Never Mind the Engineers, Here are the Physicists!

[sumgai]

Now that I've got your attention.

I don't know where half the crud on my computer comes from, particularly in my Favorites folder, but somehow it just "gets there". Some of the more recent stuff has come directly from this site (thanks to all of you!), and more than a few pages were found while Googling for another topic that was cued from these discussions. Such is the case here.

This site has an article on small FET preamps that can be built into a guitar or a cable. I'm pretty sure that I found this thanks to JohnH, but I don't rightly recall whether he first gave it up, or I just lucked onto it. In either event though, there's a veritable treasure on those pages, one relating to not just the physics of a vibrating string, but the relation between said vibrating string and a pickup.

To be sure, this guy may have done my work for me. He has made note of just how a pickup responds to a string, not just in one location along the string, but in every conceivable location, within reason. But here's where it gets interesting. He then wrote a Java applet that graphically demonstrates the resultant frequency response curve of a plucked string, in real time, as you move the pickup on the graph! Then he just goes over the top, and lets you insert as many more pickups as you wish (no need to stop at "just" three), all of them being visible at the same time. As you move them about on the graph, the representation of the combined response curves updates faster than you can say "Holy....."!

It occurs to me that those of you wishing to see if there'd be any difference between the inner and outer coils of a humbucker, this is your lucky day! Take a few measurements on your guitar, and plug the values into the calculator, and watch the blinking lights!

I need to start in on my little project. But if it looks like I'm getting essentially the same results as this guy, then I'll just take a few samples to be sure, then just leech off his work! ;D

Have fun! Don Tillman's Articles


sumgai

[gumbo]

Oh MG....!!!!
...now you've started something....Thanks for the link (I think!).....:-)
Gumbo
ps
Dja get the schematic?

[CheshireCat]

sumgai said:

But here's where it gets interesting. He then wrote a Java applet that graphically demonstrates the resultant frequency response curve of a plucked string, in real time, as you move the pickup on the graph! Then he just goes over the top, and lets you insert as many more pickups as you wish (no need to stop at "just" three), all of them being visible at the same time. As you move them about on the graph, the representation of the combined response curves updates faster than you can say "Holy....."!

That is way way cool!! And not only is it way cool, I'm just the guy to test it out, and perhaps the guy most in need of it.

Right now I'm looking at 4-5 mag pickups, including one embedded in the neck.

This will definitely come in handy.

Chesh

[sumgai]

Gumbo,

....
ps
Dja get the schematic?

My apologies. While my health was on the fritz for a few days, I lost track of several things, obviously this being one of them.

Yes indeed, the document arrived all safe and sound, mucho thanks for passing it along. Got any other Roland related stuff like that, just laying around in your rubbish bin? ;D


sumgai

[ChrisK]

I've exchanged a couple of emails with Don Tillman. He's pleased to see our interest in his work.

[dunkelfalke]

i remember i have raved about till preamp two years ago on gn1 ;-)

[jhng]

That is an excellent page. Thanks for pointing it up, Sumgai.

It occurs to me that it would be very useful to have a sub-board here just for collecting useful links to other web resources like this.

In honour of Don Tillman's work (see his third pup article) I think we should now abandon the phrase "out of phase" and refer exclusively to "opposite polarity".

In the spirit of online co-operation we will, of course, make our best attempts to assist new members despite demonstrating ectreme bafflement when they use the OOP phrase.

Good plan?

Hastings

[vonFrenchie]

It's amazing but makes no sense to me. Oh well... good find.

Jhng.... the term out of phase is almost like tremolo. A guitar tremolo would be a volume pedal. What people call a tremolo is actaully a vibrato. Reversed or Opposite polarity is better than out of phase or inverted phase.

[jhng]

Or even, if Archelectroluthier Leo I is to be believed, a "tremelo". I suspect that the grandmaster was better with a bandsaw than a pen...

Hastings

[ChrisK]

'Tis true that Leo cared little about formality.

The "tremolo" thingy on a guitar bridge is a vibrato.

The "vibra" thingy in a VibroWhatever amp is a tremolo.


However, regarding:

In honour of Don Tillman's work (see his third pup article) I think we should now abandon the phrase "out of phase" and refer exclusively to "opposite polarity".

The correct term (IMHO) is out of phase for AC circuits. Transformer windings have phase relationships to each other (like pickups).

Phase infers a relationship to another (signal) only.

Polarity is an instantaneous (and absolute) relationship to a standard reference. Polarity infers an absolute and leads to confusion with DC circuits.

In an AC circuit, polarity is meaningless unless referred to another reference as a function of time.

Unless we wish to represent polarity as a function of time and frequency (for which it is different as a function of each frequency), phase is the correct term since it is independent of frequency or any absolute.

Even when we get into LCR circuits with their sub-180 degree phase relationships, it's still phase and not polarity that is used for representation.

[jhng]

Chris, I will bow to your superior wisdom and revert to using the phrase "out of phase".

The funniest thing about Leo's naming is that the whammy bar on a Strat is strictly not called a "tremolo" but a "tremelo". Which is not only inaccurate but misspelt too!

Hastings

[ChrisK]

Well, as a Fellow Engineer myself;


"Engineering is the art of good enough."