Author Topic: Extending the soundscape of a hexaphonic guitar pickup  (Read 4268 times)

Offline sorveltaja

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Extending the soundscape of a hexaphonic guitar pickup
« on: March 23, 2020, 08:24:37 PM »
So this is going to be an attempt to make sense, of what kind of simple circuits could be used with analog hexaphonic guitar pickup.
I felt that it isn't fair to clog the optical pickup thread with this subject, so here we are.

But to the point. To get started, I'm aiming for outputs, that have more harmonics in them, than the plain square waves, that the pickups produce(there are clips on the optical pickup -thread).

Here is the first circuit, that I have already simulated, and tested on breadboard:



That waveform isn't in sawtooth form, that I was after earlier, as it was used on many analog synthesisers. It sounds like this(saved from the simulator, but the breadboarded circuit sounds practically same):

http://www.elisanet.fi/kz1706/optical_pup/4040_testi.mp3

It has one drawback in it, though. The fundamental frequency of the output is input divided by 8(In this case the input frequency was 1000Hz, and output was 125Hz).
There was only one thing, that I could think of, to multiply the input by 8, to get the input and output frequencies to match - 4046 pll(phase locked loop).

As the form of the input is square wave, it wasn't problem. That 4046(standard version) requires input to be close to the supply voltage, which was 9 volts.
The amplifying circuits of the optical pickups provide enough output, so that the 4046 is able to track the input signal.

I'm not too good on drawing schematics, but here is the circuit, as it was breadboarded(10k resistors on the right present resistor network):



In practice, it seems to work.

Then, after some searching on the net about "staircase generator", I found something like this, kind of "sampler" that is based on 4051(8-channel multiplexer):



It sounds like this:

http://www.elisanet.fi/kz1706/optical_pup/4051_testi.mp3

For some reason, it also has fundamental output frequency, that is divided by 8. The 10k resistor network might not be necessary, but the point is, that the resistors on the 4051's outputs could be replaced with trimmer pots, to adjust the combined output to make arbitrary waveforms.

I haven't breadboaded that yet, but what the heck, there is only one way to find out.



 

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #1 on: March 24, 2020, 05:59:41 PM »
The 4051-based idea of arbitrary waveform 'generator' is now tested on the breadboard, and it works. The circuit:



And same on the breadboard:



The stepped output waveform is easily modified with trimpots. As there are 8 outputs, there are also 8 adjustable steps in the wave. Triangle-ish one:



And same after filtering:



One thing, that I noticed, when looking the combined waveforms on the scope, is that it couldn't track them too well. All kinds of wiggling happened. Maybe the produced waveforms are more complex, than they look.

But on the other hand, I think I'm going to build(at least) two or three of those 4051-based contraptions. Perhaps some with fixed waveforms. For the adjustable ones, some kind of futuristic, retro indicators would be nice to have, to visualise the form of the wave without the need of using scope. Something like 8x8 Led matrix comes to mind. But we'll see.

As mentioned before, that circuit also divides the input frequency by 8, and therefore needs 4046 and 4017 before it, to multiply the input frequency first by 8.



Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #2 on: March 25, 2020, 11:17:32 PM »
So now I'm hooked into testing/making a visual waveform indicator for that 4051-based generator. As usual, the simpler it is, the better it is.

One possible candidate is something like this:



I already have the two 3914's(actually from an ancient led-oscilloscope project) and 4017's on my shelf. Plenty of leds also(from the same scope project).

I tried to simulate the above circuit, but the results were very quirky and useless. That's why I'm not a big fan of simulations. Certain rules must be obeyed, or the result is garbage.
So not much of  'diy circuit bending' allowed.

Usually at that point I move straight on to breadboarding, but this time both boards are occupied by other circuits, that are still under testing. Jolly good.

But no matter what, I'm going to test that circuit above, to see if it's clumsy or useful in practice.

In fact, even if there are several of those 4051-based devices, only one "plugin"- 'display unit' is actually required. After all, they need visual indicator only, when adjusting the waveform. Multiple, permanent displays would be a lot nicer, though.

In the end, a spin-off of the recent brain hickup was to make a steampunk-like, victorian style, mechanical indicators for each of the trimpots, that are used to adjust the waveform.
All the gears and stuff.. some of them could be rather easily printed out... and the end result would be - bulky.

And other than that, I had an idea of using the pickup's outputs to control some kind of mechanical devices. Sort of like Mellotron(https://en.wikipedia.org/wiki/Mellotron), that has a tape loop for each keys of the keyboard. Very heavy yes, and the tape technology is getting rare these days.

Instead, for more precise(like industrial) response, stepper motors could be used to rattle whatever objects, or what the heck, even plain cheapo small electric motors for more "organic" sound.


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #3 on: March 27, 2020, 11:03:34 PM »
Led matrix isn't easy to breadboard, so I decided to build one, for 10x8 leds. Last two rows will be added tomorrow, and rest of the wiring:



So far, all the rows seem to work, as expected. Needless to say, that it's rather tedious to build things like that. Local suppliers have a very limited selections of the led displays, so one should see what's available on Ebay. But for now, I'll skip that option.

On the other hand, what could be better, than recycling components, that have gathered dust for years on the shelf?

What comes to that 10x8 led matrix, if the idea, that I'm after, works, it could be used as a single display for something, like three 4051-based generators. Not really multitasking, but for one generator at a time, when checking/adjusting the waveform.

While scavenging leds from the old led-oscilloscope project(it had 16x10 leds), I got an idea, that the 8-step waveform generator could be extended to have 16 steps for finer adjustment. Probably not worth doubling the parts count, as it could still sound the same as 8-step one does.

After all, using simple filter(s) to alter the stepped waveforms could be easier to deal with.

   

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #4 on: March 28, 2020, 09:10:03 PM »
So the led matrix is built, and the circuit is breadboarded:



The led "display" shows different waveforms, but not exactly in a way, that I was after.

As on the oscilloscope, there should be a trigger function, which keeps the waveform from wandering back and forth. It is possible to do, by adjusting the 4017's frequency, but the "triggering" depends also on 3914's input signals frequency.

One might wonder, why I'm so eager to add a visual indicator for that 4051(8-channel multiplexer)-based waveform generator. It's simply because I just love all the bells and whistles it could be a lot easier to remember, what kind of set of adjustments sounds good or bad.

Like a connection between aural and visual 'image'. For example, a guitarist, that uses one or more effect pedals, has an image in his mind, of what his favourite sound 'looks' on those pedals in a form of settings.

Currently, the 4051-based circuit is on the breadboard, and has 10k multiturn trimpot for each channel. Dirt simple option could be to use slide potentiometers instead, for a good visual reference.

Although the slide pots tend to be quite pricey(at least the decent ones), I consider that as a plan b, if that led display-based idea fails.


 


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #5 on: March 29, 2020, 09:47:55 PM »
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.


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #6 on: March 30, 2020, 07:19:05 PM »
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).



Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #7 on: March 31, 2020, 08:17:30 PM »
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.

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #8 on: April 01, 2020, 06:51:36 PM »
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.

 

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #9 on: April 03, 2020, 09:07:47 PM »
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




Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #10 on: April 05, 2020, 07:35:46 PM »
Current circuitry had one stubborn bug in it, but finally I managed to stomp it out without using bug spray

Circuit with correction in red:



Now it works, as it should. 1M pot on the right side will probably replace the 100k resistor, to make 4046's tracking speed adjustable. That together with 100n capacitor(can be anything from say, 10n to 10uF) provides the "timing" for it.

As mentioned before, 4046 has plenty of options, of how to make it sound/behave. In the past, I once found(accidentally) a combination for 'portamento' -like effect.
Back then, I used guitar with standard monophonic electromagnetic pickup, as a signal input. In certain frequency range, it sounded like a Theremin(https://en.wikipedia.org/wiki/Theremin), that 'slides' between notes.
Outside of that range it just went nuts, and sounded like farting bagpipe. If memory serves, I recorded that. Not sure if it still exist on the hard drive, though.

But yes, I'm eagerly waiting for the ordered linear slide pots to arrive, to make an enclosure for them, with that circuitry, to get them in more usable form.

I have almost finished a simple mixer also(project 18 from the earlier mentioned Craig Anderton's book ), which currently has only three channels(I ran out of several components), but should be enough for starters.

Originally it had 4739 dual op-amp, but luckily there is an updated version of that pcb(and some other projects too), that uses 5532 dual op-amp instead: http://www.generalguitargadgets.com/effects-projects/extras/epfm-book/

While scavenging 10k pots from the abandoned projects, I found almost intact adsr-device. I wondered, why the heck have I built that for. In short, adsr stands for attack-decay-sustain-release.
Mostly used with sequencers, and other rhythm-based things(as far as I know).

After some searching on the net, it seems to be a part of many analog synth setups. When looking the pcb with magnifying glass, there it was: Yusynth adsr: http://www.yusynth.net/Modular/EN/ADSR/index_new.html

I'm not sure, if it's usable with all the other recently built stuff, but we'll see.

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #11 on: April 07, 2020, 07:01:47 PM »
Not much of a progress, as I'm still waiting for those linear pots. In the meantime, the mixer now has an enclosure:



For now, I'll probably use two 9V batteries to power it, to keep amount of running wires as low as possible, as it needs bipolar supply.

After I manage to make few more devices to form a 'basic' effect setup, then it could be sensible to gather them in one single, larger 'panel', where connections between devices could be made by using patch cables. A bit like an oversimplified version of this(https://synthesizers.com):



I have one of those 80's cassette player enclosures ready for that. As can be seen, it was once used for a project, that never happened:



Another one is this stereo graphic equaliser, which should still be in working order:



It could have its uses, as a part of the effects board, as it is now. But if not, again one enclosure more, to use for something like a vocoder. After all, it has been gathering dust for last 15 or so years.

So the overall possible scenario might look rather ambitious, but I don't care too much about that. One step ahead, at a time, and sometimes(in my case often) two steps back.


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #12 on: April 09, 2020, 07:16:37 PM »
Circuitry with linear slide pots:



It has a skeleton 'enclosure', as I'm not yet sure about possible additions. 1M pot on the left is for 4046's tracking speed, but it needs one of the timing capacitors to be  "variable" also. It needs to be tested, which cap values are most usable, though. Then rotary switch to select between them.

This current circuitry's output should be made ready to be fed to more than one devices, like mixer, filters, or echo/delay simultaneously. So It might need a buffer/splitter for its output. There is a project 26, 'Spluffer' in the Craig Anderton's book, which does exactly that. 

Once I get the mixer together, then could be a time for a bit of break in building, and trying to figure out, how the hex pickup setup works/sounds with this circuitry, that is monophonic after all, meaning, that it should handle single notes(like on single string) just fine, in the range of 80-300Hz, with current 4046 configuration.

So it should be good to use with thickest string(e) output to accompany other strings. But we'll see, how that turns out in practice, as there are already many(so far uncertain) factors involved.




Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #13 on: April 10, 2020, 05:36:12 PM »
Today, when testing the mixer, using function generator and a scope, I found it to be mesmerising to watch the waveform to morph from one shape to other, as I turned the mixer's knobs.
Yes, I'm easily amused by things like that.

But anyways, there were only two waveforms to play with, and I haven't even yet listened, how they sound, when mixed together. Should be hours/days/weeks of fun. Especially, when third waveform/source, or filter is added to the mix.

All the stuff are almost ready for aural testings. If(when) that works out as expected, then it's time for replacing the tiny, battery powered audio amp with some kind of headphone setup, to hear the nuances better.


Offline AdeV

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #14 on: April 10, 2020, 05:53:06 PM »
I have to say - this is a fascinating project, even if I haven't got a clue what most of what you're doing is...! Lots of good circuity stuff though :)

A question - what software did you use to produce that circuit layout? I've used kicad for all my recent attempts at circuit board making, but I think that it's more suitable for producing layouts for commercial operations, given the default track width is, if I recall correctly, just 0.25mm wide... which looks great on the design, and usually vanishes when I try to etch it!

Also, have you heard of Martin Molin's (Wintergatan) "Marble Machine MMX"? It's nothing like your project, but is similar insofar as being a musician building an engineering device - in this case, a musical instrument played by dropping marbles... it's quite the adventure (I suggest starting with some of the early videos, then maybe jumping ahead a bit, as there's around 120 mostly weekly updates by now!) Here's a link to the full playlist: MMX playlist
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #15 on: April 10, 2020, 07:34:13 PM »
Ade, thanks for the heads up.

I'm using Rhinoceros to draw the pcb layouts. Tracks can have any width, but I've used mostly the "beefy" 1,8mm ones, as they seem to transfer rather well. Sometimes, if some pcb has very thin traces, I just re-draw it to have thicker ones.

I guess all that could be done with something like 2d-vector software perhaps? I wish I could recommend something, but as I've used Rhino for pretty much everything, from 3d-modeling to 2d-stuff for years, I haven't looked for the alternatives. Ideas anyone?

I haven't heard of Martin Molin before, but will check it out. Thanks for the link :beer:.
« Last Edit: April 10, 2020, 08:42:15 PM by sorveltaja »

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #16 on: April 11, 2020, 10:10:14 PM »
I was going to test the hex pickup today, with the step waveform generator. I had completely forgotten, that it has a very quirky power connector, that needed to be wanked around to make a contact.
Like wallwart ones, that has a center hole in the plug. Both the plug, and socket are brand new, so perhaps they are of different size.

But yeah, that bugger ended the testing session effectively. Instead of feeling like flattened pancake, I'll get armed with the trusty stomping shoes.

I'm thinking of ordering mono jack -type connectors instead. Also the whole power supply scenario needs to be replaced with something more 'universal', or 'centered', having several regulated 5 and 9 volt outputs, and (possibly variable)split power supply outputs for 15-18 volts too.

Hmm. So many plugs and sockets, and wires. Maybe it would be a better idea to gather all, so far built circuitry, including power supplies, in a one larger box, that was mentioned earlier.
So that will be the subject of the next sub-project.

Other than that, I've been trying to find an article, that is about building 8-channel vocoder. I used to have copy of that article in printed form, but can't find it anymore. If memory serves, it was originally in Keyboard magazine. Even online search didn't give any usable results, although when I get to the mood for searching something, if it exist online, I tend to find it.

Anyways, I built that vocoder in the past, using perfboard. Apparently it didn't survive, having wildly running wires around, and all that stuff. But it was good fun to play with.

I'll have to admit, that having a vocoder is an obsession for me, as it could be used in so many more ways, than just 'talking' instrument. For those interested, Kraftwerk is one of the first/most well-known groups, that used variations of it to make the "robot" voices. It was used also by Walter/Wendy Carlos in movie Clockwork Orange's soundtrack. Cylons from Battlestar Galactica, and so on.

Fortunately, there are other versions to build. Possible candidates are the Elektor, Okita, and Mfos(music from outer space) ones.

Besides all that, easy shortcut could be to buy one of the digital ones, that have reasonable price tag, but in my case, no way Jose. There just isn't easy ways to modify/abuse that kind of devices.

 

   


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #17 on: April 12, 2020, 06:16:35 PM »
The 8-channel vocoder, that I mentioned earlier, I found stuff about it on my hard drive. What makes it better, is that it's so much simpler, than any other ones that I've checked so far.

I'm going to draw the pcb using this image, as I haven't found any better images of it:



Length of that pcb is about 430mm. Too big for me to make, so I'll divide it to 3 or 4 parts.


 

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #18 on: April 13, 2020, 06:49:24 PM »
The vocoder pcb almost redrawn:



It has some tight spots, that needs to be taken care of, though.

I'm redrawing the component designators also, as the image is too blurred to be (possibly)transferred to the component side of the pcb(haven't done that before, but well see):



As can be seen, it's Paia Vocoder. Originally it was published as a project in Keyboard Magazine by Craig Anderton, in the 80's.

There doesn't seem to be too much info about it on the net, as many of the builders seem to look for fancier, 12, 14, 18, or even 24 channel ones.
I have a feeling, that this humble, 8-channel one is overlooked. One reason for that could be, that the actual kit on the Paia website is out of stock.

But on to the pcb itself. As mentioned before, it will be divided to 3, 4 or 5 parts, and probably stacked together, to make it a whole lot narrower.

Of course there is one major factor, of how to verify, that the redrawn pcb actually works, as it should? I'll be doing some checkings/comparisons with component designators, and what not, before dividing it into smaller parts.

It uses 5 x 4136, and 1 x 301 -op-amps, which are fortunately available from my local supplier. It also uses 4 x 570 or 571 compander chips, that I already have in my shelf. Rest of the parts are resistors, pots, caps, switches, and connectors.

It requires bipolar -15/+15V supply, which takes us back to the previously mentioned need to make a more 'universal' power supply.

After all, I have to remind myself(all the time) to take only one step at a time.

 

 

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #19 on: April 14, 2020, 05:48:44 PM »
Divided vocoder pcb:



I decided to use 75 x 100mm pcb's as they are already available in that size. Cutting the pcb is something, that I've never managed to do properly.

On the other hand, I have only used 1,6mm boards, and have scored them to get cleaner results, but they seem to be too thick for that, and the edges tear. Maybe 0,8mm ones, which I'm going to order next, are more suitable for the 'score and snap'.

While reading through the vocoder's assembly and user manual, there is a mention about "clarifying mod". It uses 4 x 084 op-amps, and some resistors, so I'll order parts for that too.






 

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #20 on: April 16, 2020, 06:40:10 PM »
While waiting for the ordered parts, I made a 15V split power supply pcb: http://musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/wallwartbtmcopper.gif

It needs an ac wall wart to power it. I have only one, that is for 12V. I was ready to order 15V one, but then thought: hold on, doesn't dc wall warts have already an ac output in them, that is rectified by using diodes to make dc voltage?

So I had to look, what I have in my boxes of 'stuff'. Surprisingly, there was 15V/500mA dc adapter, that didn't seem to belong to any device, that I use. I managed to open its enclosure, and took some measurements with multimeter. Yep, it could perhaps be used for the purpose.

Only two wires needed for straight ac output. Actually I'm going to use its dc wires for that, as they have a nice strain relief clamp already. No extra wires or holes needed.

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But there is one very serious precaution, though: to do something like that, one must be extra careful, as there is live 220V(in Europe) involved, when that adapter is connected to mains.

Disclaimer: If in any doubt, don't do it. If one still insist doing it, that one takes full responsibility, of what he's doing.

Only once I've had 220V shock, and yes, it was indeed very nasty, so I'll do my best to avoid messing with it.
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But enough of that. The 15V split psu will be a 'master' one, that feeds lower ones(like devices, that have 9V regulator in them). But we'll see, what comes out.

When looking inside of that previously mentioned ex-tape recorder enclosure, there was dust and a phase shifter:



I doubt, if it's still in working order, after two decades, due to corrosion of the pcb traces. As can be seen, two ic's are configured to substitute original op-amps(super-rare 4739's). White blocks are diy optoisolators(led/ldr), to replace original Clairex CLM6000's(that were probably never available outside US, but what do I know).

Quite a mess, that is worth only for looting socketed ic's, pots and switches.

I'm considering of rebuilding that, but what comes to optoisolators, they need some fiddling(when using ordinary leds and ldr's) to get them to the 'working range'.
Or just re-use the components inside white blocks, and look, what kind of mods I did use back then, to get them to work.

Offline Sea.dog

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #21 on: April 17, 2020, 02:31:25 AM »

Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #22 on: April 17, 2020, 07:15:14 PM »
Seadog, yes quite a price for single led/ldr -pair. One way, at a fraction of the cost, is to make ones using a heat shrinking tube.

If memory serves, it wasn't that difficult to get ordinary led/ldr pairs to work, as required in that phase shifter. In schematic, there is a 470k resistor in parallel with ldr, and 200 ohms current limiting one in series with led. The circuit itself:



Playing with those two resistor values should do the trick. Nowadays the leds are much more brighter(and/or efficient?), so they need to be tamed down, to fit for the rest of the circuitry.
Ldr's responses (could) vary between maker/model, so some tinkering with them also, I guess.

More about that, when I get to building the actual device.

Ordered parts came today, so I managed to finish the 15V split power supply circuitry. I also did the previously mentioned ac-mod for the 15V dc wall wart.
I'll have to admit, that I got a bit nervous, when testing those out. I had already a box of fuses, and some other measures of precaution, just in case, that something goes horribly wrong.

But it went well, and they work nicely together. Fortunately there are very rare occasions, where I have to do projects like that.

Next thing to do is either:

- print an enclosure for that split power supply(not sure yet of its final assembly, though)
- build that phase shifter
- build the vocoder
- drink few more beers

Somehow I have again this familiar feeling, that I'll have to start with the most complex one, that is vocoder(well maybe not that complex, but considering its parts count).

Yep, vocoder it'll be.

In the end, I think I should provide some audio clips every now and then, considering so far built devices/circuitry. But easily accessible/usable audio recording interface is still missing.
I'm thinking something like a usb-based ones. But we'll see.


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #23 on: April 18, 2020, 06:49:05 PM »
The pcb for the vocoder needs thorough cross-checking, using the schematic(down-sized to fit for the page):



Luckily most of it is repeated 'blocks', like op-amp and compander sections in the middle. Only the component values vary between them. But still, tedious task to do, so I'm expecting to take a break of it at some point, and do something else, like building the phase shifter.

What comes to the previously mentioned audio recording interface, there seems to be a lot of those usb-based soundcards.

Without knowing too much about them, something like Behringer U-Phoria UMC22 could do the job for 39 euros, but it's currently out of stock on local supplier:


Offline sorveltaja

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Re: Extending the soundscape of a hexaphonic guitar pickup
« Reply #24 on: April 19, 2020, 08:38:47 PM »
Cross-checking that vocoder pcb is indeed very slow thing to do. I had to restart from the beginning a few times, to find better ways to approach it, and perhaps learn something in the way.
So far I've found several missing traces, and errors, when compared to previously drawed one, using that blurry image.

But after all, no matter how long it takes, I guess it could be worth the effort. If not, there are always plenty of other vocoders to choose from.

In the meantime, I have also had some ideas, like making the filter sections 'variable', using headers for their capacitors. Originally the cap values are for 200, 400, 600, 950, 1300, 2200, 3000, and 4900 Hz. But we'll see, once I get there.