Magnetar UDP900 4K Ultra HD Universal Blu-ray Disc Player–DAC Measurements

Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on March 1, 2024

General Information

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

The Magnetar UDP900 was evaluated as a DAC and was conditioned for 30 minutes at 0dBFS (1.95Vrms RCA out) into 100k ohms before any measurements were taken. But as mentioned below, the headphone output was also measured.

The UDP900 is a universal 4k UHD Blu-ray player. It offers one digital input (asynchronous USB) allowing for its evaluation as a DAC. It is important to note that the Audio Precision (AP) analyzer does not have a dedicated digital-audio output over USB. Audio data over USB to the device under test (DUT) is achieved via a computer (in our case a Lenovo ThinkPad X1 laptop running Windows 11) running the APx software controlling the AP analyzer. The dedicated Magnetar Windows USB driver for the UDP900 was downloaded from the Magnetar website and installed on our laptop. The driver control panel allows for the selection of 16-bit or 24-bit two-channel data. This, along with the APx software controlling the sample rate, allowed for true 16-bit/44.1kHz, 24/96, and 24/192 audio data to be sent to the UDP900 DAC. The UDP900 has seven user-selectable digital-filter options, but for the digital measurements below, the default filter, labeled Brick Wall, was used.

The UDP900 has both balanced (XLR) and unbalanced (RCA) line-level analog outputs. Typically, we find very little performance difference between both types of outputs (other than an extra 6dB of gain over balanced). In the case of the UDP900, however, noticeably more THD was measured over the balanced outputs. Further, the balanced outputs yielded 7.5dB (as opposed to the typical 6dB) more gain than the unbalanced outputs. At 0dBFS (1.95Vrms over RCA and 4.6Vrms over XLR), the balanced outputs yielded 5dB more THD at 1kHz, and a very significant 20dB more at 20kHz (graphs included in this report) than the balanced ouptuts. For this reason, unless otherwise stated, the unbalanced (RCA) analog outputs were used. The UDP900 also offers a ¼ ″ TRS headphone output, which was also evaluated.

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 to 90kHz), and THD vs frequency (10Hz to 90kHz). The latter to capture the second and third harmonics of the 20kHz output signal.

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Magnetar for the UDP900 compared directly against our own. The published specifications are sourced from Magnetar’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), assume, unless otherwise stated, 1.95Vrms output (RCA) into 100k 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 USB input and the unbalanced line-level outputs (unless specified, assume a 1kHz sinewave at 0dBFS, 100k ohms loading, 10Hz to 22.4kHz bandwidth):

Our primary measurements revealed the following using the USB input and the headphone output (unless specified, assume a 1kHz sinewave at 0dBFS, 300 ohms loading, 10Hz to 22.4kHz bandwidth):

Frequency response (16/44.1, 24/96, 24/192 with Brick Wall filter)

The plot above shows the UDP900’s frequency-response (relative to 1kHz) as a function of sample rate. The blue/red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz, the purple/green traces are for a 24/96 dithered digital input signal from 5Hz to 48kHz, and finally orange/pink represents 24/192 from 5Hz to 96kHz. The behavior at low frequencies is the same for all digital sample rates—perfectly flat down to 5Hz. The behavior at high frequencies for all three digital sample rates is as expected, offering sharp filtering around 22k, 48k, and 96kHz (half the respective sample rate). The -3dB point for each sample rate is roughly 20.3, 44 and 81kHz respectively. The ripples (about +/- 0.2dB) in the frequency responses at higher frequencies are real—confirmed with steady-state measurements.  In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue, purple or orange trace) is performing identically to the right channel (red, green or pink trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

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

The graph above shows the results of a linearity test for the digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line-level unbalanced outputs of the UDP900. The digital input was swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output was analyzed by the APx555. The ideal response is a straight flat line at 0dB (i.e., the amplitude of the digital input perfectly matches the amplitude of the measured analog output). The 24/96 input data is perfect down to -120dBFS, while the 16/44.1 input data began to over-shoot significantly below -90dBFS. The 24/96 data yielded such superb results that we extended the sweep down. . .

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

. . . to -140dBFS. Above we see that even at -140dBFS, the UDP900 is only overshooting by 1dB. This is an exemplary linearity test result for the 24/96 data, but somewhat poor for 16/44.1 data (a good result would be flat down to -100dBFS).

Impulse response

The graph above shows the impulse responses 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, fed to the digital input, measured at the unbalanced analog outputs, for the left channel only. We can see that UDP900 DAC reconstruction filter exhibits symmetrical pre/post ringing as seen in a typical sinc function.

J-Test (USB input)

The plot above shows the results of the J-Test test for the USB input measured at the unbalanced line-level output of the UDP900. 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 (fundamental at 250Hz) down to -170dBrA for the odd harmonics.  The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to also show how well the DAC rejects jitter.

The USB digital input shows an average J-Test result, with a few peaks at the -125dBrA level and below, clearly visible both near the primary 12kHz signal peak, and below 1kHz. This is an indication that the UDP900 may be sensitive to jitter.

Wideband FFT spectrum of white noise and 19.1kHz sinewave tone (Brick Wall filter)

The plot above shows a fast Fourier transform (FFT) of the UDP900’s line-level output with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1 (purple/green). There is a steep roll-off above 20kHz in the white-noise spectrum, characteristic of a brickwall-type filter. There are no imaged aliasing artifacts in the audioband above the -130dBrA noise floor. The primary aliasing signal at 25kHz is at -100dBrA.

THD ratio (unweighted) vs. frequency vs. load (24/96)

The chart above shows THD ratios at the line-level output into 100k ohms (blue/red) and 600 ohms (purple/green) as a function of frequency for a 24/96 dithered 1kHz signal at the USB input. Also shown are THD ratios for the balanced output (pink/orange) into a 200k ohm load. The 100k and 600 ohms data are identical throughout the audioband, which is in indication that UDP900’s outputs are robust and can handle loads below 1k ohms with no difficultly. THD ratios from the unbalanced outputs into 100k ohms ranged from 0.005% from 20Hz to 800Hz, then up to 0.01% at 3kHz, then down to 0.006%at 20kHz. The balanced outputs yielded THD ratios from 0.005% from 20Hz to 100Hz, then a steady rise to 0.06% at 20kHz.

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

The chart above shows THD ratios at the line-level output into 100k ohms as a function of frequency for a 16/44.1 (blue/red) and a 24/96 (purple/green) dithered 1kHz signal at the optical input. THD ratios were identical and ranged from 0.005% from 20Hz to 800Hz, then up to 0.01% at 3kHz, then down to 0.006% at 20kHz.

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

The chart above shows THD ratios measured at the line-level unbalanced output as a function of output voltage for the USB input into 100k ohms from -90dBFS to 0dBFS at 16/44.1 (blue/red) and 24/96 (purple/green). Also shown are THD ratios for the balanced output (pink/orange) into a 200k ohm load. For the unbalanced output, the 24/96 data outperformed the 16/44.1 data at low output voltages by roughly 20-30dB, with a THD range from 0.1% at 200uVrms to 0.0002% at 0.25Vrms, then up to 0.005% at the maximum output voltage of 1.95Vrms. The 16/44.1 data ranged from 10% down to 0.002% at 0.5 to 1Vrms, then up to 0.005% at 1.95Vrms. The balanced output (at 24/96) yielded slightly higher THD ratios (2-3dB) than the unbalanced output up to about 0.1Vrms. From 0.1 to 1Vrms, THD ratios over the balanced output were as much as 15dB higher than the unbalanced output.

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

The chart above shows THD+N ratios measured at the line-level unbalanced output as a function of output voltage for the USB input into 100k ohms from -90dBFS to 0dBFS at 16/44.1 (blue/red) and 24/96 (purple/green). Also shown are THD+N ratios for the balanced output (pink/orange) into a 200k ohm load. For the unbalanced output, the 24/96 data outperformed the 16/44.1 data at low output voltages by roughly 15dB, with a THD+N range from 1% at 200uVrms to 0.0015% at 0.5Vrms, then up to 0.006% at the maximum output voltage of 1.95Vrms. The 16/44.1 data ranged from 10% down to 0.003% at 1Vrms, then up to 0.006% at 1.95Vrms. The balanced output (at 24/96) yielded slightly higher THD+N ratios (2-3dB) than the unbalanced output up to about 0.2Vrms. From 0.2 to 1Vrms, THD+N ratios over the balanced output were as much as 5dB higher than the unbalanced output.

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 line-level unbalanced output into 100k ohm for the USB digital input, sampled at 16/44.1. The third (3kHz) signal harmonic dominates at -85dBrA, or 0.006%. There are also a multitude of low levels peaks from 100Hz to 20kHz just below the -120dBrA, or 0.001%, level.

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 unbalanced output into 100k ohm for the USB digital input, sampled at 24/96. We see the same signal harmonic dominate at 3kHz at -85dBrA, or 0.006%, as is seen in the 16/44.1 FFT above. We find a power-supply-related noise peak at 120Hz at -130dBrA, or 0.00003%.

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

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the balanced output into 200k ohm for the USB digital input, sampled at 24/96. Compared to the FFT above with the unbalanced output, here we see clearly visible higher odd-ordered signal harmonics (5/7/9/11kHz, etc.) from -95dBRa, or 0.002%, to -130dBrA, or 0.00003%, at 20kHz.

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

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the line-level output into 100k ohms for the USB digital input, sampled at 16/44.1 at -90dBFS. We see the signal peak at the correct amplitude, with significant odd-ordered signal harmonics at -100dBrA, or 0.001% and below.

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

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the line-level output into 100k ohms for the USB digital input, sampled at 24/96 at -90dBFS. We see the signal peak at the correct amplitude, no signal harmonics, and even-ordered power-supply-related noise (120/240/360Hz) dominated by the 120Hz peak at -125dBrA, or 0.00006%.

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 the line-level unbalanced 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 1% down to 0.005% at -10dBFS, then up to 0.03% at 0dBFS. The 24/96 data yields IMD ratios from 0.1% down to 0.002% at -15dBFS, then up to 0.03% at 0dBFS.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 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 unbalanced line-level output into 100k ohms for the USB input at 16/44.1. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 1.95Vrms (0dBrA) at the output. We find it difficult to identify the second-order modulation product (i.e., the difference signal of 1kHz) amongst the array of noise peaks just below the -120dBrA, or 0.0001%, level, while the third-order modulation products, at 17kHz and 20kHz, are at -95dBrA, or 0.002%.

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

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the line-level output into 100k ohms for the USB input at 24/96. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 1.95Vrms (0dBrA) at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz), is at -135dBrA (right channel only), or 0.00002%, and the third-order modulation products, at 17kHz and 20kHz, are at -95dBrA, or 0.002%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, 24/96, balanced output)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the balanced line-level output into 200k ohms for the USB input at 24/96. The input dBFS values are set at -6.02dBFS so that, if summed for a mean frequency of 18.5kHz, would yield 4.6Vrms (0dBrA) at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz), is at -130dBrA, or 0.00003%, and the third-order modulation products, at 17kHz and 20kHz, are at -70dBrA, or 0.03%. Again, the result for the balanced output is much worse than for the unbalanced output.

Intermodulation distortion FFT (24/96 input, APx 32 tone)

Shown above is the FFT of the unbalanced outputs of the UDP900 with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 1.95Vrms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products and are around the extremely low -120dBrA, or 0.0001%, level.

Diego Estan
Electronics Measurement Specialist