Where do you guys buy tubes?

I can buy anywhere as long as the seller guarantee it's tubes on test results on what tester but not on emission test.Pay attention for matched transconductance and  plate current.Double triode like 12A( )7,6sn7,ecc88 etc.,they must be matched at least 10% or tighter triode-triode for Gm & Ip,non-microphonic,very low noise and no hum.

Question for Atmasphere:  Do you think JJ has resolved quality problems?  I had some KT88s from them a while back.  They sounded great but did not last.  Failed in a damaging way to the JoLida integrated I was running at the time.  I'd be pleased to hear they've resolved those issues, though I do note some of the suppliers above (Jim McShane & Kevin Deal) still do not carry any JJ product.  Just curious on your read of that situation.  Thanks.  

We've been using them in guitar amps and they've been holding up really well. As a side note though- a couple of tips:

1) all power tubes should be preconditioned if possible. This would be the process of applying filament current to the tube but no B+ (power). The tube should be lit up in this way for 3 days and nights for best effect. If B+ is applied, the preconditioning process is ended so you have to be patient. This can double the life of the tube and dramatically reduce premature arcing that might simply be the result of damage to the cathode coating in shipment.

2) in many transformer coupled amplifiers that employ a pentode or a tetrode, the cathode resistors and screen resistors are always at risk in the event of a tube failure. IOW this is nothing unique to JJ! I've Genelex and GE and you name it do exactly the same thing- its the result of the tube arcing. To reduce that in a new tube, see 1) above. 

@atmasphere  Is preconditioning what tube-sellers are usually talking about when they offer 24 hour burn in of power tubes?

Ralph,What value of B+?since  those tubes you got from the seller, he already applied B+ on them when they were tested.And one more thing about cathode poisoning if you run it for 3 days?

If you want some of the best matched and quietest tubes available try Roger Modjeski at The Tube Audio Store/RAM Tubes. I also like Andy at VTS as well.