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Extending the soundscape of a hexaphonic guitar pickup
sorveltaja:
Well, I did tinker with that led display, and it was hours of fun, but to make it usable.. too much of a hassle.
Now it's time to get back to actual sound making circuits. Next thing is going to be to test, how these can be used, instead of 10k trimpots(to adjust 4051's output levels to form the waves):
They are 45mm ones from Velleman's graphic equaliser kit, that I once built, but never used.
Circuitry for a single 4051-based generator will (most probably)include:
- 4046 pll and 4017, to multiply the input frequency first by 8, so the input and output frequencies are the same
- 4040 to make the 4051 to do the 'multiplexing'
- buffer for the combined waveform output(not sure about that yet)
So I'll stick with that composition for now.
sorveltaja:
Test setup with slide pots:
Although the pots are logarithmic(audio), they already feel a lot more natural, when adjusting the waveform. Almost like kind of an audio mixer. But instead, they adjust steps of the waveform. If it was an audio mixer, log pots should be perfect for it.
But is it(an audio mixer), as its output is audible, but the signal is made of dc voltage? Beats me, as there are plenty of different elements in project like this, of which I can't make any sense at all.
So after all, linear slide pots would be a better option for a visual reference of the waveform, and I'll probably order some in the future.
It's been a while, since I tested how the built(or breadboarded) circuitry actually sounds like, when using a guitar/hex pickup as a signal source. Basic external 'effect' circuits already sit on the breadboard, so it should be good to go.
All kinds of crazy ideas keep popping up, one of them is to control the 4051's stepped waveform with light, by using ldr's(light dependent resistors) instead of pots. Then whatever light source, and some simple rotating mechanical contraption, to create shadows for the ldr's to modulate the waveform, without added complex electronics, that is usually involved.
In the end, the amount of possible options is vast. All that is left, is to choose all one of them(at a time).
sorveltaja:
This time a bit about 4017-4046 -based frequency multiplier, like it's wired on the breadboard:
4017(decade counter) divides its input frequency by 2 to 10, depending of how it's wired. On the above pic it's wired to divide by 8.
Quite straightforward, when compared to 4046 (phase locked loop), that does the exact opposite - frequency multiplying, by the factor, that 4017 divides it. 4046's output frequency is then input * 8.
That output is then fed to 4051-based stepped waveform generator, and as it is 8-channel multiplexer, it's output frequency is divided by 8(took me a while to figure that out).
Anyways, that 4046 needs some 'tuning', to get it to work on a desired frequency range. It's easier to do that on higher frequencies, but under 100Hz it gets finicky.
On a guitar(using standard tuning), lowest frequency is about 82Hz(e).
It's not a problem to get the 4046 to track even lower frequencies, but, lower the needed minimum frequency, the narrower the range. There might well be more 'advanced' ways(meaning, that I should understand, what I'm reading) to expand the lower frequency ranges, but, again, simpler it is, the better.
After some fiddling, the above circuit now works from ~80 to ~300Hz, using 9V supply. That should be enough for the three thickest strings(e-a-d), if played on the 12th fret, or lower.
When adjusting, or 'tuning' the 4046, using first potentiometers, makes it a lot easier. But not so on capacitors, as the variable ones seem to be on the picofarad range only(as far as I know).
Then I got this idea of making sort of adjustable capacitor board, by using a rotary, or other switches for the range of 1 to 470 nanofarad. After all, it could make dialing between different values more sensible, instead of having dozens of capacitors, that need to be plugged in and out one by one.
Don't know yet, how to achieve that, though. Maybe it's good enough subject for the next sub-project.
sorveltaja:
Today I got an idea of using 4017(decade counter) as a simpler, single chip alternative to 4051-4040 based waveform generator, as its outputs are sequenced similar way.
It doesn't need a counter chip to do the sequencing, so I breadboarded it, and it worked... sort of. It made stepped waveforms, but when adjusting one step up, others moved around.
I guess its outputs needs to be buffered before they go to the potentiometers, or something like that. Overly simple idea wasn't so simple anymore.
Next I'll be drawing pcb for the 4017-4046 freq. multiplier, and 4051-4040, which so far seem to work, as expected. I ordered 60mm linear slide pots, and the plan is to stack the pcb under them.
There should be plenty of room for other possible circuits also, like filters and such, but we'll see.
To get back to that previously mentioned 'variable' capacitor board, I had this in my mind, where caps could be added one by one, in parallel(to add capacitance).
But naah, I can't figure out, how to do it that way. Then on to the net to see, what kind of devices are available. Decade resistor boxes, also some capacitor ones, but not really anything dirt and cheap enough for diy purposes.
Actually, just minutes ago, when writing this, this half-baked idea popped out of thin air:
So then I thought: hmm, why not use 45 caps instead of 9, to make steps from 0 to 90nf ?
Using the same pattern, first select hundreds, then tens, and then ones, if needed. Three 10-step rotary switches for that perhaps. Definitely not as pocket friendly, as the potentiometers are.
135 caps for the range from 1 to 999nf. Plus three rotary switches. Plus I have no clue, does it work in practice.
Price of the components shouldn't be too prohibitive, if the aim is to use that contraption for lo-fi audio, or other such things.
I have one old rotary switch somewhere, if memory serves. If I manage to find it, I'll do some testings with say, 6 cap sets, using probably other switches too.
sorveltaja:
Almost finished new board for frequency multiplier 4046-4017 and waveform generator 4040-4051:
I used headers for the parts, that adjust the capture range of the 4046, so they can be changed, if needed. Longer headers on the left are for slider pot connections(and also for future testings with something like ldr's).
Sometimes I wonder, why on cmos counter chips(like ones used here), the outputs are in awkward order. Should need hair-thin pcb traces to get them all to the same side in order, and even then, some of them cross each other.
On the other hand, that shouldn't be a problem, if one was able to make two-sided pcb's. I have some in my shelf, but haven't yet got that far, to start testing different methods/techniques.
Could very well be worth it, because I just hate using many jumper wires for a pcb, like above. Lots of room for stupid mistakes.
But otherwise, it's time to take a peek, what's on the to-do list.
- to make an audio mixer, that can handle wide variety of signals, and -levels.
- to make 4049(Hex Inverting Buffer) -based fuzz unit(s). Let's be honest, certain kind of distortion adds plenty of texture to the overall soundscape, if desired.
What I mean by certain kind of distortion is, that 4049-chip, when configured as a linear amplifier, clips the input signal gently, very much like tube amps do.
It must be one of the few of the logic chips, if not the only one, that can be (ab)used that way. As far as I know, one of the first ones to notice that, was Graig Anderton(author of still excellent book Electronic Projects For Musicians), back in the seventies.
So no wonder, that it's used in some of the commercial "tube sound" effect pedals.
- to add some kind of (possibly modulable/envelope) filters for the outputs
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