Trevor Wilson wrote:

I don't want to argue the relative merits of autoformer output amps, but
does anyone know why McIntosh uses them, and what advantages they claim
for them?

**They make the amp heavy.
* They allow McIntosh to offer a USP (Unique Selling Proposition) to
gullible consumers.
* They give McIntosh to charge more for the product.
* They have this warm, fuzzy, old fashioned 'feel' about them.

C'mon Trevor, there must be some plausible excuse.

**Why? What is wrong with my reasons? They are perfectly valid and some can
be used to excuse the existence of some tube amps (notably SETs).

I can't believe the
McIntosh design team got together and agreed on the arguments you
mentioned. They must have some technical reason for this design. After
all, they could have made it heavier by just using a bigger power xfmr.

**I provided FOUR reasons, not one.


Is it possible that an autoformer was the way they chose to secure the
same ouput power at any load impedance, instead of the usual constant
voltage out, which would make the maximum output inversely proportional to
the load Z? That has a sensible ring to it.

**Not to any sane person. Speakers are not resistors. Speakers (usually)
present a lot of reactive components in their impedance characteristic. A
transformer is exactly what is NOT needed.

Instead of X watts out into 8 ohms and
2X into 4 ohms, they can offer a unform power output at any nominal load
Z.

It's an assumption that a speaker is the load. A safe one today, but
in McIntosh history a LOT of Mc amps were sold to drive motors, small
shake tables, load coils, and a cornucopia of weird loads. Some of
those had bizarre characteristics.

The solid state autoformer circuit was developed back then and they
have stuck with it. Attempts on their part to get away from it have
been met with buyer resistance. Mc sells their customers what they
want, within limits.

The fact is the Mc amplifier is a successful product at an excellent
profit margin whether or not you like it, Trevor. They will probably be
building them after both of us are dead and buried, so I'd just get
over it.

Mc electronics are not cheap compared with typical mass market
consumer equipment but as compared to military or telecom grade
equipment or first tier test equipment it's obvious many cost cutting
measures are used. Electrolytics are a consumer grade, the chassis is
bent up of prechromed mild steel and silkscreened rather than aluminum
sandcast or extrusion or a welded steel then polished and triple plated
and engraved or stamped. Circuit boards are the common fiberglass and
not conformal coated. Wire is the common stuff and passives, caps and
resistors, are the regular kind and no high dollar audiophile parts are
used even where all other "high end" manufacturers do. Tube models are
built with power tubes on the PCB, which is quite objectionable. Output
is by open binding posts even on models that could put lethal voltages
on them. A Mark Levinson or Rowland or Krell by contrast uses much
better parts and more expensive chassis, not that the sound necessarily
benefits, buit the build cost is higher. In my opinion, in these price
classes construction should rival Tek scopes of Vollum vintage, Collins
avionics, telco CO equipment. Mc is more reminiscent of Fender guitar
amps or early 60s Zenith TVs.