Had my Overtone for a couple of weeks now and finally had the time to experiment with changing the tubes.  What's other people's experience with this in the Overtone?  I believe the Tung-Sols are quite highly rated generally - but sound a little 'stiff' to my ears.  I experimented in lowering the bias to around 35ma from the stock 42ma setting, and this seemed to loosen up things a little, although it's all very subjective.  I also tried a matched set of Groove-tubes 're-issue' 6L6 GE cleartops with a 3 rating- meaning they distort fairly quickly with mixed results- to be fair I had previously given these tubes a real hammering over a year in a Marshall Bluesbreaker amp- and when I measured each individual bias one tube was adrift from the other by around 5ma!  Pardon my ignorance but does that really matter as long as both tubes are biased within tolerance?  Anyone know why Nik changed over to the Tung-Sols to the JJ 6L6's?  I am a fan of the stock JJ 12AX7's & use them in all my amps-  anyone have any opinions/experience in using anything else?  I have some KT66/EL34's kicking around & the bias seems to be capable of a very wide setting- anyone try those?

Some useful discussion here might save us all a lot of money and time!