MC501's double down

[1KW]

I always wondered why Mcintosh amps. were rated at the same power for ever impedance tap ? According to ohms law if you decrease impedance power should increase. The following excerpt is taken from the stereophile review of the MC501 and does show that the MC501 does double down. I never really read the measurement section until today. I was surprised to learn that on the 4 ohm tap to MC501's are capable for 1 kw of power and 720 watts on the 8 ohm tap rather then the rated 500 watts in the Mcintosh literature. This makes the MC501's a very good value especially when you consider that on the used market they are around $5500 for the pair. Following this logic if you have 4 ohm speakers using the 4 ohm tap you essentially have a 1 kw mono amp. for short peaks anyway so as not to trigger the power guard which I assume is set go off if 1 kw is sustained ?



"The McIntosh's maximum output power depended on the output tap chosen and the load, but when the tap was matched to the load, the amplifier easily exceeded its specified 500W at our 1% THD definition of clipping. The 8 ohm tap delivered no less than 720W into 8 ohms (28.6dBW), for example (fig.4), with similar deliveries into 4 and 2 ohms from their respective taps (figs.5 and 6). 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 (17.5dBW), for example, while the 4 ohm tap delivered 1000W (24dBW), the 2 ohm tap 630W (22dBW)."

[Masterlu]

All of Mac's amps are conservatively rated.

[Jerome W]

Originally Posted by 1KW

" Following this logic if you have 4 ohm speakers using the 4 ohm tap you essentially have a 1 kw mono amp. "

David, following this logic, you should change your pseudo to 2 kW, which will make you closer to Ivan !

Jérôme

[1KW]

Originally Posted by C220MC275

David, following this logic, you should change your pseudo to 2 kW, which will make you closer to Ivan !

Jérôme

Very good Jérôme

Following your logic you should change your name to : C1000MC501(2) or C10002KW

[jdandy]

David.......1% distortion is not the way McIntosh rates their output power, even if that is the arbitrary number Stereophile choses to use for their power tests.

Maximum power from the MC501 is of no meaning to you anyway. Aren't you the guy who thinks 37 on the C220 volume is "rockin"?

[Hey you!]

Originally Posted by 1KW

I always wondered why Mcintosh amps. were rated at the same power for ever impedance tap ?

That's exactly what the output transformers are supposed to do - match the load impedance so the output stage "sees" the same impedance for 2, 4, or 8Ω speakers connected to the matching tap. Since the load impedance presented to the output stage is the same, the power is the same.

According to ohms law if you decrease impedance power should increase.

Only if the voltage stays the same. By changing transformer taps you change the voltage. By design, if the tap matches the load impedance, the power should stay the same.

The following excerpt is taken from the stereophile review of the MC501 and does show that the MC501 does double down. I never really read the measurement section until today. I was surprised to learn that on the 4 ohm tap to MC501's are capable for 1 kw of power and 720 watts on the 8 ohm tap rather then the rated 500 watts in the Mcintosh literature.

Reading the quote, they measure 720W driving an 8Ω load with the 8Ω tap, "with similar deliveries into 4 and 2 ohms from their respective taps". The 1000W measurement seems to be driving a 2Ω load with the 4Ω tap. 720 actual watts from a "500-watt amp" used according to design is, as Ivan notes, because they rate their equipment conservatively.

This makes the MC501's a very good value especially when you consider that on the used market they are around $5500 for the pair. Following this logic if you have 4 ohm speakers using the 4 ohm tap you essentially have a 1 kw mono amp. for short peaks anyway so as not to trigger the power guard which I assume is set go off if 1 kw is sustained?

As noted, they measured 1000W when they drove a 2Ω load with the 4Ω tap. Presumably you could achieve similar results driving a 4Ω speaker from the 8Ω tap, but remember that you are operating the amp in a way it was not designed for (no doubt it will survive, though). As far as I know, PG is activated when distortion exceeds a certain level, not a specific power level.

"The McIntosh's maximum output power depended on the output tap chosen and the load, but when the tap was matched to the load, the amplifier easily exceeded its specified 500W at our 1% THD definition of clipping. The 8 ohm tap delivered no less than 720W into 8 ohms (28.6dBW), for example (fig.4), with similar deliveries into 4 and 2 ohms from their respective taps (figs.5 and 6). 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.

Exactly as it should. For instance, 8V across 8Ω causes a current of 1A to flow and the power is 8W; 4V across 2Ω causes a current of 2A for the same 8W. Quarter the impedance and you need twice the current and half the voltage for the same power.

The 8 ohm tap was limited to 225W into 2 ohms (17.5dBW), for example, while the 4 ohm tap delivered 1000W (24dBW), the 2 ohm tap 630W (22dBW)."

Driving that 2Ω load from the 8Ω tap is a significant mismatch; no surprise the power is reduced.

[1KW]

Originally Posted by jdandy

David....... Aren't you the guy who thinks 37 on the C220 volume is "rockin"?

[crytklmass]

Does that also mean an MC205/207 200wpc is actually more or does this only apply to Monoblocks amps?

[TommyC]

Originally Posted by crytklmass

Does that also mean an MC205/207 200wpc is actually more or does this only apply to Monoblocks amps?

To my understanding, McIntosh rates all their amps very conservatively. You should expect those amps to output more power than 200w.

[magnmac]

Originally Posted by crytklmass

Does that also mean an MC205/207 200wpc is actually more or does this only apply to Monoblocks amps?

When a MC275 was reviewed it put out over 90 wpc; that is 20% more than it is rated, by that margin your 200 wpc is more like 240 wpc.