Advice: Amp building
 

I would suspect valve makers stopped making direct heated valves
because
the people who wanted to buy valves started buying - and preferred -
those
which were *not* direct heated.

I would suspect that the change was done entirely in terms of
convenience, rather than sound quality. The sound quality was no doubt
considered "close enough not to make a difference". And this is the
issue really - when even small changes in sound quality do make a
difference, then builders will use what they empirically find to be
better. No doubt nothing except a few volumes of statistics will have
any effect on your judgement, so it's pointless pursuing this,
particularly since you admit you know virtually nothing about DHTs.

Advice: Amp building
 

In article . com,
Andy
Evans wrote:
I would suspect valve makers stopped making direct heated valves because
the people who wanted to buy valves started buying - and preferred -
those which were *not* direct heated.

I would suspect that the change was done entirely in terms of
convenience, rather than sound quality.

Which, correct or not, would be consistent with what I wrote, and which
you quote above. However, either way, what we 'suspect' isn't actually
evidence w.r.t. your assertions about the 'sound' of such valves. Your
statements continue to have the status of an assertion of belief on
you part for which you have offered no evidence.


The sound quality was no doubt considered "close enough not to make a
difference". And this is the issue really - when even small changes in
sound quality do make a difference, then builders will use what they
empirically find to be better. No doubt nothing except a few volumes of
statistics will have any effect on your judgement,

It is a shame that you seem not to understand the distinction between a
dismissive phrase like "a few volumes of statistics" and the value of
reliable and relevant evidence, rather that an assertion of faith.

Please note that I have not asserted that direct heating does not, or
cannot have any effect. What I did was ask you to provide some evidence for
your assertions that it does. You have provided no evidence.

so it's pointless pursuing this, particularly since you admit you know
virtually nothing about DHTs.

....and you seem unable to tell us much more than "virtually nothing" about
them - at least in terms of useful evidence rather than your personal
faith. :-)

Hence I'd agree that trying to pursue this with you would be pointless. I
feared this might be so, but was curious for the reasons I gave, so
wondered if you could provide some useful information. Alas, not.

However the exchange has served the useful purpose of illuminating that you
seem unable to offer any evidence to support your personal beliefs. In that
way, I think it has made a useful point which the OP and others can take
into account if they so choose.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Advice: Amp building
 

"Arfa Daily" wrote in message
...

"Andy Evans" wrote in message
oups.com...
Note that most transistor amp designs tend to have a flat response, low

distortion, and a low output impedance. Whereas zero-feedback 'SET'
designs
tend to have a tailored response, distortion that rises rapidly with
output, and a relatively high output impedance. All of these factors
may
cause the SET design to change the signal patterns and cause audible
changes in some circumstances.

It may be useful to seperate out some of the commonly used expressions
regarding SETs and valve amps, since I know several have been confused.

a) One of the common characteristics of SETs (though NOT implicit in
the term "single ended triode") is the use of a DHT (directly heated
triode) in the output such as 2a3, 6B4G, 300B and 845 - this can be a
major positive factor in the overall sound, against which can be set
the drawbacks Jim has listed above. .
b) When we come to DHTs we are in another ballgame, in my opinion.
Those who habitually use DHTs, do extended listening tests with DHTs,
and are familiar with their characteristic sound will claim they offer
quite audible gains in clarity over indirectly heated valves. This is
only partly a question of output valves, but in practice only a small
handful of people will have used small signal DHTs for preamps, input
and driver stages of amplifiers. Reason being that while output DHTs
are available in current production, there are zero small signal DHTs
(except one or two rare boutique ones at huge prices). They are
available on ebay since they were used in countless old radios from the
20s and 30s, and there are good but dwindling stocks still to be had.
Some on the other hand have become quite rare. As you might guess, I'm
a huge fan and use them in preference to anything else.
c) DHTs and zero feedback can be used in push-pull amps with different
results from their use in SETs. Each of these factors contribute -
feedback, push-pull/single ended, indirectly heated or directly heated
and so forth (we could go on)

I don't personally use SETs and never have, and it is useful in terms
of general attribution theory to consider what we attribute to which
factors. In particular DHTs and SETs are absolutely not equivalents -
one refers to valve construction and the other to circuit topology. One
might consider that SETs with DHTs are a bit of a curates egg - both
good and bad factors. I'd personally opt for all-DHT push pull amps
given the choice. We haven't even come to another common SET feature -
interstage transformers - but that's enough to be getting on with. Andy

What is the theory behind an indirectly heated valve, having an inferior
performance to a directly heated one ? Not being contentious - just
interested ...

Arfa



Ah. OK ... Looks like I have might have my answer from some of the other
posts that have appeared since I posted my question. Once again, it seems to
be one of those " in listening tests 99% of people could hear a difference "
situations, with no actual published measured data to back the claims up. It
seems to me anyway, that unlike in the ongoing interconnect debate, where
everything stays fundamentally the same bar the cable, in this case, it is
apples and oranges both being classified as fruit ...

Since you can't buy the same valve in directly and indirectly heated
versions, you can't cross substitute to see if one performs differently from
the other in the same amp. Even if you could get both versions of the same
valve, you would have to have differently designed support circuitry for a
cathode-less valve. As Andy has noted, because the cathode now is the
filament, radically different heater circuitry has to be employed.

As far as I understand valve theory and historic development, the only
reason that valves were originally directly heated, is because they were
basically modified light bulbs. Once the makers had got the hang of
producing harder vacuums, it was then possible to use thermo-emissive
chemicals in the valve, which allowed for operation at a much lower
temperature. To improve the efficiency of the emission process, these
chemicals were deposited evenly on a cylinder, heated from the inside by the
filament, threaded up the middle. This also allowed the filament or heater
circuitry, to be separated from the cathode circuitry, making possible
simple AC powering of the heater. All very simple and logical historic
progression, as production technology and materials progressed.

Whether the electrons are forced off the surface of a tungsten filament by
viciously heating it, or produced as a result of applying more gentle heat
to chemicals which readily give up large quantities of electrons, is neither
here nor there, so I can't basically think of any reason that - setting
aside differing electrical characteristics that all valves have designed-in,
dependng on the job they are intended to do - there should or could be any
audio-affecting performance difference between correctly operated valves of
either type.

Perhaps someone who purports to know the difference could enlighten me, as I
really am interested in knowing.

Arfa

Advice: Amp building
 

Arfa Daily wrote:


Perhaps someone who purports to know the difference could enlighten me, as I
really am interested in knowing.

Arfa



Well, I don't purport to KNOW if there is a difference, but one thing
comes to mind. Once the makers start to use a cathode, which is
effectivly a rigid cylinder, then the grid to cathode spaceing can be
much reduced. Ending up in the 50's with the very high gm frame grid
valves like the e810f and d3a. The DH valves, because of its "floppy"
fillament needed to keep the first grid out of the way. I wonder if this
is in part the cause of the difference. Its certainly the case that IH
valves seem to show far more of the island effect in their curves. You
only have to compare (for example) a 2a3 and a triode connected 807 to
see the difference, and this effect is a direct result of grid to
emmiter spacing.

--
Nick

Advice: Amp building
 

In article , Nick Gorham
wrote:
Arfa Daily wrote:


Perhaps someone who purports to know the difference could enlighten
me, as I really am interested in knowing.

Arfa



Well, I don't purport to KNOW if there is a difference, but one thing
comes to mind. Once the makers start to use a cathode, which is
effectivly a rigid cylinder, then the grid to cathode spaceing can be
much reduced. Ending up in the 50's with the very high gm frame grid
valves like the e810f and d3a. The DH valves, because of its "floppy"
fillament needed to keep the first grid out of the way.

This would also presumably affect the inter-electrode capacitance values,
etc.

At least you have suggested an plausible hypothesis for some difference in
performance.

I wonder if this is in part the cause of the difference.

Alas, this pre-supposes that there *is* an audible difference when the
devices are used in a well-designed amplifier. So far, all we have on that
is Andy's assertions which failed to back up with any plausible explanation
or reliable evidence.

TBH It seems to me to be daft to try and suggest someone who wishes to
start experimenting with building their own amp should begin with such
arkane and evidence-free matters, involving parts that have not been made
for decades. However this is for the OP and others to decide, each for
themselves.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Advice: Amp building
 

Perhaps someone who purports to know the difference could enlighten me,
as I
really am interested in knowing. (Arfa)

Hi there - I use valves on a daily basis, but I don't know the
construction details. As they say, "I know a man who does" but he's in
France working on Italian sports cars! There are some books on this,
though I don't have the references. When the weather cooled down last
night I did try and google a bit, since I'm curious myself. The sites I
came across tended, again, to be enthusiastic DHT users/designers. You
will find masses of references to DHTs in any search on:
www.audioasylum.com
www.diyaudio.com
These two sites are about the best for design details and user
experiences. Particular sites referring to designing with DHTs include:
http://www.nutshellhifi.com/triode1.html - Lynn Olsen's many DHT
designs
http://members.aol.com/sbench101/ - Steve Bench's designs
http://www.vt52.com/diy/philosophy/philosophy.htm - Jim de Kort's
designs
http://www.audiodesignguide.com/se/katelelo.html - an example of DHT
small tubes
http://www.6moons.com/audioreviews/steve/steve.html - a little history
of the re-introduction of the DHT into current design
http://www.positive-feedback.com/Issue16/kennedy.htm - Preamp design
with DHT small tubes and reference to filament supplies (this is a
whole subject on its own, and filament supplies do sound different in
experiments we've carried out)

I don't know if any of the above will exactly answer your question, but
it should provide some knowledge of the current DHT design scene. Andy

Advice: Amp building
 

"Nick Gorham" wrote in message
...
Arfa Daily wrote:


Perhaps someone who purports to know the difference could enlighten me,
as I really am interested in knowing.

Arfa

Well, I don't purport to KNOW if there is a difference, but one thing
comes to mind. Once the makers start to use a cathode, which is effectivly
a rigid cylinder, then the grid to cathode spaceing can be much reduced.
Ending up in the 50's with the very high gm frame grid valves like the
e810f and d3a. The DH valves, because of its "floppy" fillament needed to
keep the first grid out of the way. I wonder if this is in part the cause
of the difference. Its certainly the case that IH valves seem to show far
more of the island effect in their curves. You only have to compare (for
example) a 2a3 and a triode connected 807 to see the difference, and this
effect is a direct result of grid to emmiter spacing.

--
Nick

OK Nick, thanks for that. It's valid and useful input, and a situation that
I hadn't considered. I will ponder further ...

Arfa

Advice: Amp building
 

However the exchange has served the useful purpose of illuminating that
you
seem unable to offer any evidence to support your personal beliefs.

No, Jim, the exchange has once again shown that you seem unable to show
any constructive support or understanding of the empirical creative
process, how it takes place, its essential features and the
personalities of creatives. Building a new project - the OP's purpose
in posting - is a creative act, and falls within the usual stages and
parameters of creative acts. I would direct you to any study of the
creative process, such as the four stage model of preparation,
incubation, inspiration and completion, which will do for starters. The
OP is at the stage of preparation, and probably the first stages of
inspiration, though I would expect that this is a fairly dormant stage
where a large variety of ideas are assembled and mulled over. The
materials used at this stage may (or may not in many cases) include but
will not be restricted to theoretical data and statistical analysis.
Personality wise, the driving force in this early stage will be
curiosity, and many ideas will be worked on, most being rejected at
some point during the empirical testing stage. It is essential that any
ideas are considered on their own merits, and not on the say-so of
others or past historical usage, since the purpose is innovation and
the selection of ideas is radical rather than conservative. The
selection of ideas in the creative process will almost by definition be
made by the creative himself or herself, otherwise it would not be a
creative process. So the usefullness of moralistic directions do do
"this" or "that" because one "should" will be of little final
consequence, though such practical information will be useful in the
stage of prototyping and testing.
In terms of the personalities of creatives, we should expect
difficulties with the establishment and in particular conflict with
"teachers" or similar figures (Getzels and Jackson 1962), independence
of ideas, stubborness, tolerance of ambiguity and absurdity,
symbolistic linking of ideas and divergent thinking (though convergent
thinking is important to the integreation of ideas in the final
stages), competitiveness, abundant imagination, and of course
non-conformity. This is not an a-la-carte list - you get the creative,
warts and all. No doubt the champage socialists of this world would
prefer a Van Gogh on the wall of their salle de sejour rather than in
the kitchen drinking pastis and cutting his ear off, but that's
creatives for you.

In that way, I think it has made a useful point which the OP and others
can take
into account if they so choose.

Yes, you do like to support your moral standpoint on things with sly
references that 'other people will find I'm right and you are wrong'
don't you. I usually note this has been slipped in at some point. I
think that in reality you will have no more or less interest shown in
your own particular views than the interest shown in any apparatchik
who has historically stood in the way of dissidents. While the
apparatchiks - believing themselves on safe ground - built all the dams
and power stations, the dissidents advanced the culture and took risks
with new ideas. Fair enough, but imagine a world where the apparatchiks
were put in charge of new ideas.

Advice: Amp building
 

In article . com,
Andy
Evans wrote:
However the exchange has served the useful purpose of illuminating that
you seem unable to offer any evidence to support your personal beliefs.

No, Jim, the exchange has once again shown that you seem unable to show
any constructive support or understanding of the empirical creative
process, how it takes place, its essential features and the
personalities of creatives.

Sorry, but I am afraid that you are missing the point. What I don't show
"constructive support" for is people presenting their personal beliefs as
if they were established by some reliable evidence, but then failing to
offer any assessable evidence or plausible explanations when invited to
do so.

It is quite possible to employ what you call "empirical" or "creative"
processes, indeed, I'd expect these to be a part of serious sustained
R&D. But the methods used don't preclude (or absolve) the expectation
that any assertions that follow may require some assessable evidence
to support them.

I'm quite happy to leave it to others to decide if your personal
comments about me above have any worth or relevance. To me, though,
they read like you decided to "go for the man, not the ball".

Building a new project - the OP's purpose in posting - is a creative
act, and falls within the usual stages and parameters of creative acts.

Agreed. But was not what I was asking about.

Perhaps it has escaped your attention that I have also engaged in such
'processes' over the years, and I agree they often involve impirical
methods. Yet the results can be tested and produce evidence others can
assess. Being 'creative' does not make this totally irrelevant. The
process is not the result. Nor do I think we should expect others to
accept whatever we claim even if we fail to give any evidence they
can assess or explanations they can consider for plausibility.

Regardless of how an amplifier has been designed and built, it is
still possible for someone to use it as part of some suitable
tests to obtain evidence to support or confound the idea that it
'sounds different' to some other amp(s) for some reasons.


[big snip]

So the usefullness of moralistic directions do do "this" or "that"
because one "should" will be of little final consequence,

I'm afraid that it is yourself who is injecting "moralistic" approaches and
inventing "directions" to do things. All I was looking for was some
evidence upon which the OP and the rest of us could judge your assertions.

[big snip]

In that way, I think it has made a useful point which the OP and others
can take into account if they so choose.

Yes, you do like to support your moral standpoint on things with sly
references that 'other people will find I'm right and you are wrong'
don't you.

The process seemed to be that I asked for evidence/plausible explanations,
and your response is as exampled above. To invent words to put into my
mouth and try to criticise me. i.e. "go for the man, not the ball".

TBH Andy, I don't think you do yourself (or those who are enthusiasts
for valve amps) much of a favour by writing as you have in the posting
I am responding to.

I usually note this has been slipped in at some point. I think that in
reality you will have no more or less interest shown in your own
particular views than the interest shown in any apparatchik who has
historically stood in the way of dissidents.

Actually, what happened was that I was curious about what you claimed and
wondered what basis in reality it might have. Hence my questions. They gave
you an opportunity to give an explanation and present any evidence.
Instead, we had the posting to which I am responding.

I was (and still am) quite open to the *possibility* that direct heated
valves do have some specific effect on the results in some designs. Hence
my curiosity. I did find what Nick wrote on this quite interesting.

While the apparatchiks - believing themselves on safe ground - built all
the dams and power stations, the dissidents advanced the culture and
took risks with new ideas. Fair enough, but imagine a world where the
apparatchiks were put in charge of new ideas.

Nice as a sweeping statement in a political speech, but alas it tells us
nothing about valves or amplifiers, I'm afraid.


I can't speak for others, but I am afraid that I don't regard you simply
presenting yourself as a "creative" person employing "empirical" methods
to be, in itself, of much use as evidence. But it may be that others
will regard what you say differently.


Slainte,

Jim


--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Advice: Amp building
 

I can't speak for others (Jim)

Well, that's a step in the right direction.

but I am afraid that I don't regard you simply presenting yourself as a
"creative" person employing "empirical" methods to be, in itself, of
much use as evidence. But it may be that others will regard what you
say differently.

You can't stop speaking for others even if you try can you?

We can go on forever like this but what's the point. You lecture at
university level in engineering and publish books (as far as I know), I
lecture at university level in the psychology of media, creativity arts
and performence and I also publish books. Drop your arrogant and
dismissive tone with me and I'll do the same with you. And could I
suggest that if you want to hear what DHTs sound like, you BUILD
something with them rather than annoying those who actually do so do
with your insatiable needs for evidence and proof of everything.