Ampeg Scrambler (AKA Revolcador) build report

[jmusser]

First of all, this circuit ranks right up there with the most difficult I've had to wire on perf. I worked off the "Revolcador" schematic from  Tone Pad, and I was very surprised that it worked the first time I plugged it in, as I was expecting a lengthy debug. I will have to go listen to the sound sample again on Tone Frenzy, to see how this one measures up to the original. First of all, it's a very nasty beast! It is different from any other circuit I've built, in that the octave up part of this is not really apparent as it is in most every other up octave circuit. The octave up, is always added into the mix of the dry signal, and I was unable to separate it with the balance pot. It goes from barely there boosted and brightened, to absolutely nasty, up octave laden fuzz. It has some aspects of the Octave Up Sick Box, when it's maxed out. As you just pass out of boost, and into fuzz, it does a very nice Sitar down in the bridge postion of my Fat Strat. It's every bit as good as the Psychtar. When I set the little Epi to max gain, this effect has great sustain. It has fair sustain anyway. I haven't listened to the Tone Frenzy sample for awhile, so I didn't really know what to expect. It has a heaver fuzz than I exected, and if you could somehow add up octave up to the Sola Sound Tone Bender maxed out, you'd have pretty close to what my clone sounds like maxed out. It was mentally challenging for me to wire up (of course to me how a rubber band snaps back is still a mystery), but it was well worth it. I used MPSA13s for the Darlingtons in Q1, 3 & 4, and a 2N3904 in the Q2 position. I've been accused of being a little "Harmony Central" in my reviews, but there are some circuits that warrant bragging on. This one is one of them.

[Fret Wire]

Yes, that is a nice sounding octave. Notice there aren't many mods for it around? Ampeg got it's craziness down right the first time. The Scrambler and Octavia are my favorites. Did you use D3, D4, and D5? What did you use for C3?

Damn, I wanted to hear "warm, buttery, smooth, transparent, and tube-like".

[jmusser]

Yes, I used all 5 diodes in there, and I used for C3. It's built directly to the schematic. I haven't read much on mods as you said, so I don't know if you get a whole lot of difference out of leaving the 3 extra diodes out or not, or whether the stock 3N5306 Darlingtons sound better than the MPSA13s. Until I looked at the Tone Pad schematic, I didn't know that these transistors were Darlingtons, and that you could sub them, or I would have built it quite awhile back. It actually ended up a little more tame than what I expected, which I feel makes it more useful. It doesn't do a whole lot of intermodulation distortion either, no matter how you adjust it, which is different from most up octaves. The Sitar part of it, I never expected at all. I don't ever remember reading about that feature anywhere or hearing it on a sound sample, so that was a pleasant surprise. I actually think I would rate it's Sitar immulation better than the Psychtar, because it's more dynamic and touch sensitive, and you don't have to work as hard to project that tone.

[Fret Wire]

There's really not much to play with on that. The 5306's work fine, but you could experiment. You could also play around with matching the diode pairs more closely. If you used an electro for C3, and followed the schematic exactly, you'll get some slight wierdness in the sound, plus switch popping when it's boxed up. C3 is shown backwards on that schematic, the pos lead should go to the emitter, not the neg lead as shown on the schematic. I didn't know that when I built my first one, but since I always use 1uf film caps, it wasn't a problem.

[jmusser]

Well Fret Wire, I changed the C3 cap around and it made some difference. I believe that it is supposed to be turned around like the one on Fuzz Central. One thing it did do was take the real nice sitar tone away. It's still there, but not near as pronounced as it was. Maybe thats why no one ever wrote about it. It would almost be worth putting a reversed cap switch on there, if you really liked the sitar. I'm not sure what else it did to it besides that. I would have to be able to chane the cap polarity around  by a switch to be able to hear it. It's odd that it would work both ways to start with. I like this effect more and more every time I play it. The fuzz is very thick, and even though there is an octave "splat" when you hit a chord, it still isn't pronounced and overwhelming like say, the Super Fuzz. This effect plays chords well. One thing that I noticed it did now, was that when you hit a certain note on a string, and hit the same note on the string above, it goes ballistic trying to track on it. It's a good thing though. This is not all notes, just certain ones.