Upgrade From SME IV to V - Worth It

It actually depends on the individual specimen. You probably know the V came out first, and the IV followed. The IV is said to be made with unselected parts, while only selected parts go into the V. So if you're lucky, you may get a Series IV just as good as any Series V. There are some small differences in function - there is a VTF wheel on the V, and the thumbscrew on the counterbalance is just used to balance the arm before setting VTF. There is a damping trough by default on the V, and it is an add-on for most IV arms (I think the IV.VI also has the trough standard). Finally, there is a VTA screw to allow fine adjustments of tonearm height whilst the mounting clamp is loosened.

I have one Series V, two Series IV, a 309 and two M10 (a simpler arm made for the Model 10) arms. If I compare the V with the M10, I can certainly hear a difference, but I'd be hard pressed to hear the difference between the IVs and the V.

@dogberry I agree with @ pindac. There will be cartridges that actually work better in the IV, but the differences are minor. Both are very good arms. I think the Tri Planar, the Reed 2G and the Schroder CB would be significant steps up, but again that money might be spent to better effect elsewhere. 

My take on the IV is that it served a few purposes as follows:

1, I was in possession of a TA that was claimed to be competitive with the best from the era it was purchased.

2, There was a pride in having been the owner / user of the TA.

3, I was not shy to make it known I had a IV in use and did not sense the need for many years of ownership to investigate changes that could be made for it.

What changed I investigated upgrading the owned IV, from recollection there was discussions about ADEC 7 or even ADEC 9, as well as reproducing some critical parts from different materials, to be produced to extremely tight tolerances, using a very stable material and polishing this material to not usually produced surfaces finishing.

At the same time I was introduced to a TA, that had been created using a selection of the methods on the table for the IV, following the demo' of the TA compared to the IV, I was immediately convinced the IV was to be superseded, which it was.          

IMO upgrade the phono stage you get much better results