252 vs 275

[1KW]

Find a dealer who has both amps. and go listen for yourself, then share your findings with us.

[thughes]

For a whille I owned both and had them in the same room where I could switch back and forth. Musically, the 275 have it over the 252. I tried to move from the care of feeding of tubes back to the 252 and couldn't do it. After I sold the 275s, I had to replace the 252 with the 501s.

[bradleyc]

Originally Posted by thughes

For a whille I owned both and had them in the same room where I could switch back and forth. Musically, the 275 have it over the 252. I tried to move from the care of feeding of tubes back to the 252 and couldn't do it. After I sold the 275s, I had to replace the 252 with the 501s.

I've been told by a Mac tech rep that moving up from the 252 to the 501's would get me a lower noise floor and more umph, no other mentionable differences. The 252 has a very low noise floor, please share any other sonic differences you heard.

[1KW]

Originally Posted by bradleyc

I've been told by a Mac tech rep that moving up from the 252 to the 501's would get me a lower noise floor and more umph, no other mentionable differences. The 252 has a very low noise floor, please share any other sonic differences you heard.

You may want to look at this thread http://audioaficionado.org/mcintosh-...finally-2.html

[Uberbrown]

Originally Posted by Ron-C

PCH,

McIntosh transistor amps with the autoformer will certainly "double down" just like any other transistor amp. If you match the Autoformer tap to the speaker impedance you will not 'have up' so full power will be available when higher impedance speakers are used.

Thanks,

The 501 is a tremendous amp, offering gobs of power and a very liquid sound. But I was not aware that it doubled down. If it did, one would expect 2000 watts into 2 ohms on the 8 ohm tap. This is what I had read.

In the Stereophile review they claimed...

The 8 ohm tap delivered no less than 720W into 8 ohms, with similar deliveries into 4 and 2 ohms from their respective taps. Despite the slight increase in source impedance, the MC501's ability to deliver current into the speaker load did increase with the decreasing output transformer tap. The 8 ohm tap was limited to 225W into 2 ohms, for example, while the 4 ohm tap delivered 1000W [into 2 ohms]...

Thus, according to Stereophile, the 501 put out 720w into 8 ohms (on the 8 ohm tap), but 225w into 2 ohms (on the 8 ohm tap). So thus according to them, the power output decreases to 31% of its original output, when the amp goes from an 8 ohm load (on the 8 ohm tap) to a 2 ohm load (on the 8 ohm tap,) and does not output 400% or "double down twice," but outputs 31% of its 8 ohm vs. 2 ohm (on the 8 ohm tap) output, I suppose their measurements might be wrong, I do not know.

Then, according to them the 501 put out ~720w into 4 ohms (on the 4 ohm tap), but 1000w into 2 ohms (on the 4 ohm tap). So thus, according to them, the power output increases to 138% of its original output, meaning 4 ohms (on the 4 ohm tap), when the amp goes from a 4 ohm load (on the 4 ohm tap) to a 2 ohm load (on the 4 ohm tap,) and thus does not output 200% (but outputs 138%) of its original output when the amp goes from a 4 ohm load (on the 4 ohm tap) to 2 ohm load (on the 4 ohm tap), or the amp does not "double down." (the argument could be made here that if the 501 outputs 1000 into 2 ohms (on the 4 ohm tap) then it is doubling its 500w rated output, but the actual output of the 501 is ~720w into 4 ohms (on the 4 ohm tap) not 500w into 4 ohms (on the 4 ohm tap). Look below at a comparison between actual and rated outputs. I suppose their measurements might be wrong, I dont know.

As a measurement comparison only, look at the Levinson 33h. Stereophile measured it in the following way...

Levinson is a powerhouse of an amplifier, comfortably exceeding its rated power. Specified at 150W into 8 ohms, it actually didn't clip (defined as 1% THD+N) into that load until 265W...Into 4 ohms, the maximum output power almost doubled, to 500W; into 2 ohms, 900W was available. As we don't have a dummy 1 ohm resistive load capable of sinking the almost 2kW that the Mark Levinson is presumably capable of putting out into this load, I wasn't able to check its clipping power into 1 ohms. However, the fractional decibel drop in dBW each time the load is halved suggests that this amplifier behaves as an almost perfect voltage source

The 33h, admittedly without an autoformer, (though it is rated at 150w into 8 ohms) put out 265w into 8 ohms on the only tap it has, and increased to 500w into 4 ohms (188% of the original 8 ohm figure.) (Note that the Levinson did double down (essentially) from 8 ohms to 4 ohms on its actual output, and increased 333% from its rated output into 8 ohms.) Into 2 ohms, the 33h output was 900w, which is 339% of its original 8 ohm figure, and 180% of its 4 ohm figure. (Note that the Levinson increased 600% from its rated output as well) Thus the Levinson does double down from 8 ohms to 4 ohms, and from 4 ohms to 2 ohms.

This is in no way saying Levinson if better. It is simply using Levinson as an example of an amp that does double down (essentially).

[tdelahanty]

Well the idiots from Stereophile strike again. The concept of the autoformer is to ensure the amplifier operates into an optomum load, keeping current at safe levels and avoiding excessive heat. The various taps ensure the amp sees the same load regardless of speaker impedance that is why Mac amp are not spec'd to double power. Proper loading avoids power supply modulation and contributes to the very natural sound of a Mac amp. The autoformer may get too hot if operated at too low a speaker impedence for the given tap.

[tdelahanty]

Most all amps will deliver slightly more power than specified. That is due to the standardized testing proceedures which determine output power. The spec requires an amp to be preconditioned (operated) at 1/3 rated output for a period of time (30 minutes I think ???). 1/3 power demands the highest bias level, generating more heat. Manufacturers derate output slightly so the 1/3 output level is more comfortable for the amp to attain.

[PHC1]

Uberbrown, thanks, you've saved me lots of typing.

Tdelehanty, unfortunately the 501s went into thermal shutdown indicating heatsinks were inadequate to sustain the thermal load. Fortunately it would be very rare to experience that under real listening conditions.. I've never had anything like that happen with any of the 3 different pairs of speakers I've tried them on.

[Uberbrown]

Originally Posted by tdelahanty

Well the idiots from Stereophile strike again.

Well, they named the 501 amplification product of the year in 2004, so they must have loved the 501s (They are special amps!) So are they idiots or right on the mark?

[PHC1]

Originally Posted by Uberbrown

Well, they named the 501 amplification product of the year in 2004, so they must have loved the 501s (They are special amps!) So are they idiots or right on the mark?

And strangely enough, the same reviewer had Lamm M1.2s in his system at the same time. Care to guess which amp is still his reference?