Build Your Own Clone Message Board

i just finished my Scrambled Octave (component side pictured below), and i'm wondering about a few things. perhaps both things are normal, i don't know...

1. i'm getting a pretty severe "gate" effect. a note will ring out for a few seconds, and then it's clamped down by a gate. this only happens to the "wet" sound, when the Blend knob is at 50/50, you can clearly hear the gate only affects the fuzzy side of things. the clean side of things decays normally.

2. the actual octave effect is clearly heard when i pick lightly on the strings, but it pretty much disappears when i hit them with a normal amount of attack.

any feedback is appreciated. thanks!

I don't see any obvious component problems. Suggest you double check to make sure the transistor placements are all correct/match the silkscreen.

Would be very helpful to see the solder side of the board.

transistor placement looks ok.

after playing with it a bit, i'm starting to think that the two issues i mentioned are normal. the octave seems to be apparent in some settings (bridge position, tone rolled back, higher on the neck), and almost non-existant in others...but that's perhaps the nature of the beast. it's a strange pedal, for sure.

I suspect you may still have a problem.

To quote from the BYOC Scrambled Octave into bumpf -

In addition to being an extremely rare and expensive vintage effect, the Ampeg Scrambler is also an
extremely cool octave up fuzz. The actual fuzz itself is very unique. Like most octave fuzzes, it's a very rude,
nasty, ripping-velco sort of fuzz. But unlike most other octave fuzzes, it's not overly saturated or gated. It's
surprisingly open, articulate, and responsive to pick attack. And the actual octave up part of its sound is very
thick.

Which doesn't seem to be what you get with your build.

On the other hand although I could not find any You Tube demos of the BYOC Scrambled Octave there are quite a few of the Ampeg Scrambler and various clones and self builds. Listening to some of those may give you a better idea of how it should sound. I have to say I found some of the demos put my teeth on edge. This one is pretty good - http://www.youtube.com/watch?v=XfzP7ubrYlM&feature=related

I prefer the sound of my JOYO Voodoo Octave (post my fixing all its reversed electolytics) which is a clone of the fOXX Tone Machine as cloned by Fulltone in their Ultimate Octave. I use it followed by the BYOC Envelope Filter which takes a lot of the nasty edges off the sound. As already pointed out the cleanest octave sounds are achieved with a neck pickup with the tone rolled off.

Ouch!! just checked the price of the Fulltone - £154.40 ... glad I paid about £25 for the JOYO.

viewtopic.php?p=328655#p328655

Just to cross-reference the other thread... Gating problem solved by replacing silicon diodes with germanium diodes.

I use it mostly on bass, and the octave is quite subtle, and is slightly more pronounced in certain ranges. It is nothing like the over-the-top octave up that comes out of, say, a whammy pedal.

Good luck.

Oh that's cool, jruberto, I didn't realise you had got the germanium's into your pedal.

Having played around with some simulations of full wave rectifier circuits I realise that only very pure inputs i.e. sine waves, will produce the maximum octave effect. If you drive a full wave rectifier with clipped waveforms the octave effect is diminished. A equal ratio square wave isn't turned into an equal ratio squarewave at twice the frequency, but into a waveform of short spikes that last as long as double the rise and fall times of the squarewave. An input with any kind of asymmetric distortion tends to come out of the octave circuit as something close to what went in.

I don't know why BYOC ship the 1N456 diodes with this kit (silicon fast switching diodes). I suppose they are what was used in the original Ampeg Scrambler.

Another thing to try in these octave rectifier circuits is schottky diodes like the 1N5819. These can have a lower forward voltage drop than even germanium.

Yes, I finally got around to doing it this morning after the parts sat on my bench for a few weeks. The silicon diodes that I took out out measured about a 1.2v forward voltage drop, and the 1N34A's that I got tested at a 0.44v drop. No noticeable gating when I let bass notes ring out until totally gone. Very nice. Thanks for the suggestion!

ghetto3jon, if you are still hatin' the gatin', do give this a try.

That is very interesting, I'll have to try this pedal with my Zon bass; it has the lightwave optical pickup system which produces beautiful clean sine waves, I'll see if the octave effect is more pronounced.

A Zon bass with lightwave pickups!! Very nice.

However I'm not sure how much that will help. The Scrambled Octave has that single BC169 gain stage in front of the four diode rectifier which could produce enough gain to go into clipping much of the time. So no matter how clean the instrument input is the octave up rectifier still gets fed with a clipped and quite possibly asymmetric signal. The only thing you can do to clean it up is roll down the instrument volume control.

For a clean (well cleaner) octave up rectified effect you need something like the Dan Armstrong Green Ringer. Which BYOC provide as one half of the Armstrong Twin kit, partnered with an Orange Squeezer compressor.

Ahh I understand.

Yes, I notice the beautiful clean waveforms when i'm recording & editing, also when using my Strobostomp tuner.. No other instrument I have produces such rock solid readings on that tuner.

Gigged with the Scrambler last night -- I think I now notice a small volume drop that wasn't there before when I engage the pedal? Am I imagining things or could this be a result of this mod? Thanks again for all the info & help.

No I don't think changing to germanium diodes would affect the level through the pedal. Although it isn't easy to work out exactly what the gain structure through this pedal is.

On the input you have three 1M resistors effectively in parallel resulting in an input impedance of 333K. This might produce some noticeable loading on passive instruments.

The input signal passes through an emitter follower, so no gain there. Then the clean signal goes direct to a blend control and out, so with the blend all the way over to clean you should get no gain change through the pedal (apart from the previously mention possibility of loading). Is that what you get, or do you hear a drop even when the Blend is hard over to clean?

You have it right -- no gain drop if the blend is fully off, just a straight, clean passthru indistinguishable from bypass. Good to know that it isn't a result of loading. I need to do more testing with the pedal by itself & try a few different inputs. Might be interesting to run a tone generator through it.

I have now run some SPICE simulations of that circuit to try and see what is going on.

The transistor Q2 combined with all the diodes operates as a symmetrical clipping stage (when the texture control is set equal to R8 at 8.2K).

Running into a high impedance the 50K blend control operates as simple resistive mixer, so as far as I can see if the signal on both ends is same then the signal in the middle should sum to unity. It seems like what is happening is that the signal on the octave side is a bit low. You can boost this by increasing R14 - changing it to 2.2K will a bit more than double the octave signal, so you would probably only want to increase it to maybe 1.5K.

However this is a bit odd because my simulation shows you should have a strong signal at the collector of Q4 - about 4 times the input for 100mV pk to pk input.

I think I want to put a pot on this.