Koetsu -- Do all longbodies have platinum/alnico magnets?

Perhaps you mean platinum cobalt magnets instead of platinum AlNiCo. Back in the late 50's - 60's the Pt Co magnets would have had the highest energy product and coercivity of any magnet of the time, besting the more pedestrian aluminum nickel cobalt (AlNiCo) iron magnets. The 70's saw the advent of neodymium iron boron and samarium cobalt magnets where the neo magnets are the current kings of the hill. 

I can't help you with the lineage of Pt Co magnets at Koetsu, but they certainly could have been a sexy choice decades back.

Brock

Thanks Brock. I always wondered what Alnico meant! I also thought they were synonymous with the Platinum magnets Koetsu uses. Thanks for setting me straight.

I don’t know much about the long bodies - other than they’re the oldest Koetsus, and I’d guess that few if any would have the Platinum magnets, which were only introduced well after the later short bodies. I have a 1980s short body Onyx Signature with AlNiCo magnets, dated before the Platinum line; it’s been recently rebuilt by Koetsu to full modern internals, with the exception of keeping the old alnico magnets in place. I also have some of the current Platinum short bodies.

Though all of these sound unabashedly "Koetsu", there’s definitely a sonic difference between the magnet types that’s much more significant than the minor differences between stones (e.g. Onyx vs. Jade vs. Coralstone), and the difference in output level. The alnico model yields fully TWICE the signal vs. the platinums, surprisingly - perhaps it’s simply much larger in size.

The alnico Onyx has really come about with some burn-in, and is my current favorite of the lot (including a Coralstone Platinum). It has a little better depth in its image, a little more neutral tone, and a slightly more punchy/dynamic sound. The Platinum models, on the other hand, are a bit smoother and creamier/richer sounding. My rankings may change again when I switch from my Phantom Supreme to a Fidelity Research FR64S arm (soon).

The modern entry-level, Rosewood Sig, and Urushi use Samarium Cobalt magnets, which are different again from Alnico and Platinum. I’m not sure where Koetsu gets its platinum magnets, when other manufacturers seem to be unable to get them (e.g. Lyra needing a donor Parnassus to make a new Olympos).

Thanks for the details, Mulveling. I am not certain this is true but a reviewer told me that some time ago Koetsu bought every platinum magnet available and stockpiled them. This is supposedly why no other mfg can source them. Seems silly that someone else could not make them, but perhaps tooling and materials are cost prohibitive for small runs.

@montaldo
Interesting, and certainly possible, given that no one else offers Pl magnets. With flagship cartridge prices skyrocketing lately (5-figures is becoming ubiquitous), I wonder if it will become enough to renew interest in the manufacture of new Platinum magnets.

Neodymium  produces the strongest field by size/mass, but it doesn’t seem to satisfy everyone sonically (Alnico an Pl do seem to have an ease and organic flow to the music they produce, compared to the Nd cartridges I’ve owned; my Tannoy speakers also use Alnico magnets). Koetsu doesn't use Nd on any of its line. Even Ortofon has incorporated some Alnico in its new Century flagship.