Re: Single ended triode amplifiers



Bret Ludwig wrote:

Generally I am against them, but it has to be admitted that there is
no intrinsic reason they can never succeed, and there is an
application in which their vices are not only tolerable but give a
certain advantage.

The SET amplifier has to do the same things any amplifier has to, it
has to have sufficient bandpass, level flatness, low distortion and
sufficient power so as never to clip under the normal dynamic range of
the music (or other program material). Now if it imparts coloration
and one likes that coloration, this is well and good provided we are
upfront about the result not being fidelity but modification.

The problems are thus:

In single ended Class A service, "enough power" is beyond most
receiving type tubes. If the most efficient speakers are used, the
8-10 watts a 300B will give if run at its prudent limits is barely
acceptable for pop music or chamber groups. It is ludicrous for
symphonic or film music, or any modern film soundtrack.


Who said most receiving tube types were incabable of giving enough
power?

What twaddle!

The receiving tubes so vilified may be paralleled to make any amount of
power you want.

OR, the speakers used are horns, or things like Tannoys, some JBLs et
all
which are over 95dB/W/M. 8 watts then becomes plenty.

AND many listeners don't like being slowly deafenened by their systems
or deserted by their wives because of the high levels.



Sufficient bandpass is achievable with only very good transformer
design, and the low end always suffers at that.

Rubbish.

Its quite easy to make SE OPTs with 20Hz to 50kHz BW
at full power,
and more at lower levels.

The achievable bandwidth is easily achievable,
but the non achieving bean counters in charge of
production ensure all their might is pitched against
giving bandwidth to the consumer.

Its not the technology that limits the technical performance,
its the human profit motive which ensures iron weight and copper turns
are minimised.

So blame humans, and leave the tubes alone.



With excellent design and judiciuous use of NFB the distortion and
damping factors are tolerable, arguably, but SET fans generally eschew
this. That's because they like a lot of coloration, coloration
achievable at far lower cost with line level circuits.

More twaddle.

Users of SET amps in my experience don't like coloration
and distortions of any kind. They just expect their amps to function
well
without corrective circuitry, rather like having their
children learn their lessons well without corrective canings.

Good design principles earnestly applied
have always produced SE triode amps with utterly negligible levels of
distortion.

That some SE amps are true horrors is a fact due to the fuctards
who persist in designing very poorly concieved designs with groos
mistakes in their
B+, RL, etc.

It happens with many PP amps as well. Samples from
many asian amps makers bring disrepute upon the
art of producing fablulous SET amps.
Many asian makers beaver away eagerly to make appalling amplifiers
not as good as the worst made in the West in the 1950s.
EG, the SILK range of SE amps are all crap from Thailand,

The faults are in the minds of the creators, but SET hardware is well up
the
task of giving hi-fi, and uncoloured hi-fi at that
which is in fact interpreted as being coloured, often because users of
hi-fi gear don't often go to concerts to find out what reality really
is.



With more conventional speakers the situation is of course quite
hopeless indeed.

One solution is going to larger tubes, such as the 812, 211, 845,
GM70, and points north. Unfortunately the transmitting tube industry
never made bigger triodes except in very high mu, Class B or Class C
configuration for RF linear amplifier use, such as the 833 and
3-500Z. Still, a single 211 or 812 can give 20+ watts, enough for
some full range use.

It may seem to some that using a 211 or 845 is like
commuting to work across say 300 miles by means of a privately owned
WW2 Mustang or Spitfire.

But two or four 211 can give up to 120 watts SET of totally class A
power.

Usually most people I know get by with no more than 1/2 a watt average
level per channel.
if they are listening to most music I can think of.

Adolescents have no perception of volume, sometimes needing police to be
called to
have them turn it down, but once they reach 25 have to pay for the
damage they
do to systems, and relationships, they learn about volume control.
By 25 many have tinnitus badly and loud sound isn't a priority,
because it feels painful or irritating at least to have hi volume.

They often ( but not always ) mature their taste, and music must be
intrinsically
interesting, and not a full throttle bunch of noise such as Heavy metal,
punk et all.

So the average levels plummet, and the full high dynamic range of
classical
is accomodated.


What works best, though, is to do what C.G. McProud and the staff of
Audio Engineering (later Audio) magazine recommended and use the
single ended amp strictly as a treble driver in a biamp arrangement.
In this way the lame output power is not so bad: indeed, with a
modestly tough driver, it protects the driver against overload.

Of course, while it has been done, few of the Twiode Twats actually
do this. This is because they have had so much fermented pig slurry
pumped up their ass by Gizmo, Bob Fulton, Waterbong Medwin, and the
New York crew they can't distinguish reality from nonsense any more.


Well done! fine sunday insulting session will get you all the right
points.

The people I deal with want their SE amps to be able to do full range.

They sometimes listen at high level as well. They don't like amps
to clip any more than you do at whatever absurd your levels used might
be.

Its all too easy to hook up a lone 300B to speakers of 87dB efficiency,
then turn up the volume, and say only and idiot wanker
would choose an 8W SET.
I know ppl who have such a set up and they simply are not deaf,
and they quite enjoy their music.
They don't expect huge volume.

Try using just ONE lone power transistor in class A for the output
device.

You will find the device can dissipate about 30 watts long term,
and you'll get about 13 class A watts, and comparing this to a single
triode
is the only fair comparison.

Soon you'll realise the single transitor has all the same limitaions as
the
single triode.

Oh, and because the transistor circuit is so non linear, more so than a
pentode circuit, lots of loop and current NFB must be used to
at least equal the triode without any loop FB, and only its own
small amount of internal NFB.

the following list indicates the SE amp power I recommend for 99% of
home hi-fi listeners :-
Horns...103dB/W/M,
Plain dynamics...
96dB,6W 1 x EL34/KT88
93dB,12W 1 or 2 x 300B, KT90
90dB,25W 4 x EL34, 3 x 300B/KT88/KT90, 1 x 211/845
87dB,50W double the 90dB tube count
84dB,100W quadruple the 90dB tube count
81dB,200W. SET not recommended unless living in a cold climate and you
have plenty of money.
ESL are usualy rated at low sensitivity PER 2.83V sometimes might need a
300W amp, but not to use the watts, but
take advantage of the high output voltage available.

Notice that the amount of SE power recommended is no different to power
available from other
types of amp, ie, PP tube or PP SS et all.

Many folks like to use half the power I recommend, some even less.

Patrick Turner.
.

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