If you have mixed up your tubes, you will need a tube analyzer to pair them again. If you can bias tubes individually on your amp you need not have matched tubes.
The KT88 is a kinkless tetrode, i.e. the cathode and one of the grids are shorted. In spite of being called a tetrode, it has three grids like a pentode. Ditto for the 6550 tubes, which are known as a beam tetrode. EL34s are 'pure' pentodes. I have a couple of amps where I can use KT88s, 6550s or EL34s (and I guess a couple other tubes as well)
Depending on how the amplifier is wired, you can run the KT88 in triode, tetrode or ultra linear. You can run any the majority of tetrodes and pentodes in these three configurations. (There may be ones you cannot, I dont know)
Running a pentode/tetrode in triode mode normally gives a forward sounding midrange, but you pay a price as you restrict the output of the vacuum tube. Most folks seem to prefer this configuration. Ultra linear and tetrode mode allows the tube a higher output, but is not generally a preferred configuration.
To my ear a tetrode wired pentode/tetrode mode sounds the most dynamic and 'peppy'; consequently I prefer this layout. My all time favorite tube amp is a single ended tetrode wired 6550.
Run in single ended triode mode, I generally prefer the sound from EL34s.
In a push-pull configuration with so many tubes, you may as well stick to the KT88 as they have lots of oomph and given the configuration, will give more or less the same detail as any other tube.
Regards
Paul
The KT88 is a kinkless tetrode, i.e. the cathode and one of the grids are shorted. In spite of being called a tetrode, it has three grids like a pentode. Ditto for the 6550 tubes, which are known as a beam tetrode. EL34s are 'pure' pentodes. I have a couple of amps where I can use KT88s, 6550s or EL34s (and I guess a couple other tubes as well)
Depending on how the amplifier is wired, you can run the KT88 in triode, tetrode or ultra linear. You can run any the majority of tetrodes and pentodes in these three configurations. (There may be ones you cannot, I dont know)
Running a pentode/tetrode in triode mode normally gives a forward sounding midrange, but you pay a price as you restrict the output of the vacuum tube. Most folks seem to prefer this configuration. Ultra linear and tetrode mode allows the tube a higher output, but is not generally a preferred configuration.
To my ear a tetrode wired pentode/tetrode mode sounds the most dynamic and 'peppy'; consequently I prefer this layout. My all time favorite tube amp is a single ended tetrode wired 6550.
Run in single ended triode mode, I generally prefer the sound from EL34s.
In a push-pull configuration with so many tubes, you may as well stick to the KT88 as they have lots of oomph and given the configuration, will give more or less the same detail as any other tube.
Regards
Paul