gordonl@microsoft.UUCP (Gordon Letwin) (09/04/84)
Re: the query as to the source material used to "null" the Carver M1.5t
against the Mark Levinson ML-2:
The article never spells it out, but they do enlighten us in two
significant ways:
1) when discussing the nulling technique, they say:
"The inputs of the two amplifiers are fed exactly the same signal,
which can be music from a phono or tape source, white or pink
noise from a generator, or any other signal that the tester fancies
and considers representative of real-world conditions. A large
variety of music undoubtedly provides the most thorough test, and
the signal level should also be varied, almost up to the clipping
point of the less powerful amplifier."
So they're clearly aware that a simple sine wave would not be
a sufficiently complex source to indicate "nulling"
2) To double-check the nulling the A-B tested, blind, the two amplifiers:
"When the test was completed, the scorecards proved conclusively
that the panelists had absolutely no idea which amplifier was the
Carver and which the Mark Levinson, even though in the course of
listening some of them had claimed to have zeroed in on the
difference."
Although they do not, unfortunately, specify their source material
for the A-B test I think its safe to assume they used a high quality
musical source, not sine waves...
Finally, they went the "last mile"; Carver substituted load resistors
for the speakers so that he could use a bridge circut and compare his
amp at 300 watts against the Mark Levinson at 30, to verify that they
still nulled in the power range unobtainable by the Mark Levinson unit.
Gordon Letwin
Microsoft