Fleetie wrote:
Yes agreed, but while I can't prove anything, it just worries me being
constantly one sided.

There are a couple of us intending to investigate the hf ac heating, so
we will see...


Course, you could circumvent all these worries by just heating a
plate of suitably-coated metal from outside the glass, with a big
****-off laser.

Just a BIT inefficient, but hey, you gotta pay to have the best!

Well efficiency is not one of the things a valve can be accused of
anyway :-)

--
Nick

Nick Gorham wrote:

Ian Bell wrote:
Nick Gorham wrote:


Fleetie wrote:

I am VERY interested in learning about how to design valve amps,
but before I do that, I want one for my hi-fi, that just works.
Then I'll worry about how to design them myself. I guess the
simplest design to start off with is a Single-Ended Triode
amp - would that be right? Only one grid to worry about, and
only one power valve. Might as well walk before one tries to
run!

But for now, I just want a working valve amp for my hi-fi.


Ok,

First up, Single ended anything is simple on paper. BUT. to actually
make it sound as you might wish, its not quite that simple. As SE is
simple everything is important. Its very dependent on the regulation of
the power supply, so either you have a complex regulated supply, or you
use choke regulation, which means big (as possible) chokes, Then the
last cap in the power supply is in parallel with the output transformer,
so you can't just use any old electrolytic and expect good results. Most
SE designes are limited in gain, so feedback is not used


I don't know of anything that inherently means an SE design is gain
limited. The very first one I built back in the 60's used feedback from
the output
transformer. It consisted if a 6J7 and a 6V6.

Ian

Agreed, but what I said was most designs are gain limited, not that they
had to be.


Fair enough provided you can justify that remark. Are you saying that is
just how ?current? SE designs happen to be? If so is there any reason for
this?

Ian

"Fleetie" wrote in message
news:Z7iwc.38$SC4.37@newsfe5-win...
"Trevor Wilson" wrote
[stuff]

Oh. I stand corrected.

**It doesn't bother me, one bit, how far you shove your head into the sand.
It is your problem, not mine, that you care not one bit for logic and
reason. If you want to buy *any* piece of audio equipment, without first
listening to it, you deserve exactly what you are likely to receive.

Good luck. Because that is what you are relying on.


--
Trevor Wilson
www.rageaudio.com.au

Ian Bell wrote:
Nick Gorham wrote:


Agreed, but what I said was most designs are gain limited, not that they
had to be.



Fair enough provided you can justify that remark. Are you saying that is
just how ?current? SE designs happen to be? If so is there any reason for
this?

Ian

No, of course you can have as many stages as you want so as much gain as
you want, however its gets harder to apply global feedback with more
stages as you start to run into problems with phase shift.

The other side of the above statement, of course, is that the rationall
that goes behind the reintroduction of SE designs tends to frown on the
use of global feedback. It can be heard that increasing feedback will
tend to cause the sound to become closed and in some way deader. Now
some will prefer that effect, but in that case, the same sound can be
obtained by PP amps using feedback, so there is little point in
accepting the other SE problems, including cost and efficiency if the
same percieved sound can be gained elsewhere.

However for those that prefer the result of SE with little or no
feedback, then the additional problems are seen as acceptable.

There is a element of fashion attached to SE design and currently, part
of that fashion is zero negative feed back.

As I said, I am not trying to convince anyone of the "correctness" of SE
designs, but just trying to give some answers to the questions that were
raised. Which got onto feedback via the fact that without global
negative feedback its hard to make anything like a linear amp from non
linear devices.

--
Nick

Nick Gorham wrote:

No, of course you can have as many stages as you want so as much gain
as you want, however its gets harder to apply global feedback with
more stages as you start to run into problems with phase shift.

Managing this sitaution is one of those things they teach in engineering
school.

The other side of the above statement, of course, is that the
rationall that goes behind the reintroduction of SE designs tends to
frown on the use of global feedback.

The goal of modern SE design is obvioiusly to design the least accurate
amplifier possible.

It can be heard that increasing
feedback will tend to cause the sound to become closed and in some
way deader.

In the minds of certain delusional persons, yes.

Now some will prefer that effect, but in that case, the
same sound can be obtained by PP amps using feedback, so there is
little point in accepting the other SE problems, including cost and
efficiency if the same percieved sound can be gained elsewhere.

The interesting question is what there is about a high-distortion amplifier
that audiophiles should prize.

However for those that prefer the result of SE with little or no
feedback, then the additional problems are seen as acceptable.

Think of the modern SE amplifier as a good amplifier, front-ended with an
EFX box, such as might be used with an electric guitar.

There is a element of fashion attached to SE design and currently,
part of that fashion is zero negative feed back.

Good choice of words - the modern SE amplifier is a device borne of fashion,
not technology.

As I said, I am not trying to convince anyone of the "correctness" of
SE designs, but just trying to give some answers to the questions
that were raised. Which got onto feedback via the fact that without
global negative feedback its hard to make anything like a linear amp
from non linear devices.

An obviously ignorant statement, given the effectiveness of local feedback.

Arny Krueger wrote:
Nick Gorham wrote:


No, of course you can have as many stages as you want so as much gain
as you want, however its gets harder to apply global feedback with
more stages as you start to run into problems with phase shift.


Managing this sitaution is one of those things they teach in engineering
school.

Yes,thats why I said you start to run into problems, not that you can't
do it, as you say, part of any engineering discipline is learning how to
solve problems.



The other side of the above statement, of course, is that the
rationall that goes behind the reintroduction of SE designs tends to
frown on the use of global feedback.


The goal of modern SE design is obvioiusly to design the least accurate
amplifier possible.

Don't know, I suspect the goal of a commercial SE designer would be
different from mine, so you would have to ask them.



It can be heard that increasing
feedback will tend to cause the sound to become closed and in some
way deader.


In the minds of certain delusional persons, yes.


I think the word you are thinking of there is "listeners".


The interesting question is what there is about a high-distortion amplifier
that audiophiles should prize.


Yes I agree fully, that is the interesting question.


However for those that prefer the result of SE with little or no
feedback, then the additional problems are seen as acceptable.


Think of the modern SE amplifier as a good amplifier, front-ended with an
EFX box, such as might be used with an electric guitar.


Well yes, you could think of that, or you could show me how to create
such a circuit to put in front of a "good amplifier" that will produce
the same effect in a listener that SE designs can. If it was that
simple, then please tell me how, and lets see if people can tell the
difference. Maybe they could, if so my life would be much simpler, and
yours would involve much more cash.


There is a element of fashion attached to SE design and currently,
part of that fashion is zero negative feed back.


Good choice of words - the modern SE amplifier is a device borne of fashion,
not technology.


Yep, no disagreement there.


As I said, I am not trying to convince anyone of the "correctness" of
SE designs, but just trying to give some answers to the questions
that were raised. Which got onto feedback via the fact that without
global negative feedback its hard to make anything like a linear amp
from non linear devices.


An obviously ignorant statement, given the effectiveness of local feedback.



Yes of course smaller feedback loops can do the same thing. Remember I
am not claiming to be anything but ignorant of modern designs, just
answering the questions raised about the use of triodes.

--
Nick

The message
from "Trevor Wilson" contains these words:

**It doesn't bother me, one bit, how far you shove your head into the sand.
It is your problem, not mine, that you care not one bit for logic and
reason. If you want to buy *any* piece of audio equipment, without first
listening to it, you deserve exactly what you are likely to receive.

Good luck. Because that is what you are relying on.

I doubt is the situation is often as simple as not caring for logic and
reason. Few audiophiles are in the position of being able to audition a
wide range of valve gear.

New gear (of any quality) seems to be priced way out of Martin's budget
range, and be offered for sale secondhand very infrequently (and snapped
up very quickly). Apart from Nick's suggestions about kits, I would
suggest that he contact some reliable dealers as a serious buyer, and
then be prepared for a long wait. Audio engineers who work on valve
equipment may also offer some leads.

Meanwhile, his choices a trawl the web and the mags (luck needed
there too) and ask for advice from ngs like this one, where wider
experience can be drawn on.

FWIW, I notice that there is a company which advertises in HiFi World
(www.audioclassics.co.uk) with powers (£260) and preamps (£190) but I
have no personal knowledge of their products.

David

Nick Gorham wrote:

Ian Bell wrote:
Nick Gorham wrote:


Agreed, but what I said was most designs are gain limited, not that they
had to be.



Fair enough provided you can justify that remark. Are you saying that is
just how ?current? SE designs happen to be? If so is there any reason for
this?

Ian

No, of course you can have as many stages as you want so as much gain as
you want, however its gets harder to apply global feedback with more
stages as you start to run into problems with phase shift.

Agreed but surely true of any topology?


The other side of the above statement, of course, is that the rationall
that goes behind the reintroduction of SE designs tends to frown on the
use of global feedback. It can be heard that increasing feedback will
tend to cause the sound to become closed and in some way deader.

I can understand that they will sound different and that different people
will prefer with and without feedback.

Now
some will prefer that effect, but in that case, the same sound can be
obtained by PP amps using feedback,

Interesting. IIRC PP systems can only produce odd harmonic distortion which
sounds more musical. I am not sure what the primary distortion mechanisms
are in valve SE designs but you statement infers it must be mainly eben
harmonics.

so there is little point in
accepting the other SE problems, including cost and efficiency if the
same percieved sound can be gained elsewhere.

However for those that prefer the result of SE with little or no
feedback, then the additional problems are seen as acceptable.

There is a element of fashion attached to SE design and currently, part
of that fashion is zero negative feed back.

Not entirely unexpected.


As I said, I am not trying to convince anyone of the "correctness" of SE
designs, but just trying to give some answers to the questions that were
raised. Which got onto feedback via the fact that without global
negative feedback its hard to make anything like a linear amp from non
linear devices.


And I am just curious to know more. I have no axe to grind either way.

Ian

Nick Gorham wrote:
Arny Krueger wrote:

Think of the modern SE amplifier as a good amplifier, front-ended
with an EFX box, such as might be used with an electric guitar.


Well yes, you could think of that, or you could show me how to create
such a circuit to put in front of a "good amplifier" that will produce
the same effect in a listener that SE designs can.

It appears that many of the effects of SE designs are not technically based.
There is clearly a mystique associated with SE designs. Therefore,
alternative circuit designs all by themselves can't possibly produce the
same effect in a listener that SE designs can.

Ian Bell wrote:

No, of course you can have as many stages as you want so as much gain as
you want, however its gets harder to apply global feedback with more
stages as you start to run into problems with phase shift.


Agreed but surely true of any topology?

Yes, anything with RC stages and transformers is prone to this, its part
of why valve amps tend to have low (or none) feedback.


Now
some will prefer that effect, but in that case, the same sound can be
obtained by PP amps using feedback,


Interesting. IIRC PP systems can only produce odd harmonic distortion which
sounds more musical. I am not sure what the primary distortion mechanisms
are in valve SE designs but you statement infers it must be mainly eben
harmonics.

Yes, traditionally SE produces predominantly second order harmonics.


And I am just curious to know more. I have no axe to grind either way.


Fair enough :-)

--
Nick