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Bob Morein
 
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Default old solid state circa 70-80's`


"Chad Williams" wrote in message
om...
In researching solid state integrated amps/receivers I've come across
several proponents of old receivers, circa '75-early 80's, who say
that these solid state systems are every bit as good as anything being
made now. While I don't disbelive this statement, I'd like to
understand why this is the case. Was the build quality simply better
back then? Are the transformers higher quality???

I notice on ebay that a lot of these "vintage" models aren't even that
cheap. Some sell for well over $100. For another $100-200 you could
have something new, with new technology and a remote. So why would you
buy old?


It's not true.
If you're into vintage equipment, and you want that sound, or that memory,
then, of course, it might be worth it to you.
However, in terms of quality of the amplifier, it is definitely false, for
several reasons:

1. Designs in the 70's suffered from transient intermodulation distortion.
Around 1979, this was discovered and eliminated.

2. Bipolar transistors suffer from "thermal runaway", which occurs when a
small area of the junction heats up locally and becomes more active than the
rest of the transistor. Once it starts, the transistor is quickly destroyed.
The only solution available in the 1970's was brick-wall current limiting.
However, amplifiers which use this kind of protection cannot handle the
dynamic range of a CD at greater than low volume.

3. The noise figure of bipolar transistors dropped about 10 dB around 1980.
Prior to that, equipment had an S/N ratio of around 70 dB. After 1980, S/N
ratios of 90 dB and greater became the norm.

4. In 1981, David Hafler was the first to build an audio amplifier with
Hitachi's new "power MOSFET." This was a major watershed in amplifier
design. Concurrently, new methods of protecting bipolar transistors were
implemented. Both Hafler's and Strickland's MOSFET designs had interesting
qualities that raised the bar for bipolar designers. The result was an
informal competition which lead to rapid advances in amplifier design. This
continued up until about 1991. Since 1991, high end amplification has shown
no significant advances, although variations occur from time to time.

Home theater has had a negative impact on amplifier design. Nevertheless,
there is one company, Pioneer, which makes MOSFET receivers of heavy
construction that are notable for reproduction of music.

The key years were 1981-1982. The CD propelled an advance in the state of
the art.