Musical Fidelity V90-DAC D/A processor Measurements

Sidebar 2: Measurements

I examined the measured behavior of the Musical Fidelity V90-DAC with my Audio Precision SYS2722 system (see www.ap.com and the January 2008 "As We See It"). For some tests, and to check the results of others with a different measurement system, I used my vintage Audio Precision System One DSP. My sample of the V90-DAC was serial number "RRY0135 (JUNE 2013)."

I used my 2012-vintage Apple MacBook Pro, running on battery power, to examine the V90-DAC's performance via its USB port. Apple's USB Prober utility identified the Musical Fidelity as having the manufacturer string "Musical Fidelity" and the product string "Musical Fidelity V90-DAC 24/96." USB Prober confirmed that the processor operated in the preferred isochronous asynchronous mode, and that V90-DAC would accept 16- and 24-bit data at sample rates of 44.1, 48, 88.2, and 96kHz. The coaxial S/PDIF input locked to datastreams with sample rates ranging from 32 to 192kHz. The optical TosLink input was restricted to sample rates of 96kHz and below.

The V90-DAC preserved absolute polarity, and its maximum output level at 1kHz was 2.18V, or 0.73dB higher than the CD standard's 2V. The output impedance was low, at 99 ohms at high and middle frequencies, rising to a still-low 124 ohms at 20Hz, but these values are all higher than the specified 47 ohms. The impulse response with 44.1kHz data (fig.1) was usual for a digital FIR reconstruction filter, with symmetrical "ringing" either side of the impulse.

414MFV90fig01.jpg

Fig.1 Musical Fidelity V90-DAC, impulse response (44.1kHz data).

The magenta and red traces in fig.2 reveal that this filter rolls off the output sharply above the audioband with 44.1kHz data, but doesn't reach full attenuation until a little higher than the Nyquist frequency (half the sample rate), indicated in this graph by a vertical green line. However, the 25kHz aliasing image of a full-scale tone at 19.1kHz (cyan and blue traces) is completely suppressed by the filter. The harmonics of this tone are all low in level, with the third harmonic, at 57.3kHz, the highest in level, at –87dB (0.014%). Fig.3 shows a more conventional plot of frequency response, taken at 44.kHz (green and gray traces), 96kHz (cyan, magenta), and 192kHz (blue, red). With each sample rate, the high-frequency rolloff follows the same shape: a gentle rolloff starting in the top audio octave, broken by a sharp cutoff just below the Nyquist frequency. With 192kHz data, the response is down by 3dB at 70kHz. Note the superb channel matching in this graph.

414MFV90fig02.jpg

Fig.2 Musical Fidelity V90-DAC, wideband spectrum of white noise at –4dBFS (left channel magenta, right red) and 19.1kHz tone at 0dBFS (left cyan, right blue), with data sampled at 44.1kHz (20dB/vertical div.).

414MFV90fig03.jpg

Fig.3 Musical Fidelity V90-DAC, frequency response at –12dBFS into 100k ohms with data sampled at: 44.1kHz (left channel green, right gray), 96kHz (left cyan, right magenta), 192kHz (left blue, right red) (1dB/vertical div.).

Channel separation (not shown) was superb, at 115dB (R–L) and 125dB (L–R) in the midrange, these decreasing to a still-excellent 100dB in both directions in the bass, presumably due to increasing power-supply impedance in this region. The low-frequency noise floor while the V90-DAC decoded data representing a full-scale 1kHz tone (fig.4) was clean, and free from any power-supply artifacts. Of course, this is what should be expected from the V90-DAC's use of a switch-mode supply. But peculiarly, when I tested the Musical Fidelity's resolution with the legacy technique of sweeping a 1/3-octave bandpass filter from 20kHz down to 20Hz while the DAC decoded dithered data representing a 1kHz tone at –90 and –120dBFS, a small peak could be seen at 180Hz with 24-bit data (fig.5, bottom traces). With 16-bit data, all that can be seen in the graph is the spectrum of the dither noise (top pair of traces); but with 24-bit data, the noise floor dropped by almost 18dB, which implies intrinsic resolution of 19 bits or so. This was confirmed by FFT analysis (fig.6). This graph, however, reveals a low-level tone at 7.4kHz with 24-bit data, presumably an idle tone of some kind.

414MFV90fig04.jpg

Fig.4 Musical Fidelity V90-DAC, spectrum of 1kHz sinewave, DC–1kHz, at 0dBFS into 100k ohms (left channel blue, right red; linear frequency scale).

414MFV90fig05.jpg

Fig.5 Musical Fidelity V90-DAC, 1/3-octave spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel, bottom, at 20kHz), 24-bit data (right, bottom, at 5kHz) (right channel dashed).

414MFV90fig06.jpg

Fig.6 Musical Fidelity V90-DAC, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data (left blue, right red) (20dB/vertical div.).

Linearity error with 16-bit data was very low, at less than ±1dB to –110dB (fig.7), while the V90-DAC's reproduction of an undithered sinewave at exactly –90.31dBFS was excellent, with the three DC voltage levels described by the data well defined (fig.8). With 24-bit data at the same level the result was a well-defined sinewave (fig.9), though both the 16- and 24-bit waveforms were overlaid with intermittent high-frequency noise.

414MFV90fig07.jpg

Fig.7 Musical Fidelity V90-DAC, linearity error, dBr vs dBFS (2dB/vertical div.)

414MFV90fig08.jpg

Fig.8 Musical Fidelity V90-DAC, waveform of undithered 1kHz sinewave at –90.31dBFS, 16-bit data (left channel blue, right red).

414MFV90fig09.jpg

Fig.9 Musical Fidelity V90-DAC, waveform of undithered 1kHz sinewave at –90.31dBFS, 16-bit data (left channel blue, right red).

As is usual with Musical Fidelity products, the V90-DAC featured low levels of harmonic distortion. Fig.10 shows the spectrum of the processor's output while it drove a full-scale 50Hz tone into 100k ohms. The highest-level harmonic is the second, at a low –102dB (right) and –110dB (left). Reducing the load impedance to a punishing 600 ohms increased the levels of all harmonics by 10dB or so, though they all remained low in absolute terms. The picture was similar when it came to intermodulation distortion, with very low production of distortion products (fig.11). However, this graph reveals a strange rise in the noise floor around the 19 and 20kHz tones, in only the right channel (red trace). If you look closely at fig.2, you can see a similar rise in the noise floor around the 19.1kHz tone in the right channel (blue trace), but not in the left (cyan).

414MFV90fig10.jpg

Fig.10 Musical Fidelity V90-DAC, spectrum of 50Hz sinewave, DC–1kHz, at 0dBFS into 100k ohms (left channel blue, right red; linear frequency scale).

414MFV90fig11.jpg

Fig.11 Musical Fidelity V90-DAC, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 0dBFS into 100k ohms (left channel blue, right red; linear frequency scale).

This noise-floor modulation in the right channel can also be seen in a narrowband spectrum of the Musical Fidelity's output while it decoded 16-bit data representing the Miller-Dunn J-Test signal (fig.12). However, no jitter-related sidebands are visible, and the odd-order harmonics of the low-frequency, LSB-level squarewave are all at the correct levels (green line). These harmonics disappeared with 24-bit J-Test data (fig.13), but the spectral spreading can still be seen in the right channel. These two graphs were taken with TosLink data; the behavior was identical with coaxial S/PDIF and USB data.

414MFV90fig12.jpg

Fig.12 Musical Fidelity V90-DAC, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 16-bit data via TosLink from AP SYS2722 (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

414MFV90fig13.jpg

Fig.13 Musical Fidelity V90-DAC, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit data via TosLink from AP SYS2722 (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

Overall, other than that peculiar noise-floor modulation in the right channel, which didn't seem to affect what ST or I heard, the V90-DAC measures very similarly to Musical Fidelity's V-DAC II, which definitely punched above its weight on the test bench.—John Atkinson

COMPANY INFO
Musical Fidelity Limited
US distributor: Musical Fidelity North America
PO Box 51206
Phoenix, AZ 85076
(480) 297-4053
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COMMENTS
awehns's picture

So what is the difference between fig. 8 and 9?

John Atkinson's picture
awehns wrote:
So what is the difference between fig. 8 and 9?

Both show the waveform of a 1kHz tone at -90.31dBFS. Fig.8 shows the waveform with undithered 16-bit data, fig.9 that with undithered 24-bit data. Despite the lack of dither, the 24-bit waveform resembles a good sinewave, confirming the V90 DAC's excellent resolution.

John Atkinson
Editor, Stereophile

audiolab's picture

Fig 8 = 16 bit
Fig 9 = 24 bit
"Linearity error with 16-bit data was very low, at less than ±1dB to –110dB (fig.7), while the V90-DAC's reproduction of an undithered sinewave at exactly –90.31dBFS was excellent, with the three DC voltage levels described by the data well defined (fig.8). With 24-bit data at the same level the result was a well-defined sinewave (fig.9), though both the 16- and 24-bit waveforms were overlaid with intermittent high-frequency noise."

Scorpio69er's picture

"But from my own listening and my comparisons with the outstanding Auralic Vega and my workhorse Benchmark DAC1..."

Without controlled double-blind testing, subjective opinion about alleged sonic differences between DACs (or cables, etc.) is just nonsense.

"Audio as a hobby is dying, largely by its own hand. As far as the real world is concerned, high-end audio lost its credibility during the 1980s, when it flatly refused to submit to the kind of basic honesty controls (double-blind testing, for example) that had legitimized every other serious scientific endeavor since Pascal. [This refusal] is a source of endless derisive amusement among rational people and of perpetual embarrassment for me, because I am associated by so many people with the mess my disciples made of spreading my gospel...Remember those loudspeaker shoot-outs we used to have during our annual writer gatherings in Santa Fe? The frequent occasions when various reviewers would repeatedly choose the same loudspeaker as their favorite (or least-favorite) model? That was all the proof needed that [blind] testing does work, aside from the fact that it's (still) the only honest kind. It also suggested that simple ear training, with DBT confirmation, could have built the kind of listening confidence among talented reviewers that might have made a world of difference in the outcome of high-end audio."
--J.Gordon Holt
http://www.stereophile.com/asweseeit/1107awsi/index.html

John Atkinson's picture
Scorpio69er wrote:
Without controlled double-blind testing, subjective opinion about alleged sonic differences between DACs (or cables, etc.) is just nonsense.

If you feel that way, then why on Earth would you read Stereophile or its website?

Scorpio69er wrote:
J.Gordon Holt: http://www.stereophile.com/asweseeit/1107awsi/index.html

It is fair to point out that the late Gordon Holt almost never practiced what he preached in this interview I conducted before his passing, with respect to double-blind tests. All Gordon's review auditioning was performed under sighted conditions and the only blind tests in which he participated after I replaced him as editor in 1986 were ones that I organized.

Please go peddle your trolls somewhere else.

John Atkinson
Editor, Stereophile

Scorpio69er's picture

You don't bother much with credibility, do you?

re: "why on Earth would you read Stereophile or its website?"

Perhaps in the vain hope that you guys will, someday, live up to the legacy of JGH.

But I'm not holding my breath.

Further, I was reading Stereophile and corresponding with its writers long before you ever showed up. The issue of subjective testing was questioned and discussed within its (paper) pages. Back then, there was a genuine concern with truth. And there was also a sense of humor about this obsession. You may recall the Bob Carver amp challenge, which Carver won. That was honesty.

re: "the late Gordon Holt almost never practiced what he preached in this interview"

Within the interview, he talked about "those [blind] loudspeaker shoot-outs we used to have during our annual writer gatherings in Santa Fe". He also understood quite well, as he articulated, that "[blind] testing does work, aside from the fact that it's (still) the only honest kind". So JGH understood full well the validity of DBT, and, indeed, had he remained at the helm of Stereophile, that is the direction he would have certainly gone, since he was concerned with honesty and credibility.

re: "Please go peddle your trolls somewhere else."

Oh, I'm so sorry! I didn't realize that this had become the audiophile equivalent of the Rush Limbaugh show!

RUSH: "The earth is flat, by golly -- and that's the truth!"
CALLER: "Ditto, Rush!"

You, sir, can kiss my, er, amp. ☺

John Atkinson's picture
Scorpio69er wrote:
John Atkinson wrote:
the late Gordon Holt almost never practiced what he preached in this interview

Within the interview, he talked about "those [blind] loudspeaker shoot-outs we used to have during our annual writer gatherings in Santa Fe."

Yes, and as I wrote above, "the only blind tests in which [Gordon] participated after I replaced him as editor in 1986 were ones that I organized." It is those tests to which Gordon was referring in the text that you are quoting. Despite his advocacy of blind testing in my 2007 interview with him, Gordon performed all his review listening under sighted conditions, just as he had been doing since launching Stereophile in 1962.

Scorpio69er wrote:
had [Gordon Holt] remained at the helm of Stereophile, that is the direction he would have certainly gone.

Gordon worked for Larry Archibald and for me for 17 years since selling Stereophile. In all that time he was free to practice blind tests if he so wished. The fact is that he didn't so wish, even after trying the ABX comparator box. So please stop projecting your fantasies on to Gordon who, sadly, is no longer here to speak for himself.

Scorpio69er wrote:
You, sir, can kiss my, er, amp.

You don't like or appreciate what Stereophile does, please stop reading the magazine.

John Atkinson
Editor, Stereophile

Scorpio69er's picture

re: "stop projecting your fantasies on to Gordon who, sadly, is no longer here to speak for himself."

So you'll speak for him, since he's no longer here. Yeah. Right. But we are to ignore his own published (right here in Stereophile!) words. That's just me "projecting". Got it.

re: "You don't like or appreciate what Stereophile does, please stop reading the magazine."

Gee, can I get you a crying towel?

What "Stereophile does" is proclaim that various mega-expensive DACs, cables, etc, possess sonic attributes not possessed by standard items (that meet the required specs for the job at hand). But it flat refuses to validate any of its claims with what JGH plainly stated were "the kind of basic honesty controls (double-blind testing, for example) that had legitimized every other serious scientific endeavor since Pascal." Then, your poor feathers are ruffled when questioned about this nonsense. Cry me a river. You recommend gear that cost more than most folks make in a year, but whine when asked to justify it, scientifically. Audio reproduction is, after all, science -- not magic. Oh, that darn icky science stuff!

As noted, I was reading Stereophile before you ever got here, and I'll be reading it -- and holding its feet to the fire -- long after you've gone the way of the eight-track cartridge. After all, someone has to hold up the legacy of JGH around here!

ChrisS's picture

Hey sixtyniner!

Still going on about DBT...when nobody else is?

Where is the Calvary of Truth?

Where are your Minions of Science?

Just you?

Oh, dear.

Must be lonely.

ChrisS's picture

Hey sixtyniner, again!

Did you know you were paying John Atkinson's salary each time you buy a copy of Stereophile?

How comical is that?!

bapcha's picture

I love giant-killers. Keeping in mind that the top of the line TI (Burr-Brown) or ESS DAC is under $20, in volume, EVERYONE should be able to design elegant circuits that perform and sound as good as anything from Harman's high-end or Burmester for that matter :-)

Sincerely,
Bapcha

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