bone43 wrote:

Patrick Turner wrote in
:



Chuck Harris wrote:

Patrick Turner wrote:

Electronical regurgitations.

See this, http://www.welbornelabs.com/ultra.htm

Battery powered tube audio.
Back to 1925........

Patrick Turner.



My, now isn't that Special!

They also have Direct Reactance Drive
for an SET amp at http://www.welbornelabs.com/drd.htm

Dirty Real Drivel?, or what?

All sorts of claims, and no proof for its validity,
Aye, that's the Web for ya.

The blokes in the audio club down here read all the silken tongue
clap trap about "the sound", and then start thinking it just has to be
better
than anything else, and because price is low, are tempted to buy it.
But when I see the schematic, I start thinking of 101 ways
which could be better.
But what is important is the information which is missing about the
amp,

and its parts.
I have no doubt it works OK, and probably sounds well,
but it ain't hard to get a good sound from a 300B, and you don't need
a
550v PS.
And with no loop FB, surely the brand of 300B is important......

Patrick Turner.




-Chuck


Chuck,

I built this amp very good sounding, actually Designed by "jack at
Electra Print" but nothing new its also called the monkey by some it
came up on the joe list some years back the ideas not new but very old
just a new name for a old design but most are its all been done before.
where there could be some amazing advances made would be in tubes with
today's materials and computer aided design and manufacturing but you
have to have the demand for the money on R&D and that just not there
Tube audio is still just a niche market big companies won't bother
With it.

I don't doubt the "amp that jack built" works very well.

To me the use of a 550v supply and the choke to supply the
DC to the 6N1P driver tube is quite the same as if you set up
the 300B with a normal cathode biased stage with say 430v supply
and you had a filtered down separate 150v supply for the 6N1P.
The only difference is that you'd need one extra C&R to couple the
anode of the 6N1P to the 300B grid.

As it is the welborne circuit is elegantly simple.

Alternatively, the 430v supply would allow a resistor load to be used from a

filtered down rail of say 400v and this R would be a high enough value to
be a large multiple of the 6N1P Ra, to keep the tubes thd low.
There is still a need to use CR coupling, but a cap is a "pure reactance"
and is not any more blame worthy than a choke, and in fact a cap doesn't
suffer from the production of iron caused distortion products
and its a lot cheaper.

I enjoy the fact that such SET amps are not the product of
computer aided design or efforts by big business
with its tendency to produce dumb everything down to make it as
cheap as possible to make.
Some areas of manufacturing need computer aided design in the same way a
whale needs an umbrella, imho.

I doubt all the efforts using modern ideas would give us much better tubes
than we have already,
with any greater sonic benefits than the 300B which first appeared in 1928
after being
designed in preceeding years. My history report could be out by a couple of
years,
but its not important.
I'd like to see an indirectly heated 300B but everyone knows
that option is possible now; just triode strap a KT88, and that's about near
enough.

Of course to purists it isn't, since its a beam tetrode with heavy screen
feedback.

I'd say that a triode with 50 watt Pda, Ra of around 1k, µ = 10 could be
made possibly using cool cathodes like the 6146, and rather smaller,
like some of the strange looking metal& ceramic transmitting tubes, but they
cost a lot more to make than a glass
bulb type.
The anode is a large external heat exchanger in some of these types of
tubes, useful where fan cooling is
wanted, ok for a transmitter where fan noise is not a problem but to make an
anode
that just needs bolting to a normal heatsink like modern transistors isn't
easy, and afaik, hasn't
been done, and couldn't be done economically, and has no need to be done
because a
glass tube gets rid of its heat through the glass radiantly quite well as
things are.

If one had a vacuum tube amp that looked identical to a transistor amp
except
for the slightly larger "strange looking" devices bolted to the heatsink,
and the giveaway OPT, would such amps have the same appeal as present
day tube amps? I doubt it.
Pretty soon bean counters would be begging engineers to put more
transconductance into the tubes they designed to allow heavy class AB to be
used,
at great sacrifice to the class A linearity of the devices if used as
individual
class A SE devices.
The cry for more at lower cost would then reduce new world imagined triodes
down to
lowest common denominator real fast.
All this would have happened had transistors not been invented.
But even if transistors hadn't been invented some digital techniques still
would have been,
and pulse width modulation would have become a routine way in which to get
rid
of the weight in OPTs, and hence the darn cost.

The latest pwm transistor amps with 95% efficiency look like making
all preceeding class AB "linear" transistor amps obsolete within 10 years.

Tubes will still be with us, since I doubt class A linear circuits
will ever be bettered sonically.


Maybe other civilisations on distant planets around our universe have come
to
some other arrangements, but it seems we may never benefit from knowing
what they have done.

The corporate world will be hugely and greedily interested in any
contact we may make with other civilisations out there.
Anyone who does establish contact with aliens will keep it very hush hush
until they can sell their achievement somehow.
Just imagine if we found ways to make a light bulb for 10c, which used
10% of the power, and ways to make food grow 10 times faster
in fields ruined with salt after such long periods of human stupidity!

Patrick Turner.


















Bone43