Hi Zumbo!
I have also just read through all the posts. You would have learnt a couple of things:
One cannot generalise or even necessarily form an opinion based on people's hearing experiences. I am not saying all are misleading; the thing is one doen't know which is/is not. In fact, I was rather amazed at the verocity and hardly veiled personal/emotional content of many, as if trying to make a point by "shouting"?
Generalising made up a high percentage of "truths" uttered. Some think tubes are rubbish because they have never heard a good product. Often guitar amps were mentioned, where electronics were specifically designed to have a sonic signature - nothing to do with the active devices. (For the record, similar and greater effects are possible with semiconductors. That does not make the transistor inferior.)
I do not have hearing experience of the dozens of products boasted by some. On the other hand (and purely for the record, though I expect labels to come flying soon, seeing as how some have a predisposition thataway), I have been involved in the professional design and construction of amplifiers for 55 years, and stil am. I have done many tube and semiconductor designs and still do, although I miss the spectrum analyzer equipment that was in my laboratory before retirement.
One does not begrudge people their preferences; as said it is their money. They can mount their amplifiers upside down in the oven or put their speakers in the toilet; it is everybody's right. But to generalise to the extent shown here is a bit thick. Perhaps I can start by setting a few basic things straight (and forgive if I do not follow each statement by umpteen references - there is a word count limit here).
It has become tradition to belittle measurements, but mercifully such opinions here were in the minority. I was bemused by someone stating that the eyes can also be bluffed - sure! But in context: I really do not think it could be seriously meant that because hearing is subjective, the same is optically valid when reading off a meter or amplitude on a spectrum analyser. Fact is that modern spectrum analysers can resolve below to what is audible. But to be meaningful one must look at the right parameters.
I have sorely missed one factor here (apology if I overlooked it; it was rather a long read), and that is the influence of high order harmonic distortion products. One can have the same thd figure in two amplifiers, but the one will sound "clean" while the other will cause definite listener fatigue. If the distortion consists of mostly 2nd and 3rd harmonics the ear will not be sensitive to that at least up to 0,2 - 0,4% (accorcing to controlled tests), but have some 7th, 9th and 11th products, and these will cause auditory annoyance even when on the threshold of audibility. (This again as tested in some Scandinavian laboratories; those folk are tops in this sort of research. Ref. AES papers, etc.) In that sense thd is with all respect an outmoded parameter - but manufacturers will quote that fullstop, because why bother with more if the amplifier sells anyway? Properly designed tube amplifiers mainly present lower order products if at all audible, while the same is by no means true of even expensive transistor amplifiers. (Put some of these on an analyser and some real horror shows can be observed.)
The important point here is to realise that the accumulative auditory contribution of these is just about impossible to measure. Picture all the frequencies present in any moderately complex piece of music, then all those harmonics of each frequency, and finally the multitude of strident combinations that may or may not exist at any moment. This will of course vary continously (which is a very simplistic explanation of the major cause of listener fatigue). Point is then, rather avoid high order products altogether - and this is where some, especially transistor amplifiers, don't quite succeed.
I am not making a great contribution in helping you with your original question regarding what to buy or make, but trying to set direction in the presence of some pretty sweeping statements. Other points:
I am glad that Pierce set the record straight regarding damping factor in the quote given in post #86 (if I am correct). This is an often overrated parameter. In that sense it is not true that tube amplifiers are worse that transistor amps (but some are; again we are hopefully not referring to the inferior examples of either topology).
Another point (I am trying to be brief) is that some real loudspeaker loads can push an amplifier into momentary instability, and this is unfortunately more common especially with some transistor amplifiers of the very low distortion variety, obtained by inornately high feedback, than with tube amplifiers. By that I mean that it can happen, although one does test the way one member mentioned regarding L, R and C loading. (A phase angle of +/- 50 degrees can unfortunately occur with some loudspeakers, judging from published graphs.)
Zumbo, this was a totally inadequate contribution to try to bring some truths regarding the two topologies. Books were written and papers delivered on these subjects. I also did not repeat; yes, tube amps are more expensive plus the other factors mentioned by others. Yet they sell! Manley and all the others will not survive otherwise.The most expensive tube one I know is a $100 000 plus job by Wavevac (spelling?), the Ongaku, etc. Rediculous? Yes, to my mind. Do I think it is necessary? No, not really. Both a properly designed tube amplifier and proper transistor design can be "clean" - and the latter is less expensive. But in practice ...... The preference is individual. I prefer transistors, but still get asked for both. Customers are satisfied, so perhaps it is possible to do something right.
Regards!
