Clueless: My experience has been that transistors made by the same manufacturer from the same batch are relatively close in operation. In fact, so long as the manufacturer maintains consistent standards, i've found them to be pretty good from batch to batch. As a case in point, i've been able to pull a dead transistor(s) out of a circuit and install a new one of the same brand with nary a problem. Bare in mind that this is taking place at RF frequencies with multiple pairs ( up to 96 output devices ) running in parallel. Should something be funny, i.e. dis-similar conductance characteristics, the results would show up VERY quickly in terms of distortion and circuit instability.
Obviously, others share similar experiences / thoughts as to what you stated about mismatches, especially between npn & pnp's. Some manufacturers have gone WAY out of their way to avoid such situations. I know that Plinius uses outputs of only one type ( can't remember if it's PNP or NPN ) in their output stages.
I can't say the same thing about tubes based on my own past experiences and those of others. One of the EE's that i used to work with at another job used to work for RCA in one of their tube production facilities. He told me that tubes were all over the place in terms of specs and that they varied the "acceptable performance standards" based upon how each batch of tubes turned out. As such, the "best" of one batch might be equal to the "mediocre" tubes from the last batch. As such, not only did the "best" tubes from each batch vary, so did those that were at the bottom of the barrel.
I found much of what i know about tubes the hard way after purchasing a company that manufactured tube based RF amplifiers. The funniest thing that i've noticed is that specific tubes that are highly desireable in RF circuits in terms of high output levels and ruggedness are supposedly less desirable in audio circuits. The green label Sylvania's come to mind here. Another thing was that tubes that we knew to be of very high conductance were rarely used in audio circuits. While some amps did use 8417's, i've never seen an 8908 or 2057 in an audio amp. I have to imagine that there are reasons why, but my thoughts are that a tube that had high output levels up that high and was quite rugged would be coasting down low in the audio band. The interesting thing is that i'm beginning to see more tube amps using tubes designed for transmitting purposes pop up lately, so maybe my thinking was that far out of line.
Marakanetz: There are SS devices that can put out GOBS of power by themselves. The only problem is that they require both very high voltage and very high current and require tons of heat sinking. This means that the manufacturer has to have very sturdy power supplies capable of very high steady state current levels with enough heatsinking to handle such tasks. As such, they are not suitable for high profit margin operations or where one would need mass production / mass distribution. The weight alone would kill them in terms of shipping. As to whether or not such devices are suitable for use in the AF ( Audio Frequency ) range is also another matter.
As a side note, what are commonly called "ceramic" or "steel" broadcast tubes are basically a hybrid between a tube and a transistor. There are devices like this that can output 15 KW on a steady state basis that you can hold with one hand. The amount of heat generated by such a device is absolutely incredible though and i would not want to be in the same room that it was being used in : ) Sean
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