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I cut my audiophile teeth on Krell amplifiers. I loved them and owned many of them, from KSAs to MDAs to FPBs -- even the flagship Krell Audio Standards. Back in the day, Krell amps provided what I wanted from an audio power amp: the control, the sweetness, the bass. To say I held founder-designer Dan D’Agostino’s work in high regard would be an understatement.

Jeff Fritz

I haven’t had in my system any components from Dan D’Agostino Master Audio Systems -- the company D’Agostino founded after leaving Krell years ago -- but I’ve sure admired their gleaming casework, and I’ve heard at audio shows a number of systems powered by D’Agostino’s current work. So it was interesting to hear, at the Florida Audio Expo 2020, held in Tampa, Florida, February 7-9, a conversation about D’Agostino’s recently released Momentum HD preamplifier. The folks I was listening to were discussing the review of the Momentum HD published in the February 2020 print edition of Stereophile, and on the Stereophile website on January 29 -- a little more than a week before FAE 2020.

The original Momentum preamplifier ($32,000) had been reviewed by Michael Fremer in the August 2014 issue of Stereophile, and on the magazine’s website in July 2014. The new Momentum HD, reviewed by Jason Victor Serinus, costs $40,000. Looking at the D’Agostino website as I write this, it appears that the HD is now the only version of the Momentum available. In Serinus’s review, he interviews D’Agostino about the new preamp’s inspiration and design. “I was trying to get the kind of dynamic contrast and extra layer of detail from a preamp that I get from the Relentless amplifier,” D’Agostino says, speaking of his company’s flagship monoblock power amp ($250,000/pair). “Once I heard a huge improvement, I started to try to fit all the Relentless stuff I could inside the Momentum preamp. That led to the HD version.” After D’Agostino had completed the Momentum HD, his listening sessions revealed “tremendous dynamic range and extraordinary fine grain detail at both low and high levels.”

Serinus’s profoundly positive review, chock-full of descriptions of the Momentum HD’s sound that attribute to it all manner of audiophile delights, seems to confirm what D’Agostino himself heard. My attention was particularly caught by Serinus’s statement that, “thanks to the additional clarity and resolution that the Momentum HD preamp brought to recordings old and new, I discovered new details and colors previously only hinted at.”


Back to that conversation in Florida among some showgoers and a speaker manufacturer. Essentially, everyone had the same question: How could a review be so positive when . . .

Because it seems that John Atkinson’s measurements show that, in some parameters, the HD version of the D’Agostino Momentum HD measures worse than the original:

The original Momentum had low levels of noise, with an unweighted, wideband S/N ratio with the volume control set to its maximum of 75.3dB ref. 1V output, this improving to 92dB when the measurement bandwidth was restricted to the audioband. The Momentum HD wasn’t as quiet, the wideband, unweighted signal/noise ratio, taken under the same conditions, measuring 60.2dB, again ref. 1V output. Restricting the measurement bandwidth to the audioband increased the HD’s S/N ratio to 77dB, while switching an A-weighting filter into circuit gave a further improvement to 79.7dB. . . . While the Momentum HD’s measurements in some areas -- channel separation, S/N ratios -- are not the equal of the original Momentum’s, this doesn’t detract from the fact that it is a well-engineered preamplifier.

Summarizing the Florida conversation: How could a product that costs $40,000 measure worse than the original version, which cost $8000 less? And why was the reviewer so taken with the product?

For comparison, the showgoers mentioned Kalman Rubinson’s review, in the January 2020 issue of Stereophile, of the Benchmark LA4 line preamplifier. John Atkinson’s measurements of the LA4 revealed that “The wideband, unweighted signal/noise ratio, measured with the balanced input shorted to ground but the volume control set to its maximum, was 71.4dB, left, and 83.6dB, right, both ratios ref. 1V output. It is possible that with its very wide bandwidth, the LA4 was picking up some RF-related noise in my test lab. Restricting the measurement bandwidth to the audioband increased the S/N ratio to an astonishing 105.5dB for both channels, while switching an A-weighting filter into circuit further improved this ratio, to 108.7dB!”

The Benchmark retails for $2599.

First, kudos to Stereophile for publishing a review and measurements of a product that, on the surface, seem to, well, contradict each other. We at the SoundStage! Network have been doing the same for many years with our measurements of loudspeakers, taken in the anechoic chamber of Canada’s National Research Council. When a reviewer’s love of a product’s sound seems unconfirmed by that product’s measurements, we’ve taken the same tack as Stereophile: we publish both, and let readers draw their own conclusions. Still, it’s hard to wrap your head around: The measurements are what they are -- and you trust the reviewer to assess the sound correctly.

Folks endlessly debate this. Some argue that, in these matters, the final arbiters must be our ears. After all, audio products are meant to be heard -- and if we enjoy a product’s sound, then it must be a success, regardless of how it measures. Others argue that ears can be fallible, that measurements are excellent verifiers of high fidelity, and that from super-expensive products such as the D’Agostino Momentum HD we should expect engineering that produces measurements that are beyond reproach.

But for me, this has never been an either/or proposition -- I agree with both sides. When considering buying a component for my own use, and/or to use in my reference system for reviewing other audio products, I have two requirements: My listening experience of that component and its measurements must both be outstanding. If they aren’t, I don’t buy it. Why not have it all when you so easily can? I’m aware that a component that measures well in some parameters may sound horrible. I’m also aware that I might find a product that I like on first hearing, but that might have flaws that measurements will easily reveal right away, but that only extended listening would expose.

I also believe that, eventually, the results of measuring and listening do intersect. As evidence for this, I consider the components I’ve most enjoyed and have owned for the longest periods of time: electronics from Boulder and Soulution, and speakers from Magico, Rockport, and Vimberg. All of these are products that I absolutely love listening to, and that measure exceptionally well. Slam dunk.

As for Stereophile’s review of the Dan D’Agostino Master Audio Systems Momentum HD . . . well, the unanswered questions are troublesome. It may sound great to some ears, but I’d still like to know why, for $8000 more, it measures less well than the model it replaces. Perhaps there’s a plausible explanation -- maybe the sample measured was damaged in some way.

As I said, many products out there sound fantastic and measure like champs. That’s where I’ll be spending my money.

. . . Jeff Fritz