Guitar Pickup switching system (using microcontroller)

[bucks bunny]

free download of a compendium worth reading (German language)

www.gitarrenphysik.de © Manfred Zollner
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Willkommen bei meiner Website "Physik der Elektrogitarre". Hier
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[bucks bunny]

What are these HC 132A PHUY and HC 14A PXTU?

CMOS gates 74HC132A and 74HC14A - but hey - this will not help you in any way.
I would not even try to reverse-engineer this piece of electronics - no way.
Meanwhile I had a glance at the link above and discovered it is a selection of videos, to be viewed online.
I keep the original full text pdf from 2009 that has disappeared completly from the internet including wayback machine.

 

[gamerock]

Thanks! I will definitely do a reading these weekend. I hope Google translator is good for German to English 🙂

I would not even try to reverse-engineer this piece of electronics - no way.

I agree, reverse engineering doesn't make sense here. Rather, I was curious to get some hints from the circuit to at least find a direction to go. E.g., the pickup connection and transistors attached to it may very well give a hint to someone who understands these things a little bit better, than me. If Music Man guys did buffer the pickups, then it means they went the road of "emulating" wiring. If not, then they do real high-impedance connection. Which means, they most probably don't use the matrices and switches.
Stupid question: does a connection of two pickups in series via the transistor makes similar sense as just two pickups in series without it? I am trying to understand, whether anything apart from a "wire" makes a genuine connection between two pickups, so they act as a "single" coil.

 

[bucks bunny]

I did not see series wiring of p.u.s, anywhere and I was never intrigued to test this.
Because I would expect problems with additional hum in this configuration.
And I am pedantic in keeping hum and noise as low as possible.

 

[b_force]

I want to raise a topic of a Guitar pickup system, where it is possible to connect them in any possible way (parallel, series, out of phase) with the help of a microcontroller onboard.

I am a little confused why you need to use a whole ucontroller system for this with analog switches?

I have a very similar system on one of my guitars and all is done with just a simple multi pole switch and an additional one for phase.
If you work out the possibilities, you quickly discover that there aren't that many useful options.

I also agree with some comments before, out of all those options, there are only a few very usable soundwise.
It very quickly ends up in choice paralysis instead of making music.

 

[b_force]

Btw, I did not mention all issues with CMOS switches/mulitplexers:
They distort signals that come close to voltage supply rails.
They are prone to catastrophic failure due to latch-up.
There are better alternatives nowadays.

TI has a decent paper on getting rid of distortion from analog switches by putting them into the feedback path of a opamp.
Since we have buffers here anyway, that could be a nice solution.

I still think it's a bit over the top here

 

[bucks bunny]

TI has a decent paper on getting rid of distortion from analog switches by putting them into the feedback path of a opamp.

That is the way my cirfcuit proposal works.

 

[bucks bunny]

free downloadable pdf, German language
http://www.guitar-letter.de/Free/Download/GuitarLetter02v012.pdf

 

[gamerock]

I also agree with some comments before, out of all those options, there are only a few very usable soundwise.
It very quickly ends up in choice paralysis instead of making music.

While this may be true, a possibility to re-wire the p.u.p-s in any possible way with just few clicks of the mouse sound very appealing. You can switch between different configurations and hear yourself what is the different, which sound is useful and which is not.

I have a very similar system on one of my guitars and all is done with just a simple multi pole switch and an additional one for phase.

I suppose that system has ~10 possible wirings, correct? So the ones you found useful for yourself.

It very quickly ends up in choice paralysis instead of making music.

I still want to emphasize, that the biggest joy from this project is its accomplishment, and smaller part of that joy is to try and use it in music afterwards.

 

[bucks bunny]

I still want to emphasize, that the biggest joy from this project is its accomplishment, and smaller part of that joy is to try and use it in music afterwards.

I went this road some decades ago. Milled caves into the body of my 1972 stratocaster for additional circuitry.
And tested everything that came into mind.
That was fun and I learned a lot about the physics of oscillating strings, magnetic and pieco p.u., wiring etc.

 

[gamerock]

I went this road some decades ago. Milled caves into the body of my 1972 stratocaster for additional circuitry.

Yeah, I saw a lot of guitar projects with dozens of switches and "kilometers" of wire inside, for all the possible options as well. But the most intriguing part for me, is to understand, whether it is possible to achieve the same with controlling everything digitally. I first had a feeling a matrix will do most of the job here, as one matrix will replace number of real circuits you would build trying to achieve the same in a conventional way. However, the more I read their specs, the more I understand they are not good for High Impedance environment and even maybe for that project at all. The inside circuit of the IC is built on transistors. And two coils connected together, are not the same as two of them connected together via the transistor legs, I believe. I don't want to put the verdict "impossible", as Music Man did it somehow, however, it looks to be trickier, than seemed originally.

 

[b_force]

I suppose that system has ~10 possible wirings, correct? So the ones you found useful for yourself.

I think a bit more even, I have to check again, I don't play that guitar much anymore.

Maybe I have the schematics somewhere, but I really have to search.

In this case it's a two humbucker system, with some split coil and phase change possibilities, as well as series/parallel etc etc.

 

[gamerock]

I think if I am able to find a cross-point switch array with really ultra low R-on, I will be able to deal without the need of the buffers. The one which was proposed in my original post has quite a big R-on ~35 Ohm. I saw some switch multiplexers with 0.X ohm R-on, which is good, but it means, that I still have to form a matrix from them. The only Matrix I was able to find with really low R-on has the inputs buffered, which again spoils everything, as it brings me the same problem as if the p.u.p-s were buffered.

 

[bucks bunny]

I will be able to deal without the need of the buffers.

I do not think so. But it is your project.
Learning by doing...