Yo UT...keep a hold of them - and not just as an investment, lol...the more I hear them with my new tube DAC, the more heartbroken I'm becoming about my beloved EL3Ns! My ECC31s
never sounded this good (which is saying something, as they were GREAT!), even though my previous DAC was no slouch. Obviously, another prime example of system synergy at work here - the tube DAC's implementation of the Sabre ES9018 chip, plus the Tesla E88CCs must be doing far more for the Mullards than the EL3Ns, alas! There are odd moments when the EL3N's extra warmth and intimacy are enticing - especially on some female vocals - but the 31s are now bringing out even more detail, with even more 'air' and separation than ever before.
This is going to take me much longer than I thought to get a full and final assessment between these drivers - for the first time ever, I may just have to consider choosing tubes to match the music/recording...something I was (and still am!) very reluctant to do, given my amp's sockets punishment LOL! (I suppose I could always make myself some 'super' socket saver adapters, but I hate adding any extras to the signal line...).
And so, UT, in the event of you possibly upgrading your already very good DAC in the future (but would certainly recommend a
tubed one!), I repeat...KEEP THOSE ECC31s!!
...CHEERS!