T-40 pickup differences

[cdef]

I'm taking a belated interest in the Peavey T-40 bass. I hear the original pickups were designed by Red Rhodes. A later model, introduced in about 1980 (?), had an exposed blade-type polepiece within each coil. How do these two versions compare in general, and was Rhodes himself the author of the modifications?

[luknfur]

Funny I don't remember the blades, just the bake-like looking ones I've had.

Seems there's either a PV forum or T-forum but there's a couple of dudes on TB that know their T stuff. Probably the only way to know yourself is to have them both and do a side by side. If they were to change anything my guess is they'd have a more modern tone (clearer more defined) which was the trend for the period. The ones I had sounded similar to Alembics.

[millahh]

The info you're looking for should be available here in some form or another:

http://www.peaveyt60.com/

Chip Todd is the brain behind all things T-40/60.

[cdef]

Many thanks for the steer. The T-60 forum indeed has the info I wanted.

[luknfur]

Originally Posted by lmoh

Many thanks for the steer. The T-60 forum indeed has the info I wanted.

Lazy but curious never the less, what might that be in a nutshell?

[cdef]

Originally Posted by luknfur

Lazy but curious never the less, what might that be in a nutshell?

I can't do better than copy a chunk of Chip Todd's explanation here (hope he won't mind):

... We found that changing from a magnetic return, (iron plate on the bottom connecting the two vertical magnets), to a magnet between two vertical iron pieces. not only enabled the magnetic field to get closer to the strings, but did so without the pickup being so much in the way.

A lot of other pickups had the two magnets or magnetic polepieces just going through two coils, so that there were two magnetic fields; one above and one below the pickup. By utilizing a "short circuit" between the bottoms of the two magnets, we transferred the lost lower field to the top to intensify the upper magnetic field. We later found that the same would apply, but be even more efficient if a single magnet was to be in the center and bottom.

... The original pickups had two magnets; one through each of the coil's bobbins. These magnets were ferrite material and were rectangular in cross-section and were stood on edge. There was a magnetic return strip of iron laid flat across the bottom of the pickup and magnetically attached to the bottom edges of the pickups. This iron kept the magnetic field from forming on the bottom of the pickup identical to the top field, so the field on the topside was greater than of that of the pickups like Gibson, (without magnetic returns).We used iron, as opposed to steel, as iron is more compatible with magnetism than steel. Steel won't remain magnetized as long as iron.

The blade type pickup had two thin strips of plated iron arranged on edge through the bobbins, (which had to be redesigned with a thinner slot through the centers). The magnet was quite like the magnets of the early pickups and was held between the two blades. The magnet was laid flat, (not on edge), and took the position of the earlier magnetic return. We found the position of the magnet was more efficient, so only one magnet was used, with the overall result a stronger and better-shaped magnetic field around the strings. ...

The consensus seems to be that the "blade" p/u's are a little hotter and noticeably brighter than the "toaster" ones.

[luknfur]

Originally Posted by lmoh

I can't do better than copy a chunk of Chip Todd's explanation here (hope he won't mind):



The consensus seems to be that the "blade" p/u's are a little hotter and noticeably brighter than the "toaster" ones.

Ah, saved by the nutshell. That last part I understood.

Interesting clip and reflects with some detail what goes into mag location and the effect on the mag field. Lot more to tone shaping in a pup than just the winding and type of mag.