So let's say I want to boost all the harmonics...

[smashinator]

I've been kicking around the idea of trying to design my own microsynth sort of pedal.  I'm thinking what I want to do is send in a signal (from a guitar), and have some kind of circuit in place that will boost all the frequencies so they're at the same amplitude (is that the right use of the word?), which I can then apply various filters to shape the sound.

How could I do that?  Should I just boost the hell out of the entire signal, and then compress it WAY down again?  Any thoughts?

[toneman]

there's an infinite number of frequencies.
So U would need an infinite number of bandpass filters.
And a recitfier on the output of each to give U a voltage
proportional to the amplitude of each frequency.
How big did U want this pedal 2 B???
Maybe the size of a Buick???
Or, to "simplify", count the number of frets on your guitar
and make a parametric EQ for each.
Now U R down to the size of a Jetta.

tb

[Mark Hammer]

Well, you sure as hell aren't going to do it with a bunch of diode clippers.

Even analog synths where there is far more fine control over harmonics have a difficult time generating the spectrum of harmonics you dream about.  generally, they work from predefined waveforms that have a given distribution of harmonics (e.g., lotsa 3, 4, 7, a smidgen of 2, 5, and 8, etc.) and subtract from there via filters.  FM synths like the venerable DX7 will throw predefined waveforms up against each other in a "modulation clash" to produce harmonic content, and many hybrid sampling synths will use stitched or entire samples as sources of harmonic content and subtract from there too.   The only device I have ever seen that does what you describe is something like the old Fairlights, where you could design a waveform by using a lightpen to "draw" the amplitude of individual harmonics across the audible spectrum and shape their levels over time.  That's bloody time consuming, though.

The other question is whether, given the limited range of the guitar as a signal source, you even need the kind of capacity you describe.  If I'm working with oscillators and a keyboard that permit me to generate fundamentals that challenge subwoofers, having creative control over the 10th partial makes sense.  It doesn't make sense when most of the notes I play will have fundamentals whose 5th harmonic is pretty much out of the range of what my amp and speakers can reproduce.

So, not to rain on your parade, but you may well be after the sort of harmonic control that, in realistic terms, serves no practical purpose, whether you can achieve it or not.

Having said all of that, the idea of being able to tackle individual harmonics and shape them over time is not unreasonable at all, though it likely WILL require either a mono signal or divided/hex pickup so that processing is done at a notewise level.

It's gonna be a whole lotta work, though.  May just be better for now to experiment with fuzzes and filters.

[smashinator]

After re-reading what I wrote, I realized I was asking too much.   :shock: What I really want is just to be able create resonance and cutoff filters.  
Chalk it up to posting before waking up all the way.

What's important to me is that it sound more like a synth than, say, a wah.

[puretube]

I guess some hard clipping square-wave generation with lots of sustain (beforehand) will suffice for a starting "lotsofharmonix" source...

followed by some statevariable filter...

[Mark Hammer]

Thanks for your humility, Smash, and the revised question.

Anderton's Ultra-Fuzz, which uses a comparator to produce square waves or varying duty cycle, is a great start.  Once you have a square wave, you can then use Tim Escobedo's adaptation of Bobby Beausoleil's Square-wave Shaper that appeared in Polyphony.  Congratulations, you now have a square and triangle/ramp wave source to filter, whether one at a time or in parallel.

The only constraint is that the Ultra-Fuzz is mono, meaning that it only handles a single note at a time.  If you are industrious, though, snag yourself a hex pickup (e.g., by buying a G-Vox on e-bay) and feed each string's output to it's own Ultra-Fuzz for fully polyphonic alternate waveforms to tinker with.

[StephenGiles]

Front end of EH Guitar Synth perhaps??
Stephen

[RDV]

Bobby Beausoleil? "Now that's some quality H2O!"  :lol:

Sorry, couldn't help myself. Sleep depravation.

RDV

[DDD]

I could not understand the final purpose of the "device", but maybe MXR BLUE BOX is to be a part of what you want? (Please read opinions on the Blue Box at Harmony Central).