Optical pickups

[SamIAm]

Can anyone advise how they work?

 

S'manth x

[itu]

There's optical sensor beside a string that measures the vibration.

 

To enhance the SNR, because typically a sensor has limited bandwidth (which in this case is an advantage: all light could be source of distortion), there is a light source that lights the measured string. Then it is easier for the sensor to measure the vibration. (Think about yourself in a dark room trying to see the vibes, and then someone puts lights on.)

 

As said before, the (wideband sun/artificial) light which does not belong between the sensor and the string may result in awkward noise. That's why the sensor is usually covered.

 

There was one optical pickup company (Lightwave), but I think this system is too modern for most of us bassists (really!) and certainly too modern for g-word players. You know Leo and everything.

Edited August 6, 2022 by itu

[BigRedX]

I used to own a Lightwave bass with the optical pickup system. 

 

The idea is great because you can use all sorts of strings and not limit yourself to ones with magnetic properties.

 

In practice however you need to consider the following:

 

1. There's a lot of electronics that need to be fitted into the instrument. On the bass I had all of the space beneath the bridge/pickup construction and most of the lower half of the body was routed out for this. Great if you like a light-weight bass, but also plenty of things to potentially go wrong, although they didn't while the bass was in my ownership.

 

2. To provide power for all of this required a rechargeable battery and propriety PSU unit for charging. Also because my bass was imported from the US I also needed a 240-110V step-down transformer for the PSU.

 

3. Setting up the pickup mechanism when you changed strings was a complicated and time-consuming task. Not only did you have to re-align the pickup with the string (very important if the new set required intonation adjustment), but there were also individual trim pots on the circuit board that had to be adjusted for each string to ensure a balanced output across them all.

 

4. The bridge design on the bass I had (mk2 bridge and pickup system, and I believe that there is an even newer design now), didn't make adjusting the intonation easy and there was more vertical travel available in the saddles than the optical sensor mechanism, which meant that is was possible to position the string out of range. My bass came with both a fretted and fretless neck, and the fretless neck had to be shimmed in order to keep the saddles within range when fitted.

 

5. I could never get on with the piezo pickup that was also fitted, probably because I'm quite a physical player and the amount of body routing meant that this was essentially a hollow-bodied instrument, and therefore it picked up too much handling noise.

 

As a result I tried two different string types before the hassle of having to completely reset the bass for each new type, became too much bother and then I stuck with my second choice. 

 

So if you want to experiment with lots of different types of strings and have the time and inclination for the set up required every time you change, then it's worth looking at. If you are buying second-hand make sure that you get a bass with at least the MK2 bridge and pickups (the original system had even more problems) and that if necessary it comes with a transformer for the PSU.

 

Here's some photos of the bass I used to own showing the bridge, and the size of the electronics cavity (IIRC all the space below that cover is full of circuit board).

 

 

 

 

 

Edited August 6, 2022 by BigRedX

[warwickhunt]

Like @BigRedX I owned a Lightwave bass and a Zon Sonus equipped with the technology and I have to say it worked flawlessly and I never had any real hassle adjusting it BUT I always felt like I was just waiting for it to fail.  Absolutely no reason to think it would glitch or be any worse than a mag or piezo system but it was just too new fangled for me.    

[Richard R]

A long, long, time ago I used to.work for a part of Lucas Industries that researche and made optical sensors. Some were very clever, some were very good. But I was left with the opinion that if there is ever a straight choice between optical and electrical sensors, the latter will be simpler, more effective, more efficient, and more reliable. 

[neepheid]

3 hours ago, BigRedX said:

 

 

 

Reminds me of the back of a Gibson RD Artist - in appearance only - pretty much all circuit board under there and it still ends up weighing as much as the Moon...