AmpCableSpeaker interaction
 

I enclose the following, from Geoff Mead (Audiocircle): does anybody know
anything about this? Quote goes:

Re the current thread on speaker cables and sonic differences between
different amp/cable/speaker combinations. There has been an interesting series
of articles in Electronics World staritng June 2004 if anyone hasnt seen them.
The author Graham Maynard started looking at the old chestnut as to why valve
amps sound different from S/S ones particularly when played loud. To cut a long
story short he proposes that Miller compensation and series output inductors
are responsible in causing what he calls First Cycle Distortion. His
proposition
is that the reactive impedance characteristics of most loudspeakers interact
with s/s amps that have these features over the first cycle of each frequency
component that makes up the music waveform. He suggests that these effects
disappear after the first few cycles and therefore do not show up in pure sine
wave testing. An interesting conjecture, yet to be fully proven, but the point
is that
the reactive elements of connecting cables would also figure in this argument.
If this were true then valve amps should be much less affected ( SE types
excepted?) Geoff Mead

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

AmpCableSpeaker interaction
 

"Andy Evans" wrote in message
...
I enclose the following, from Geoff Mead (Audiocircle): does anybody know
anything about this? Quote goes:

Re the current thread on speaker cables and sonic differences between
different amp/cable/speaker combinations. There has been an interesting
series
of articles in Electronics World staritng June 2004 if anyone hasnt seen
them.
The author Graham Maynard started looking at the old chestnut as to why
valve
amps sound different from S/S ones particularly when played loud. To cut a
long
story short he proposes that Miller compensation and series output
inductors
are responsible in causing what he calls First Cycle Distortion. His
proposition
is that the reactive impedance characteristics of most loudspeakers
interact
with s/s amps that have these features over the first cycle of each
frequency
component that makes up the music waveform. He suggests that these effects
disappear after the first few cycles and therefore do not show up in pure
sine
wave testing. An interesting conjecture, yet to be fully proven, but the
point
is that
the reactive elements of connecting cables would also figure in this
argument.
If this were true then valve amps should be much less affected ( SE types
excepted?) Geoff Mead

**Nope. There are a goodly number of reasons why valve amps *may* sound
better, when driven loud, or connected to difficult loads. The output
inductor *may* be partially responsible. Here's my thoughts:

* Valve amps Voltage limit rather gracefully. They do so, because not much
Global NFB is normally employed. Clipping distortion tends to contain lower
levels of high order harmonics. The output transformer tends to limit the
production of these harmonics as well. IOW: Valve amps can be pushed harder
than typical SS amps, whilst still remaining somewhat listenable.

* Valve amps current limit rather gracefully. They do so, due to the
horrendously high internal impedances of the tubes themselves. Again, since
Global NFB is usually quite low, gross amounts of distortion is usually
avoided. Typical SS amps employ current limiting systems which sharply
affect the waveform, when triggered. This effect is exacerbated by the
Global NFB system.

* Valve amps demonstrate a partially 'current source' output characteristic,
which, when presented with a rising impedance characteristic (such as the
rising impedance of the bass driver in a typical enclosure) will deliver a
far higher output Voltage and more apparent power. Again, valve amps may
sound louder than their SS equivalents. Ironically, triodes are much closer
to BJTs in this area, since triodes act more like Voltage sources, than
pentodes. I guess that is why triodes are more highly prized.

* When driving VERY LOW impedances, the output inductor in most SS amps, may
present a significant effect on the Voltage output at high frequencies.
(You'll note that very few amplifier manufacturers quote damping factor at
20kHz).

* The output transformer in valve amps, is it's best and worst attribute.
The transformer adds significantly to cost and mass and severely affects
linearity, frequency response and damping factor. On the plus side, the
output transformer effectively isolates any load anomalies from the active
devices.

Of course, none of the above need be a problem. Good SS amps do not require
output inductors, Global NFB, or audibly problematical Voltage and current
limiting. Then, the advantages of SS amps (low distortion, wide power
bandwidth, high damping factor, excellent load tolerance) can be realised,
with none of the downsides normally associated with SS amps.


--
Trevor Wilson
www.rageaudio.com.au

AmpCableSpeaker interaction
 

"Andy Evans" wrote in message

I enclose the following, from Geoff Mead (Audiocircle): does anybody
know anything about this? Quote goes:

Re the current thread on speaker cables and sonic differences between
different amp/cable/speaker combinations. There has been an
interesting series of articles in Electronics World staritng June
2004 if anyone hasnt seen them. The author Graham Maynard started
looking at the old chestnut as to why valve amps sound different from
S/S ones particularly when played loud.

It might be more to the point to explain why tubed amps have this nasty
tendency to change how they sound when you hook different speakers to them,
even more so than that which can be explained by the sonic differences
between the speakers.

To cut a long story short he
proposes that Miller compensation and series output inductors are
responsible in causing what he calls First Cycle Distortion.

If this purported distortion existed it would be easy to measure. Did he
show any measurements showing that it actually exists?

Let me guess - he wasn't able to mesure it, but instead provided a lengthy,
hand-wavy theory of questionable merit.

AmpCableSpeaker interaction
 

In article , Andy Evans
wrote:
I enclose the following, from Geoff Mead (Audiocircle): does anybody
know anything about this? Quote goes:

Re the current thread on speaker cables and sonic differences between
different amp/cable/speaker combinations. There has been an interesting
series of articles in Electronics World staritng June 2004 if anyone
hasnt seen them.

It is my misfortunte that I have been reading this series of articles. I'm
afraid that to me they seem like a catalog of confusion, incorrect
information, and statements made well out of context so as to give a wholly
misleading impression. Thus some of the individual statements made in the
articles are correct, but used in inappropriate ways. I would strongly
recommend anyone reading the articles to treat what they say with great
caution and look with care for the 'errors and omissions'.

Hesitate to say this as my own writings can sometimes be unclear, but the
articles also suffer in places from a style which seems rambling and
ambiguous. Some of the 'sentences' are rather long-winded and - to me -
make it harder to work out what he really means.


The author Graham Maynard started looking at the old
chestnut as to why valve amps sound different from S/S ones particularly
when played loud. To cut a long story short he proposes that Miller
compensation and series output inductors are responsible in causing what
he calls First Cycle Distortion.

Yes. That is one of the muddles he gets into. :-)

He also dislikes input filters, based upon a similar muddle. :-)

His proposition is that the reactive impedance characteristics of most
loudspeakers interact with s/s amps that have these features over the
first cycle of each frequency component that makes up the music
waveform.

However if you examine his examples and aguments with care you will find
them misleading and often out of context so as to 'exaggerate' or imply
significance that may be absent in reality.

He suggests that these effects disappear after the first few
cycles and therefore do not show up in pure sine wave testing. An
interesting conjecture, yet to be fully proven,

Afraid the problem here is not 'proof' but of the author actually
understanding and explaining clearly. :-)


but the point is that the reactive elements of connecting cables would
also figure in this argument.

Yes, they could. Thus if he worries about the output inductor he also
should worry about cable inductance. And, of course, the effective output
impedance of valve amps... :-)

If this were true then valve amps should be much less affected ( SE
types excepted?)

They would only be 'less affected' by virtue of the following two possible
factors:

A) The valve amp having less output at the high frequencies implicit (but
hidden) in his argument due to the amp having a limited HF output reaching
into the audible range.

B) The valve amp having such a high across-the-band output impedance as to
swamp the cable inductance. However this simply means you are producing a
larger problem in order to make a small one matter less.

TBH I have been wondering about producing a detaild 'critique' of the
Maynard series as they are riddled with some many misleading statements and
evidence present out-of-context. However I have so far been dissuaded as
the series hasn't finished, and I also have an article (on a quite
different topic) to be published in a later EW. :-) Been hoping that
someone else would be willing to spend the time pointing out the problems
with his articles. ;-

I would recommend the articles to any engineer or academic who wants to
have material for a 'forensic analysis' of the mistakes people can make
when trying to understand or explain a technical topic. Indeed, such an
analysis might make a neat MSc dissertation for someone. The articles are
well filled with bones which can be picked out. :-)

More seriously, I must admit I sighed when I first saw these articles. I
had hoped people would no longer be getting confused like this. Must admit
I am wondering if the editor of EW is running it deliberately to stoke up
loads of 'letters to the editor', etc. ;-

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

AmpCableSpeaker interaction
 

In article , Arny Krueger
wrote:
"Andy Evans" wrote in message


To cut a long story short he proposes that Miller compensation and
series output inductors are responsible in causing what he calls First
Cycle Distortion.

If this purported distortion existed it would be easy to measure. Did he
show any measurements showing that it actually exists?

I am not sure how many articles there are in the series. I have only read
three so far. From a comment I've had from the people at EW I think there
may be five in the series, but there may only be four. Either way, in
fairness we should note that we have not got to the end yet, so that may
justify some of the odd things I've read so far. However...

He has presented some 'modelled' results, but at least some of these are
given in a somewhat out-of-context manner. Thus used to imply things in a
way that looks quite misleading to me.

Let me guess - he wasn't able to mesure it, but instead provided a
lengthy, hand-wavy theory of questionable merit.

Hard for me to criticise anyone else's writing style as I am aware of the
saying about "people in glass houses." :-) However I find the way he has
written the articles to be somewhat long-winded and rambling. Ahem. I
should note that EW pay on a 'per published page' basis. ;-

In at least one place he describes what is in a waveform plot, but what the
plot actually shows seems inconsistent with his (imprecise and ambiguous)
description. However you have to spend time diagnosing this and work out
what the plot *does* show. Do this, and you realise that his inferences are
suspect in practice. However, if you take the article at face value it
would be easy to get the impression that his 'results' support his
arguments in places where I do not think that they do.

He also criticises some aspects of common solid state design without
apparently noticing that equivalent effects also arise in valve designs,
sometimes to a greater extent. :-) Also ignores the possibility that
similar effects elsewhere ( e.g. in speakers) might swamp what he
describing. This leads me to suspect that he may not have thought about any
of the underlaying physics, etc. :-)

The approach taken thoughout seems to be "My feeling is that A sounds
better than B. Therefore I am trying to find 'reasons' to justify this'. In
itself, that is fine. The problem is that he does not seem to consider the
'reasons' he finds with sufficient critical care to ensure they would stand
up as an actual explanation of his preferences.

The editor of EW adds a preface to the first article in the series saying
that some readers might not like the author's conclusions. This seems to me
to miss the real point. I'd say that the problem isn't the conclusions, it
is the muddled arguments employed to reach them. :-)

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

AmpCableSpeaker interaction
 

"Jim Lesurf" wrote in message

In article , Arny Krueger
wrote:


Let me guess - he wasn't able to mesure it, but instead provided a
lengthy, hand-wavy theory of questionable merit.

The editor of EW adds a preface to the first article in the series
saying that some readers might not like the author's conclusions.
This seems to me to miss the real point. I'd say that the problem
isn't the conclusions, it is the muddled arguments employed to reach
them. :-)

I think we're pretty much on the same page, here. ;-)

AmpCableSpeaker interaction
 

Arny Krueger wrote:

It might be more to the point to explain why tubed amps have this nasty
tendency to change how they sound when you hook different speakers to them,
even more so than that which can be explained by the sonic differences
between the speakers.

Large complex output impedance ?

Makes for an interesting potential divider effect.


To cut a long story short he
proposes that Miller compensation and series output inductors are
responsible in causing what he calls First Cycle Distortion.

If this purported distortion existed it would be easy to measure. Did he
show any measurements showing that it actually exists?

Let me guess - he wasn't able to mesure it, but instead provided a lengthy,
hand-wavy theory of questionable merit.

It sounds like total hogwash to me but probably likely to provide a great
source of aftermarket add-ons.


Graham

AmpCableSpeaker interaction
 

"Pooh Bear" wrote in message

Arny Krueger wrote:

It might be more to the point to explain why tubed amps have this
nasty tendency to change how they sound when you hook different
speakers to them, even more so than that which can be explained by
the sonic differences between the speakers.

Large complex output impedance ?

Makes for an interesting potential divider effect.

It can be pretty nasty.