Mcintosh ma6100 schematic

AMBIENT SOUND

By Len Feldman

A postscript to MR's product-testing philo­sophy or "The Great McIntosh Controversy."

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LAB REPORT

By Norman Eisenberg
and Len Feldman

McIntosh MA-6100 Preamp-Amplifier

Reprinted with the kind permission of

MODERN RECORDING

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15 Columbus Circle New York, N.Y. 10023 [phone]

YOU SHOULD BUY

MclNTOSH BECAUSE

• McIntosh instruments are designed and manufactured for long life.

• McIntosh instruments have always been designed for long life with
low maintenance costs and high quality performance. McIntosh in­struments have been and are the LABORATORY STANDARD for
the world. Until 1949 the performance requirements for a McIntosh
had long been an engineering dream. They became a reality with the
introduction of the first McIntosh amplifier. Through all these years
McIntosh has produced instruments that have exceptionally long life.

Regardless of age, most McIntosh instruments are still in use today.
Amplifier clinics held all over North America have shown that most
of the McIntosh instruments ever manufactured are still in service
today and still meet or exceed original exacting requirements for
performance that were required of them when new.

• Used McIntosh instruments enjoy the highest resale value in this
field. Retailers report that customers are constantly searching for
used McIntosh instruments. A McIntosh does not remain on the
"Used" display long. You'll get more when you trade-in your McIn-

tosh assuring you of maximum return on your investment.

• McIntosh dedication, not only to improvements, but also to funda­mentals, has justified many patents on refinements as well as basic

circuit structures.

• The size of the McIntosh investment in professional testing instru-

ments bears eloquent testimony to the commitment to acquire
knowledge for the benefit of our customers. On a percentage basis
McIntosh probably invests more of its sales dollars in testing facilities
than anyone else in a like business. As new testing instruments are
produced that update the McIntosh ability to know, McIntosh invests
in them . . . wave form analyzers-real time analyzers-low distortion
signal generators, etc. Only through this impressive investment,
through continuous testing and research, through product analysis,
and endless measurement can McIntosh promise and deliver to you
reliability, long life, performance, highest value, and freedom from
service.

• Since its beginning in 1949, McIntosh Laboratory has had the same
ownership and management. McIntosh is the only company in this
industry that has had this kind of history. McIntosh has been and is
still dedicated to the best possible values.

• Doesn't it make good sense to deal with a company that wants to do
as much for you as it possibly can?

BY LEN FELDMAN

Postscript to Our Product

Testing Philosophy ...

In the very first issue of Modern Recording, I went
into some detail regarding MR's approach to product
reviews and test reports. I discussed the importance of
lab measurements versus listening tests, and the for­mat that Norman Eisenberg and I would use in trying
to fairly report the merits (or demerits) of a variety of
audio products. I did not detail how we would "sam­ple" products for testing. A recent series of episodes
took place in our labs which points up some of the
problems and conflicts inherent in attempting to test
electronic equipment, and I'd like to share the exper­ience with you.

Basically, we obtain equipment in one of two ways.
Either we ask a manufacturer to send us a representa­tive sample of the unit to be tested, or we obtain one on
temporary loan from a dealer. In rare cases, if we can­not obtain a sample by either of these approaches we
will go out and purchase the required unit in hopes
that we might sell it at a minimum loss after our tests
are completed. Personally, I prefer getting a unit di­rectly from the manufacturer, and the story I'm about
to tell will show why.

As many readers may know, the Mclntosh Company
has, for many years, refused to "lend" equipment to
publications for review purposes. That is one of the
main reasons why MR, believing that the consumer
should have the right to know, wanted to test a piece
of Mac equipment. Mac's reasons are many - some of
which I cannot argue with, others of which I feel are
not justified. For one thing, the people at McIntosh
feel that if a manufacturer supplies equipment directly
to a magazine for review, the manufacturer has an op­portunity to "tweak up" the sample (or even possibly
modify it or improve it) for better results. On this
point, I can only speak from experience dating back
some six years, during which time I have probably
tested several hundred components sent to me directly
from manufacturers. I cannot remember a single in­stance in which a manufacturer "phonied up" a circuit
so that the unit would yield better measurements. Of
course, I cannot deny that many manufacturers prob­ably "double-check" such samples before sending
them to me, but, frankly, I see nothing wrong with a
manufacturer making doubly sure that a unit he sends

for review performs in accordance with specs and is
not the occasional "lemon" that any manufacturer of
complex electonic gear is liable to turn out once in a
while. In fact, I wish more manufacturers would dou­ble-check the units they send for evaluation. If 1 re­ceive a faulty unit from a manufacturer (and, indeed, I
have in the past received several defective pieces of
equipment) that I know to be defective (not poorly de­signed - just defective), I don't have the same war­ranty privilege of having it fixed up by a local service
agency. I will have wasted the better part of a day (it's
usually the last measurement that shows up the fault-

- hardly ever the first; a variant of Murphy's law, you
know) only to have to start all over again with a re­quest for a second unit from the manufacturer. I see no
point in printing a report based upon a defective unit
that does not represent what the model can do!

McIntosh's other argument against supplying
equipment to "reviewers" for test purposes is that
they have no way of knowing whether the particular
tester or reviewer has the necessary test equipment or
knowledge with which to properly evaluate that equip­ment. I certainly can't argue with that one-though I
believe that a simple bit of investigation on the part of
McIntosh (or any other company that may feel the
same way) could insure that samples are sent only to

qualified reviewers possessing reasonably up-to-date
test equipment.

Be all that as it may, MR decided that we wanted to

do a report on a piece of Mclntosh equipment for this
issue. Knowing that McIntosh would not supply
one, MR decided to borrow a unit from one of their

authorized dealers for that purpose. We did just that,
and that's how we obtained our first MA-6100 Inte­grated Amplifier for testing. We were all prepared for
an exciting "first" at our lab. Preamp section tests
went smoothly enough, with all published specs met or
exceeded by far. Construction was excellent, as the
famed McIntosh reputation had led us to believe.
Then, we came to the power output measurements
and-sure enough-we realized at once that the unit

was defective. Output sinewaves were being clipped se-

verely on one side only before rated power was at­tained. What to do? We couldn't go back to the manu­facturer-they hadn't supplied the unit in the first

place. We asked the dealer if this were, indeed, a unit

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