February 2009
Luxman L509u
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.
 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 "linestraight" mode unless otherwise noted.
 Input/output polarity
 Unbalanced inputs: noninverting
 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: noninverting
 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
 Output noise, unbalanced inputs, 8ohm load, 1kohm 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, 8ohm load, 1kohm 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
 Phonoreferredequivalent input noise, Lch/Rch
 MM, input 1kohm termination resistance
 wideband: 5.8uV / 5.6uV
 A weighted: 0.27uV / 0.28uV
 MC, input 100ohm termination resistance
 wideband: 0.65uV / 0.69uV
 A weighted: 0.13uV / 0.12uV
Power output with 1kHz test signal
 8ohm load at 1% THD: 156.1W
 8ohm load at 10% THD: 247.8W
 4ohm load at 1% THD: 130.8W
 4ohm load at 10% THD: 300.4W
General
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 L509u is a mediumpower solidstate integrated
amplifier. As this unit has a preamplifier line stage within, overall lineinput gain of
this unit is somewhat high compared to the general current trend in integrated amplifiers,
where the gain is generally near poweramplifieronly gain. Still, the gain combination of
the L509u is that of a typical power amplifier  only gain plus that of a modestgain
linelevel 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 volumecontrol position as set
for 0.5V input to produce 5W output into an 8ohm load. The highfrequency 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
dummyload response is not shown, as its variations would not show at the plot's vertical
resolution. As is frequently the case, highfrequency response was somewhat a function of
volumecontrol 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 rolledoff
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 solidstate lowdistortion behavior of noisedominated 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 4ohm 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 solidstate 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 ACline
harmonics are low. Signal harmonics are low, and intermodulation effects of the ACline
harmonics on the signal harmonics are quite absent here.
With the Line Straight button disengaged to allow balance
and tonecontrol use, tonecontrol 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 
1A
volume control at reference position
Red line: open circuit
Magenta line: 8ohm load
Blue line: 4ohm load
1B
volume control full up, 8ohm load
Red line: open circuit
Blue line: 8ohm load
1C
volume control 20dB below reference position, 8ohm load
Red line: open circuit
Blue line: 8ohm load
Chart 2  Distortion as a Function
of Power Output and Output Loading 
(line up at 20W to determine lines)
Top line: 4ohm SMPTE IM
Second line: 4ohm THD+N
Third line: 8ohm SMPTE IM
Bottom line: 8ohm THD+N
Chart 3  Distortion
as a Function of Power Output and Frequency 
4ohm 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 4ohm load
Chart 6  PhonoStage RIAA
Equalization Error 
7A
moving magnet (MM)
Red line: left channel
Blue line: right channel
7B
moving coil (MC)
Red line: left channel
Blue line: right channel
Chart 8  ToneControl 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
