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Equipment Measurements

February 2009

Luxman L-509u Integrated Amplifier: Measurements

All  amplifier measurements are performed independently by BHK Labs. Please click to learn more about how we test amplifiers there. All measurement data and graphical information displayed below are the property of SoundStage! and Schneider Publishing Inc. Reproduction in any format is not permitted.

Additional Data
  • Measurements were made at 120V AC line voltage with both channels being driven.
  • Measurements were made on the left channel on the unbalanced inputs in the "line-straight" mode unless otherwise noted.
  • Input/output polarity
    • Unbalanced inputs: non-inverting
    • Balanced inputs: inverting
      (note: balanced inputs do invert polarity in the "normal" position of the balanced input phase switch as Luxman has defined pin 3 "hot" for their balanced inputs. This is easily changed by pressing the switch to "reverse.")
    • Phono inputs: non-inverting
  • AC line current draw at idle: 1.1A
  • Input sensitivity for 1W output into 8 ohms, volume at maximum, Lch/Rch
    • Unbalanced inputs: 17.3mV / 17.3mV
    • Balanced inputs: 17.5mV / 17.6mV
  • Input impedance @ 1kHz
    • Unbalanced inputs: 51k ohms
    • Balanced inputs: 65k ohms
    • Phono MM inputs: 46k ohms
    • Phono MC inputs: 100 ohms
  • Output impedance at 50Hz: 0.027 ohm
  • Gain, output voltage divided by input voltage, volume at maximum, Lch/Rch
    • Unbalanced inputs: 163.6X, 44.3dB / 163.2X, 44.3dB
    • Balanced inputs: 161.3X, 44.2 dB / 161.1X, 44.1dB
  • Phono gain, at 1kHz to tape out
    • MM: 59.8X, 35.5dB
    • MC: 550.0X, 54.8dB
  • Phono overload, input voltage at 1kHz at onset of visual distortion
    • MM: 165.0mV
    • MC: 21.6mV
  • Output noise, unbalanced inputs, 8-ohm load, 1k-ohm input termination, Lch/Rch
    • Volume control at reference position
      • wideband: 2.1mV, -62.6dBW / 2.1mV, -73.9dBW
      • A weighted: 0.30mV, -79.5dBW / 0.28mV, -80.1dBW
    • Volume control full clockwise
      • wideband: 3.8mV, -57.4dBW / 4.0mV, -57.0dBW
      • A weighted: 0.20mV, -83.0dBW / 0.23mV, -81.8dBW
    • Volume control set for 20dB attenuation below reference
      • wideband: 1.7mV, -64.4dBW / 1.7mV, -64.4dBW
      • A weighted: 0.18mV, -84.0 dBW / 0.17mV, -84.4dBW
    • Volume control full counterclockwise
      • wideband: 1.6mV, -65.0dBW / 1.6mV, -65.0dBW
      • A weighted: 0.18 mV, -84.0dBW / 0.16mV, -85.0dBW
  • Output noise, balanced inputs, 8-ohm load, 1k-ohm input termination, Lch/Rch
    • Volume control at reference position
      • wideband: 2.1mV, -62.6dBW / 2.1mV, -62.6dBW
      • A weighted: 0.31mV, -79.2dBW / 0.29mV, -79.8dBW
    • Volume control full clockwise
      • wideband: 3.9mV, -57.2dBW / 3.9mV, -57.2dBW
      • A weighted: 1.1mV, -68.2dBW / 1.1mV, -68.2dBW
    • Volume control set for 20dB attenuation below reference
      • wideband: 1.7mV, -64.4dBW / 1.7mV, -64.4dBW
      • A weighted: 0.20mV, -83.0dBW / 0.17mV, -84.4dBW
    • Volume control full counterclockwise
      • wideband: 1.5mV, -65.5dBW / 1.6mV, -65.0dBW
      • A weighted: 0.17mV, -84.4dBW / 0.15mV, -85.5dBW
  • Phono-referred-equivalent input noise, Lch/Rch
    • MM, input 1k-ohm termination resistance
      • wideband: 5.8uV / 5.6uV
      • A weighted: 0.27uV / 0.28uV
    • MC, input 100-ohm termination resistance
      • wideband: 0.65uV / 0.69uV
      • A weighted: 0.13uV / 0.12uV
Measurements Summary

Power output with 1kHz test signal

  • 8-ohm load at 1% THD: 156.1W
  • 8-ohm load at 10% THD: 247.8W

  • 4-ohm load at 1% THD: 130.8W
  • 4-ohm load at 10% THD: 300.4W


A few preliminary points about the measurements. It was found that there was virtually no difference in distortion between the unbalanced and balanced inputs. Therefore, the unbalanced inputs were used for most tests. Also, the performance with the tone and balance controls engaged was about the same as with the Line Straight mode, so the latter was used for testing.

The Luxman L-509u is a medium-power solid-state integrated amplifier. As this unit has a preamplifier line stage within, overall line-input gain of this unit is somewhat high compared to the general current trend in integrated amplifiers, where the gain is generally near power-amplifier-only gain. Still, the gain combination of the L-509u is that of a typical power amplifier -- only gain plus that of a modest-gain line-level preamp -- and that is known to work just fine in practice.

Chart 1 shows the frequency response of the integrated amp with varying loads. This plot was made with the reference volume-control position as set for 0.5V input to produce 5W output into an 8-ohm load. The high-frequency response at the reference setting of the volume control is reasonably wide, having a -3dB point of about 100kHz. Further, the output impedance of the amp is quite low and, therefore, the NHT dummy-load response is not shown, as its variations would not show at the plot's vertical resolution. As is frequently the case, high-frequency response was somewhat a function of volume-control setting, varying from what looks like a higher bandwidth but different response between channels at full volume as shown in Chart 1A, to a more rolled-off response below full volume than in Chart 1, to an almost flat response out to 200kHz at 50dB of attenuation. Bandwidth is widening toward this at -40dB of attenuation, as shown plotted in Chart 1B.

Chart 2 illustrates how total harmonic distortion plus noise vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load. This unit exhibits typical solid-state low-distortion behavior of noise-dominated distortion at low powers, with actual distortion starting to show at powers of about 50W and above.

Total harmonic distortion plus noise as a function of frequency at several different power levels is plotted in Chart 3 for 4-ohm loading. A good result is that the amount of rise in distortion at high frequencies is moderate.

Damping factor vs. frequency is shown in Chart 4 and is of a high value at low frequencies and, as typical of many solid-state power amplifiers, begins to fall off rapidly with frequency at about 500Hz.

A spectrum of the harmonic distortion and noise residue of a 10W 1kHz test signal into 4 ohms is plotted in Chart 5. The magnitudes of the AC-line harmonics are low. Signal harmonics are low, and intermodulation effects of the AC-line harmonics on the signal harmonics are quite absent here.

With the Line Straight button disengaged to allow balance and tone-control use, tone-control characteristics were measured and are shown in Chart 6.

Lastly, RIAA equalization error was measured for both MM and MC modes and is shown plotted in Charts 7A and 7B.

Chart 1 - Frequency Response of Output Voltage as a Function of Output Loading

volume control at reference position

Red line: open circuit
Magenta line: 8-ohm load
Blue line: 4-ohm load

volume control full up, 8-ohm load

Red line: open circuit
Blue line: 8-ohm load

volume control -20dB below reference position, 8-ohm load

Red line: open circuit
Blue line: 8-ohm load

Chart 2 - Distortion as a Function of Power Output and Output Loading

(line up at 20W to determine lines)
Top line: 4-ohm SMPTE IM
Second line: 4-ohm THD+N
Third line: 8-ohm SMPTE IM
Bottom line: 8-ohm THD+N

Chart 3 - Distortion as a Function of Power Output and Frequency

4-ohm output loading
Green line: 100W
Blue line: 70W
Magenta line: 10W
Red line: 1W

Chart 4 - Damping Factor as a Function of Frequency

Damping factor = output impedance divided into 8

Chart 5 - Distortion and Noise Spectrum

1kHz signal at 10W into a 4-ohm load

Chart 6 - Phono-Stage RIAA Equalization Error

moving magnet (MM)

Red line: left channel
Blue line: right channel

moving coil (MC)

Red line: left channel
Blue line: right channel

Chart 8 - Tone-Control Response

Data below 1kHz
Blue line (top): maximum bass boost
Red line: intermediate bass boost
Green line: flat
Magenta line: intermediate bass cut
Blue line (bottom): maximum bass cut

Data above 1kHz
Magenta line (top): maximum treble boost
Blue line (second from top): intermediate treble boost
Blue line (third from top): flat
Light blue line: intermediate treble cut
Green line: maximum treble cut


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