almarg,
I agree completely with your assessment.
N
I agree completely with your assessment.
N
Which watts are the right watts in SS amps?
Pass Labs is another that truly doubles down Many manufacturers understate in their literature the 8ohm wattage so the 4ohm and 2ohm wattage looks to be doubling. It's only on independent tests this shows up the 8ohm to be higher and the 4ohm or 2ohm not doubling. Here's what I mean, both taken from Stereophile on one of the latest 60 .8 series. Manufacture: Specified as putting out 60W into 8 ohms and 120W into 4 ohms (both 17.8dBW), Stereophile measured: The XA60.8 considerably exceeded that power, delivering, at 1% total harmonic distortion (THD), 150W into 8 ohms (21.8dBW, fig.4), 240W into 4 ohms So you see 150w into 8ohms but only 240w (not 300w) into 4ohms, where's the other 60w gone???? Cheers George |
Because of this "voltage source" characteristic, the 300- series amplifiers double their power demands every time a loudspeaker impedance is cut by half. For example, the no. 336’s continuous rated output is 350 watts per channel at 8ohms; 700 watts at 4ohm; 1400 watts per channel at 2ohms. Again, many manufacturers understate in their literature the 8ohm wattage so the 4ohm and 2ohm wattage looks to be doubling. It’s only on independent tests this shows up the 8ohm to be higher and the 4ohm or 2ohm not doubling. Levinsons specs: for 334. 300 series 8ohm=125w 4ohm=250w 2ohm=600w Stereophiles tested specs 8ohm=139.9w 4ohm= 242.4w 2ohm= 430w As you can see they don’t double, when tested. Cheers George |
Hi George, The no.334 manual does not give a rated output for a 1ohm output load. 8 ohm- 125; 4 ohm- 250; 2 ohm- 500 watts. However John Atkinson found his test sample to measure quite closely to the ML literature: "..John Atkinson also measured the No.334’s maximum output power using the Miller Audio Research Amplifier Profiler and a low-duty-cycle 1kHz toneburst to avoid loading down the AC line and the amplifier’s power supply. The result is graphically shown in fig.8. Though with this signal and one channel driven, the amplifier did meet its specification into 4 ohms, there was still a very slight shortfall into the demanding 2 ohm and 1 ohm loads. Into these impedances, 492W and 829W were available, these powers equivalent to output currents of 15.7A and 28.8A, respectively..." N |
So the upshot is, if you have speakers that are a kind load to the amp, then the amp is not called for to deliver current, and will stay reasonably flat in frequency response. But if the speakers are a load that asks the amp to deliver current at certain frequencies, and the amp can't, then what happens at those frequencies is the amp "sags" in power at those frequencies and therefore cannot stay flat in frequency response, and becomes a tone control instead. EG: Like the blackish grey trace shows in this graph of a tube amp that can't stay flat into a easy simulated speaker load. Which is plus and minus 6db!!! very far from sounding flat, and very mush a tone control. https://www.stereophile.com/images/1116PLPPfig01.jpg Cheers George |