PM-11S1 Measurements & Analysis

Amplifier Efficiency

Amplifier efficiency measurements for linear A/B amps such as the ones employed in this receiver typically range from 40-50% depending on the load the power supply of the amplifier sees. The closer you get to full load, the higher the efficiency usually becomes (assuming you aren’t over taxing the power supply and power devices of the amp causing excessive thermal losses). The PM-11S1 achieved around 65% efficiency which is rare for a conventional linear amp design and indicates to me that Marantz implemented some serious power factor correction in their power supply and/or has very tight tolerance on power supply ripple.

Note: All power output figures above were conducted at 1kHz and 0.1% THD + N

Power Bandwidth

Marantz PM-11S1 Frequency Response

The Marantz PM-11S1 possesses a wide bandwidth amplifier topology with a -3dB point in excess of 170kHz. The frequency response was ruler flat as expected.

At full continuous unclipped power; 175wpc x 1; 8-ohms– full bandwidth with less than 0.1% THD+N, the PM-11S1 still maintained its excellent bandwidth linearity despite the fact we were driving this amplifier way beyond its rated 100wpc power specification. Into 4-ohms, the PM-11S1 was able to deliver continuous power levels at a whopping 295wpc x 1 with less than 0.1% THD + N. The amplifier section of this integrated amp seems purposely underrated to inspire reviewers like myself to praise its design merits and conservative ratings.

For more info on amplifier measurements, see: The All Channels Driven (ACD) Test

FFT Distortion Analysis

FFT Analysis @ 1 watt

At 1 watt into 8-ohms, the PA350B exhibited impressively low distortion (8.999+89.889)dBv = 98.888dbV or 100*alog^-1(-98.9/20) = .001% THD + N which is super clean as expected from a design of this caliber.

FFT Analysis @ 100 watts

(28.852 + 57.791)dBv = 86.64dBv or 100*alog^-1(-86.64/20) = .005% THD + N which indicates as per my power measurements, the amp section in this integrated amplifier is too conservatively rated.

Amplifier Output Impedance & Damping Factor

Amplifier Output Impedance

The amplifier output impedance fell right within our desired 100mohm or less mark for the entire audible bandwidth up to 10kHz with just a slight increase above at the upper 20kHz frequency range. This is the type of performance I like to see in any high quality amplification and it's obvious the Marantz PM-11S1 exemplifies this.

Amplifier Damping Factor

The amplifier damping factor is about what I expected based on the measured output impedance. It is uniformly good across the entire audio frequency range and hovers around the 100 mark we like to see on uncompromising designs. All in all, this is quite an impressive result and rivals many exotic amplifiers in this price range while exceeding our minimum 50 value we like to see in all amplifier designs.

Signal to Noise Ratio (SNR)

Channel A's signal to noise ratio came in at -107.32 dB below 31.79 dBV Reference Level (at 1.07 % THD+N). This was with a frequency response of <10 Hz - 22k Hz bandwidth, no option filter. This equates to a SNR of 84dB @ 1 watt

With a 200mVrms signal input and the output adjusted to 1 watt, I measured an excellent SNR of 84dB (unweighted). This didn’t surprise me as I knew this amp was clean from our listening tests.