Can you extend the high frequency response of a pickup with individual coils?

[Mike Sulzer]

The two plots below show the magnitude of impedance versus frequency. The one that shows the big difference is when the pickup is unloaded. The resonance of the four coil pickup is above the range of the measurement. The one that shows very little difference is with a 778 pf capacitor across the pickup.


You can expect a somewhat bigger difference between the single and four coil pickups (when loaded by the cable capacitance) as you wind on more turns. Both the inductance and capacitance of the coils will increase. However, only the increasing capacitance contributes to the difference between the resonant frequencies. This is because the inductances of both single and four coil pickups increase similarly, and both contribute to lowering the resonant frequency. On the other hand, only the increase of the capacitance of the single coil pickup contributes because the capacitance of the four coil pickup is still too low to matter much relative to the cable capacitance. So one does not expect doubling the number of turns to make the difference large.

[Mike Sulzer]

Corrected Plots

*****new plots*****
Part of the processing to get impedance consists of going from db back to linear. I screwed that up. The discussion does not change.

[Mike Sulzer]

Here are very brief sound clips pf the two pickups in question. The only bass I have is the primitive solid aluminum one I made in about 65 or 66 when I was in high school. It has a scale length of 30.5 inches, weighs 6.6 lbs. and uses a thick piece of piano wire under high tension along the back of the neck and body to establish the correct shape. The neck and headpiece are extensively milled out for lightness, but the balance is still not so great. The original pickups used ceramic magnets with lots of wire, largely than 42, if I recall correctly. The pick guard is new for this test. I recently recoverd the bass from the attic of my parent's house.




thatOne.mp3thisOne.mp3

[David King]

This one sounds a tiny bit brighter whereas that one sounds like it went through a flanger and an autowah. Neither sounds anywhere near as bright as I would have expected considering the low number of turns (I don't do much under 9K these days). Could it be the strings are from 1966 as well?

[Steve Conner]

Thanks for posting the clips Mike. Also, that bass certainly has character, the screwhead "inlays" are a nice touch.

I think "this one" sounds fuller and fatter, "that one" sounds kind of phasey. I'll save my guess as to which pickups they are for later.

[David Schwab]

That's a cool bass Mike!

I don't know if you alternated magnets on the 4 coil version, but the "that one" clip is kind of phasey sounding.

The "this one" clip has more low end. The "that one" clip is thinner sounding in the low end. I don't hear either one as having more high end, and that was why I said you should wind them much hotter. Wound this low you won't hear much difference.

[Mike Sulzer]

This one sounds a tiny bit brighter whereas that one sounds like it went through a flanger and an autowah. Neither sounds anywhere near as bright as I would have expected considering the low number of turns (I don't do much under 9K these days). Could it be the strings are from 1966 as well?

Thanks for the response, David. The pickup was loaded with something like 143 K to simuate volume and tone controls of about 250K. The input impedance of the preamp (not in the bass) was 1 M. The cable had about 650 pf. Not sure if that has anything to do with the lower than expected brightness.

I think the flanger phasey sound has to do with the strength of the magnets. Thatone came out a bit closer to the strings. I used the smallest magnets that I have (1/8" diameter disk, 1/32" thick neo) on top of the 1/4" 5/8" long pole pieces. The field is quite strong, too strong especially on that one, but I hear the effect on both, but much more on that one with the closer distance to the strings. You should hear it when I used the larger diameter magnets shown in the photo in the first post! This is a very high sustain bass; I think that makes the string pull worse than normal because of the string iteractions. The bridge compensation is off and that makes for some funny effects between fretted string fundamentals and open string harmonics because of the funny coupling from the magnet pull. I suspect that this bass needs both bridge and nut compensation, especialy if you want to use all 25 frets. (But what did I know about that in my teens?)

[Mike Sulzer]

Thanks for posting the clips Mike. Also, that bass certainly has character, the screwhead "inlays" are a nice touch.

I think "this one" sounds fuller and fatter, "that one" sounds kind of phasey. I'll save my guess as to which pickups they are for later.

Thanks for listening, Steve. There is also another one, with some change made on one of them. This is not quite fair since this recording was made later and the record settings were a bit different and the load on the pick up might have been a bit different. Almost anything you do changes the sound, and so sometimes it is hard to track down small differences.



thisOtherOne.mp3

[Mike Sulzer]

That's a cool bass Mike!

I don't know if you alternated magnets on the 4 coil version, but the "that one" clip is kind of phasey sounding.

The "this one" clip has more low end. The "that one" clip is thinner sounding in the low end. I don't hear either one as having more high end, and that was why I said you should wind them much hotter. Wound this low you won't hear much difference.

Thanks, David. I agree that if you wind on about twice as many turns, there will be more difference in the top end, but I doubt that it will be the difference between a mudbucker and a normal pickup.

[David Schwab]

Thanks, David. I agree that if you wind on about twice as many turns, there will be more difference in the top end, but I doubt that it will be the difference between a mudbucker and a normal pickup.

Well as I said, wind a 20k two coil humbucker with 42 gauge wire. Then wind up 8 coils with 10,000 turns each of 42 gauge wire. The two coil pickup will be darker sounding. I think you really need to wind a pickup past the point of getting muddy to see the difference.

On the Mark series Wal basses they have each string's pair of coils in series, and then all the pairs in parallel. That will f course make the pickup brighter. But my testing was done with the older Pro series pickup I have here.

Of your two test clips, I liked "this one" better.