Which SPU have I bought?

[esperowl]

Hello again, as my first foray into vintage Ortofon cartridges I recently bought an SPU GT and then a few weeks later another SPU which was described as an SL15 GT. It is the latter cartridge that has me a little puzzled.
Trawling through the Archives here, I came across Barry's very informative 'A short history of early Ortofon pickups' and noticed that only the S15-T has the integral transformer. I assume that the lighter weight SL cart is lighter because the transformer is external and that by defintion the SL15 GT does not exist.
So, have I actually purchased an S15-T?

Also, the coils from the transformer are missing. As Marvin Gay would have said, what's going on?

http://i1212.photobucket.com/albums/cc459/esperowl/Mobile%20Uploads/DSC_0157_zps12c12766.jpg

http://i1212.photobucket.com/albums/cc459/esperowl/Mobile%20Uploads/DSC_0154_zpsddb8f675.jpg

[RobbieGong]

I reckon Marco's ya man, he knows a bit about SPU's :)

[Barry]

You lucky 'so and so' - I've been after an ST-15 for ages, especially one mounted in an Ortofon headshell!

The designation for your cartridge is a bit of a mongrel one. It should be described as the S15-MT, however I can see how it became SL15GT.

The generator of the S15-T and SL15 are identical, so that is where the "SL15" bit come from. The "T" presumably denotes the integral transformer and the "G" denotes the fitting of the cartridge into the Ortofon headshell (as in SPUG, SPUGE and SPUGTE).

When fitted in the (original) Ortofon headshell the combined weight is 29.5g. Are you able to remove the fixing screws and see what is written on the side of the cartridge body? It ought to be marked "S15-T".

It looks like the version complete with integral transformer, so you will be able to connect it directly to the disc input of your amplifier. Recommended tracking force is 1.5g, though you may find it needs a little more.

[esperowl]

Thanks Barry. The cart hasn't arrived yet (the photos are from the advert).
Do you think that this cart was an SL originally and then had the transformer fitted at a later date, or has the seller just got it wrong and it is actually an S15T?

What about the absent springs / coils at the rear of the transformer, as in the pic below (not my cart BTW) -

http://i1212.photobucket.com/albums/cc459/esperowl/Mobile%20Uploads/40d016f3b61680e038865194afd2b9128_zpse286965b.jpg

[Barry]

No, I think it is, and always has been, an S-15T. The SL15 looked quite different as can be seen from my article in The Knowledge:

http://theartofsound.net/forum/attachment.php?attachmentid=328&d=1239893741
SL15 cartridge

Don't worry about the springs/coils - these were a simple connection device used by Ortofon to connect the pins of the cartridge to those of the headshell. My SL15E came with a set, though I never used them.

[esperowl]

Cheers Barry. One more thing - why do some head shells have a cut-out at the front?
In the first two pics above (the S15 I've purchased) there is no cut out.
In the third pic above (not my cart) there is a cut-out.
In the picture below, illustrating how head shells for the S15 series had a different arrangement to the 'normal' SPU head shells for mounting the cart, the headshell has a cut-out.

http://i1212.photobucket.com/albums/cc459/esperowl/Mobile%20Uploads/4ec1a1cd18802fcc02e171778b66c97da_zpsc6ebdecb.jpg

[Barry]

The honest answer is I don't know. I assume the two versions of the headshell with different fixing points, is perhaps due to the first one (with the cut-out) housing the S15 generator (that is the S-15T / SL15 design) and the second, where the distance of the fixing points from the bayonet stub is larger, is that for the SPU generator.

Likewise, I can only speculate that the cut-out was there to aid cuing. Both the S15T and SL15 have cantilevers that emerge from a diagonally cut tube, which acts as a convenient cuing guide. Without the cut-out this would be difficult to see. I find cuing the SPUs difficult, unless one can stoop down to stylus level and look at the stylus from the side.

These are only speculations on my part; it would be interesting to know the real reason - perhaps Ortofon themselves might be able to help?