McIntosh Amp Ratings

Most of these posts are right on. Although I think the doubling up and halving down isn't exact with Autoformers due to coupling effects. Theoretically, yes, but in reality, no. Take a look at the Stereophile measurements of the MC501 and you'll see what I mean. For example, peak output power was 1000W with 4 Ohms taps driving a 2 Ohm load.

Incidentally, check out also how the 501 only has +-0.1dB modulation with the reactive loudspeaker load. The 8 Ohm tap has a damping factor of 100 and the -3dB is at a high 120kHz.

Undertow - I made a similar observation as you about damping factor. Some tube amps really have wonderful bass - perhaps not the most "potent" but very natural. John Atkinson and Roy Gregory also made this oberservation. Many forget that damping factor is related to both the frequencies of the musical signal and to frequency-dependant reactances. So an amp's ability to handle phase shifts is the real deciding factor for how well controlled the bass is or not. Besides, a driver is going to have its own mechanical and electrical impedances, especially a bass driver, so its own decay time will impose real limitations. From what I have seen, these limits basically render any DF above 50 a wash.

But we really knew all this already - particularly if you agree that global negative feedback is bad or that parallelling a bunch of BJTs (or even worse, MOSFETs) is not the best way of keeping a signal pure and unadulterated.

Arthur

Arthur
Aball
I guess that is the best way to describe..Natural, I feel much more Power in bass from Tube amps.. And have also from Mcintosh amps, but to be fair most of the Mcintosh amps I have heard were using Mcintosh preamps with Attenuation of the Bass knob or loudness control..But still they have a very full midrange and vocals, I have never really bought into the Mosfet argument either, I have owned several and they never quite did it for me.. I believe all Mcintosh are Bi-polar correct? I have found them more natural devices in most amps I have owned, but thats a whole other argument, and who cares anyway?

I don't own mcintosh and I do not necessarily defend them as being the best, just interesting and how I feel that they do give more of a Tube character to loads driven than that of most extreme cost SS amps. Again it was just an observation being that Mcintosh amps at the very hi price points are some of if not the only Solid state amps with super low damping factor.

Aball-

You're spot on about the McIntosh Autoformer...it can deliver more power at lower impedances but it, like all other amplifiers, is limited. The Mac is probably more conservative as part of their design intent is to minimize heat generated to prolong life.

also, Autoformers kill damping factor, which probably explains why traditional output designs that offer better control of the woofers are prefered by some.

I have owned quite a few Mac amps.  My favoirte was the MC-2300, which did not have an autoformer.  With regard to Macs power rating CONSERATIVE is their practice.  The MC-2300 could put out nearly 500 watts into an 8 ohm load though rated at 300 per side.  Strapped in mono, power deliery was astronamical, as it would easliy better 1500 watts.  I know beacuse I still have the bench sheet from my personal amp tested during a Mac clinic.

Further, this amps was factory rated to drive a half ohm load.  Not many compaines have that type of confidence in their products ability to drive loads.  Damping factor was always stated with low numbers.  This is because a damping factor of more than 20, was thought to be inaudible and ridiculous according the Mac engineers of the day, so that was all they ever tested for.  Any Mac amp when tested will easily give you a high damping factor.

Mac specs are always quoted as "worst case".  Who else does that? No one I can think of..

Norman