I got a pair of Mullard KT88 tubes today.  Soon, I'll swap 'em out on my Audio Note Kit 2 and give 'em a few weeks listening time.  Then I'll report back.

I also noticed on another thread that pos was asking about quiescent current in the Audio Note amp.  I'll try to remember to open up the bottom, power it up and measure the voltage across the cathode resistors to know the current.

OK, so I've had my new Mullard KT88 tubes in my amplifier for a little less than a month now and have listened for probably a couple dozen hours or so, mostly in two hours stretches or thereabouts.  So it's time to report back.

This is just a listening evaluation without measurements, and that's something I normally don't do.  That said, take this post for what it is.  Total seat of the pants observation.

So far, I think I like these tubes.  They are somewhere between the Tung-Sol 6550 and the Electro-Harmonix 6550 in the range of smoothness.  Neither of those tubes lack smoothness, but the EH sounds a little more detailed and the TS sounds a little more laid-back.  The Mullard KT88 is sort of in-between.

To be honest, I am interested also in the longevity of these Mullards in my Audio Note Kit 2.  I think I may have mentioned this here or in another thread, but just in case I hadn't, I find that KT88 tubes don't last as long as 6550 tubes.  They don't fail right out of the box, but they do seem to have a shorter lifespan.  We'll see on these.

They do sound nice though.  Time will tell if they get to be "regular stock" tubes for me like the Tung-Sols and the Electro-Harmonix.