In article , JustMe
wrote:
What you *could* do, though is something like the following.
Play music through the Alchemist into a pair of speakers. While doing
so, connect leads to the speaker terminals and record the signals
there onto CD-R using a reasonably quality recorder. Note the signal
level with a meter.
[snip details]
I would be happy to try something like this blind. I'd be really curious
to see if such "filters" were possible and whether I would be able to
tell differences, or recognise my favourites as superior to those which
I'd previously rejected.
The snag is that even if the above allowed you to 'record' or 'reproduce'
the specific effect of a given amp, you may still need it as the 'filter'
unless we could establish what it was doing to be able to 'mimic' it in
some other way. That said, what your reactions were to such a test would be
interesting.
Presumably the playback equipment would have to be that which is
considered as "straight-line" - the CD player and amp?
Depends what you are trying to detect or establish. For example, it may be
easier to determine if you think the sounds are 'similar', but harder to
establish what it involved or what may affect the degree of 'similarity'
(if any).
But is there a danger of a cumulative effect? If I use the same speakers
in replaying the signal as it's been recorded from the system, would the
effects of the speaker's balance not be duplicated?
Not their conversion efficiency, etc. Just the effect of their input
impedance upon the signal at the speaker terminals. In effect, this is the
'break point' in the comparisons as I described them.
Would this be cumulative? Presumably, any small deviance from
"straight-line" in the CD or amp's replay would undermine such an
experiment.
It may do. However it may also turn out to be small enough not to have a
significant effect on the results.
In principle, you can perform the kinds of tests I am describing in
various ways. e.g. Do a 'speaker terminals' recording using amp 'A',
and then another using amp 'B'. Then compare the two recorded CD's
using first 'A' and then 'B' to see if you can distinguish them
in each case, and hear the effects of 'AA' 'AB' 'BA' and 'BB' if
you see what I mean.
Also, could record one channel (left or right) using 'A'. Use the
power amp input for one recorded channel, and the loudspeaker
terminal signal for the other recorded channel. Repeat this
for amp 'B'. Then replay each of the recorded 'mono' discs via
'A' and then 'B' and listen for any departures for 'mono'.
None of these tests in themselves are 'perfect' in terms of
excluding all other effects, etc. However by doing a series
of such tests you might be able to form some conclusions about
what is happening that is consistent with the comparisions they
represent.
Many of you chaps believe that the Peter Walker(?) "straight-wire" ideal
is that which any "hifi" designer should aspire to construct.
The designer should design what people want. This way he gets to eat. :-)
The snag is, no-one can fully define that, and people argue about what they
want. ;- Hence you just have to make a best guess...
I personally tend to prefer amps with a fairly flat response and low
distortion. (Both terms relative to what can be expected compared with
other places in the chain. e.g speakers and room acoustics.)
Do you think that this is attainable?
I would say 'yes' with the qualifiers that:
1) Close enough to the 'Walker' definition so that any changes produced by
the chain in which the amp is a part tend to be mainly due to things like
the speakers, room acoustics, decisions made by those who made the
recording, etc. i.e. sufficiently close that departures from the 'Walker'
definition are small w.r.t. these other sources of departure from an ideal.
2) Still may not be what everyone wants. :-)
FWIW I feel that a lot of equipment comparisions (and arguments) tend
to become hung up on worries about things not being 'identical. However
in practice I think what matters is a set of slightly different levels
of comparison. e.g. Are the units 'indistingushable' in the conditions
of use? (i.e. may well differ, but in ways that are small enough to
go un-noticed). Or are any differences between two units so small that
they really don't matter much when other items in the 'chain' produce
much more noticable effects?
Also, some 'effects' may be useful in some contexts, but not others.
The obvious example is that if your speakers/room cause a change in
response at some frequencies, you might prefer an amp in the system
that counteracted this. However if so, my personal preference would
be to know this was happening so it was a conscious decision to
do this, not an 'accident' in the sense that you just find a given
system preferrable but have no idea why. Knowing the reasons gives
you the ability to make other changes which you might prefer at a
later date, and not be 'tied' to a given unit without knowing
why this is the case...
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
Every amp in one
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