RLBJR65s Pushme Pullyou transistor changes work!

[jmusser]

On one of the threads the other day, I was mentioning Tim's Pushme Pullyou up octave circuit. I had used the transistors that were shown on the drawing (Q1&Q2 2N3904, Q3 2N3906), and with this transistor set up, all I really got out of this circuit, was overdrive. RLBJR65 had mentioned he had to really mismatch the HFE in the transistors to get the octave effect to show up. I used his suggestion, being: Q1 2N5088, Q2 2N2222, and Q3 2N5087, and it worked like a charm. He reported that he got an octave up fuzz out of his at full gain, but mine gave me a clean octave up even if the gain was maxed out. It still sounds crunchy on two fingered power chords because of the intermodulation distortion, but it's basically a clean octave up at least for me, in it's current configuration. The ring mod stuff is there as usual, but you have to really listen for it to detect much of it. I would guess on this circuit in particular, that you are going to have to select the best transistor selection for your specific rig. Thanks RLBJR65, for the sub suggestion.

[WGTP]

I had similar problems, thanks for the advice.  

[RLBJR65]

Glad I could Help I got side tracked and didn't follow up on your last post. After revisiting I found that I had removed the 470 ohm resistor from the battery supply and used 470k's instead of 500k on the base to collectors of Q2 and Q3. No other subs or mods.

Removing the 470 ohm is probably the reason for the fuzz, more power!  
On mine, It is a clean octave up to about 1/2 gain, 1/2 to 3/4 sounds like it's slightly over driven but still fairly clean and after about 3/4 gain I get an octave fuzz, that gets some good feed back going. Nice not really over the top.

I still would like to know why mismatching the hfe's works better. I'm going to put up anouther post on that to see if I can get a good explination.

[jmusser]

I'll try the resistor sub, and see what that does for me. That would explain why yours had fuzz and mine didn't. I may end up leaving it as is anyway, since I don't have any clean octave up circuits. I need to order a couple pots, and then I can build Scott Shwartz's Octave Screamer. The sound samples show it being a real nice clean octave up. Would you have any recommendations on Tim's "Octup" circuit? I'm in the same boat with that one. It's basically just an overdrive in it's current configuration. It uses an MPSA13 to drive two unmatchet J201s. It's the very last circuit on his "Snippets" page. Did you read my "Something I didn't expect SOU" post? If you like up octave fuzzes, your going to be thrilled with Gusses Simple Octave Up! That ones a sleeper. Since there are no sound samples on it, I had never heard it until I built it, and Man, it's scream miester!

[RLBJR65]

Yes, I saw you're other post great discriptions, should be very helpfull to  others. Nope never built Gus's SOU. I did a Bobtavia though, it can be a pretty sick hard driving octave up fuzz.
http://www.generalguitargadgets.com/diagrams/bobtavia.jpg

A word of warning if anyone tries this, DO NOT CONNECT PINS 1 & 8!!!!!
I thought, hey why not put a pot on there for more gain, sounded like a good idea, all I accomplished was TOASTING the transformer!! 3 bucks down the drain.

Never tried Tim's Octup, looks like he never did much with it either V. 1.0, no revisions. He noted that maybe it needed more gain on the input. Have you tried an OD or booster in front of it? Maybe that will help.

[jmusser]

I'm very well aquainted with the Bobtavia. It was the first circuit I ever built, and as you say, it is a sick, hard driving octup fuzz. I had not played it for awhile, since I had been building other stuff. I put it through it's paces along side the Simple Octave Up, and the SOU out sicks it, and has even more octave and sustain. "The Bob" is still near and dear to my heart, but it has stiff competition with the SOU. No, I haven't tried anything in front of the Octup, but I'll have to give it a wirl