Harmony Central Octophant (Verified)

[aelling]

This was requested over 4 years ago and just got bumped yesterday. I have not build this but I think it should be okay, let me know if you find any errors though.

Schematic can be found here
http://guitar-fx-layouts.42897.x6.nabble.com/OctoPhant-td11966.html

Layout (UPDATED 01/10/18-- moved some things and shaved off a column)


Layout 2 (WITH ADDED 470pF CAP)

[WeStartToDrift]

One of the things that I changed fairly regularly through my share of the Octophant run was the final gain stage transistor & feedback resistor. I highly suggest building this with sockets and experimenting as I found the old Soviet MN138A's sounded heads and tails better than the stock AC187's. Also halfway through I added a 470pf cap between the collector and base.

[BetterOffShred]

That's great information sir!  Thank you for sharing it. I have never heard of this device but I do love octave stuff.    

[aelling]

Thanks, unfortunately I made the layout smaller before I saw your post, but I added a second layout (and back to being 19x11) with the cap added.

[BetterOffShred]

I think D1 is backwards, that would be a big short as shown.  Then on the right side on layout 2, the jumper is moved from the Ge emitter over 2 columns.. It'll still work, but you just have to rearrange those caps.  Going to make this soon.. already built a box

[aelling]

Thanks, nicely spotted. I made the corrections, though I am still not entirely happy with the added 470pF cap, adding an entire column for just that one cap. I would probably just solder that cap on the back of the vero or over top of the 470K resistor at A12 & B13.

[BetterOffShred]

Happy to contribute anything I can, you did the real work man.   I cut my board at 19 so it all worked out hehe

[aelling]

Well, you could make a cut at F17 and have an onboard LDR.

EDIT: Sorry, CLR of course.

[BetterOffShred]

I was thinking about which control to put an eye on

Any idea what is a good gain range for the Ge? I got some 404Bs that get pretty high

[aelling]

BetterOffShred wrote

Any idea what is a good gain range for the Ge? I got some 404Bs that get pretty high

I don't, but like all Ge transistors, best just to socket and try them out.

[BetterOffShred]

Well I built it, layout 2.  It works and sounds great but there is quite a volume difference between fuzz 1 and 2 modes.  I will play around with it a bit after I examine the schematic. Not sure if that's intended.   Right now I have a 404B in the Ge socket and it sounds huge.  It's like 80hfe.  I have some that are like 140 ish so I will try that and report back

The octave sounds awesome.  

[BetterOffShred]

Sustain was best all around with a 92hfe 404B. Also I ended up using a 4401 and 4403 for the octave part and it really came to life.  Most of my 3904s are not near 300hfe.. but the 4401 and 4403 are like 280s.. sounds way better.  Anyway.  It's legit.  I figured out the toggle is adding a booster based off the 2N7000? There's a buffer and a boost and a fuzz and an octave all rolled up.  

[aelling]

Thanks, I've tagged them as verified. I am interested in the circuit but the demos I found was not impressive, I thought they all sounded way to noisy/buzzy. I love octave fuzzes but more quite like the univox superfuzz or fulltone ultimate octave/foxx tone machine.

[BetterOffShred]

Oh for real man, the demos are abysmal.  Sorry dudes who made them... It's a fact.  

Mines quiet AF,  like no noise.  It's a really fun build the way the texture and gain knobs are super interactive.  I like the bleeding lungs nearly gated octave, which you can totally get with the txt and gain back and volume up.. all kinds of artifacts.

Its nothing like the demos.  Build one  you won't regret it.  It has a great fuzz, and you can dial in a fat dirty boost green ringer type shit too.  Love it  

Thanks man

[BetterOffShred]

Also I only have 1 left for something else, but I'm thinking C1M for gain may be the ticket.  I'll report back once I get another and pop it in.  It kind of bunches up at the end like most stuff that calls for a B1k.  I bought like 20 C1k for all the fuzz face style stuff that needs a 1k gain pot heh..

It's workable .. I just have opinions on shit

[aelling]

Thanks, I might put this one on the breadboard and try it out. I have been building guitars (candy apple red fender mustang with matching headstock and competition stripes ) lately so it's been a while since I made an effect.