Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs and 8-ohm outputs unless otherwise noted.

Power output

• Output power at 1% THD+N: 26.0W @ 8 ohms, 15.0W @ 4 ohms
• Output power at 10% THD+N: 40.0W @ 8 ohms, 32.0W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 1.42A, 0.89PF, 151W
• Gain: output voltage divided by input voltage, volume at maximum, Lch/Rch: 18.61X, 25.4dB:
  •      Balanced inputs: 39.75X, 32.0dB / 40.31X, 32.1dB
  •      Unbalanced inputs: 50.32X, 34.0dB / 52.18X, 34.4dB
• Input sensitivity for 1W output into 8 ohms, volume at maximum, Lch/Rch:
  •      Balanced inputs: 0.071mV / 0.70mV
  •      Unbalanced inputs: 0.56mV / 0.54mV
• Output impedance @ 50Hz: 2.15 ohms
• Input impedance @ 1kHz: 50k ohms
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
  •      Volume control at reference position
              Wideband: 0.89 mV, -70.0dBW / 4.88mV, -55.3dBW
              A weighted: 0.21 mV, -82.6dBW / 0.70 mV, -72.1dBW
  •      Volume control full clockwise
              Wideband: 1.11mV, -68.2dBW / 5.08mV, -54.9dBW
              A weighted: 0.28mV, -80.1dBW / 0.71mV, -72.0dBW
  •      Volume control full counterclockwise
              Wideband: 0.89mV, -70.0dBW / 4.89 mV, -55.2 dBW
              A weighted: 0.18mV, -83.9dBW / 0.68 mV, -72.4 dBW
• Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm, Lch/Rch
  •      Volume control at reference position
              Wideband: 1.12mV, -68.1dBW / 5.09mV, -54.9dBW
              A weighted: 0.20mV, -83.0dBW / 0.74mV, -71.6dBW
  •      Volume control full clockwise
              Wideband: 1.59mV, -65.0dBW / 4.97mV, -55.1dBW
              A weighted: 0.25mV, -81.1dBW / 0.73mV, -71.8dBW
  •      Volume control full counterclockwise
              Wideband: 0.95mV, -69.5dBW / 5.32mV, -54.5dBW
              A weighted: 0.19 mV, -83.5 dBW / 0.72 mV, -71.9 dBW

Measurements summary

The JE Audio VS70.1 is a medium-power tubed power amplifier with a front-panel volume control. Its overall gain is 6-7dB over the "nominal" power gain of 26dB. However, the extra gain would be useful for low-output CDs, such as Reference Recordings’ HRx discs.

Chart 1 shows the VS70.1’s frequency response with varying loads. This was made at the usual 1W/8-ohm level, with the volume control turned fully clockwise. The frequency-response variation with the NHT dummy load is of the order of ±1.5dB. The high-frequency rolloff is nicely controlled in that its shape is quite independent of load.

With the reference condition set up for measuring integrated amplifiers -- i.e., volume control set for 5W output into 8 ohms for 500mV input -- another response was run, and is shown in Chart 1A. Here we see that the HF response is a little more extended, and the very low-frequency level is starting to roll off because of output-transformer limitations. Channel tracking as a function of volume-control position down from this reference condition was generally within ±1dB down to 50dB of attenuation, below which hum, noise, and capacitive coupling altered the response and the channel separation.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load. It is apparent that the power is maximized for the 8-ohm load, whereas the power for a 4-ohm load is lower at higher distortion. Further, the amounts of intermodulation distortion are rather excessive at the higher power levels.

Chart 3 plots THD+N as a function of frequency for 8-ohm loading at several different power levels. The rise in distortion at higher frequencies is reasonably low. Because of output-transformer characteristics, low-frequency distortion gets progressively worse as the bass frequency rises and the power level increases.

The VS70.1’s damping factor vs. frequency (Chart 4) is fairly low, but not unusually so for a tubed power amplifier. What is good is that it is quite flat with frequency.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal into 8 ohms is plotted in Chart 5. The magnitudes of the AC-line harmonics are quite high and complex, as are the signal harmonics. Intermodulation components of line harmonics with signal harmonics are numerous, and can be seen at the baseline of the signal harmonics.

Chart 1 - Frequency response of output voltage as a function of output loading

(Volume control fully clockwise)
Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy load

Chart 1A (Additional Measurement) - Frequency response with volume control at reference position (8-ohm load)

Red line = left channel
Blue line = right channel

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 distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 1W
Magenta line = 5W
Blue line = 15W
Cyan line = 30W
Green line = 35W

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 an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs unless otherwise noted.

Power output

• Output power at 1% THD+N: 224.8W @ 8 ohms, 372.2W @ 4 ohms
• Output power at 10% THD+N (est., see text): 250W @ 8 ohms, 400W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 1.52A, 0.75PF, 137W
• AC-line current draw at standby: 0.4A, 0.77PF, 37W
• Gain: output voltage divided by input voltage for balanced inputs: 18.61X, 25.4dB 
• Input sensitivity for 1W output into 8 ohms, balanced inputs: 152.0mV
• Output impedance @ 50Hz: 0.15 ohm
• Input impedance @ 1kHz: 1M ohm
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
  •      Wideband: 0.369mV/0.363mV, -77.7 dBW/-77.8dBW
  •      A weighted: 0.078mV/0.076mV, -91.2dBW/-91.4dBW

Measurements summary

The VX-R, one of Ayre Acoustics’ newest models, is a medium-power solid-state stereo power amplifier. Though of relatively small size, this dual-mono design, milled from a solid block of aluminum, is one heavy beast of an amp: It weighs almost 80 pounds.

Chart 1 shows the VX-R’s frequency response with varying loads. The high-frequency response is quite wide, with an approximate 3dB down point in excess of 200kHz.

The frequency response varies a small amount with load; therefore, the VX-R’s output impedance is reasonably low. The effect of the NHT dummy load is hard to see at the resolution at which this chart is usually shown; it amounts to a frequency-response deviation of about ±0.2dB.

Chart 2A illustrates how the VX-R’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output for 8- and 4-ohm loads. The protection fuses in the “front end” of the VX-R blew repeatedly when I attempted to drive it to 10% THD+N, so the values listed in the Additional Data are estimates. The amount of distortion is reasonable for what is claimed to be a no-overall-feedback design.

Chart 3 plots the THD+N as a function of frequency at several different power levels. The amount of increase in distortion at high frequencies is admirably low up to 150W. Attempts to get data at the 200W level blew the front-end fuses.

The VX-R’s plot of damping factor vs. frequency (Chart 4) is unusually flat. I have seen only a few amps with this characteristic. This usually goes along with flat distortion amount with changing frequency, as is the case with this design.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Chart 5. The magnitudes of the AC-line harmonics are very low, and the signal harmonics are predominantly the second and third; all higher harmonics are an order of magnitude lower.

Chart 1 - Frequency response of output voltage as a function of output loading

Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy load

Chart 2 - Distortion as a function of power output and output loading

(Line up at 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 70W
Cyan line = 150W

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 an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Notes: Measurements were made at 120V AC line voltage with both channels being driven. Measurements were made on the left channel through the balanced input unless otherwise noted. The Audio Precision AUX-0025 measurement filter was used unless otherwise noted.

Power output

• Power output at 1% THD+N: 187.5W @ 8 ohms, 348.8W @ 4 ohms
• Power output at 10% THD+N: 272.7W @ 8 ohms, 448.8W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 0.14A, 0.63PF, 10.0W
• AC-line current draw in operation: 0.59A, 0.67PF, 48.8W
• Gain: output voltage divided by input voltage, 8-ohm load
  •      Unbalanced inputs: 39.5X, 31.9dB
  •      Balanced inputs: 39.5X, 31.9dB
• Input sensitivity for 1W output into 8 ohms
  •      Unbalanced inputs: 71.6mV
  •      Balanced inputs: 71.6mV
• Output impedance @ 50Hz: 0.018 ohm
• Input impedance @ 1kHz
  •      Unbalanced inputs: 135k ohms
  •      Balanced inputs: 135k ohms
• Output noise, 8-ohm load, balanced inputs terminated with 600 ohms and unbalanced inputs terminated with 1k ohms, without AUX-0025 filter, Lch/Rch
  
  •      Wideband: 471mV/477mV, -15.6dBW/-15.5dBW
• Output noise, 8-ohm load, balanced inputs terminated with 600 ohms and unbalanced inputs terminated with 1k ohms, with AUX-0025 filter, Lch/Rch
  
  •      Wideband: 0.87mV/0.91mV, -70.2dBW/-69.9dBW
  •      A weighted: 0.29mV/0.34mV, -79.8dBW/-78.4dBW

Measurements summary

The Rogue Audio Medusa is a high-power hybrid stereo power amplifier with a vacuum-tubed front end coupled to a pair of Hypex switching-amplifier modules.

Chart 1 shows the Medusa’s frequency response with varying loads. The amp’s high-frequency response is rolled off before the cutoff frequency of the Audio Precision AUX-0025 measuring filter used for measuring switching amplifiers. As a result, the high-frequency response remained virtually unchanged, regardless of whether or not it was sent through the filter. The -3dB point is about 26kHz. Further, the -3dB down point at 26kHz is independent of load -- a feature of the Hypex modules.

As can be seen, the Medusa’s output impedance is so low that the variations with the NHT dummy speaker load don’t show up on the response plot.

Chart 2 illustrates how the Medusa’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load for loads of 8 and 4 ohms. The amount of distortion, and how it rises with output level, are similar to those of tube power amplifiers, and are no doubt caused by the Medusa’s tubed front end.

THD+N as a function of frequency at several different power levels is plotted in Chart 3. The degree of increase in distortion at high frequencies is admirably low.

Damping factor vs. frequency, shown in Chart 4, is of a value and nature typical of many solid-state amplifiers: high up to about 1kHz, then rolling off with increasing frequency.

Chart 5 plots the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The magnitude of the AC line harmonics is relatively complex, with 120Hz being the dominant one. Not surprisingly, the dominant signal harmonic is the second, coming from the tube circuitry. All higher harmonics quickly disappear into the noise level.

Chart 1 - Frequency response of output voltage as a function of output loading

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

Chart 2 - Distortion as a function of power output and output loading

(Line up at 100W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 70W
Cyan line = 200W

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 an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage and through the balanced input unless otherwise noted.

Power output

• Output power at 1% THD+N: 355.2W @ 8 ohms, 520.7W @ 4 ohms
• Output power at 10% THD+N: 447.2W @ 8 ohms, 663.1W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 1.39A, 0.64PF, 105W
• Gain: output voltage divided by input voltage, 8-ohm load
  
  •      Unbalanced inputs: 31.4X, 29.9dB
  •      Balanced inputs: 30.4X, 29.7dB
• Input sensitivity for 1W output into 8 ohms
  •      Unbalanced inputs: 91.1mV
  •      Balanced inputs: 93.0mV
• Output impedance @ 50Hz: 0.026 ohm
• Input impedance @ 1kHz
  •      Unbalanced inputs: 10.8k ohms
  •      Balanced inputs: 50.5k ohms
• Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm
  •      Wideband: 0.175mV, -84.2dBW
  •      A weighted: 0.042mV, -96.6dBW
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms
  •      Wideband: 0.991mV, -69.1dBW
  •      A weighted: 0.188mV, -83.6dBW

Measurements summary

The Jones Audio PA-M300 Series 2 is a high-powered, solid-state, monoblock power amplifier.

Chart 1 shows the frequency response of the PA-M300 with varying loads. The response is quite wideband, with a -3dB point of over 200kHz. Although the NHT dummy load shows no appreciable variation in the audioband, it does have some visible effect above 50kHz.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output for 8- and 4-ohm loads. The amount of distortion and how it rises with output level is typical of most solid-state power amplifiers, except that the IM distortion is not materially higher than the harmonic distortion. Also of note: The low-power THD+N with the unbalanced input (not shown) is quite a bit lower due to that input’s lower noise.

Chart 3 plots THD+N as a function of frequency at several different power levels. The amount of increase in distortion at high frequencies is very pronounced as the power level rises.

Damping factor vs. frequency, shown in Chart 4, is of a value and nature typical of many solid-state amplifiers: high up to about 1kHz, then rolling off with increasing frequency.

Chart 5 plots the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The magnitude of the AC-line harmonics is relatively complex, with mostly odd harmonics of 60Hz extending way up into the midrange. Signal harmonics are low, with the second, third, and fifth harmonics being visible in the spectrum.

Chart 1 - Frequency response of output voltage as a function of output loading

Magenta line = open circuit
Red line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy load

Chart 2 - Distortion as a function of power output and output loading

(Line up at 100W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 4-ohm THD+N
Third line = 8-ohm SMPTE IM distortion
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 150W
Cyan line = 300W

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 an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on right channel digitally fed via the AES/EBU input at a 24/96 sample rate. Unless otherwise noted, the Audio Precision Aux 0025 external low-pass filter was used to keep high-frequency spuria from contaminating the Audio Precision SYS 2722 measuring instrument.

Power output

See "Additional data" section (these are manufacturer-supplied specs)

• Output power: 190W @ 8 ohms, 240W @ 6 ohms

Additional data

• This amplifier does not invert polarity through the digital or analog inputs.
• AC-line current draw at idle:
  •      Gain set +20 & 0, AES/EBU input, 96k Fs: 59W, 0.96PF, 0.5A
  •      Gain set -20 & below, AES/EBU input, 96k Fs: 30W, 0.94PF, 0.27A
• Gain: output voltage divided by input voltage, analog line input, gain set to 0dB: 13.0X, 22.3dB
• Input sensitivity:
  •      For 1W output into 8 ohms, analog line input, gain set to +30dB (max): 6.9mV
  •      For 1W output into 8 ohms, digital input, gain set to +30dB (max): -52.2 dBFS
• Output impedance @ 50Hz: 0.0024 ohm
• Input impedance @ 1kHz: 14.2k ohms
• Output noise, digital input, digital input level at 0, 8-ohm load, Lch/Rch:
  •      Gain at -30dB, wideband: 123/130uV, -87.2/-86.7dBW
  •      Gain at -30dB, A weighted: 40/40uV, -97.0/-97.0dBW
  •      Gain at 0dB, wideband: 137/143uV, -86.3/-85.9dBW
  •      Gain at 0dB, A weighted: 42/39uV, -96.6/-97.2dBW
  •      Gain at +30dB, wideband: 174/180uV, -94.2/-83.9dBW
  •      Gain at +30dB, A weighted: 74/71 uV, -91.6/-92.0dBW
• Output noise, analog input, input termination 1k ohm, 8-ohm load, Lch/Rch:
  •      Gain at -30dB, wideband: 124/118uV, -87.2/-87.6dBW
  •      Gain at -30dB, A weighted: 40/45uV, -97.0/-96.0dBW
  •      Gain at 0dB, wideband: 296/298uV, -79.6/-79.6dBW
  •      Gain at 0dB, A weighted: 154/160uV, -85.3/-85.0dBW
  •      Gain at +30dB, wideband (note: values in mV): 8.4/8.6mV, -50.5/-50.3dBW
  •      Gain at +30dB, A weighted (note: values in mV): 4.6/5.0mV, -55.8/-55.0dBW

Measurements summary

The Devialet D-Premier is unique -- a volume-controlled power DAC that accepts both digital and analog inputs. Its uniqueness is in how it generates its output, being a combination of a low-powered, class-A analog output stage and a digital-switching section. The class-A stage controls the output voltage, and the switching section adds the necessary current to supply the output power. Also of note is the power-factor-corrected power supply, which measures close to unity. This is a good thing, as it makes the incoming AC line current sinusoidal rather than the usual 120Hz, 2-3ms rectifier-charging pulses of conventional capacitor input power supplies. The result is less crap on one’s AC power line, and less messing up of the sound of the other connected gear.

This D-Premier is extremely well protected against various things that might damage it or the load. As a consequence, it was difficult, if not impossible, to produce curves of power output vs. distortion that went into clipping below loads of 8 ohms, as is usual with other, more conventional amps that have been measured. Therefore, the usual measured output powers at 1% and 10% distortion are not shown in the additional data. A Devialet publication, "Advanced Practical Information," indicates that the D-Premier’s short-term RMS power output is doubled each time the load is halved, to a maximum total power of 600Wpc.

Another observation was that the D-Premier’s distortion and noise floor was pretty much the same at the 192kHz sample rate, so we used a 96kHz sample rate for most of the measurements. The output noise, measured without the Aux-0025 filter, varied from 5 to 12mV over the gain range of ±30 for the digital and analog inputs.

Chart 1 shows the frequency response of the D-Premier with varying loads. The Devialet’s output impedance is so low that no difference can be seen at the scale we usually use in testing analog amplifiers. Also of great significance is that the D-Premier lacks an output low-pass filter, as is necessary in almost all other switching amplifiers; as a consequence, the high-frequency response is not load dependent -- an interesting plus among many of this design.

Chart 1A is a plot of the D-Premier’s frequency response as a function of the incoming sample rate, at 44.1, 96, and 192kHz. (Note: This plot is exactly what one sees for regular D/A converters used to decode signals from the digital outputs of CD transports and other digital sources to produce analog outputs.) The frequency response for analog inputs is similar to that shown in Chart 1, as the sampling rate for the analog input is also 96kHz. Not shown is the low-frequency response, which was flat to below 10Hz at all sample rates. The pulse and squarewave response shape, with its symmetrical ringing, is indicative of FIR filters being used. This plot is done without the Aux-0025 low-pass filter, to allow the full bandwidth of the D-Premier to be measured.

Chart 2 illustrates how the D-Premier’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load for 8- and 4-ohm loads. Amount of distortion is noise dominated up to perhaps 10-20W and then rises as distortion, per se, at higher power up to the power outputs shown on the chart. The amount of THD+N with the analog inputs was roughly twice as much. Looking at the D-Premier as a high-voltage-output D/A converter, I plotted the THD+N amplitude not as a percentage of reading, but as dB down from full scale as a function of decreasing input level below 0dBFS. I and others commonly do this to reveal any glitches in distortion level at various input levels, and also to easily illustrate the noise floor of the device when its input levels get way below where distortion, per se, occurs. This is shown in Chart 2A. A major aspect of this curve is that the noise floor is at about -115dBFS -- one of the lowest I have measured for a D/A converter over the years. However, the analog inputs were not so quiet, with a noise floor closer to -105dBFS.

Chart 3 shows the D-Premier’s THD+N as a function of frequency for 4-ohm loading at several different power levels. The apparent increase in distortion at high frequencies is reasonably low. Again, the Devialet’s protection circuitry prevented the taking of any measurements near the maximum amount of power the amp can deliver with music signals.

The damping factor vs. frequency, shown in Chart 4, is very high, and remains high to a far higher frequency than is typical of analog power amplifiers.

Chart 5 plots a spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The magnitude of the AC-line harmonics is relatively low, except for a prominent output at 120Hz. Signal harmonics are low in amplitude, the second, third, and fifth harmonics being the most significant.

I listened to this amplifier in my system quite a bit, and found it to be most revealing, clear, and musical. I wish I owned it!

Chart 1 - Frequency response of output voltage as a function of output loading

Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
(Note that the curves are so close together, it is not possible to see the different colors.)

Additional: Chart 1A

Red: 44.1kHz
Magenta: 96kHz
Blue: 192kHz

Chart 2 - Distortion as a function of power output and output loading

(Line up at 10W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Additional: Chart 2A

THD+N vs. decreasing input level in dB down from full scale; 0 dBFS = 35.8V output

Chart 3 - Distortion as a function of power output and frequency

(4-ohm loading)
Red line = 2W
Magenta line = 20W
Blue line = 60W
Cyan line = 150W

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

Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage and through the balanced input unless otherwise noted.

Power output

• Output power at 1% THD+N: 428.2W @ 8 ohms, 618.2W @ 4 ohms
• Output power at 10% THD+N: 515.3W @ 8 ohms, 739.6W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 0.31A, 0.58PF, 22W
• Gain: output voltage divided by input voltage for unbalanced and balanced inputs: 64.7X, 36.2dB 
• Input sensitivity for 1W output into 8 ohms, unbalanced and balanced inputs: 43.7mV
• Output impedance @ 50Hz: 0.0052 ohm
• Input impedance @ 1kHz
  •      Unbalanced inputs: 23.6k ohms
  •      Balanced inputs: 45.3k ohms
• Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm
  •      Wideband: 0.300mV, -79.5dBW
  •      A weighted: 0.095mV, -89.5dBW
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms
  •      Wideband: 0.236mV, -80.0dBW
  •      A weighted: 0.085mV, -90.4dBW

Measurements summary

The Simaudio Moon 400M is a high-powered, solid-state power amplifier, and the least expensive of three monoblock models in Simaudio’s line. Utilizing a full-bridge design, it has two output devices in each of the four corners of the bridge.

Chart 1 shows the frequency response of the 400M with varying loads. The high-frequency response is moderately wide, with a 3dB down point of about 120kHz. Because the 400M’s frequency response is quite invariant with load, the amplifier’s output impedance is quite low. As a consequence, the response with the NHT dummy-speaker load is not shown in the chart.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output for loads of 8 and 4 ohms. What is of interest in these results is that the distortion is relatively constant with power level over a very wide range. In its list of specifications, the 400M’s manual states that the amp’s level of IM distortion is “unmeasurable.” As Chart 2 shows, that is not the case.

THD+N as a function of frequency at several different power levels is plotted in Chart 3. The small increase in high-frequency distortion is one of the 400M’s admirable attributes. At higher powers, the amp’s protection circuitry activated and shut it down before the power sweep could be completed at low frequencies.

The plot of damping factor vs. frequency, shown in Chart 4, is of a value and nature typical of many solid-state amplifiers: high -- in this case, very high -- up to about 1kHz, and then rolling off with frequency.

Chart 5 plots the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal with 8-ohm loading. The area of the AC-line harmonics is relatively free of discrete harmonics, but is up somewhat in level, with what would be a relatively higher noise level in this frequency range. The signal harmonics are dominated by the second, third, and fifth harmonics, with higher-order harmonics being lower but numerous in the spectral plot.

Chart 1 - Frequency response of output voltage as a function of output loading

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

Chart 2 - Distortion as a function of power output and output loading

(Line up at 200W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(4-ohm loading)
Red line = 1W
Blue line = 10W
Cyan line = 300W
Green line = 500W

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

Details

Parent Category: Products

Category: Amplifier Measurements

All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs unless otherwise noted.

Power output

• Output power at 1% THD+N: 216W @ 8 ohms, 381W @ 4 ohms
• Output power at 10% THD+N: 276W @ 8 ohms, 472W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 1.3A, 0.61PF, 97W
• Gain: output voltage divided by input voltage for unbalanced and balanced inputs: 40.5X, 32.5dB 
• Input sensitivity for 1W output into 8 ohms, unbalanced and balanced inputs: 69.8mV
• Output impedance @ 50Hz: 0.018 ohm
• Input impedance @ 1kHz
  •      Unbalanced inputs: 45.5k ohms
  •      Balanced inputs: 9.4k ohms
• Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm, Lch/Rch
  •      Wideband: 0.32mV/0.32mV, -78.9dBW/-78.9dBW
  •      A weighted: 0.067mV/0.041mV, -92.5dBW/-96.8dBW
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
  •      Wideband: 0.58mV/0.59mV, -73.7 dBW/-73.6dBW
  •      A weighted: 0.11mV/0.10mV, -88.2dBW/-89.0dBW

Measurements summary

The H20, a medium-powered solid-state stereo power amplifier, is the smallest of three models in the Hegel line.

Chart 1 shows the frequency response of the H20 with varying loads. The high-frequency response is wide, with an approximate 3dB-down point beyond 200kHz. The frequency response is quite invariant with load over the audioband, and so the response with the NHT dummy-speaker load is not shown in this chart. Of note, this design includes a low-frequency rolloff.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output for 8- and 4-ohm loads. The amount of distortion is dominated by noise up to perhaps 10W, then rises as distortion per se at higher power, up to clipping. 

Chart 3 plots THD+N as a function of frequency for 4-ohm loading and at several different power levels. The apparent increase in distortion at high frequencies is admirably low. 

The H20’s damping factor vs. frequency (Chart 4) is typical of that of many solid-state amplifiers: high up to about 1kHz, then rolling off with increasing frequency. At low frequencies, however, the effect of what causes the low-frequency rolloff also affects the output impedance, and causes the damping factor to decrease below 100Hz. 

Chart 5 shows the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The AC-line harmonics are relatively low in level but complex in nature. Signal harmonics are about equally second and third; the fourth and fifth harmonics are somewhat lower in level.

Chart 1 - Frequency response of output voltage as a function of output loading

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

Chart 2 - Distortion as a function of power output and output loading

(Line up at 100W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(4-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 70W
Cyan line = 150W
Green line = 300W

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

Details

Parent Category: Products

Category: Preamplifier Measurements

Created: 01 January 2026

Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on January 1, 1026

General Information

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

The Audiolab 9000Q was conditioned for 30 minutes at 4Vrms in/out into 200k ohms before any measurements were taken.

The 9000Q offers a multitude of inputs, both digital and analog (balanced and unbalanced), as well as line-level analog balanced outputs over XLR and unbalanced over RCA. For the purposes of these measurements, unless otherwise stated, the following inputs were evaluated: digital coaxial S/PDIF (RCA), analog balanced (XLR), as well as phono (RCA, moving magnet MM), over the balanced outputs.

There is also a headphone output on the front panel over a ¼” TRS connector. Comparisons were made between unbalanced (RCA) and balanced (XLR) line inputs and outputs, and the unbalanced inputs/outputs offered an improvement of approximately 9dB in signal-to-noise ratio (SNR) and roughly 10dB less THD compared to the balanced inputs/outputs (FFTs for different configurations can be seen in this report, and SNRs can be seen for both configuration in the main table).

Most measurements were made with a 4Vrms line-level analog and 0dBFS digital input with the volume set to achieve 4Vrms at the output.  For the phono input, a 5mVrms MM level was used to achieve 2Vrms at the balanced output. The SNR measurements were made with the same input signal values and, 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 4Vrms output.

The 9000Q offers five different reconstruction filters for the DAC inputs; however, on our review unit, changing these filters made no difference (i.e., it appeared that Audiolab had not enabled the feature). This was verified over RCA, optical, and USB digital inputs. Based on the impulse response results, it appears the filter being used is Minimum Phase (Fast Roll-Off). The 9000Q also offers a range of gain settings, with the 0dB default setting used for these measurements. 

Based on the accuracy and random results of the left/right volume channel matching (see table below), the 9000Q volume control is likely digitally controlled but operating in the analog domain. The 9000Q offers 78 volume steps from -77dB to 0dB for the line-level inputs. Step sizes are between 1 and 2dB.

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

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Audiolab for the 9000Q compared directly against our own. The published specifications are sourced from Audiolab’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 set at its maximum (DC to 1MHz), unless otherwise stated, assume a 1kHz sinewave at 4Vrms or 0dBFS at the input, 4Vrms at the output into 200k ohms, and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Our primary measurements revealed the following using the balanced line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 4Vrms or 0dBFS, 4Vrms output, 200k ohm loading, 10Hz to 22.4kHz bandwidth):

*due to low noise levels of DUT, analyzer self-noise has been subtracted

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz sinewave at 5mVrms, 2Vrms output, 200k ohm loading, 10Hz to 22.4kHz bandwidth):

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sinewave, 4Vrms input/2Vrms output, 300 ohms loading, 10Hz to 22.4kHz bandwidth):

Frequency response (line-level input)

In our measured frequency response (relative to 1kHz) plot above, the 9000Q is perfectly flat within the audioband (0dB at 20Hz/20kHz). At the extremes, the 9000Q is 0dB at 5Hz and 0dB all the way up to 200kHz. The 9000Q appears to be DC-coupled, as there is no attenuation at low frequencies, even at 5Hz. 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 (line-level input, bass and treble)

Above are the frequency response (relative to 1kHz) plots with the bass and treble controls set to minimum and maximum. We find a boost/cut of 5dB at 20Hz/20kHz.

Phase response (line-level analog input)

Above is the phase response plot from 20Hz to 20kHz for the balanced line-level input. The 9000Q does not invert polarity and exhibits essentially no phase shift in the audioband. This is as expected given the very high bandwidth of this preamp.

Frequency response vs. input type

The chart above shows the 9000Q’s frequency response (relative to 1kHz) as a function of input type. The green trace is the same (but limited to 80kHz) analog input data from the previous graph. The blue/red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, the purple/green traces for 24/96 from 5Hz to 48kHz, and finally pink/orange for 24/192 from 5Hz to 96kHz. The behavior at low frequencies is the same for all the digital sample rates, as well as the analog input—flat down to 5Hz. The behavior at high frequencies for all three digital sample rates is as expected, offering filtering around 22, 48, and 96kHz (half the respective sample rate). The 44.1kHz sampled input signal exhibits sharp but not “brick-wall”-type behavior, with a -3dB point at roughly 21kHz. The 24/96 and 24/192 signals show softer attenuation around the corner frequencies with -3dB points at roughly 36kHz and 80kHz.

Phase response (digital input, 16/44.1, 24/96, 24/192)

Above are the phase-response plots from 20Hz to 20kHz for the digital coaxial input at 16/44.1 (blue/red), 24/96 (purple/green), and 24/912 (pink/orange). Predictably, the 16/44.1 data yields the highest phase shift at -100 degrees at 20kHz. The 24/96 input signal is just shy of -10 degrees at 20kHz, and the 24/192 signal shows no phase shift in the audioband.

Frequency response (MM input)

The chart above shows the frequency response (relative to 1 kHz) for the phono input (MM configuration). What is shown is the deviation from the RIAA curve, where the input signal sweep is EQd with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). Between 20Hz and 20kHz, we find strict adherence to the RIAA curve, within roughly +/-0.1dB from 30Hz to 20kHz, and -0.3dB at 20Hz. At 5Hz, the response is at -3dB. This is an example of exceptional RIAA tracking implemented in the analog domain.

Phase response (MM phono input)

Above is the phase response plot from 20Hz to 20kHz for the phono input. 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 200Hz and -90 degrees at 20kHz.

Digital linearity (16/44.1 and 24/96 data)

The chart above shows the results of a linearity test for the coaxial digital input (the optical input performed identically) for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the balanced outputs of the 9000Q. For this test, the digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. At -120dBFS, the 16/44.1 data overshot by only 1-3dB, while the 24/96 remained perfect. To verify how well the 24/96 data would perform down to -140dBFS, we extended the sweep in the chart below.

Here we can see that the 24/96 data only missed the mark by +/-1dB (left/right) at -140dBFS. This is an exceptional digital-linearity test result.

Impulse response (24/48 data)

The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the balanced outputs of the 9000Q. We can see that the 9000Q utilizes a reconstruction filter that favors no pre-ringing.

J-Test (coaxial input)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the 9000Q. J-Test was developed by Julian Dunn the 1990s. It is a test signal-specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below.  The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial S/PDIF input of the 9000Q shows a near-perfect J-Test result, with only very small peaks observable at a vanishingly low -155dBrA.

J-Test (optical input)

The chart above shows the results of the J-Test test for the optical digital input measured at the balanced outputs of the 9000Q. The results here are essentially the same as the coaxial input above.

J-Test (coaxial, 2kHz sinewave jitter at 10ns)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the 9000Q, with an additional 10ns of 2kHz sinewave jitter injected by the APx555. The tell-tale peaks at 10kHz and 14kHz can be seen, but at very low -155dBrA. The optical input yielded the same result.

J-Test (coaxial, 2kHz sinewave jitter at 100ns)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the 9000Q, with an additional 100ns of 2kHz sinewave jitter injected by the APx555. This time, the tell-tale peaks at 10kHz and 14kHz can be seen at a still very low -135dBrA. The optical input yielded the same result.

Wideband FFT spectrum of white noise and 19.1kHz sinewave tone

The chart above shows a fast Fourier transform (FFT) of the 9000Q’s balanced outputs with white noise at -4 dBFS (blue/red) and a 19.1kHz sinewave at -1dBFS fed to the coaxial digital input, sampled at 16/44.1. The gentle roll-off past 20kHz in the white noise spectrum shows that the 9000Q doesn’t use a brick-wall-type reconstruction filter. There is one aliased image within the audioband at -110dBrA at roughly 13kHz. The primary aliasing signal at 25kHz is barely suppressed at -20dBrA.

THD ratio (unweighted) vs. frequency vs. load (analog)

The chart above shows THD ratios at the balanced line-level output into 200k ohms (blue/red) and 600 ohms (purple/green) as a function of frequency for the analog balanced inputs. The 200k-ohm THD data are lower than the 600-ohm data by a full 20dB. The 200k-ohm data are around the 0.0001% level from 20Hz to 2kHz, then up to 0.0005% at 20kHz. The left channel did exhibit about 3dB lower THD compared to the right channel. Into 600 ohms, THD ratios ranged from 0.001% up to 0.002% at 20kHz.

THD ratio (unweighted) vs. frequency vs. sample rate (16/44.1 and 24/96)

The chart above shows THD ratios at the balanced line-level output into 200k ohms for a 16/44.1 (blue/red) dithered 1kHz signal at the coaxial input and a 24/96 (purple/green) signal, as a function of frequency, at 0dBFS. The 16/44.1 THD ratios ranged from 0.0006% from 20Hz to 1kHz, then up to beyond 1% at 20kHz. It’s important to note that the digital signals were at 0dBFS, and that this level sampled at 16/44.1 causes clipping at high frequencies. Had the sweep been done at -1dBFS, the 16/44.1 data would have looked nearly identical to the 24/96 data. The 24/96 data ranged from 0.0004% from 20Hz to 1kHz, then up to 0.001% at 20kHz.

THD ratio (unweighted) vs. frequency (MM phono input)

The graph above shows THD ratios as a function of frequency for the phono input. The input sweep is EQ’d with an inverted RIAA curve. The THD values vary from around 0.007% (20Hz) down to around 0.0006% (2kHz to 3kHz), then up to 0.0015% at 20kHz. 

THD ratio (unweighted) vs. output (analog)

The chart above shows THD ratios measured at the balanced outputs of the 9000Q as a function of output voltage for the balanced line-level input, with the volume control at maximum. THD values start at 0.07% at 1mVrms, down to a low of 0.00006% at 2-3Vrms, then a steep rise past 5Vrms to the 1% THD mark at 5.9Vrms.

THD+N ratio (unweighted) vs. output (analog)

The chart above shows THD+N ratios measured at the balanced outputs of the 9000Q as a function of output voltage for the balanced line-level input, with the volume control at maximum. THD+N values start at 0.7% at 1mVrms, down to a low of 0.0003% at 3-4Vrms, then a steep rise past 5Vrms to the 1% THD mark at 5.9Vrms.

THD ratio (unweighted) vs. output (16/44.1 and 24/96)

The chart above shows THD ratios measured at the balanced outputs of the 9000Q as a function of output voltage for the digital coaxial S/PDIF input, swept from -90dBFS to 0dBFS, with the volume control at maximum. Blue/red traces are for 16/44.1 data and purple/green for 24/96. For the 16/44.1 data, THD values start at 2%, and predictably, reach their low at the maximum output voltage of about 4Vrms, at 0.0005%. For the 24/96 data, THD ratios ranged from 0.1% down to 0.00015% at 1-2Vrms, then up to 0.0005% at the maximum output voltage.

THD+N ratio (unweighted) vs. output (16/44.1 and 24/96)

The chart above shows THD+N ratios measured at the balanced outputs of the 9000Q as a function of output voltage for the digital coaxial S/PDIF input, swept from -90dBFS to 0dBFS, with the volume control at maximum. Blue/red traces are for 16/44.1 data and purple/green for 24/96. For the 16/44.1 data, THD+N values start at 20% and reach their low at the maximum output voltage of about 4Vrms, at 0.002%. For the 24/96 data, THD ratios ranged from 1% down to 0.0003% at 2Vrms then up to 0.0005% at the maximum output voltage.

Intermodulation distortion vs. generator level (SMPTE, 60Hz:4kHz, 4:1, 16/44.1, 24/96)

The chart above shows intermodulation distortion (IMD) ratios measured at balanced output for 16/44.1 (blue/red) input data and 24/96 input data (purple/green), from -60dBFS to 0dBFS. Here, the SMPTE IMD method was used, where the primary frequency (F1 = 60Hz), and the secondary frequency (F2 = 7kHz), are mixed at a ratio of 4:1. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 16/44.1 data yields IMD ratios from 2% down to 0.003% at 0dBFS. The 24/96 data yields IMD ratios from 0.15% down to 0.0005% (right) at 0dBFS. The left channel at 24/96 saw a rise in IMD ratios beyond -5dBFS, up to 0.003% at 0dBFS.

FFT spectrum – 1kHz (analog line-level input, XLR in/out)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the balanced outputs for the balanced line-level input. We see that the signal’s second harmonic, at 2kHz, is at -120dBrA or 0.0001%, with subsequent signal harmonics at and below -130dBrA, or 0.00003%. Below 1kHz, we see power-supply-related noise peaks at -130dBrA and below, dominated by the 180Hz peak.

FFT spectrum – 1kHz (analog line-level input, RCA in/out)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced outputs for the unbalanced line-level input. We see improvements in signal related harmonic peaks (-130dBrA vs -120dBrA) and power-supply-related noise peaks (-140dBrA vs -130dBrA) compared with the XLR in/out FFT above.

FFT spectrum – 1kHz (analog line-level input, RCA in/XLR out)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the balanced outputs for the unbalanced line-level input. Signal related harmonic peaks are similar to the RCA in/out FFT above, while the power-supply-related noise peaks are similar to the XLR in/out FFT above.

FFT spectrum – 1kHz (analog line-level input, RCA in/XLR out)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the unbalanced outputs for the balanced line-level input. Signal related harmonic peaks are similar to the XLR in/out FFT above, while this combination yielded the best results in terms of power-supply related noise peaks (all below -150dBrA, or 0.000003%).

FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the balanced outputs for the coaxial digital input, sampled at 16/44.1. We see the third (3kHz) signal harmonic dominating at roughly -100dBrA, or 0.001%. The second (2kHz) and fifth (5kHz) signal harmonic peaks are at the -125dBrA, or 0.0006%, level. The noise floor is much higher (-140dBrA) due to the 16-bit depth limitation. Because of the elevated noise floor, no power-supply-related peaks can be seen.

FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the balanced outputs for the coaxial digital input, sampled at 24/96. We see the third (3kHz) signal harmonic dominating at roughly -100dBrA, or 0.001%. The second (2kHz) and fifth (5kHz) signal harmonic peaks are at the -125dBrA, or 0.0006%, level. Higher signal harmonics can be below -130dBrA, or 0.00003%. We see power-supply-related noise peaks at -140dBrA, or 0.00001%, and below, with the peak at 180Hz dominating.

FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the balanced outputs. We see the 1kHz primary signal peak, at the correct amplitude, and no signal or noise related harmonic peaks above the -140dBrA noise floor.

FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the balanced outputs. We see the 1kHz primary signal peak, at the correct amplitude, and signal related harmonic peaks at 2kHz and 6kHz below -140dBrA, or 0.00001%. Power-supply related noise peaks can be seen at and below -140dBrA, or 0.00001%.

FFT spectrum – 1kHz (MM phono input)

Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the balanced outputs across for the phono input. The dominant signal-related harmonic can be seen at 2kHz, at -105dBrA, or 0.0006%. Power-supply-related noise peaks can be seen at -90dBrA, or 0.003%, at 60Hz and at 180Hz, with subsequent peaks at and below -100dBrA, or 0.001%.

FFT spectrum – 50Hz (line-level input)

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the balanced outputs for the balanced line-level input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peak is that of the signal’s second (100Hz) harmonic at -120dBrA or 0.0001%. The third signal harmonic (150Hz) and third power-supply-related noise peak (180Hz) are both at -130dBrA or 0.00003%.

FFT spectrum – 50Hz (MM phono input)

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the balanced outputs for the phono input. The most predominant (non-signal) peaks are power-supply-related noise peaks at -90dBrA, or 0.003%, at 60Hz and 180Hz. The second signal harmonic (100Hz) is just below -100dBrA, or 0.001%.

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 balanced outputs for the balanced 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 -130dBrA or 0.00003%, while the third-order modulation products, at 17kHz and 20kHz, are at -120dBrA or 0.0001%. This is a very clean IMD result.

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

Shown above is the FFT of the balanced outputs of the 9000Q with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 4Vrms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the preamplifier and are around the extremely low -150dBrA, or 0.000003%, level.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the balanced outputs for the digital coaxial input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -130dBrA, or 0.00003%, while the third-order modulation products, at 17kHz and 20kHz, are at -110dBrA, or 0.0003%. We also see the main aliased peaks at 25.1kHz and 26.1kHz at around -30dBrA.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the balanced outputs for the digital coaxial input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -130dBrA, or 0.00003%, while the third-order modulation products, at 17kHz and 20kHz, are at -110dBrA or 0.0003%.

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 balanced outputs across for the phono input configured for MM. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -110dBrA, or 0.0003%, while the third-order modulation products, at 17kHz and 20kHz, are just below -120dBrA, or 0.0001%.

Square-wave response (10kHz)

Above is the 10kHz squarewave response using the analog line-level input, at roughly 4Vrms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the 9000Q’s slew-rate performance. Rather, it should be seen as a qualitative representation of its very extended 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. The 9000Q reproduction of the 10kHz square wave is very clean with sharp corners devoid of ringing.

Diego Estan
Electronics Measurement Specialist