027 for OCT2, then blocks out the various components that control the envelope and separately the filter. There's not a lot of components in either section.

Here's a different page that appears to detail the Japanese board. I'm basing that on the smaller in-the-pedal diagram which matches my board and control knob sub-board layout. Boss OC-2 Dual Octave Down Guitar Pedal Schematic Diagram

Finally, here's my notes based on the YouTube video. http://www.cgraham.com/chris/music/b...nth_mod_01.png I just transposed what he drew out in the video so I had a hard copy to look at. Ignore the red arrow at the top, that's bleed through from notes on the back regarding the DPDT switch.

Again, my skills mostly end with following directions composed by someone that actually knows what they're doing. Based on the schematic and colored sections for the filter I could probably follow the traces to determine the point where to pull the signal AFTER the envelope section, but wiring a variable LPF to a knob and what not is beyond what I can do as I have no idea what components change the filter frequency/cutoff/slope/etc. etc.

Besides sharing bass clips with everyone I was hoping it'd spark some additional mods from someone that knows what they're doing so I could then do them too.

[wolffman]

thanks for the fast clips & regualr oc-2+fuzz clips. Although the synth mod sounds great it doesn't sound as thick and full as the oc-2+fuzz combo. It's def a nice cheap single pedal solution to a similar sound. I could see putting one on my board, but I'm not certain about replacing the octave fuzz combo.

[gastric]

Originally Posted by wolffman

thanks for the fast clips & regualr oc-2+fuzz clips. Although the synth mod sounds great it doesn't sound as thick and full as the oc-2+fuzz combo. It's def a nice cheap single pedal solution to a similar sound. I could see putting one on my board, but I'm not certain about replacing the octave fuzz combo.

I do not disagree with you. I haven't yet determined why it sounds thinner than OC-2 into fuzz. I thought it was a volume drop, or maybe it's the same volume output but the sound output is more slanted towards the high end now, thus not as heavy as a low end push which is what the LPF does? Or that it's a more or less pure square wave VS whatever overtones/etc a fuzz adds to the factory OC-2 tone. But either way there's not as much beef, and it sounds quieter, doesn't push downstream filters as hard, etc.

I haven't had a lot of time to investigate further beyond wiring it up, creating the clips you've heard, and typing here. It's an easy enough mod to undo. Simply remove the wire from the resistor on the PCB and solder it to the cut leg of the OCT1 pot which reverses it totally, at least for me on the Japanese PCB. Again, I just took what's #1 and wired it to #3 in the video for Japanese boards.

[Kwesi]

Originally Posted by wolffman

thanks for the fast clips & regualr oc-2+fuzz clips. Although the synth mod sounds great it doesn't sound as thick and full as the oc-2+fuzz combo. It's def a nice cheap single pedal solution to a similar sound. I could see putting one on my board, but I'm not certain about replacing the octave fuzz combo.

You think so? Sounds pretty phat to me. I'm tempted to grab an OC-2 now but I don't have any space on my board, lol.

[Bryan R. Tyler]

Kwesi you sweet young thing- that's why they make bigger pedalboards