Click Here: Cheap FIJI Rugby Jersey I thought I knew what a preamp could do. But when the Dan D’Agostino Master Audio Systems Momentum HD preamplifier ($40,000) arrived for review, all my expectations flew out the window.
The two-piece Momentum HD preamp wasn’t exactly a stranger. I’d heard it in two of the finest sounding systems I have ever encountered, at a March 2019 event at Seattle’s Definitive Audio and, a month later, at Chicago’s 2019 AXPONA. Both systems included Wilson Audio Specialties’ Alexx loudspeakers and Subsonic subs; D’Agostino Relentless monoblock amplifiers paired with the Momentum HD preamp (and other D’Agostino products); dCS Vivaldi digital stacks; Clearaudio Master Innovation turntable and cartridges; top-level Transparent Audio cabling; and HRS racks. But without hearing the Momentum HD preamp in my own system, I had no idea what it had contributed to the outstandingly open and clear, precisely focused, naturally balanced, and superbly musical sound I gushed over. All I knew for certain: If that preamp was doing something wrong, everything else had to be doing something very right.
Hence to my reference system did the Momentum HD preamp come. Arriving just one month after I had used the one-box tubed Audio Research Reference 6 line preamplifier ($15,000) to review the Gryphon Audio Ethos CD player/DAC, I took advantage of the Ref 6’s presence for easy comparison. Being an all-balanced, fully discrete, zero-feedback design, the Momentum HD preamp also benefited from the extra pair of loaner Nordost Odin 2 balanced interconnects that I had used in the Gryphon review.
With its battery of six sets of balanced inputs, two sets of balanced outputs, Bluetooth antennafor its uniquely round Bluetooth remote handsetand more, the Momentum HD’s rear panel has a quasi-military appearance that seems to prioritize uniformity over grace. That look contrasts with the front panel’s distinctive audio-jewelry profile, in which a large, green-lit volume meter, surrounded by a rotating volume control, reigns supreme. Other controls include eight input and operation buttons, each center-lit by a different color (footnote 1) and prominently placed bass and treble controlswhich, as you’ll read below, serve on a part-time basis. The Momentum HD’s regal air is enhanced by its position atop its thronea combined stand/power supply from which the preamp proper is isolated by three spiked feet. All in all, the Momentum HD, the substantial copper-and-aluminum aesthetic of which reflects the preamp’s substantial cost, is anything but a plain-Jane design.
And then there’s the soundbut first, a few . . .
Whys and wherefores
“I was listening to the Relentless amps at home, and I wanted to see the dynamics,” Dan D’Agostino explained during a Skype screen-to-screener in which he touched upon his company’s three model ranges: Progression, Momentum, and the top-of-the-line Relentless. “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. The original Momentum preamp was doing an awesome job, but I decided to try putting part of the Relentless preamp (footnote 2) circuit that I was working on into the Momentum preamp. 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. It’s a monster that swings over 40 volts at the output, and has tremendous dynamic range and extraordinary fine grain detail at both low and high levels. It’s not a Relentless preamp, which is much more elaborate and will cost much more, but it has some of the same circuitry and ability to reproduce the leading edge of notes and musical passages.”
Dan D’Agostino designed “almost all” of the Momentum HD preamp’s audio circuitry. Everything in his current line uses entirely different circuits than what he designed and used at Krell, the company he co-founded, co-owned, and served as chief engineer.
“At Krell, I used to suffer under the burden of the commonly pronounced judgment, ‘The amplifiers are fabulous, but the preamps are okay’,” he confessed. “I figured that if more than one person said that, I wasn’t hitting the home run with the preamps like I was with the amplifiers. When I designed this preamp, I really wanted it to be over-the-top. I had to do something completely different.”
Among the HD’s many changes to the original Momentum preamp design is the use of a Bluetooth remote, which is said to extend its range around the corner, so to speak. The Momentum HD’s ladder volume control, which D’Agostino claims “places a single resistor between you and the sound,” now has an additional 60dB more volume-control steps, with 1dB increments in the critical range between 10pm and 2pm where most people listen. Every touch of the remote’s volume buttons adjusts volume by 1dB.
“There’s nothing digital about the volume control save for the relays, which are governed by a digital controller,” he said. “But the relays are not in the volume path; it simply selects the different resistor values.”
The Momentum HD’s power supply/stand has grown much larger, due in no small part to a much larger high-current transformer, much higher voltage rails, and three added stages of regulation. There’s a new input board that uses military-grade FETs to give the preamp a 1M ohm input impedance, and an additional output stage that has been modified to take advantage of the very high voltage swing.
D’Agostino described one of the reasons he endowed the Momentum HD with tone controls: As he was getting more involved with analog, he discovered that many of his prized records needed “a little tweak of the tone control.” Rather than place the tone controls in the middle of the gain stage, as is often done, and which in his opinion invariably affects sound quality, he added a completely separate tone-control amplifier that, when engaged, diverts the signal through a circuit that is exactly the same, sonically, as in the preamp.
“When you engage the tone controls, you’re not affecting how the rest of your preamp sounds,” he said. “It only affects the band you’re operating in. For the treble, you’re working from about 7 or 8kHz up, and on the low side, from about 50 or 60Hz down. They’re not big tone controls; they’re not going to shake the earth, but they are going to make slight differences.”
Installation and setup
Removing the two-piece Momentum HD preamp from its secure, wheel-equipped flight case and setting it up was a snap. Given the high power output of my reference D’Agostino Progression monoblock amplifiers1000W into 4 ohmsthere was no need to raise the preamp’s gain from the default setting. The only question concerned whether to use the AudioQuest Niagara 5000 power conditioner into which I usually plug all my equipment, with its two high-current outlets reserved for the Progressions.
During our chat, I read Dan an email from Niagara designer Garth Powell, who wrote that my Niagara 5000, fed by a 1m 20V AQ Dragon power cable, performs at “20 Amps RMS, with a 90 amp peak current reservoir that can sustain up to 25mS at 120 VAC input. If you get a 1000 watt class A operation power amplifier, it could be an issue. Otherwise the 5000 will make the amplifier better, given its transient power correction circuit. Many companies are justifiably concerned, because many AC filters, isolation transformers, and AC regenerating circuits raise AC impedance, create a phase lag, and therefore current compress the power amplifier. We do the opposite (if you use the high current outlets).”
D’Agostino responded, “If I were listening at your house, I would plug the amps directly into the wall and plug the preamp into the power conditioner. I don’t know the Niagara 5000 so I can’t speak definitively, but my experience with power conditioners is that they’re not doing my amps any favors. I think you should leave everything the same in order to do the initial listening to the preamp, because that way you don’t mess up your reference.”
I followed Dan’s counsel. First, with the monoblocks plugged into the Niagara 5000, I used the Momentum HD preamp with two excellent DACs that have their own volume controls, the dCS Rossini and EMM Labs DV2. After more or less removing those volume controls from the equation by setting them to 0dB, I allowed the Momentum HD preamp to control volume and evaluated the sonic differences. I next compared the sound of the solid-state Momentum HD preamp to that of the tubed Audio Research Ref 6. I also listened to the DACs with no preamp in the chain and later evaluated the sound with the amps plugged into the wall.
Footnote 1: Illumination can be set to only turn on momentarily during changes.
Footnote 2: Tentatively due 2nd quarter 2020.