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RE: The best way to use feedback

I agree that usually-- higher impedance loading
of vacuum tubes delivers less measured distortions of
most kinds, and while I agree that this is true, I
experiment.

Not to try to prove anything, not to say that I might
be right or wrong.

There is, and has always been with me-- a better
objective, and that is to observe what the result
SOUNDS LIKE.

I always demand conservative operation of all parts.
That's a given. Loading is a variable that I play with
as I see fit. I like to see all the stages in an
amplifier run with minimal loading--high impedances.

BUT-- at the output stage, I prefer heavy loading.
The reason is PHYSICAL and is not according to the
dictates of calculation freaks.

This end-point loading could be described as all wrong--
the output tube delivers more distortions this way.

At this point, I have to inject some logic into this
discussion, and that is-- we don't know what levels
and kinds of distortions are relevant, and which ones
are mere mathematics. I said we don't know. Others
could very well say they DO know, and can easily supply
all kinds of easy to prove examples, according to
electrical laws that we all already know.

I don't break those when it comes to reliability.
I DO, however, do anything else I want if it improves musical
performance-- that is, relegates a recorded performance better.

The "overloading" of the output stage can be envisioned
as a Penstock, carrying water, driving a turbo-generator.

I have built several of these high-pressure Hydro-Electric
systems, which are running today.

Something I did to get the most out of those systems is
that the intake pipe diameter is the largest pipe size used.

As the water proceeds down the mountain, pipe diameter lessens
as pressure increases. At the water turbine, the water output
orifice is suddenly "necked-down" in diameter even further.

This sudden "overload" delivers more power to drive the
turbine, increasing system efficiency.

This is easy to do with an amplifier. Let's say you calculate
that your output transformer should be 2500 ohms, or more.

Try all of your values. Now, connect one that is 1200 ohms.

IF your power supply can handle the current demands, into an efficient
speaker, it will deliver far more realistic-sounding music, with
dynamics that you won't believe. Unwanted distortions won't
occur unless your power supply can't handle it. If it can,
measured distortions will be higher, but actual high-fidelity
listening will be far superior.

Too bad people don't understand this. Laugh all you want,
I have learned to expect it.

Oh, I also tune engines using the same principles. And
they sure do run!

-Dennis-






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