Tube rolling and SAC Glowmaster KT88?

First of all, congrats on discovering this amp. There's not to many owmers of this one out there as far as I can tell. Out of interest, what led you to your choice?

I've had a Glowmaster KT88 for a while and have tried using 'winged C' Svetlana KT88's from St Petersburg in place of the SED Svetlana's; to say there was an improvement would be somewhat of an understatement. More depth, clarity, realism and tangible presence. A cracking amp as it is, but changing the output tubes to the winged C's IMHO is a cost effective and dramatic upgrade.

I looked at changing the 6N1p driver tubes, but upon researching this it looks as though whichever manufacturers label is on these, new one's all come from the same factory in Russia. Although there's the option of looking for NOS 6N1p's which seem to come in different flavours as in how closely they were factory matched, differentiated by two letters after the 6N1p i.e. 'EV' or 'IV'.

Thanks for taking the time Hiker to post your thoughts. I was really led to the Glowmaster by a desire to try valves after 10 years or so of solid state. I picked up an Art Audio Concerto power amp earlier in the year to experiment and whilst it was good it didn't quite have the grunt to drive my speakers like my Gamut D200. I emailed George at NorthCreek and he recommended a well designed tube amp of around 70 watts should be ideal. So I poked around a few forums and came across someone who had replaced a D200 with the SAC KT88 and was delighted with it. I checked out the Hifi World review, which seems to be about the only one out there and then bought it without first hearing it...and don't regret it for a second.
I was considering the Winged C myself and I have also heard good things about the Electro Harmonix KT88 generally but your positive experience has probably just tipped the balance in favour of the Svetlanas.
I also did some research into swapping out the 6N1P tubes but like you I found that all new production units are identical. Out of interest have you tried rolling in some NOS 6N1P valves?

Hiker363, I'm confused by your comments regarding the Svetlana tubes.

SED KT88's with a Winged C logo are made in St Petersburg, and Svetlana KT88's with an S logo which were made in St Petersburg preceeded them and are the same tube. The latter haven't been made for many years.

The current Svetlana KT88 is not made in St Petersburg but is often confused by the unwary with the original "Svetlana KT88". It is not marketed as a SED tube.

As I read your comments I suspect you may have been comparing the current SED KT88 (identical to the original Svetlana) with current production Svetlanas, not made in St Petersburg, and which sound (IMHO) very different and justify your observations about the differences.