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Aragon A2004 to NCx500 Monoblocks

May 13, 2024
Auburn Hills, MI
Dear esteemed ASR colleagues,

I've been on the lookout for cost-effective amplifier upgrades for my audio system, and my pie-in-the-sky option was originally the Benchmark AHB2. After reading the ASR review of the Hypex NCx500 reference design, and other very positive reviews of the Hypex NCore amps in general, as well as having my own good prior experiences with A/B comparing some NC400 monoblocks to a pair of Pass Aleph 0 on a friend's Thiel CS5i, I bought a pair of amplifiers built and assembled according to the NCx500 reference design. The builder isn't really important; they were built with the same internal layout and same set of parts as the reference NCx500 monos tested on this site.

My speakers are the (rare) Thiel CS1.7, and I have a pair of KEF Q100 to represent a smaller speaker. I have found the Thiels to be bass-light, with no 'fluffing' of the low end, and even lacking what I would call 'solidity' or 'impact' - they seem to just track what they are sent, down to about 80 Hz where roll-off begins and they are mostly done by 50 Hz, so I usually supplement them with subwoofers. They're just a two-way speaker with a 6.5" woofer, so I don't begrudge them not being bass monsters. Otherwise, they are pretty magical with the right power. I'm not a tube nutter, and I listen to digital sources, not vinyl, because I appreciate a more accurate sound, and the Thiels have been pretty good to me.

I bought an Aragon A2004 from a friend in 2016, and I'm at least its third owner. Apart from discernible transformer hum from the unit itself, which is only barely audible within less of a foot from the unit (but it's there), I have been loving how the amp sounds. What I love a little less is its size and weight, but I found it subjectively very enjoyable, with the hallmarks of the Dan D'agostino house sound - firm, forceful bass, warmish lower midrange, spacious upper midrange, and light/restrained but airy and delicate top end. I feel it was also a good match to the Thiel speakers. Before that, I had an Emotiva XPA-2 Gen3 that I was moderately satisfied with. My source is an Emotiva DC-1 DAC, which I preferred in A/B testing with a Wyred4Sound DAC2 as having a more relaxed presentation than the Sabre-based DAC2, although I'm casting a suspicious eye on it nowadays in a world where SINAD now reigns as a leading measurement of DAC performance.

I have many amps, and I am familiar with how they each sound, both Class AB and Class D. The idea that all amps sound the same is usually preceded by the qualifier "All properly-designed amps sound the same". Unfortunately this doesn't hold true in the real world, where there's lively debate about what a properly-designed amplifier even means, and seemingly few properly-designed amplifiers to show for it, though there are plenty of good-sounding amps each with very subtly different personalities. With all of the positive hype surrounding the NCx500 amps and the rose-colored glasses based on my prior experience with the NC400, I expected to be blown away by limitless reserves of perfect power, effortless dynamics, and unassailable clarity. The reality was a little bit less spectacular. To compare apples to apples, I disconnected my subwoofer amplifier, and fed the balanced output of the Emotiva DAC into the NCx500 monos, while feeding the unbalanced output of the DAC into the Aragon, and I just powered down and disconnected the speaker cables of whichever amplifier I wasn't listening to. The NCx500 certainly are clear, very literal, and ultra-squeaky-clean through the midrange and treble. But what I lost was the bass weight and the spacious soundstage and sense of the wraparound 'venue' provided by the Aragon, through speakers that tend to need a little help in these areas. The image also took a step forward of the speakers, and the depth of field was reduced by about half of what I'm accustomed to. I suspect the bass issue could be confirmed through measurement, and probably could be traced to the usually greater bass damping provided by Class-D amplifiers due to low output impedance, but the soundstage changes would be more tricky to competently explain.

Am I the only one to hear sonic perfection in the flesh from the current crop of ultra-linear Class-D amplifiers and yet feel a little bit let down? Could the reality be more sinister, that I somehow 'like' a form of audible distortion from an inferior amplifier, and need it in order to feel sonically satisfied? The Hypex amps are probably staying, because they didn't cost me so much that I feel the need to sell them and they might find a better match to other speakers later on, but I'm hesitating to make them my favorites with the speakers that currently anchor my system.

Love and light,
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I will comment only on one thing:

Dear esteemed ASR colleagues,[...]
The idea that all amps sound the same is usually preceded by the qualifier "All properly-designed amps sound the same".

Anyone that affirms this is completely wrong. The proper way is All properly-designed and properly interfaced amps will sound the same when connected to the same components."

The important point is the first one of the additions in red.

An amplifier with a low input impedance Zin or a high output impedance Zout is not necessarily "not properly designed" — at least considering what goes for "properly designed" in the objective-fi world — i.e., very low noise, distortion, and phase rotations, and very flat frequency response (usually for a constant sink impedance). [*]

There are many reasons for a low Zin or a relatively high Zout, for instance reducing the complexity of the design which implies reliability, which could be considered part of a "proper design".

So, if you connect a properly designed preamp with a high output impedance to your low input impedance properly designed amp (like a naked Purifi module), or you connect your properly designed power amp with a high Zout to a low impedance speaker, you may have frequency response artifacts, or speaker control, etc. Same if your amp is excellent according to the [*] criterion, but deliver little power and your speakers are hungry — you will get distortion and clipping. All these artifacts will be audible.

Therefore, i agree with you: the idea that you mention is wrong. But if you have two properly-designed amps (in the narrow meaning I marked with a [*] sign) and the rest of the chain is such that the amp interfaces in a close to ideal way both upstream and downstream, then, they will be indistringuishable.
Same for a preamp wrt source and power amp, or source to preamp (only downstream).
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