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Re: long answer

Some alternate interpretations.

Marantz built tube products up 'til the day they were sold to the Superscope people, 1968 or thereabouts. Their 10B tuner drove them into bankruptcy. Dick Sequerra, the head designer for the tuner project, told me at a CES many years ago on the introduction of his new universal tuner (solid state), that a 10B in factory alignment was just as good as his new tuner up to 15kHz. Of course it didn't have digital readouts, PLL tuning as such, but he personally told me not to bother with his new tuner since I already owned a 10B. The 10B was as close to theoretical perfection as the existing circuits of the day could provide was what he told me, with more than a bit of pride showing (justifiably, if you ask me).

What killed tube amps was the Acoustic Research AR-3 with it's requirement of 60 Watts of power. Up till then, bass extension was achieved only with an extremely large box (think Klipschorns). The AR-3 marked the first commercially made speaker that was affordable and significantly smaller. A 60 watt tube amp pretty much marked the top end of most electronic lines: Marantz 9, Dyna Mk III, Mac MC-60 or 275. Some did not even have models in that power range: Scott, Eico. Dyna, incidentally, made tube units well into the 70's.

I distinctly remember and still have the issue of TAS in the late 70's which printed a cartoon of a tombstone with '12AX7, RIP', written across it.

Tweeters were already a popular add on throughout the decade of the 60's: Janzsen had their electrostatic arrays, Bozak concert grands had an array of something like 16 tweeters, and then there was the Ionovac plasma tweeter. Even the Decca ribbons were available, IIRC, in the late 60's, but I could be wrong there, but then they do use a transformer....
With the advent of transistors, the catch phrase was that they were cheaper, smaller, and generated way less heat. Power became extremely cheap. Bose had their 500 watt amplifier, and similar sized or larger amps were made by Phase Linear and others. As a result, speaker designs lowered their sensitivity to avoid consumers blowing them out.
With massive amounts of power and current available, speaker designers went crazy. Apogee with their impedance's dropping to as low as 1 ohm at certain frequencies could only be run with Krell amps when they first came out. Many Infinities had impedance's which dipped to as low as .8 ohm: disaster for many amps. I have seen amps smoking in showrooms and with material that was not very difficult or demanding.
This caused a major revolution in amp designs: current dumping became the prevalent design for most s/s units, even to this day. Tubes could not do this, at least not until the Russian 6C33 tube became available in the west. In the older era, speaker designers worked around the limitations of the electronics: these days, they couldn't care less. A constant impedance load is beneficial even to a s/s amp.

While cheaper output transformers do have problems, better ones are remarkably extended. Altec Peerless 20/20 transformers had frequency responses well above the accepted range of human hearing. Try telling EE Jim McShane that his Citation II transformers are 'bad'. I believe their FR goes well above 50 kHz.
Solid state gear dominates, because they usually are smaller and cheaper to manufacture. Funny how the best s/s tend to be heavy, though, and hot to boot (of course there are exceptions). It is much easier and much cheaper to employ electronic correction than to make a mechanically precise device, whether it be a driver or a transformer.


Just my view, obviously your interpretation is a bit different.

Stu

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