Audio-gd C39-MK3 pre-amplifier and C10-SE power amplifier review


Hifi is a game of two halves, both extremes of which are different takes on the illusory nature of in-home reproduction.  Musical vs accurate.  That endless, book-bashing debate that runs endlessly and round&round – like a record, baby – on the hifi forum circuit.   ‘Musicality’ might be the ready admission that ‘accuracy’ just isn’t possible so why the heck not accept interpretations, distortion and colour?  Fans of ‘musicality’ might just go for the sound that’s most pleasing to them.  I sense that they might be the happier camp.  Glass half full.

‘Accuracy’ implies a stranglehold on truth that just isn’t attainable – we cannot know with certainty what is accurate or what is not as we were not present at the time and place of recording.  Like ‘musicality’, ‘accuracy’ is just a feeling – a different trick of the light, one with less smoke and more mirrors.  Extending the vocabulary family:  Accuracy/neutrality/clarity are three descriptors that give words to a different kind of feeling.

If that sounds overly cliched and deliberately diplomatic, it is.  A sound described as accurate might be considered by some as the superior disbelief suspender – fine – but we would also hope for a sound not so over-carved that the unpleasant elements of a recording/mastering ruin the illusion.  Possible?  Perhaps not.  She’s a dame, sure, but we don’t want to know that she’s an escort girl.  To this end, I sense that the pursuit of accuracy might be more expensive than accepting the limitations of one’s (musical – ha!) rig.  Glass half empty?  Perhaps.

Audio-gd might be Big in Japan, but they remain a relatively small player in the broader hifi markets of Europe and the USA.  Overseas pricing might also be inhibiting global market penetration.  No doubt shipping costs and dealer margin are the reasons behind King Wa’s gear costing more in the UK than it does to buy direct from his Chinese HQ.  Having earned its reputation as the go to fellas for budget DACs – check the forum chit-chat for confirmation on that score – I was curious to learn if Audio-gd’s amplifiers provided similar value for money.  That his DACs, pre-amplifiers and power amplifiers can all be connected via current-domain ACSS made the proposition more intriguing.  The review brief was to engage with a completely ACSS-chained system, thus including the Audio-gd Reference 7.1 as digital decoder.  Behind that would sit an Audiophilleo1 USB-S/PDIF converter and a 2010 MacMini.

ACSS isn’t new (or original!), but neither is it common.  Krell have been using similar technology for some time – theirs is called CAST (Current Audio Signal Transmission).  Same horse, different jockey.  On paper, ACSS/CAST points to greater bandwidth and diminished signal loss.   I put the C39MK3 pre-amplifier (US$960) and C10SE power amplifier (US$1400) in the dock.  Shipping costs from mainland China to Australia are as ball-breaking as lugging the 38kg C10SE into place.

“The C-10 provides ACSS input and XRL input. When C-10 works with ACSS preamps C-3 or C-8 or C39, it shares the isolated control circuit of the preamp causing even better signal matching and controlling. The fruitful result is: far higher s/n ratio and lower distortion than ever expected.”, explained King Wa.

“ACSS is the same as Krell’s CAST but we were advised to change the name.  ACSS is simple and offers a very short signal path compared to ‘normal’ voltage gain stage amplifiers. In our ACSS amps, only ONE stage is required for gain whereas a normal amplifier might need anything from two to four stages; a standard op-amp already has 2 stages.”

Does that sound vague?  Maybe.  A copy and paste from Krell’s website perhaps adds some clarity:

“CAST technology virtually eliminates the noise and distortions created from the use of multiple voltage gain stages. A Krell system connected in CAST transfers the signal in the current domain, throughout the signal path to the amplifier output stage where only one current to voltage conversion (I-to-V) takes place. CAST enabled products include a transmitter and receiver circuitry that transfers current from an extremely high output impedance (source) to a low-impedance input (load), minimizing the cable’s effect on signal transmission.”

The pre-amplifier and power-amplifier can be connected via Audio-gd’s ACSS connectors (for which separate ACSS cables must be purchased – they’re cheap, so don’t panic).  The serial data ports on both power and pre facilitate the unification of two amplifier stages into one ‘virtual’ amplification entity.  However, know that the user can opt for XLR cabling and still invoke ACSS connectivity.

More from King Wa:  “In each mode, the C39 and C10 will utilise all ACSS modules for playback.  In ACSS mode, the signal travels through the C39’s ACSS modules – which add gain – and then onto a direct connection with the C10’s ACSS modules. modules.  In XLR mode, the signal travels through the C39’s ACSS modules – which add gain – and is then converted to XLR signal in order to feed the C10.  The C10 converts the incoming XLR signal back to ACSS signal for gain.”

Both the pre-amplifier and power box must be setup to receive ACSS signals.  The C10 has NO single-ended inputs – it’s ACSS/XLR only – but ACSS setup was a cinch:  shut it down, connect the data cable and the ACSS cables between C39 and C10, and then power up the C10 again.

Without a user manual to refer to, C39-ACSS configuration required some email to and fro between King Wa and I.  To enable the C39 as a receiver of ACSS, one must use the rear-mounted ACSS/XLR toggle button. Shut down the C39, set this button (“out” for ACSS, “in” for XLR), and then power it up again – yup, makes sense.  The front panel display will respond accordingly.  It will show a “C” prior to the first digit if it is ready to take ACSS input.  A leading dash (“-“) indicates an XLR feed.  If nothing else, I hope the preceding information assists new users from feeling confused by ACSS setup (as I did).

Separate volume levels for each input are memorised by the C39, of which there are five: two single-ended RCA, two balanced XLR and one ACSS.  Three output options take the signal out of the C39 and onwards down the chain:  RCA, XLR and ACSS.  (Note:  the C10 power amplifier sports no RCA input!)  The front panel features face-slapping simplicity:  one endless POT for volume, one endless POT for source selection and a bright blue display.  Volume, mute and source selection can also be adjusted from the simple-but-weighty aluminium remote control.  A single line of buttons means it’s as intuitive as it gets.

The other on-paper attraction of this ACSS war machine is the power output of the C10.  250wpc into 8Ohms (double that into 4Ohms) for US$1400. Power usually costs money.  Here, not so much.  On to listening then…

…where they hit you between the ears immediately – brothers poise and heft.  The Audio-gd ACSS trio shows us the layers that comprise each moment, most notably in the front-to-back plane.  That’s the depth illusion!  The pins of such precision don’t prick – it ain’t sharp, it’s crystalline.  A window cleaner at the house of song.  No murk, no obfuscation, just clean, spotless glass.  Tied to the ProAc TR8s, team Audio-gd present Plastikman’s minimal techno as swimming pool of ticks and clicks, each with their own distinct play area of three dimensional deep space.  No doubt the Reference 7.1 fed by Audiophilleo1/MacMini ensures this illumination gets off on the right foot. Switching back to the more rudimentary, ACSS-capable Audio-gd NFB-12 (US$200) and dusk falls; (inner) light fades on the scene.

The Audio-gd-supplied ACSS cables were then switched in favour of XLR connectivity.

A minor diversion:  I don’t review cables.  I just don’t.  End of story.  For those taking notes, WLM Lyros single ended interconnects and WLM Stratos loudspeaker cable are my standard reference.

Trading under the Grave Science banner, Peter Graves is a one man cable-making operation based in the Adelaide Hills.  He provided me with some loudspeaker cabling recently “just to have a listen to”.  Wanting to support the local manufacturing scene, how could I refuse?  That there are echoes of Kimber to their outward appearance added spice to the story of a local guy sticking it to the man by not sticking it to your wallet.  Adding perhaps a hint of firework show sparkle to the top end, they are every bit as good as my reference WLM Stratos.  But hey, I don’t review cables.  This is simply credit where it is due.  (Cynics note:  Grave Science have been afforded a banner ad on this very website, gratis, because their cables are that good and they’re locally made).

Learning of this ongoing Audio-gd assignment, Graves also supplied some balanced interconnects.  These were leashed from Ref 7.1 to C39 to C10.  Remember: the internal ACSS modules were still being deployed, but with intervening XLR-ACSS conversion stages at pre and power input junctures.  XLR lasso-ing added grams to instrumental weight.  Bruce Springsteen’s furious Americana-heritage band connoted superior earth-anchor.  It dug in!  Picture the sound of a music festival tent pegged to the ground against a background of dark chocolate.  Balanced connections upped richness and life.

I am not blind to the possibility that improvements witnessed could be due to the Grave Science cabling being downright superior to the more humble wires offered by Audio-gd’s ACSS.  Perhaps a more luxurious ACSS interconnect would turn the tables again.  My point? It it isn’t as simple as ACSS uber alles.

So who needs this amount of amplification in this box size? Clearly, it’s not for those looking for discrete power.  Small form-factored juice boxes remain the preserve of Class D specialists.  However, this amplification is more engaging than the budget end of Bel Canto.  A thirty-eight kilo power box would certainly appeal to those that enjoy the show n tell.  This is trophy hi-fi on a budget, the joy of which slowly diminishes as the spend heads skyward.  The law of diminishing returns bites real hard at the high end.  The C39/C10 combination work well beneath the Conrad Johnson ceiling whilst offering comparable amounts of speaker juice.  I know not if the Audio-gd runs in the same quality circles but everything about its build – and KingWa’s pedigree as a designer/engineer – suggests that it might.  That’s one for more curious readers to discover.

My remit here is to posit the lesser-known alternative, akin to shouting “Hyundai!” in a Subaru showroom.  Who will hear me?  Those considering a AU$3k drop on an integrated design is who.  Yes, the integrated would be the tidier (higher WAF), but it leaves room for doubt.  Does the integrated bring sufficient power to the table for those that wish to dine on a diet of a feeling of unashamed neutrality?  Without any doubt, the Audio-gd C39/C10 work with a firm crispness and detailing that the Leben CS300XS’s (AU$3200) honey-infused elegance can’t hope (nor should it) approximate.  The Audio-gd offers no shades of colour – it’s music as water.

Comparing Chinese solid state with its own kind – the Exposure 2010s2 (AU$1999) – is perhaps a fairer comparison.  The feisty Brit integrated is contrasted as sounding glad/cling-wrapped.  With the Exposure, the listener must navigate the shadows of lower inner lumens.  It’s also more restrained/polite with micro dynamics and shallower of soundstage.  To expect it to approach the Windex Wipe — err — exposure of the Audio-gd is asking too much.  It’s not that the Exposure is weak – it ain’t – it’s just roundly outclassed.  Any given ‘musicality’ fan will likely damn the presentation of the Chinese pair as bleached, hospital grade.  Fans of ‘accuracy’ will likely lose their shit when faced with so much downright clarity and insight (for such a relatively small spend).

Those deceptively pesky standmounts are nearly always the first in the crosshairs with Gatling Gun amplification.  Audio-gd’s C10 is no exception here – it rules the ProAc TR8s with an iron fist.  They speak not unless spoken to.  This is Victorian English power dispensation — 250wpc really can’t fail in this finishing school.  The finishing school for small boxes (with nominal sensitivities that drop below 85db).  It doesn’t just mean they’ll go louder – it means they’ll go louder and faster with grace.  Control and elegance are the primary side-benefits of that extra juice.  Then – along with laser guided detail – microscopic nuances surface, imaging undergoes lockdown, curtain boundaries are pulled tighter to the wall giving stage players more room to move.  The Audio-gd C39/C10 is a pre-power combination that seizes each musical moment and refuses to let go.  It’s a combination that confirms ‘accuracy’ as a sensation (and not necessarily a monopoliser of recording studio truth).  Such an abundance of clarity and horsepower (for an integrated price) is majorly impressive. With both feet firmly placed in the accuracy-as-a-feeling camp, these pre-power siblings from Audio-gd offer staggering levels of insight into recorded music.


Associated Equipment

  • MacMini 2010
  • Audiophilleo1
  • Audio-gd Reference 7.1
  • Audio-gd NFB-12
  • Leben CS300XS
  • Exposure 2010s2
  • ProAc TR8

Audition Music

  • Bruce Springsteen – We Shall Overcome / The Seeger Sessions (2006)
  • David Bowie – Lodger (1979)
  • Basic Channel – BCD 1 (1995)
  • Plastikman – Artifakts BC (1996)

More 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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