I know the S is the heaviest version with a steel arm tube and the fx was introduced with an alloy tube to be a lower mass version but where does the bog standard 64 come into the mix.
I’m seeing loads of the fx versions around, does this still have enough mass to be a good match for the Io?
I think you will need the alternative heavy counterweight for it
edit
I’ve just looked at the mass of an Io1 AN website says 11;12g - is that right? I thought they were heavier. Maybe will work without heavy c/w
Io 1 has aluminum side cheeks, so is lighter. The 2 is basically a 1 with gunmetal sides (heavier), the Gold is a 2 with permendur polepieces and the Ltd. is field coil rather than the AlNiCo magnets of the others.
In theory, the 1 has higher compliance, at least according to the website, but I don’t believe it. I reckon they use the same cantilever assembly, so will still favour a heavier arm.
UK Io 2 is probably closest to original IIv from the 80’s.
Always thought the 64s was a 64 with silver wiring…
It has, but is also a heavier (Steel) arm tube. FWIW, the Io and FX64s combo sounds wonderful.
Ok Thanks, Pete.
In that case, given the usually stated acceptable range for resonant frequency of between 7 and 12 hz it should be fine at 8.3 hz (if my calculations are correct)
Be interesting to know what deck it is going on.
PT?
Yep, PT1 and I’ve seen a couple fitted with an FR-64 online
I used to use the S on the original Systemdek in the early 80s
It can work, but imo you won’t get the best from either. The Fr 64 is much better on a non suspended deck. Thought you might have bought a TD 124 
I’d have thought it’s rather heavy fir a PT, I had it on the Voyd Reference and the suspension had to be wound right up. Not ideal, it would really need re-springing with heavier springs.
Have been thinking about running 2x decks for a while.
Oracle Delphi / NA - FR-64s - Io - AN-S3 - P10
PT1 - PU7 - Koetsu - PIP2 phono
I love the oracle, don’t dismiss the Thorens though, I remember you mentioned you fancied one. Great decks and can be matched with loads of different arms. I don’t think the FR 64 would be better on a PT than the PU7.
This ^ 
The standard springs will just about manage, but will be maxed out. Making for a deck with no available adjustment. Like you say, not ideal.
I have an FR64s and am waiting in vain for a sensibly priced FRs3 head shell for the Gold, seem too be quite expensive. Any ideas for alternatives? Anyone tried Orsonic AV101B ?
Nothing else will work and you’ll never find an frs3 so give up and sell me the FR64s
To be fair, it still sounded awesome on the Voyd. It was ok levelling and bounced fine, I just wasn’t happy with having to wind the suspension up so much.
I want a Breuer to try.
Speaking of headshells, I think @murrayjohnson has my Audio Note one. (In tasty brown). Can you confirm, Guy?
Yes, still here.
Yes, I would like to try one too.