"ScottW" wrote in message
oups.com...

Robert Morein wrote:
"Sander deWaal" wrote in message
...
"Robert Morein" said:

If it's Arny Krueger's ABX box, it was constructed with inadequate
relays.
IME, this can easily mask subtle differences between amplifiers. Even
if
it
was not constructed by Krueger, that does not make it immune from
criticism.


Dunno about Arny's soldering skills, but the relays in my preamp
(gold-plated gasfilled OMRON types) sure as hell don't add or subtract
anything in the signal.

Now, if one's to ABX gear with a 4066, that's another matter :-)

The inadequate size of the relays was noted in a Stereophile article
that
predated the current acrimony.

I built a remote control AB box using garden variety P&B relays with
plated
palladium/oxide contacts.

Palladium doesn't oxidize, thats why its used.. however it's
conductivity is poor so it isn't used in high current (5 A) apps.

http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf

Even with brand new relays, there was clearly a
degrading effect. All those days of wasted fabrication!

From the change in the sound, I think there was something nonlinear
going
on, ala rectification.

I'm sure Arny used better relays, but the Stereophile comment remains,
specifically challenging the power handling capacity.

You mean current handling. If the relay is dissipating power, you f'd
up.
Relays dont care if you're delivering 10V and 1A but they sure might
care if your delivering 1V and 10A.

ScottW

No, I don't mean current handling. Palladium does have that problem, but the
timbre change could not be explained by a modest increase in the resistance
of the speaker feed.

Junction rectification effects occur whenever there is the slightest
dissimilarity in contact material. These are voltage dependent. Another
possibility would be this: Because the actual contact area of slightly
convex contacts is very small, the geometry may change as a function of
point heating. Regardless of whether these, or a third, unknown mechanism
turns out to be the culprit, the result is easily audible, as an unpleasant
artifact.

All I can tell you is: my self-constructed AB box is worthless. I have every
self-serving reason to hide this fact, because I put a lot of time in it.
But I won't, because that would be bad science.