OK, I have just completed a pretty comprehensive A/B test between Jez's demo unit, which is the standard GTi spec and the full GTi Turbo Spec one he has completed for me - which has, in addition to the demo unit, uprated caps (largely a reliability mod I am informed) and the full turbo mods including the uprated op amps which are run, IIRC, in active mode, rather than the passive mode the lower spec op amps are run in the standard version.
I asked him to send this to me as I was convinced there was a slight difference, but I did not know if it was for the better. It turns out it's a difference that makes even slightly worn discs a little worse and good discs a little better.
In the interests of full disclosure, the rest of the system is a Acoustic signature Challenger T/T with a Roksan Nima arm and AT 33 PTG II cart, a Sugden Headmaster Class A pre-amp (also recently refurbished to a very high standard by Jez), a Quad QSP power amplifier and a pair of fully refurbished Kef 104/2 speakers. I have also been doing a bit of casual testing over the last couple of days by switching between the two stages whilst working at home and listening through some Sennheiser HD600 cans and the the Headmaster.
Discs used for the speaker test were Pentangle's Reflections, Beach Boys Surf's Up and Deep Purple's Fireball.
My conclusions? Both stages are undeniably superb and whilst there is a Gnat's chuff between them, there is an audible difference. However, it is marginal and that's in the handling of the high frequencies covering sibilant sounds in the human voice and percussion. The Turbo has a little more headroom here and enunciates these with a little more clarity than the demo unit. This does mean that it exposes groove wear a little more mercilessly. It also takes breathy vocal recordings, for instance, 'Disney Girls' and 'Day in the life of a tree' from Surf's Up, to a slightly more transcendent level.
It should also be noted that this difference was more noticeable via the speakers than through the cans.
The price difference between the two was, IIRC, about £140, which isn't very much. Is it worth it? In our OCD world of extremely marginal gains, yes. I probably spent half that much on a turntable mat, which was, admittedly, stupid.
I should add, by way of testimony, that since first hearing Jez's demo unit I have bought a new cart and arm and about 20 new albums, so this little box has thoroughly reinvigorated my passion for vinyl.
If I could offer one piece of advice to Jez, it would be simplify your product offerings. Keeping it to the recapped GTi and the recapped GTi turbo as I have here would appear to be sensible.
Bom Shanka