I know this subject has been covered many times way back on the forum but I though I would just post up an interesting observation regarding the Croft 25R preamp tubes.

I initially bought my Croft 25R with all JJTesla ECC83 S tubes included, one or two of them were cryogenic. I was soon keen to fiddle and mess and so bought a couple of 1970's NOS Tesla valves which were ok but not dramatically better but here lies the conundrum, were they really NOS "New" or just NOS having been rolled a number of times over the last decade, who knows. You have to rely on the word of the vendor unless you have a valve tester.

I knew Tesla NOS valves were some of the best sounding out there so I endeavoured to purchase some more. This time they were with gold pins and had 32 after the ECC83... Well they were OK and better than the JJTesla ECC83's but not significantly better. I then purchased some more NOS Tesla from a very reputable dealer and they were stunningly good these had the 37 code after ECC83. I stuffed my preamp with these and have been happy for a couple of years. I know preamp tubes can last 10,000 hours but recently one of mine started to sound like an out of tune FM radio. This was positioned in the regulation section.

I decided to replace these with a couple of NOS valves so had a good read round the net and to my amazement the JJTesla ECC83 S tubes were recommended over a lot of tubes including Telefunkens which I have seen go for £1500 a pair recently! JJTesla ECC83S goes for around £10. Investigating further I found the JJTesla ECC83S was an upgraded replacement for the JJTesla ECC83 and a number of dealers thought very highly of them. So I decided to pop some back in the regulation section of the Croft and wow, I was very surprised indeed. Dynamics were restored and on nearly every level they contributed a superb sonic oomph to the sound. Again I have read of other folk who have found this to be the case.

I think I may have been to quick in my initial assessment of the JJTeslas and even though the NOS Teslas were running under par, I have been very impressed with the JJ version. Obviously Glenn used the JJ valves to build the sonic performance of the Croft 25 so I should not really be surprised they performed very well.
I did try them in the phono stage but here I found them a bit bright and forward compared to the NOS Teslas.

I will be keeping the new JJTesla ECC83S in the regulation stage from now on as they have performed so well in this position. Sometimes it's good to go back over changes you have made as sonic memory is not always great. I recommend to any Croft owners out there to have a go with the JJTesla ECC83S in the regulation stage, you may be as surprised as I was and you will save yourself a few bob!