Gallery, Projects and General > Project Logs
Extending the soundscape of a hexaphonic guitar pickup
sorveltaja:
Finally, first ones ready for testing:
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I think I'll start with band pass filter(on the right side). With component values that it has, the 'peak' should be at ~4900hz.
Then the compander board, which, to my understanding, acts like a dual channel... something. As it is now configured, one channel's output level controls the other channels output/gain/level.
Still, there is something about it, that I can't get my head around. Maybe it's simpler than that. But we'll see, once I start testings tomorrow.
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Regular off-topic ramble:
This week, I've been mostly fiddling with the new guitar, to make the best out of it. All the most tedious things are almost done, of which worst was trying to mill the locking nut, that had convex surface at the bottom, when it should have been straight.
Even with carbide milling bit, it was just too much for my small, humble mill. (Obvious) conclusion was, that the part is hardened, or is made of some grade of stainless steel(which I doubt in this price range).
Anyways, quite a lot of material(~1mm) needed to be removed, and the only way I could think of, was to replace the carbide bit with a 20mm diamond wheel, and humiliate that tough part by taking tiny shaves at a time.
Hours later, major pain in the rump -stuff was done. But yeah, now the bottom of the locking nut is straight, and allows a lot easier way to adjust the height of it, by using shims.
It's a part of the Floyd Rose tremolo system, which, when properly adjusted, keeps the instrument in tune, no matter how much string bending, or whammy bar is used.
That's one of the main reasons, why I have wanted a decent guitar with that kind of hardware for years.
sorveltaja:
Testing of the first boards was rather quick. Band pass filter has its peak at ~5000Hz, which I found out just by dialing the signal generator's frequency, until max.voltage was reached.
I used a scope to see the results, although same might be done using a multimeter.
Compander was tested by feeding sine wave to both inputs, of which one is for microphone, and other is for instrument(keyboard/guitar/synth, you name it).
When trying to clarify/simplify(at least for myself) of how the vocoder actually works, it's actually quite simple principle: microphone signal controls the instruments signal.
Both inputs have identical band pass filter -sections.
In practice, let's take a keyboard, that plays a sustained chord, which is then fed to the instrument input. Then some words/singing in the microphone input.
When the vocalist says 'boo', or 'ess' in the mic, that signal goes through the band pass filters, and tells the instrument side to let through only the very same frequencies of that keyboard chord.
But enough of that. After some etching and drilling, rest of the boards are on the making. Compander boards are already populated, but again, I had to cram some components in, due to making the layouts/boards as small as a stamp :
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Band pass filter boards ready for the parts. I managed to salvage all the needed components from the previously built boards:
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If and when all the 'blocks' are built, tested and working, then the aural testing -fun should be a bit closer. Some bus boarding, and other supplies need to be ordered before that, though.
awemawson:
Surely those electrolytics don’t need to be 250 volt working Rated at a lower voltage they’d be much smaller and your board less crowded.
sorveltaja:
That's a good point. I haven't paid too much attention for the voltage ratings.
sorveltaja:
Band pass filter -boards are now finished, and tested. Regardless of the clumsy looking capacitors, they work as expexted:
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Bus board for companders. I'll make the rest for others, once the ordered pc boards arrive:
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Generally, the paper(magazine, or whatever I have at the moment) that I use for the trace transfers, gives acceptable results, but could be better.
Lots of pitting, and tiny fractures in the traces. To this day, it hasn't really been too big of a problem, but I always have to check the continuity of the traces. Once drilling is done, I clean the board thoroughly, and spray a protective 'solder-active' lacquer, to prevent future corrosion of possible weak points.
Yes. there are 'press-n-peel', and UV-based products, which could be a good choice for verified pcb layouts. But for highly experimental, 'trial and error' -stuff, they tend to be rather costly.
There are lots of different ways to do the cheapo laser printed diy-transfers on the net, but it all depends of the paper and/or the method, that is used. For example, if one sees a video on Youtube about the subject, it doesn't mean that same kind of paper is used on mags/adverts around the world.
So far, I've found, that there are at least three ways to adapt the process for one's currently available paper types: ironing, water-acetone method, or combination of both.
None of the previously mentioned methods produce perfect results; but after some practice, they should get the job done adequately.
After all, the point is to not be too dependent on certain commercial brands/products, as they come and go.
Maybe it's time to end this off-topic-ish ramble for now.
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