Aspen NAKSA 100 power amplifier review


Some people talk too much.  There’s a fine line between evangelical zeal and a plain, straight-up sales pitch.  Hugh Dean knows this.  His have-a-listen-and-see-if-you-like-it approach to his Melbourne-based amplifier design operation isn’t common as one – the consumer – would like it to be.  Is there anything worse than being told by the manufacturer or retailer how amazing their product sounds?  No.  It’s an ugly behaviour that straddles arrogance and disrespect (toward the customer).  With Hugh Dean, I/you/we get none of that.  A good start.

More pointedly (to manufacturers, retailers).  Not everyone will like what you do.  That’s a fact of life.  In trying to close a deal, let the customer decide if the item in question is to their liking (good) or not.  That ‘good’ is subjective to the nth degree.  If I say something is good, great, amazing, I’m not bringing an objective truth gavel down hard on the bench, I’m merely stating what I think of it, in my system(s), on those days, with these ever-changing moods.  The subjective appraisal process is also YOURS to complete.

Aspen’s beefed up NAKSA 100 power amplifier shares an identical design philosophy with its baby brother (the NAKSA 70):  single-ended throughout with an emphasis on “musical engagement” – according to Dean, prioritising even-ordered harmonics is what leads listeners to describe (his) amplifier designs as “musical”.  [If you’re a listener that can’t even handle the ideaof distortion being considered by the designer as crucial to the sonic recipe, this amplifier probably isn’t for you].

The NAKSA 100 kit ships with a custom enclosure fashioned by LG Sheet Metal (based in Dandenong, VIC); it’s a 2mm-thick milled steel, power-coated two piece.

Pricing?  Modules alone are AU$1420.  For modules WITH enclosure, binding posts, IEC power entry socket, RCA inputs and front power switch, you’ll need AU$1635.  Achieving a broader loudspeaker jurisdiction from the NAKSA 100 means two 300VA toroidals inside the box – it’s heavy.  As per the NAKSA 70, the buyer must procure these independently of the Aspen-supplied amplifier modules/kit.

The output stage is hybrid:  bipolar transistors handle the top of the wave form and MOSFETs deal with the bottom half.  Dean calls this “a polar bear up top, and a gorilla down the bottom”.  Taking more technical aim: the signal is handled in slightly different ways so that distortion varies quantitatively and qualitatively. That asymmetry leads to predominantly even order distortion – “the good stuff”, according to Dean.

Dean continues, “My approach is essentially informed by musical considerations.  The human is unique in that he can make sense of cacophonous polytones – music by another name.  But the inter-relationships must abide by certain rules to make mellifluous music – and chief amongst them is the rule that even orders are acceptable, where odd orders, particularly the fifth harmonic and beyond, are definitely not.”

“Psychoacoustic studies reveal that to humans the fifth harmonic, sometimes called H5, is musically discordant and unappealing.  H2, the second harmonic so redolent with valve circuits, adds warmth and engagement;  H3 adds a certain sharpness, and H4 adds ‘body’.   H7, H9 and H11 are quite unattractive, sometimes described as ‘machine’ tones, since they do not sound sympathetic to music and in fact contribute to listener fatigue.  Crossover distortion on push pull amplifiers is often made up of these components.”

“Even order harmonics are produced by distortions to one half of the waveform – but NOT to the other half.  This type of distortion is sometimes called asymmetrical, because it manifests on one half of the waveform, but not the other.  Most amplifier designers strive to have the amp clip at the same amplitudes of the two waveform halves;  this is electrically efficient, and gives a pleasing symmetry.”

“However, there is a trap here.  The human animal is primordially drawn to symmetry, after all, we have two arms, two ears, two eyes, two legs, and two hands.  We are irresistibly attracted to symmetry in art, in our visual appraisal of others, in mathematics and in science.  Much of our architecture is symmetrical, and even automobiles are often marketed on the basis of symmetry, so there is clearly something to it.”

“The trap is that symmetry of waveform distortion means that any distortions will be odd order.  Be mindful that distortion is inevitable;  it is a fundamental part of the amplification process, however small, so we must design to accommodate this distortion.  Corruptions of the upper half cycle duplicated in the lower half cycle will manifest as odd order harmonic distortion, and this sounds very bad to our ears.  In fact, there is a pronounced asymmetrical quality to our hearing;  the transfer function of air is different in compression to rarefaction, and this means that everything we hear is slightly corrupted by the very medium through which we hear it!  It transpires that the human ear also deals asymmetrically with compression and rarefaction;  and as a result all incoming sound waves are augmented with H2 as they enter the ear canal.  Estimates of this phenomenon vary, but some experts put the figure in excess of 30%.  This is a shocking revelation to those who insist on vanishingly low THD, since, along with huge distortions added by the speakers, the amplifier issues are, on the face of it, dwarfed by other phenomena occurring in the human hearing system.”

“This all has repercussions for audio systems, particularly digital sources and power amplifiers.  It means that if odd order harmonics, even at very low levels, are delivered to the speakers then the human ear will respond to them, perhaps not directly, but certainly at a subliminal level.  This may cause us to cry out in sonic rapture, or quietly leave the room after only ten minutes.”

“At Aspen we believe that these considerations are pivotal to audio amplification, and our many careful tests over the years confirm that an amplifier with higher even harmonics than odd harmonics is more musical.  This has informed all our recent designs, with the NAKSA series following this philosophy to the letter.  We fervently believe we are on the right track, have developed a series of metrics to assist with the design cycle, and would ask that you listen carefully to the new NAKSAs and hear for yourself just how musical is this novel approach.”

A NAKSA 70 wasn’t available for direct comparison. Readers are instead directed to my commentary on Hugh Dean’s previous model to get a firmer foothold on the backstory.  However, I can say with reasonable confidence that the 100 is a sensatory extrapolation of its predecessor.  Note: I am not saying it’s ‘the same but with more watts per channel’; the dual mono configuration stamps out that naivety.  Experience tells me that additional grunt under the hood usually sees a more seductive teasing of finer nuances as well as greater command over more challenging loudspeaker loads – bass tautness being the primary beneficiary.  All other things being equal – and remaining aware of exceptions – this a truth/tendency that transcends design ethos and topology.  Simply put, more juice is invariably a good thing.  In these primitive terms, the NAKSA 100 is a superior beast to the NAKSA 70. Same chef, different meal.

Dean voiced both NAKSAs using direct-connected, digitally-attenuated digital sources:  a Squeezebox Classic and a Onkyo Integra CD player.  For initial listening sessions, I went with a similar vibe.  I chained PSAudio’s PerfectWave DAC direct to the NAKSA 100, which in turn pushed into Zu’s 98db Omen.  Comparisons were then made with the beatific Leben CS300XS (with volume pot fully open).  The quality I enjoy most in this Japanese integrated is its post-thunderstorm clarity.  It filters music through ozone-rich air.  The 100watt NAKSA’s sound closer approximates the charging air prior to cloudburst relief and energy discharge; it has more propulsion and energy.  It isn’t as relaxed behind the wheel.  It wants to drive you headlong through the coming storm.  The only way out is through.

This Leben is pepped with a dose of Genalex Gold Lion EL84s and a pair of Amperex Hollands.  The NAKSA is silkier up top.  It’s much smoother.  A bald(ing) pate?  Not quite. Think: freshly polished wooden floor – beautiful and striking.  Yes, the NAKSA offers more sheen-ed clarity.  If that sounds like a backhanded compliment, it ain’t.  It’s straight-up praise (and the long way ’round to saying that treble is grain free).

Turn On The Bright Lights.  In 2002, the album that Joy Division fans had waited twenty years for New Order to make, came by way of new-comer- New-Yorkers Interpol.  It’s a intense and brooding record with fair-to-middling production values.  The Leben took a run at it, then the NAKSA.  At the hands of the Australian box, the delicate cymbals that occasionally puncture the skin of murky “NYC” incise with superior mass and less pre-amble. This is a musical surgeon that doesn’t talk you through the operation: he just does.  It is with decay that clearer differentiation between Jap-tube and Oz-SS schools can be made.  the vapour-trail of the Leben is what lends it a mystical air.  The NAKSA, although warm, doesn’t work this way: it’s warmer, yes, but not as moist or ethereal.

“Evil”.  The bass line that pre-empts the (now oft-mimic-d Paul Banks-ism) “Rosemaaaaaary” reveals string textures that are indeed equal in quality and greater in quantity than that of the Leben interpretation.  NAKSA handling has greater heave-ho.  In fact, the local boy easily bests the Japanese kid for bass depth and articulation; great for more standard angsty rock n roll like this.

Through Zu Omen, the NAKSA showed little sign of humidity – that the music was cutting thicker air.  Maybe that’s the power on tap?  Maybe it’s liberation from the (artificial) meat of tubes.  No mind, this smooth way with clean lines is win-win for electronic music fans.  Zomby’s Dedication is dubstep that sounds nothing like the wump-wump of neighbouring artists.  Little wonder it’s out on 4AD: midnight black London nervousness that turns beautiful then ugly then spooky.  A modern day Haunted Dancehall.  The NAKSA works airspace into Dedication’s dark crevices and dials down the laconic drawl.  Under Leben command, musical blood runs thicker and warmer: chocolate at congealing point.  The NAKSA transfuses a thinner blood supply, one that flows faster (with oxygen delivery).  By haemoglobin!

Under such electronic music scrutiny, the NAKSA is faster and draws the rear curtain closer to the back wall.  Depth, texture and authority all push further forward. The Leben counters with thicker midrange.  Some folk would call that colouration.  Assuming all amplifiers add some dose of the aforementioned C-word, the NAKSA’s more cunning and less overt.  It’s an altogether more cerebral listen than the Japanese integrated.

Instead of going source-direct into the NAKSA, how about an intervening pre-amplifier (that also packs budget power stage integration) for comparisons in the financially opposite direction?  Enter Peachtree iNova.

The iNova alternated as solo integrated and pre-pusher for the NAKSA 100.  Loudspeakers this time around: ProAc Tablette Reference 8s.  As comparisons go, ALL points were awarded to the Melbourne power box:  it offered better scale, musical insight and immersive detail.   Pop-up alert:  the iNova’s internal tube pours on too much syrup.  Once outed as a thickening agent, the stock 6N1P remained defeated – via a single remote click – throughout its pairing with the NAKSA 100.

The NAKSA’s stewardship means a lower centre of gravity – a more grounded sound – with better corner handling through the complex twists and turns of Interpol’s “Roland”.  Even more convincing was its way with dynamics.  The ~60wpc (into 8 Ohms) iNova has just enough over hold the ProAc mini-monitors to elicit reasonably convincing dynamic shifts…but it has a tendency to homogenise.  The plainer black-box takes ’em by the scruff of the neck.  Music that’s NAKSA-charged reveals more information (as the iNova DAC always intended) and then drives it home with conviction.  The amplification stage in the iNova sometime capitulates.  Cope/Skinner’s sexually pulsating Rite sees neater, more expressive-percussive inflections, mirco-dynamically teased out by the additional, gutsier powerful Aspen box.  However, compared to the source-direct diet of PSAudio’s PWD, the iNova’s DAC/Pre handling of decay isn’t as elongated or as elegant.

This power amplifier’s downstream momentum tips into the faster side of neutral.  Its sub-tropical climate benefits best from cleaner/purer upstream waters.  Those with cooler digital converters and/or extremely neutral pre-amplifiers will find much to like here.  Hello Lightspeed Attenuator!  Want all-in-one? The Bel Canto 1.5  packs DAC neutrality and passive pre into one box.  On paper at least, these two have the potential to synergise.  Yes, lines are more clearly defined when NAKSA-d – instead of iNova-d – but they’re polished smooth and washed clean with warm water before finally being plated up.  One might simply label this NAKSA 100 sound as ‘sophisticated’ or ‘refined ‘ or ‘stately’.  Or all three.  (It easily bests the Peachtree-as-integrated along all three of these subjective/qualitative axes).

My listening experiences with the NAKSA 100 certainly reflect Hugh Dean’s design intentions: that it sounds best when fed direct from source.  The PSAudio PerfectWave DAC notwithstanding, a Fidelia-attenuated MacMini into a Metrum Octave as direct source achieved garrulous results;  superb results that are far more affordable than the PSAudio sophisticate.  The NAKSA amplifier stirs just enough cornflour into the mix such that the Metrum’s mineral upstream water flow welcomes the thickening infusion.

Tonal richness is this amplifier’s trump card.  That 100watts of solid state power come along for the ride means one has access to some tubular fattening without compromising control.  This is great news for stand mount devotees.  If you’ve monitors too inefficient for all but the most robust of tubular amplifiers, the NAKSA 100 could be a next point of call.  Power (usually) costs money.  Tubular power (usually) costs MORE money.  The NAKSA 100 offers a left-turn solution to that financial roadblock.  Now with custom casework and more power on tap, the NAKSA 100 amplifier (kit) aims squarely at those audiophiles wanting warmer hues without resorting to tubes. Go forth, listen and judge for yourself.


Associated Equipment

  • MacMini 2010
  • Audiophilleo
  • Metrum Octave
  • PSAudio PerfectWave DAC
  • Peachtree iNova
  • ProAc Tablette Reference 8
  • Zu Omen

Audition Music

  • Julian Cope & Donald Ross Skinner – Rite (1992)
  • James – Millionaires (1999)
  • Bob Dylan – The Bootleg Series Vol 4: “The Royal Albert Hall Concert” (1998)
  • Interpol – Turn On The Bright Lights (2002)
  • Interpol – Antics (2004)
  • Zomby – Dedication (2011)

Further Information

Written by John H. Darko

John lives in the NOW + HERE = NOWHERE. He derives an income from the ad revenues of DAR. John is also an occasional staff writer for Stereophile, 6moons and TONEAudio.

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