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In Reply to: RE: Classic Mac Sound posted by email@example.com on February 19, 2017 at 11:10:14
THe Classic McIntosh sound comes from their transformers - in the power amp side- and from a 'More is better' on the Pre-amp side.
McIntosh, Like the early Marantz had absolutely amazing output transformers for their tubed gear - all were Ultra-linear in topology and were potted. they had great frequency response and have a great sound.
they do not have high damping factor - hence the 'soft bass' and often the early units only were tested up to 16,000cps (Cycles per second=Hertz) so did not go the extra 4-10KHz in top end definition...
As McIntosh introduced transistors (SS) into amplifiers - they put 'Autoformers' on the output side. this did a few things - one made the amp stable into any speaker- and carried the 'house sound' into the ss gear.
Do new production units have the same sound - not fully, but close- they have expanded the frequency range of the OPTs but kept the original circuit - though with better components-
The McIntosh circuit topology was not Ultra-linear. They had a patent on so-called "unity coupled" amplifier circuitry, which was the basis for all their tube designs from the MC 30 on. They made use of a special transformer winding technique along with a cathode winding to provide large amounts of local feedback around the output stage.
Mea Culpa- Unity coupled vs Ultralinear-
I saw this video on the making of the Mac 275 power amp. When they got to the transformers they were pouring this tar goopy like liquid into the housing or bells to seal them up.
I know the Dyna transformers didn't do that and would that process make a more silent transformer?
Why I started this thread was not only the Willie Nelson cigarette I smoked but the fact of believing all this time from reading stereo mags that the best preamp is the one that least colors the signal. Barring tubes vs. transistors debates the 6000 dollar C-22 came into view.
So when the reviewer said the pre amp had that classic Mac sound it threw me for a ground loop.
Every time you guys write I get a great audio lesson...keep em coming....thanks Mark K.
Transformers are an interesting element of the audio chain-
The can generate noise
they - in the form of output x-formers- define the frequency response of the amp
however if well made- can make a unit be sublime-
putting that 'tar goopy' stuff in does a few things -
1: if done well, the material can get into the air spaces to keep the transformer quiet (from mechanical noise)
2: protect the windings from the lams - consider it added insulation
3: enable the transformer to be more uniform with respect to heat - and to then transfer the head to the external surfaces-
This is usually called 'potting' or potted transformers
not many people do it any more, as it adds expense...
but some of the best amps made have potted transformers-
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