In article ,
Keith G wrote:

"Jim Lesurf" wrote in message
...


I quite like films like "When Worlds Collide" and they cut to "the
computer" and show lots of whirling rods and cams. :-)


...... being operated by a mechanical Olivetti adding machine with the
handle ripped off, like in The Prisoner rerun, a day or two ago!

:-)

Well, I do still have a Brunsvega mechanical adding machine. At one time I
used to know how to do square roots on it, but I forgot this years ago!

Still have a slipstick as well.. ;-

Slainte,

Jim

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In article , Andy Evans
wrote:
The performance of an amplifier comes from the way all the components
work in conjunction. Just replacing one item with a 'better' one might
simply make the performance worse...

I think there's a difference between using better componants and
'voicing' an amp. My experience has been that better componants - caps,
resistors etc - almost always improve the sound - better tone, detail,
transparancy etc.

This may be where our experiences differ. Apart from straightforwards
factors like parasitic effects or microphony, I tend not to have found such
audible differences.

Slainte,

Jim

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The moral of this tale is that if you want to make sure nobody can disagree
with you, just say stuff that is devoid of any meaning.

OK, Don. you are by your own admission a consultant and this is a thread about
valve amplifiers. What I propose is that you give me a selection of your own
valve amplifier circuit designs with your detailed construction notes which
prove that substituting componants has no effect on the sound. In return I will
give you a selection of my own valve amplifier circuit designs with my detailed
construction notes on the diverse effects of substituting componants. You are
welcome to breadboard my circuits with the relevant parts to check whether your
own ears confirm the effects I have found. That sounds reasonable doesn't it?
Let's put this to the test.

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

In article , Don Pearce
wrote:


Add to this, of course the basic inconsistency here of the very idea of
"voicing" an amplifier. An amplifier should not have a voice. It should
be totally self-effacing. Anything less simply gets in the way of the
music. Of course you may actually be into sound effects - in which case
ignore me and go right ahead.

I suppose this is a matter of preference.

It is my suspicion that some people prefer, for example, the changes in
overall frequency response that may arise due to am amp having a
(relatively) high output impedance. Thus in part using something like a
low-feedback design as an expensive 'tonal adjuster'. If they like that, it
is fine with me.

My own preference, though, tends to be for amplifiers which just 'get out
of the way' and leave me to hear the actual recorded/broadcast sounds.
Hence I don't want a 'voiced' amplifier, I want to hear the music, not the
amplifier.

Cue discussion of the meaning of "fidelity"... :-)

Slainte,

Jim

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In article , Andy Evans
wrote:
An amplifier should not have a voice.

Maybe in theory, but in practice componants sound different and amps
sound different, and 'voicing' an amp is the common term used in its
development.

As I said earlier, this is not my experience in general. :-)

I should say, though, that I tend to prefer designs that have a low output
impedance, flat response, unconditional stability, etc.

I've had a few conversations about how Beard amps were
'voiced', for instance, with one of their chief designers. In terms of
valves, the common term 'tube rolling' would not exist if it were not
for the fact that tubes sound different - swap a 6J5, 6L5, 6C5 and 6P5
and you'll have subtly different sounds, not even to mention varieties
within each type like metal, G and GT, round anode, flat anode, care in
manufacture, production run etc etc.

This prompts me to ask: The only figures I have for things like valve
microphonics measurements are in old Mullard mags. Are these available for
modern valves, comparing the different makes, and showing typical
variations, etc?

Such threads on tube rolling and voicing fill the pages of
www.audioasylum.com. To suggest that this representative bunch of
electrical engineers, chemical engineers, nuclear physicists and just
plain DIY amp builders with many years of building experience don't know
what they're doing is surely stretching credulity just a bit too far.

Afraid I'm not a 'physicist' any more. I retired last month... :-)

Slainte,

Jim

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In article , Trevor Wilson
wrote:


**Ah, The Prisoner. Now THAT was a great TV show. Along with The
Avengers, it was the pinnacle of Pommy TV (thinks of Mrs Peel and that
Lotus).

Now being rebroadcast on Friday nights on BBCTV4. :-)

Pleased I now have a DVD recorder... :-)

I did buy some of the 'Avengers' DVDs, but they went out of print before I
could get them all. Agree with you that these are excellent.

Slainte,

Jim

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In article , Andy Evans
wrote:
Some discussion of voicing DIY tube amps:

Rumor has it that the Scott company brought professional musicians in
house for auditions when they were voicing the 299B.

[snip]

I wouldn't bother the -3dB point, just listen.

You seem to be responding to someone, but as you haven't quoted them, I
don't know who, or what they said...

[snip]

I generally agree with your voicing suggestion but why on earth SRPP?

As above...

[big snip]

Do you measure the stability margins, output impedance, etc, of the results
of each component change? If so, how do they relate to the changes in
'voicing' you perceive? Do you then publish these values for the final
design?

FWIW when (many years ago) I used to design amps, when I found that things
like a cap change affected the audible performance then investigation
tended to reveal something like bursts of RF instability. Hence I am
curious as to how you investigate these things and what results you have
uncovered w.r.t. correlation with factors like measured stability
performance, etc, with what you regard as 'voicing'.

Slainte,

Jim

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In article , John Phillips
wrote:
In article , Andy Evans
wrote:
Some discussion of voicing DIY tube amps: snip

Interesting thread. I guess it illustrates how far away valve/tube
amplifiers still are from the ideal of just being "an amplifier." Show
me two amplifiers that (really do) sound different and I'll show you *at
least* one which is not behaving as ideally it should.

Depends upon what the user *wants* I guess... ;-

Long live choice.


My vote tends to go for *informed* choice. :-) Hence I'd like people to
try and understand the physical and engineering reasons why there may be
differences. i.e. not just "I tried 'A' and 'B' and preferred 'A'", but
"having made appropriate investigations we found that 'B' caused the amp to
roll off LF, or produce instability, or whatever."

Slainte,

Jim

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"Keith G" wrote:

: "Jim Lesurf" wrote in message
: ...
: In article , Mike Gilmour
: wrote:
:
:
: Thats what I like about old Sci-Fi films, the lab usually has a few
: scopes dotted around displaying Lissajous figures - essential for world
: domination. )
:
: I quite like films like "When Worlds Collide" and they cut to "the
: computer" and show lots of whirling rods and cams. :-)
:
:
: ...... being operated by a mechanical Olivetti adding machine with the
: handle ripped off, like in The Prisoner rerun, a day or two ago!
:
: :-)

OOh, you're getting The Prisoner re-run, eh?
I see the Yanks have The Life Of Brian currently (re) playing in cinemas:-)
http://movie-reviews.colossus.net/movies.html

But your Olivetti note reminded me of the ElectriClerk, for some reason ...
http://www.ahleman.com/Props/ElectriClerk.html

Shades of "Brazil";- another brilliant UK film I haven't seen for a while.

In article , Andy Evans
wrote:
The moral of this tale is that if you want to make sure nobody can
disagree with you, just say stuff that is devoid of any meaning.

OK, Don. you are by your own admission a consultant and this is a thread
about valve amplifiers. What I propose is that you give me a selection
of your own valve amplifier circuit designs

Is there a reason to limit this to valve amplifiers? If not, why not expand
it to using SS designs as a basis for camparing the (possible) audible
differences between components?

I am curious about this as most of my own work/experience has been in SS
designs. Hpowever it is my understanding that valve amps (particularly
older designs) tend to be typified by factors like having low overall
feedback, valve microphony, and the problems of output transformers. Given
these effects I can see that component changes might be more noticable with
such a valve amp than with many SS amp designs. However for the same
reason I might personally tend to prefer a SS design precisely because it
might give less scope for component variations having an audible effect.


with your detailed construction notes which prove that substituting
componants has no effect on the sound.

How could a set of notes 'prove' this? Are you perhaps using 'prove' when
you may mean 'evidence' or 'personal impression'? You might percieve a
difference, but be mistaken. Somone else might fail to percieve a
difference, but simply have missed it. Neither can clearly be said to
'prove' anything beyond the report in itself.

Or do you mean notes on measured results or something like a double blind
series of comparisons?

I'd be interested to know how you verify or test your own perceptions in
this area. In my experience it is one thing to have an impression that a
change has had an effect. It is something else to test this over a period
of time in a way that can reliably rule out uncontrolled variables or
variations in hearing. How do you do this when coming to your conclusions?

In return I will give you a selection of my own valve amplifier circuit
designs with my detailed construction notes on the diverse effects of
substituting componants. You are welcome to breadboard my circuits with
the relevant parts to check whether your own ears confirm the effects I
have found. That sounds reasonable doesn't it? Let's put this to the
test.

Who is paying for the components (and the time and testgear)?... ;-

Slainte,

Jim

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