atmasphere.
It could also be the power cord, as a cord that limited the amplifier's ability to replenish its power supplies might come off with more distortion as well. This effect is quite measurable- I've seen power cords
rob a tube amp of nearly 30% of its total power!
I would like to know how to measure that. 30% is hard to imagine. I test amplifiers all the time with ordinary power cords and have never seen this. This reminds me too much of Bruce Brission's white paper which was a total embarassment to his distributor who promptly dropped his line. |
I would like to know how to measure that. 30% is hard to imagine.
+1 |
Back in 2010 I asked Ralph about that statement in this thread. Here are excerpts from our discussion:
Atmasphere: Power cords: a 2V drop across a power cord can rob a
tube amplifier of as much as 40% of its output power! Cripes! You're
trying to say you can't hear that?? [That comment was addressed to someone else]. So this is very measurable and
audible as well. On lesser transistor amps, a power cord will be less
audible as the drop across the cable is reduced, but a class A
transistor amp will easily bring out cable weaknesses.
Almarg:
Ralph, could you provide a technical explanation of why that would be
so? I don't doubt your statement, but I'm interested in understanding
why that would occur.... Re your other points, all of which strike me as
excellent, I think that it should be stated that none of those points
NECESSARILY mean, to cite an example, that a $2,000 power cord will
outperform a $200 power cord in any given system.
Atmasphere: Al,
the reason a power cord can have this effect is simple. If there is a 2
volt drop in a power cord, the filaments of the tubes will run cooler
and the B+ will be reduced. Since this is a voltage, the result is we
get less voltage output out of the amp. Less voltage=less power.
Depending on the amp this can be pretty profound. and I have seen it
with my own eyes. I do agree though that that does not justify a $2000
power cord, but it **does** justify one that has decent connectors and
conductors that will not heat up at all. That has to cost something,
probably not $2000 though. One thing about audio is that if there is a
phenomena, there is also snake oil for it.
Almarg: Thanks, Ralph.
That would also seem to say that the value of the ac line voltage at
each listener's location can be a very significant variable in the
performance of a tube amp (assuming it does not have regulated filament
and B+ supplies). Which in turn emphasizes how easy it can sometimes be
for extraneous variables to lead to incorrect sonic assessments.
Atmasphere:
No doubt! But it extends to anything that can draw significant power-
and bigger transistor amps can! Imagine the peaks just... not... making
it.
This taught us a lesson... when we set up an amplifier for
test, we test the AC line voltage from the IEC connector. The meter on
the variac (a bit of test instrumentation) cannot be trusted. A 2 volt drop in a power cord of typical length seems like a lot, of course. But if the amp draws say 5 amperes a resistance of 0.4 ohms, including the resistance of the connectors and the contacts as well as the combined resistance of the hot and neutral conductors, would do it. I'd imagine that could happen in some situations. Regards, -- Al |
I am enjoying the debate among experts, but am still not understanding how an autoformer works. The last question from the OP was a good one. I Think including ss adds to the confusion and would prefer explanations stick to tube amplifiers where they are more practical.
How does an autoformer work? Does the speaker cable mate with the windings? How is the signal changed at this point? |
@recluse---look at the 8-29 and 8-31 postings by ramtubes (Roger Modjeski of Music Reference) above. |
