I believe the speaker for that session was Bill Whitaker, a well-respected
engineer. Probably Jim, K9YC knows him on a first-name basis.
The vacuum tube v. solid-state debate has been raging on since the invention
of the transistor. Much of the vacuum tube hype among audiophiles during
the past decade has been based on non-quantifiable audio attributes.
Because so much of what we hear is arbitrary, and not measured, it has
opened up an entire cottage industry of super-high-priced audio amplifiers,
pre-amps, cabling, and accessories.
I have yet to hear a VT amp that cannot compete with a well-designed
solid-state amp when good design decisions are paid to source Z/damping
factor, power supply design, and especially negative feedback over the 20Hz
to 20 kHz response curve. In my opinion, the latter is the most deficient
design attribute today, mostly ignored by some of the world's leading audio
engineers. The link below discusses this effect in detail.
http://sound.westhost.com/highspeed.htm
Last spring, I replaced the audio output stage in my Drake R-4B receiver.
The R-4B's cabinet runs incredibly hot, primarily due to an inefficient
class-A design. Despite being class-A, distortion is relatively high (owing
to the design of the output transformer -- a mass-produced type used in ca.
1965 TV sets) as is residual hum when using high-performance headphones. In
its place is now a 4-watt solid-state amp, designed by SM0VPO. It is an
ultra-low noise class-B PP, with much attention paid to the negative
feedback loop. I won't get into all the descriptive adjectives to compare
sonic quality between the old and new amp. What I care about are the
measurements. If it cannot be measured, I don't think it's an issue worth
discussing. If it's being hyped and not measured, then time is not taken to
conduct the measurement. And, so many attributes of amplifiers described in
the media focus only on warm and fuzzy feelings, and not measurements.
There's not one attribute that cannot be measured.
Some design deficiencies of VT amps have become a positive thing. Look at
the hype concerning how good even harmonic distortion sounds. I suppose it
does, depending on the application. How about how good odd-order products
sound - the stuff we all seem to try and eliminate? A metal guitar plugged
into a deliberately over-driven Marshall amp produces much odd harmonic
content depending on how its biased and driven. That same guitar plugged
into a 100% linear amp sounds a lot different and its not a sound most
musicians want. But that is something that can also be measured and
incorporated into a solid-state amp. Even so-called "soft clipping of
tubes" can be easily emulated in a SS amp with little effort.
So, I'm not sure why this topic was presented at the NAB convention. I
can't think of anything radically new in audio VT technology that hasn't
been discussed at an NAB convention say...sixty years ago.
Paul, W9AC
----- Original Message -----
From: "Ed" <elh54@sbcglobal.net>
To: <Amps@contesting.com>
Sent: Monday, April 16, 2012 9:19 AM
Subject: [Amps] NAB...hope from the old world for the new?
> My friend just returned from NAB this morning, I thought I would share
> this line from his email with all of you:
> I attended a session Saturday at NAB - about VACUUM TUBES. They billed it
> as the first session at NAB about tubes in 30 years. It concentrated on
> the sound from tube-type audio gear (is it better or just different??).
> Thought about you.
>
> -Cecil
> 73,
> kv5i
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
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