Link: reviewed by Hans Wetzel on *SoundStage! Ultra* on August 1, 2023

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Luxman L-507Z (S/N G30100145A) was conditioned for one hour at 1/8th full rated power (~13W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The L-507Z offers three unbalanced (RCA) and two balanced (XLR) line-level analog inputs, one set of phono level unbalanced inputs (configurable for both MM and MC cartridges), one set of line-level pre-outputs (RCA), one set of line-level main-ins (RCA), and two pairs of speaker-level outputs (A and B). Also available are two headphone outputs, one unbalanced over ¼″ TRS, and one balanced over 4.4mm TRRS. For the purposes of these measurements, the following inputs were evaluated: analog line-level balanced inputs (a 1kHz FFT using the unbalanced inputs is also provided), and phono level unbalanced inputs (MM and MC).

Most measurements were made with a 2Vrms line-level, 5mVrms MM level, and 0.5mVrms MC level analog input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 110W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 110W output.

Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the L-507Z volume control is likely digitally controlled but operating in the analog domain. The volume control offers a total range from -80dB to +43.6dB between the line-level balanced analog inputs and the speaker outputs. Volume step sizes are 1dB throughout the range.

The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response (DC to 1 MHz), FFTs (10Hz–90kHz), and THD vs Frequency (10Hz–90kHz). The latter to capture the second and third harmonics of the 20kHz output signal. Since the L-507Z is a conventional class AB amp, there was no issue with excessive noise above 20kHz.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

min | 0.7dB |

-77.0 | 0.012dB |

-52.0 | 0.001dB |

-33.0 | 0.014dB |

-16.0 | 0.025dB |

-10.0 | 0.021dB |

-5.0 | 0.028dB |

-2.0 | 0.026dB |

0 | 0.024dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Luxman for the L-507Z compared directly against our own. The published specifications are sourced from Luxman’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 1MHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Rated output power into 8 ohms (1% THD) | 110W | 135W |

Rated output power into 4 ohms (1% THD) | 220W | 222W |

Maximum tone control (bass) | ±8dB at 100Hz | ±8dB at 100Hz (relative to 10kHz) |

Maximum tone control (treble) | ±8dB at 10kHz | ±8dB at 10kHz (relative to 20Hz) |

Input sensitivity (MM) | 2.5mVrms | 3.15mVrms |

Input impedance (MM) | 47k ohms | 52.7k ohms |

Input sensitivity (MC) | 0.3mVrms | 0.42mVrms |

Input impedance (MC) | 100 ohms | 140 ohms |

Input sensitivity (Line RCA) | 180mVrms | 193mVrms |

Input impedance (Line RCA) | 47k ohms | 51.6k ohms |

Input sensitivity (Line XLR) | 180mVrms | 196mVrms |

Input impedance (Line XLR) | 79k ohms | 64.4k ohms |

Input sensitivity (Main in) | 1.05Vrms | 1.06Vrms |

Input impedance (Main in) | 47k ohms | 55.2k ohms |

Frequency response (phono) | 20Hz to 20kHz (±0.5dB) | 20Hz to 20kHz (±0.25dB) |

Frequency response (line) | 20Hz to 100kHz (-3dB) | 20Hz to 100kHz (-0.05/-4dB) |

THD (8-ohm, 1kHz, 100W) | <0.007% | <0.008% |

THD (8-ohm, 20Hz-20kHz, 100W) | <0.03% | <0.04% |

Signal-to-noise ratio (MM, rated power, A weighted) | 91dB | 89.5dB |

Signal-to-noise ratio (MC, rated power, A weighted) | 75dB | 71.5dB |

Signal-to-noise ratio (line, rated power, A weighted) | 105dB | 104.7dB |

Damping factor (1kHz) | 300 | 313 |

Our primary measurements revealed the following using the balanced line-level analog input (unless specified, assume a 1kHz sinewave at 2Vrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 135W | 135W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 222W | 222W |

Maximum burst output power (IHF, 8 ohms) | 153.8W | 153.8W |

Maximum burst output power (IHF, 4 ohms) | 275.7W | 275.7W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -65.4dB | -75.0dB |

Damping factor | 355 | 314 |

Clipping no-load output voltage | 36.7Vrms | 36.7Vrms |

DC offset | <-1.6mV | <-0.5mV |

Gain (pre-out) | 14.7dB | 14.7dB |

Gain (maximum volume) | 43.7dB | 43.7dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-84dB | <-78dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-75dB | <-67dB |

Input impedance (line input, XLR) | 65.5k ohms | 64.4k ohms |

Input impedance (line input, RCA) | 51.2k ohms | 51.6k ohms |

Input sensitivity (for rated power, maximum volume) | 196mVrms | 196mVrms |

Noise level (with signal, A-weighted) | <152uVrms | <152uVrms |

Noise level (with signal, 20Hz to 20kHz) | <235uVrms | <215uVrms |

Noise level (no signal, A-weighted, volume min) | <22uVrms | <21uVrms |

Noise level (no signal, 20Hz to 20kHz, volume min) | <30uVrms | <28uVrms |

Output impedance (pre-out) | 692 ohms | 693 ohms |

Signal-to-noise ratio (110W, A-weighted, 2Vrms in) | 104.9dB | 104.7dB |

Signal-to-noise ratio (110W, 20Hz to 20kHz, 2Vrms in) | 102.5dB | 102.6dB |

Signal-to-noise ratio (110W, A-weighted, max volume) | 91.3dB | 91.5dB |

THD ratio (unweighted) | <0.0059% | <0.0165% |

THD+N ratio (A-weighted) | <0.0064% | <0.018% |

THD+N ratio (unweighted) | <0.0066% | <0.017% |

Minimum observed line AC voltage | 122 VAC | 122 VAC |

For the continuous dynamic power test, the L-507Z was able to sustain 228W into 4 ohms (~2% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (22.8W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the L-507-Z was warm but not hot to the touch.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -63.3dB | -60.0dB |

DC offset | <-2mV | <-2mV |

Gain (default phono preamplifier) | 35.7dB | 35.6dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-88dB | <-81dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-92dB | <-87dB |

Input impedance | 50.3k ohms | 52.7k ohms |

Input sensitivity (to rated power with max volume) | 3.15mVrms | 3.19mVrms |

Noise level (with signal, A-weighted) | <290uVrms | <300uVrms |

Noise level (with signal, 20Hz-20kHz) | <700uVrms | <1500uVrms |

Overload margin (relative 5mVrms input, 1kHz) | 30.2dB | 30.4dB |

Signal-to-noise ratio (full rated power, A-weighted) | 90.4db | 89.5dB |

Signal-to-noise ratio (full rated power, 20Hz-20kHz) | 83.1dB | 74.9dB |

THD (unweighted) | <0.003% | <0.005% |

THD+N (A-weighted) | <0.005% | <0.0065% |

THD+N (unweighted) | <0.009% | <0.018% |

Our primary measurements revealed the following using the phono-level input, MC configuration (unless specified, assume a 1kHz 0.5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -58.6dB | -44.1dB |

DC offset | <-2mV | <-2mV |

Gain (default phono preamplifier) | 53.3dB | 53.2dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-83dB | <-83dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-79dB | <-79dB |

Input impedance | 140 ohms | 140 ohms |

Input sensitivity (to rated power with max volume) | 417uVrms | 421uVrms |

Noise level (with signal, A-weighted) | <2.2mVrms | <2.5mVrms |

Noise level (with signal, 20Hz-20kHz) | <7mVrms | <14mVrms |

Overload margin (relative 0.5mVrms input, 1kHz) | 32.7dB | 32.7dB |

Signal-to-noise ratio (full rated power, A-weighted) | 72.6dB | 71.5dB |

Signal-to-noise ratio (full rated power, 20Hz-20kHz) | 63.6dB | 56.2dB |

THD (unweighted) | <0.006% | <0.007% |

THD+N (A-weighted) | <0.025% | <0.03% |

THD+N (unweighted) | <0.08% | <0.15% |

Our primary measurements revealed the following using the analog input at the unbalanced headphone output (unless specified, assume a 1kHz sinewave, 2Vrms input and output, 300 ohms loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 405mW | 403mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 326mW | 324mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 58mW | 58mW |

Gain | 43.6dB | 43.6dB |

Output impedance (1/4″ TRS, unbalanced) | 819 ohms | 821 ohms |

Output impedance (4.4mm TRRS, balanced) | 813 ohms | 815 ohms |

Noise level (with signal, A-weighted) | <40uVrms | <41uVrms |

Noise level (with signal, 20Hz to 20kHz) | <60uVrms | <61uVrms |

Noise level (no signal, A-weighted, volume min) | <5.8uVrms | <6.1uVrms |

Noise level (no signal, 20Hz to 20kHz, volume min) | <7.8uVrms | <9.6uVrms |

Signal-to-noise ratio (max output, A-weighted, 2Vrms in) | 106.3dB | 106.1dB |

Signal-to-noise ratio (max output, 20Hz to 20kHz, 2Vrms in) | 104.1dB | 103.9dB |

THD ratio (unweighted) | <0.007% | <0.017% |

THD+N ratio (A-weighted) | <0.008% | <0.019% |

THD+N ratio (unweighted) | <0.008% | <0.018% |

**Frequency response (8-ohm loading, line-level input, relative level)**

In our measured frequency-response (relative to 1kHz) chart above, the blue and red plots show the speaker-level outputs (relative to 1kHz, at 10W into 8 ohms). The L-507Z’s speaker outputs are near flat within the audioband (less than -0.1dB at 20Hz and about -0.2dB at 20kHz), and exhibit an average extended bandwidth (-4dB at 100kHz). The L-507Z appears to be AC coupled, due the attenuation in response below 20Hz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

** Frequency response (8-ohm loading, line-level input, bass and treble controls)**

Above is a frequency response (relative to 1kHz) chart with the L-507Z’s bass and treble controls set to maximum and minimum, measured at the speaker-level outputs at 10W into 8 ohms. The L-507Z offers about +/-7dB of bass and treble boost/cut at 20Hz and 20kHz when both controls are engaged fully. When the tone controls are used in isolation, +/-8dB of boost/cut was observed, as advertised by Luxman. Below is . . .

. . . a frequency-response chart (relative to 10kHz) with the bass control set at maximum and minimum while maintaining the treble control at zero. We see a maximum boost/cut of nearly 9dB at 20Hz. Below is . . .

. . . a frequency response chart (relative to 100 Hz) with the treble control set at maximum and minimum while maintaining the bass control at zero. We see a maximum boost/cut of nearly 9dB at 20kHz.

**Frequency response (8-ohm loading, line-level input, Loudness control)**

Above is a frequency response (relative to 1kHz) chart with the L-507Z’s Loudness control engaged, measured at the speaker-level outputs at 10W into 8 ohms. The L-507Z Loudness control provide a bass boost of 5dB centered at around 80Hz, and a treble boost of just under 4dB, centered at around 15kHz.

**Phase response (line-level input)**

Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The L-507Z does not invert polarity. Here we find +10 degrees at 20Hz, and -20 degrees at 20kHz.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response (relative to 1kHz) for the MM phono configuration. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. We see maximum deviations within about ±0.25dB from 20Hz to 20kHz. With the subsonic filter engaged, we find the -3dB point at 30Hz, and at 20Hz, we are at -5dB.

**Phase response (MM input)**

Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. The L-507Z does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about +60 degrees at 20Hz without the subsonic filter and +120 degrees with the subsonic filter.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response (relative to 1kHz) for the MC phono configuration. The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. The responses are essentially identical to the MM configuration above.

**Phase response (MC input)**

Above is the phase response plot from 20Hz to 20kHz for the MC phono input, measured across the speaker outputs at 10W into 8 ohms. The blue and red traces (left/right) are without the subsonic filter engaged, and the purple and green (left/right) are with the subsonic filter engaged. Here we find a worst case of about +80 degrees at 20Hz without the subsonic filter, and +130 degrees with the subsonic filter.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we can see only minor deviations of about 0.06dB from 4 ohms to no load throughout the audioband. This is an indication of a high damping factor, or low output impedance. The variation in RMS level when a real speaker was used is slightly lower at 0.05dB through most of the audioband.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the balanced analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at just over 100W. The power was varied using the volume control. At 1W, THD ratios were at their highest and ranged from 0.01% from 20Hz to 100Hz, then up to 0.5% at 20kHz. The left channel outperformed the right (at 10W as well) by a little over 5dB from 300Hz to 20kHz. The 10W THD data ranged from as low as 0.0015% at 30-50Hz, then up to 0.15% at 20kHz. The 100W THD data ranged from 0.007% from 20Hz to 1kHz, then up to 0.04% at 20kHz.

**THD ratio (unweighted) vs. frequency at 10W (MM and MC inputs)**

The chart above shows THD ratios as a function of frequency plots for the MM (blue/red) and MC (purple/green) phono input configurations measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The MM THD values varied from as low as 0.003% from 40Hz to 1kHz (left channel), then up to 0.02% at 20kHz. Once again, the right channel yielded higher THD results than the left, at 20-30Hz, and from 500Hz to 20kHz. The MC THD results ranged from 0.05% at 20Hz (left), down to 0.005% at 400-500Hz, then up to 0.01% at 20kHz, with the right channel yielding THD ratios 5-10dB higher at low and high frequencies.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the L-507Z as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm data outperformed the 4-ohm data by only 2-3dB, smaller than the difference in performance between the left and right channels (5-10dB). The 8-ohm data (left) ranged from 0.02% at 50mW, down to 0.003% at 3-20W, then up to 0.005% at the “knee” at roughly 110W. The “knee” for the 4-ohm data can be seen at roughly 190W. The 1% THD marks are at 135W into 8 ohms, and 222W into 4 ohms.

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the L-507Z as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar with the 8-ohm data outperforming the 4-ohm data by only 2-3dB. They ranged (left channel) from about 0.05% at 50mW, down to 0.005%.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the L-507Z as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 40W at the output into 8 ohms (and roughly 80W into 4 ohms, and 160W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find a 2-3dB increase in THD from 8 to 4 ohms, then a roughly 5dB increase from 4 to 2 ohms. Nonetheless, even into 2 ohms, these data show that the L-507Z is not only stable into 2-ohm loads, but will yield acceptably low THD values, ranging from 0.005 to 0.06%.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the L507-Z as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At lower frequencies, the two-way speaker yielded the highest THD ratios, as high as 0.04% at 20Hz. From 40Hz to 20kHz however, all THD values were essentially identical, ranging from around 0.01% up to 0.4%. This shows that the L-507Z will yield consistent and stable THD results into different loads at low power levels.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the L-507Z as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a two-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, hovering at a relatively high 0.02%.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the L-507Z as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a two-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar enough to be judged identical, hovering at a relatively high 0.08%.

**FFT spectrum – 1kHz (line-level input, balanced)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the balanced analog line-level input. In general, the even ordered signal harmonics (2/4/6kHz, etc) dominate over the odd (3/5/7kHz, etc.). We see that the signal’s second and fourth harmonics (2/4kHz) dominate at around -90/-80dBrA (left/right), or 0.003/0.01%. The other signal harmonics are below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating at and just below -100dBrA, or 0.001%.

**FFT spectrum – 1kHz (line-level input, unbalanced)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the unbalanced analog line-level input. The FFT is virtually identical to the FFT shown above using the balanced input.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input configuration. Signal harmonics can be seen up to 20kHz, with the 2kHz peak dominating at -90dBRa, or 0.003%. The worst-case power-supply-related peak can be seen at 60Hz, at -90/-70dBrA (left/right), or 0.003/0.03%.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MC phono input configuration. Signal harmonics can be seen up to 20kHz, with the 2kHz peak dominating at -85dBRa, or 0.006%. The worst-case power-supply-related peak can be seen at 60Hz, at -65/-55dBrA (left/right), or 0.06/0.2%.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s third and fourth harmonics (150/200Hz) dominate at around -100dBrA, or 0.001%. The subsequent signal harmonic peaks are below -110dBrA, or 0.0003%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating at and just below -100dBrA, or 0.001%.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input configuration. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -90dBrA, or 0.003%. The subsequent signal harmonic peaks are below -110dBrA, or 0.0003%. There are clearly visible power-supply related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating, as high as -70dBrA (right), or 0.03%.

**FFT spectrum – 50Hz (MC phono input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MC phono input configuration. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The signal harmonics are barely noticeable above the -100 to -120dBrA noise floor. The second signal harmonic (left) is at -90dBrA, or 0.003%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, with the 60Hz (right) and 180Hz (left) peaks dominating, as high as -55dBrA (right), or 0.2%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are lower at -100dBrA, or 0.001%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input configuration. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/100dBrA (left/right), or 0.0003/0.001%. The third-order modulation products, at 17kHz and 20kHz, are around -100dBrA, or 0.001%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MC phono input configuration. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is only barely noticeable above the noise floor for the right channel at just below -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are at an below -100dBrA, or 0.001%.

**Intermodulation distortion FFT (line-level input, APx 32 tone)**

Shown above is the FFT of the speaker-level outputs of the L-507Z with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—*i.e.*, the "grass" between the test tones—are distortion products from the amplifier and below the -100dBrA, or 0.001%, level, with the right channel peaks dominating over the left. The peaks at lower frequencies that reach the -100dBrA level are not IMD products but power-supply-related noise peaks.

**Square-wave response (10kHz)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the L-507Z’s slew-rate performance. Rather, it should be seen as a qualitative representation of the L-507Z’s above average bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see a relatively clean squarewave reproduction, with some mild softening of the corners, and no overshoot.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. Both channels track closely, with a higher damping factor (around 315 to 400) between 20Hz and 2kHz. Above 2kHz, we see a slight decline in the damping factor, as low as 184 at 20kHz.

*Diego Estan*

Electronics Measurement Specialist