Gallery, Projects and General > Project Logs
Diy optical pickup for guitar -- is it possible?
sorveltaja:
Not really an optical pickup related, but more about how the external enclosure has turned out. Bit too dark and fuzzy photo, and drawn one:
I used chipboard to add some extra weight for it(otherwise I hate to work with that stuff). Kitchen aluminum foil was used for shielding to see, if it has any benefit for that noisy amp board.
The cover also has foil glued in it.
Cables from the guitar(pickups and ir-leds) will go through printed strain relief clamps. Later they will be replaced with two D9-, or a single D15 connector.
Using cd-rom ide-cable for outputs, as mentioned before, didn't work that well.
As a male part, I used pins soldered to perfboard, but when pressing/connecting the female part in, some pins popped out on the other side, with the copper spots they were soldered to.
Simple pin headers were used to replace them(as on the above pics).
That box has a 7809-regulator in it(as the testings were done with 9 volts from the variable power supply), and will be powered with 24V/1500mA power supply(from an old scanner).
Combined current drawn by the amp board, schmitt triggers, and ir-leds is only under 100mA, though.
By the way, when looking videos on youtube about hex fuzz, besides the commercial ones, there was one guy, that had done a diy-version(or so I assume) of it.
Of course I forgot to bookmark it, and now can't find it anymore.
He demonstrated it on several videos on his channel. A big let down, as on numerous other youtube videos also, is to show only the results, and to refuse/to not bother to reveal any of the details, of how it's done.
I mean, what's the point making those kinds of videos anyways.
sorveltaja:
More of the interfacing hassle. Yes, it is (very)boring, but has to be done. Current version of the stuff:
Printed 'boxy' part on the guitar consist two sandwiched perfboards with pin headers, to plug in the sender- and receiver wires.
Another one is a strain relief clamp. They make it a lot easier to move the assembly around, as I have to do it often, to free some table space.
That wiring/connecting/interfacing is very finicky to work with. Apparently some of it needs to be changed at some point.
But for now, I'm going to test it as it is. I'll be surprised, if it works, as expected. If not, it's again a good chance to learn new project-concerning things.
sorveltaja:
I managed to assemble the circuits inside the enclosure, and after stomping several bugs (which were actually stupid mistakes) out, they work, as expected.
Settings for the amp board/schmitt triggers/ir-leds are still same, that were used, when the circuits were on the guitar. As a sort of a reference.
The overall noise level, although not seemingly that high, is enough to reach the schmitt triggers. The receiver/phototransistor cables are shielded, except inside the small box on the guitar.
When covering that box with a hand, it decreased the noise just a bit, so that's where the 'leak' is. As a last attempt, I'm going to try to shield it with aluminum foil.
Whether it works or not, I kind of saw that coming(shielding problems/noises), as most, if not all, optical pickup manufacturers place the amplifying circuitry as close as possible to the source.
If only I had an ability to work with smd(surface mounted device) components, all the involved circuitry would be already 'stealth' enough to fit nicely inside/outside of the guitar.
After all, if the shielding of the 'box on the guitar' fails, it's probably time to redraw the involved circuits from the very beginning, as the current ones are very clumsy, and were just thrown together for testing purposes. Maybe even fusing them together to form a single circuit board, without unnecessary pin header -connections.
But time will tell, as Frankenstein would have said it.
sorveltaja:
Shielding that small box in the guitar doesn't seem to have noticeable effect, to lessen the overall receiver/phototransistor noise.
Although the wiring for them is made of a shielded, individual microphone cables, there are differences between the pickups, in a way their noise outputs and -levels(with zero input signals) look.
Perhaps a shielded, single 6-core cable could be a better choice for that. But who knows, before testing. I'll probably add some of that to the next order.
After all, I really would like to keep the current setup, instead of redrawing/remaking the whole circuitry to fit in the guitar body.
So the next challenge is obvious; to lessen/attenuate the overall output noise levels with external circuitry, without knowing, if it's possible at all.
Schematics for simple noise gates are available on the net, and so far, I have tested one, that is based on the optoisolator(Led/Ldr pair). There might well be something in it, but it needs to be modified to suit for this project.
Probably not worth the trouble, but no matter what, I'll have to find out, how deep that rabbit hole is far I can get, before hitting the wall.
sorveltaja:
While tinkering with the optoisolator based noise reduction for the amp board, I accidentally found the major source of the noises, that appeared, after the circuits were put to an external enclosure:
Those pots, that were added afterwards, seem to act like radio towers. Just by touching the metal wiper part, the noise immediately decreased a lot.
Although the noise source is located, I'm not quite sure yet, how to shield those potentiometers causing it.
But after all, I'm rather relieved, that the noise source wasn't that much about the cables, or other wirings on the guitar side.
The residual noise can be suppressed even more, by using something like the noise gate, that I've been testing.
At the moment, it's a bit quirky one, until I find a way to smoothen out the input signal driven led's response.
The noise gate circuit itself is quite simple, consisting one npn-transistor, that is fed by the signal from the amp board, to drive the led of the diy-optoisolator.
There are few other components involved also, but I'll have to do more testings to see, how they work.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version