Sonic characteristics of various output tubes?

Varies from amp to amp, but the EL34 based amps usually are a bit warmer in balance than using 6550's, KT88's, or KT90's. EL34's usually produce about half as much power as the larger tubes and they cost about half as much +/-. Of the 3 larger power tubes, I use and prefer the 6550's which to my ear, in my stuff, are better balanced. The KT90's are a bit more powerful in the bass and, perhaps a bit cooler thru the mid range. The few KT88's I've heard have had very smooth and airy highs and a softer bass. While they haven't been my favorites, they are preferred by a lot of folks. I think a lot has to do with the way the tube manufacturer voiced the amp in the first place.

I have never used EL84's so I can't comment. The way you describe the difference between them and the EL34's is much the same way as I would describe the general differences between the EL34's and the larger power tubes.

The thing to remember is that the sound of an amp is greatly influenced by the input tubes used in the amp. I can take a 6550 and make it sound much like a more powerful EL34 (in the same amp) by just changing the input tubes. Think synergy.

Hope that helps a bit. BTW, if you're really interested in tubes I sugest that you make a habit of reading the Tube forum in Audio Asylum. There is much discussion about the various tubes and uses in that forum. I highly recommend it.

check out tube world.com they have brief descriptions of many diff. tubes,,,,,

Thanks to Newbee and Ray. I'm a little surprised that no one else has offered commentary on this thread but maybe it's not as simple as one might think.