In article , Rob wrote:
John Phillips wrote:
In article , Richard Wall wrote:

snip

BTW a set of ABX tests and results (including positive and negative)
are to be found at http://www.pcavtech.com/abx/abx_data.htm (down the
page, including a capacitor test).

That's quite interesting - some results I'd expect (speakers, tape
decks, encode-decode, cables) but some are pretty wild - a 450w ss amp
and a 50w valve amp sound the same for example.

On the power difference, with "reasonable" loudspeakers you may be
using no more than 5 Watts anyway, so unless things get loud that may
not matter. As for the technology difference, I suspect the lack of
perceived difference says they're both good amplifiers.

Linked to this is another thing I don't understand - do people know
what's going on in these experiments ('this is an abx test of cables'
for example).

I think you don't need to (probably can't) keep that information from
the participants.

Just curious!

Just curious too since I don't do comparitive tests myself except
sighted tests for once-in-a-blue-moon personal purchases.

I remain puzzled about the postulated audible superiority of teflon
dielectrics (and occasionally paper-oil - for the right type or oil
I assume).

1. The published curves for dielectric absorption etc. show what I
think of as trifling differences compared to polypropylene,
polyethylene and some other dielectrics, There are several
dielectrics which should be audibly good enough to be
indistinguishable.

2. DA and the other usual capacitor defects are primarily linear effects
regardless of what people imply when they talk about smearing of
pulses. They result in ripples in frequency response (which are
mathematically equivalent to the "pulse smearing"). These ripples
can be made so small by good design of the circuits surrounding the
capacitor so it should be a non-issue. Loudspekers have ripples
in frequency response that are orders of magnitude worse.

3. No-one that I can find right now has measured significant
non-linearity (except for some ceramics), i.e. above the level
produced by an amplifier as a whole. Perhaps someone can point me
in the right direction for material?

4. If there is an audible difference then I cannot imagine why (yet)
and it would be interesting to think of some good hypotheses for
the difference.

--
John Phillips