Pantode and Tetrode What is the difference?

KT88's often are described as clearer and more linear, pentodes like an EL34 or something, are often described as warmer or lusher. If you bought the amps new, you should have them replace the tubes. You shouldn't have to pay. If you don't have individual biasing for each socket, yes, check the manual. If it says in pairs then match. If not, don't bother.

Don't worry about the forum thing too much. If in fact you are looking for advice that's that technical let me add something about pushpull and triode v. ultralinear. B/c of the suppressor grid on the EL34, you could say that usually it sounds better in ultralinear and as someone stated, peppier. It has to do with that supressor grid, electron cloud, maximum plate voltage thing; you can probably see how. The get up to a plate voltage, max out, and output constantly at that level (no overdriving like on guitar amps, as far as I know; someone correct me if I'm wrong on this one, but it's what I've been led to understand). This is why you see EL34 amps that are *specifically* balanced designs in ultralinear more of the time than with octals like KT88's; it's about creating a really super standardized power envelope for ultra-reliable bandwidth and no power spikes or dips base on load. The KT88/66/6550's sound better in triode for the most part because you kind of rev the plate voltage up as high as you can in Class A, with no cut off; not real efficient, and can lead to clipping, but that's why they sound purer. If you have transformers that can handle it, you get the benefits of Class A and the extra bit of bandwidth from a single ended design. Single ended like RCA plug vs. balannced plugs, where with balanced all the interconnects are grounded. Not single ended like a single ended tube design vs. a pushpull design; two totally different things. I'm surprised how often I see that particular confusion even in reviews. I've said this on another forum, but I'll say it here too: it's the difference between the sound of Sun Studios say (the EL34 camp) and like a great Verve recording (the KT88 camp), though not maybe as clear cut as rock vs. jazz.

Actually if you have an old mom & pop style radio shack place or seriously old school drug store, you may be able to find a tube tester locally - I happen to have a place like that around, and just like back in the 40's and '50's you can take your tubes in and get a reading by plugging them in to various sockets, turning a dial then pressing a button. I think computer match means "pay us extra for the same service; it will be on a computer plugged-in tube tester". Basically the difference between matched an unmatched is tubes used in tandem, or each tube on its own. Different topolgies is all. Personally I don't see one as inherently better than the other. Hurricanes and Merlins should sound great. If you get bored and want a sweeter sound, you can always try the EL34's. Merlins tend to be sweet. Should be a good balanced match with the KT88's.