Product Review
 

Mark Levinson No 433 Three-Channel and No 436 Monoblock Power Amplifiers

Part III

September, 2006

John E. Johnson, Jr.

 

On the Bench

I tested the No 433 and No 436 amplifiers with a Mark Levinson No 326S preamplifier and Carver Mark IV ribbon speakers.

First, the No 433.

At 20 volts into 8 ohms (50 watts), THD+N was a very low 0.005%. The second harmonic is larger than the third, which is good. An absence of a 60 Hz peak and its harmonics indicates a clean power supply.

The SMPTE/DIN IMD test yielded 0.01% distortion. The calculations are complex, and the more important thing is to look at the actual graph and examine the peaks next to the fundamental at 2 kHz. Compare this to the fundamental on the No 436, which has fewer of these IMD peaks. Nevertheless, the No 433 is still a top performer. The No 436 just has that extra little bit of fine detail quality which qualifies it for being one of the best power amplifiers ever designed.

THD+N vs. Frequency is shown below for a 20 volt output into various loads. Notice that the distortion stays flat to about 200 Hz, then begins to rise, depending on the load. Compare this to the No 436.

Power output at clipping (1% THD+N) was 250 watts at 8 ohms, and 465 watts at 4 ohms. This exceeds specification by a wide margin.

Below are graphs from the No 436.

At 5 volts output into 8 ohms, THD+N was less than 0.03%. Again, there is not much evidence of any 60 Hz peak or its harmonics, so the power supply is very clean.

At 4 ohms, it was just over 0.03%.

At 20 volts output into 8 ohms, THD+N was reduced to 0.006%. This is typical of many amplifiers, where distortion goes down when comparing low output vs. mid-level output.

At 4 ohms, THD+N was the same as at 8 ohms.

For the SMPTE/DIN IMD test at 5 volts and 8 ohms, although the calculated IMD value is higher than that with the No 433, notice that there are actually less peaks next to the fundamental. This is what gives the No 436 that added detail in the sound.

At 4 ohms, IMD increased just a bit.

Here again, compare the actual peaks next to the fundamental, with those shown for the No 433 at 20 volts and 8 ohms. The No 436 has the better performance.

At 4 ohms, the performance actually improved. Unusual.

Click Here to Go to Part IV.

© Copyright 2006 Secrets of Home Theater & High Fidelity

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