Another Octave Up build report

[jmusser]

I love up octaves, and I'm always ready to take on another one. I've had this schematic stuck in a drawer for over a year, and finally deciced to get it out and give it a try. This schematic came from Onboard: http://img133.echo.cx/img133/573/octavefuzzopamp28ne.jpg  The text for it is at: http://www.diystompboxes.com/smfforum/index.php?topic=32836.msg227546 I built it the other day, and couldn't get a peep out of it. The way the Vref (1/2 Vcc) is applied to U2 and U4 + inputs will short these out. I tried to get hold of Onboard to see if I could get a correction, but still haven't heard from him, so I sent an PM to Gez. Gez said to put a 1 meg on the Vref to U2+ and anything from a 10 K to 100K on the Vref to U4+ (I used a 100K). He also said that all the resistor values could be made smaller for U2 and U3, and then R6 and R7 could be eliminated. Since there was no voltage splitter circuit shown for Vref voltage, I used the one off the NeOctavia. It uses two 10Ks and a 47uf cap. 9v comes in one side of one of the 10Ks, and then the two 10Ks as well as the positive of the 47uf electrolytic tie together. That tie point is where the 4.5 V (1/2 Vcc, or as he calls it "Vref") comes from, and the negative side of the 47uf goes to ground, as well as the remaining end of the second 10K. After I got that far, I fired up the circuit. I had very low output, to where my amp had to be cranked to 10 to hear anything. I figured that the 1 megs that Gez had referred to earlier, were loading down the output, so I changed them all to 10K. After that, I fired it up again, and had plenty of volume, even with my amp at 4. I like the tone I'm getting. The Octave Up is basically superimposed on top the fundamental, and it's not real high pitched and ear piercing like the Bobtavia or Simple Octave Up. I love the snarl it gets on  E & A power chords. It really lends it's self to the "Iron Man" riff. It has pretty decent sustain, and decent octave up. It is more evident as all up otaves are, past the 10th fret. With the guitar volume at about 8 and on the neck pick up, it plays a fairly clean up octave up the neck, with the tone controls rolled off. At 10, it gets a lot louder, and a little ring mod sets in, but not too bad. On the bridge pickup, you get more bite, crunch and snarl. Darken your amp a little, and your on your way to Iomi tone. Gez said also, that I could change the input buffer to non-inverting to accentuate the highs, but I already have the tone in other up octaves, and like the grind this one has just the way it is. I have no idea how On Board had his wired so it worked for him as he indicated in the text, but this is a good sounding effect wired this way. I would guess that it would make since that you would get sort of an Iomi tone, since he used a treble booster ( Dallas Range Master?) into a dark amp. Thanks to On Board for Another Octave Up, and to Gez for helping sort out yet another circuit.

[Mark F]

The schemo link seems to be dead. I tried it twice & nothing. The other link works.

[toneman]

Confirmed, the link for the schemo is dead.
Can U post schemo in another location?
say, the gallery here??
always interested a new twist on an old octave....
T

[jmusser]

Yep, it's dead. That's wild, because I just brought it up and printed a spare copy of it two days ago! I hope I have a clean copy, because mine is highlighted all over. If not, I'll redraw it and create a link to it. While I'm at it, I'll add the mods in red, that Gez sent to me. It'll be interesting to find out from On Board how he actually had it wired so it would work when he put it up initially, because it may sound totally different from what I came up with.

[toneman]

Hey Jeff,
I uploaded your schemo to the shemo gallery here-

http://aronnelson.com/gallery/Schematics-etc

it's at the very end....
seems to come up ok...
Y'a'll LMK if Y'all can read.

Then, again, why not just use 2 inverters and flip one of the diodes around(?)
Could even add more/different  gain to each half of the rectos...(?)
Then mix the output the same.
afn
T

[jmusser]

Thanks Toneman for loading that for me. I drew it up last night at work, and I was fairly fried this morning after a 12 hour night shift.  If someone needs some more clarity on it, just ask for clarification, or PM me with your E Mail address, and I'll send you a copy. Like I said, it is a pretty good sounding circuit. I used an LM324N quad op amp for this build, because I happen to have several of them, not because there's any particular magic. I'm sure an TL074 would probably sound better. Like the drawing says, use what ever you want in there, duals, singles of your preference. I have the pinouts for the LM324 on there.