Optical Pickup

[bushtech]

+1

 

[Audioguru]

The electric guitar shown in post #31 does not have a sound box or bridge for resonances. Like some electric guitars, its body is solid with no resonances.
The inductance of a magnetic pickup resonates with the capacitance of its cable to give a very high peak in the upper frequencies when the preamp has a high input impedance (usually a vacuum tube or Jfet).

 

[m1kem00re]

The electric guitar shown in post #31 does not have a sound box or bridge for resonances. Like some electric guitars, its body is solid with no resonances.
The inductance of a magnetic pickup resonates with the capacitance of its cable to give a very high peak in the upper frequencies when the preamp has a high input impedance (usually a vacuum tube or Jfet).

Hi. Actually the bass guitar is partially hollow with a sound-hole, which should afford some acoustic properties and the tail-piece also serves as an adjustable bridge.

 

[m1kem00re]

Sorry, I didn't read every post first time round.
I realize now what u want (faithfully reproduced audio waveform using optics).
Also building an electric in spare time - with inductive pickup for steel strings.

Hi Thanks for your reply, especially as it comes from North Johannesburg - I used to live in Hillbrow!
I Know that my project is possible, as others have achieved it, but I can't determine what components I need to experiment with.

 

[Audioguru]

When the guitar string is swinging back and forth making a sound, how will it amplitude modulate the IR beam when the beam is much wider than the string causing the shadow of the string to always shade the same amount regardless of it swinging? The photo detector will have a steady DC output with no audio on it.

if you make the IR beam narrower than a string then the string will cause the photo detector to output a high level squarewave like a buzzer, or no sound when the string is plucked a little less. I think the squarewave frequency will be double what the string is playing.

 

[BobK]

Doppler lidar anyone?


bob

 

[BobK]

Or, for the best accuracy. Two video cams at right angles to the string.

bob

 

[Harald Kapp]

Doppler lidar anyone?

See #17

Or, for the best accuracy. Two video cams at right angles to the string.

SD, HD or 4k?

 

[Alec_t]

Two video cams at right angles to the string.

Should be ok . Snag is, you'd need 12 cams in all. That's gonna weigh the guitar down somewhat .

 

[davenn]

Snag is, you'd need 12 cams in all.

8 .... it's a bass guitar .... 4 strings

 

[hevans1944]

Aren't we getting waaay off into left field on this? There IS a commercial optical pickup available. Quoting from the Lightwave Systems website:

The optical pickup is a proprietary type of transducer which utilizes an infrared emitter and an array of photodetectors for each string. The emitter casts a shadow of the string onto the photodetectors. As the string vibrates, the size and shape of the shadow changes accordingly and modulates a current which passes through the photodetectors. This current is the analog electrical signal which represents an accurate depiction of the vibrating string.

I think the "array of photodetectors" is actually just two differentially connected detectors for each string, but this is easily verified by simply purchasing a guitar from Willcox Guitars and applying some "reverse engineering" to figure out the optical design. Plan on spending something short of $2000 for this educational experience. Maybe a bit more if you're ham-handed and you need to purchase two guitars because you broke one or more optical pickups trying to remove them on the first one.

It looks like Lightwave Systems sells their entire optical pickup production to Willcox Guitars, so good luck trying to buy a single pickup from them. Heck, Willcox Guitars probably is Lightwave Systems... if I were Christopher Willcox I wouldn't be selling any of my optical pickups without attached guitars either.

 

[davenn]

Aren't we getting waaay off into left field on this?

yes we are

time for this thread to close as I doubt it is going to go anywhere useful