Constellation Performance Centaur II 500 power amplifier Measurements

Sidebar 3: Measurements

I measured the Constellation Performance Centaur II 500 using my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Before I test an amplifier, I precondition it with both channels driving a 1kHz tone at one-third power into 8 ohms for an hour. At the end of that time, the Constellation's enclosure was hottest toward the rear of the top panel, at 101.3°F (38.5°C).

The voltage gain at 1kHz from the speaker terminals into 8 ohms measured 25.9dB for both balanced and unbalanced signals, and 12dB for the Direct input. All sets of inputs preserved absolute polarity (ie, were non-inverting). The unbalanced input impedance was 10k ohms and the balanced input impedance 20k ohms, both from 20Hz to 20kHz. These impedances are significantly lower than the specified 100k ohms unbalanced and 200k ohms balanced, but are identical to those published for the original Centaur II amplifier.

The output impedance, including a 6', spaced-pair speaker cable, was a very low 0.08 ohm at low and middle frequencies, rising to 0.1 ohm at the top of the audioband. As a result, the modulation of the Constellation's frequency response with our standard simulated loudspeaker was less than ±0.1dB (fig.1, gray trace). The Centaur II 500's frequency response into 8 ohms was down by just 0.5dB at 200kHz (fig.1, blue and red traces); as a result, a 10kHz squarewave was reproduced with very short risetimes (fig.2), and there was no overshoot or ringing. Fig.1 reveals that the ultrasonic output rolls off a little earlier with lower impedances, but the response into 2 ohms (green trace) is still flat within the audioband.


Fig.1 Constellation Centaur II 500, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green) (1dB/vertical div.).


Fig.2 Constellation Centaur II 500, small-signal 10kHz squarewave into 8 ohms.

Channel separation was >90dB in both directions in the midrange and below, and still 83dB at the top of the audioband. The unweighted, wideband signal/noise ratio, taken with the inputs shorted to ground, was a high 74.1dB ref. 1W into 8 ohms. This ratio improved to an excellent 85dB when the measurement bandwidth was restricted to 22Hz–22kHz, and to 89dB with an A-weighting filter in circuit. Spectral analysis of the low-frequency noise floor (fig.3) indicated that the AC power-supply–related harmonics were primarily at 120Hz and its harmonics, but some odd-order harmonics of the 60Hz line frequency were present in the right channel (red trace). All of these spuriae lay at or below –90dB (0.003%), however.


Fig.3 Constellation Centaur II 500, spectrum of 1kHz sinewave, DC–1kHz, at 1W into 8 ohms (left channel blue, right red; linear frequency scale).

The Centaur II 500 is specified as outputting 500Wpc into 8 ohms (27dBW), 1000Wpc into 4 ohms (27dBW), or 1600Wpc into 2 ohms (26dBW). With clipping defined as when the THD+noise in the output reaches 1%, I measured clipping powers of 550Wpc into 8 ohms (27.4dBW, fig.4) and 880Wpc into 4 ohms (26.4dBW, fig.5). While this latter power is less than specified, note that I do not hold the wall voltage constant during these tests. The 0.6dB measured shortfall into 4 ohms will not be any kind of problem. However, when I tried to measure the maximum output power into 2 ohms with one channel driven, that channel turned off at 700W (22.4dBW) and wouldn't turn back on. Each channel is protected by two 10A and two 30A fuses, and it turned out that one of the 10A fuses had blown. Replacing the fuse brought that channel back to life.


Fig.4 Constellation Centaur II 500, distortion (%) vs 1kHz continuous output power into 8 ohms.


Fig.5 Constellation Centaur II 500, distortion (%) vs 1kHz continuous output power into 4 ohms.

To be certain that I was measuring actual distortion, I examined how the M15's percentage of THD+N varied with frequency at a fairly high level: 20V (equivalent to 50W into 8 ohms, 100W into 4 ohms, and 200W into 2 ohms). The percentage of THD+N was extremely low in the bass and midrange (fig.6), and while there was the usual rise in the treble due to the decrease in open-loop voltage gain as the frequency increases, this was still not to a significant amount.


Fig.6 Constellation Centaur II 500, THD+N (%) vs frequency at 20V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (gray).

The THD+N waveform at this level into 8 ohms (fig.7) indicates that the distortion is predominantly third-harmonic in nature, at –80dB (0.01%), though there was also some second harmonic present in the left channel (fig.8, blue trace). At the same voltage into 4 ohms (fig.9), the third harmonic dropped and the second harmonic became the highest in level in both channels, and was almost matched by the fifth harmonic at –94dB (0.002%). Tested with an equal mix of 19 and 20kHz tones, the Constellation produced low levels of intermodulation distortion, even at high powers into low impedances (fig.10), with the difference product at 1kHz lying at –86dB (0.005%), and the higher-order products at or below –84dB (0.006%).


Fig.7 Constellation Centaur II 500, 1kHz waveform at 50W into 8 ohms, 0.0012% THD+N (blue); distortion and noise waveform with fundamental notched out (red, not to scale).


Fig.8 Constellation Centaur II 500, spectrum of 50Hz sinewave, DC–1kHz, at 80W into 8 ohms (left channel blue, right red; linear frequency scale).


Fig.9 Constellation Centaur II 500, spectrum of 50Hz sinewave, DC–1kHz, at 160W into 4 ohms (left channel blue, right red; linear frequency scale).


Fig.10 Constellation Centaur II 500, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 160W peak into 4 ohms (left channel blue, right red; linear frequency scale).

Its measured performance indicates that Constellation's Centaur II 500 is a powerhouse of an amplifier.—John Atkinson

Constellation Audio
Suite 1, Level 6, 580 Street, Kilda Road
Melbourne, Vic 3004

georgehifi's picture

This amp far from doubles it power which the maker wants you to belive, in fact it actually goes backwards in the 2ohms!!!

500Wpc 8 ohms
1000Wpc 4 ohms
1600Wpc 2 ohms

550Wpc 8 ohms
880Wpc 4 ohms
700Wpc 2 ohms

When are amp manufacturers going to wake up and tell the truth.

Cheers George

dalethorn's picture

There must be something skewing that 2-ohms number, since the lower resistance/impedance should increase the wattage. I wonder what that something is.

slcaudiophile's picture

agreed ... i was shocked when i read that too. but i guess at the same time, who needs 500 Watts anymore? but i agree, manufactures should always be conservative with power ratings.

Anton's picture

Anybody remember the Chord SPM 14000 Ultimate monoblock power amplifier?

"Accurate performance specs? We don't need no accurate performance specs."


"And you may ask yourself, well how did I get here?"

Same as it ever was.

Bogolu Haranath's picture

It is not like 3 strikes .......... One measurement was (close to) a hit (for Constellation) :-) .........

Bogolu Haranath's picture

Think about this ......... When the new Centaur III comes out this one can be sold for 1/3rd the original price in the used market :-) ..........

dalethorn's picture

"The diamond dogs are poachers and they hide behind trees...."

And this amp will sell for double its original price, as a heater on cold winter nights in the post-apocalyptic city.

allhifi's picture

The internal layout is atrocious; with such haphazard wiring running wildly this way and that, two things become alarmingly clear:

1) QC is non-existent
2) no two amps from this laughable, but sad company will sound the same as a result.

If 'Constipation' products even 'last' 5-years I'd be surprised, as I would if it retained 10% of its original value over the same time frame.

What an ugly joke of an amp/company.


Ortofan's picture

...which costs only $9K for a pair of monoblocks.

400W 8 ohms
800W 4 ohms
1200W 2 ohms

586W 8 ohms
1154W 4 ohms
2255W 2 ohms
(4200W 1 ohm)

Also, for $55K, you'd think that Constellation could do a better job than this rat's nest of wiring:

Anton's picture

I have it on good authority from a fellow local Hi Fi Club member that if it costs more, it must be better.

That trumps Parasound, soundly.


Bogolu Haranath's picture

All those internal wires are cryogenically treated with a "secret sauce" ........... So, they acquire all that musicality ......... It is a very expensive process, and hence the enormous total price tag :-) ........

Bogolu Haranath's picture

If we match-up the recently reviewed $45,000 CD player with this amp, the sound is sure gonna be "heavenly" :-) ............

Ortofan's picture

... your local Hi-Fi Club member.
From their Reference series product line comes the Hercules II stereo amp. Priced at $90,000, it must be almost twice as good as the Centaur II 500.

Bogolu Haranath's picture

Hercules II does not weigh 300 pounds ......... So, it can't be twice as good :-) ............

Ortofan's picture

... the 355 lb. Boulder 3060:

georgehifi's picture

Not if the current's not up to it, either the powersupply or output stage.

Cheers George

ok's picture

any amplifier equipped with "some" 3000w power transformer could ever provide continuous output of 1600w simultaneously per channel – or anything close for that matter since there is always more to be stably fed in a power amp than merely output transistors. Curious thing is that Constellation Hercules II stereo amplifier that sports twice the aforementioned transformer and presumably larger output stages comes along with more conservative specifications which most probably will be exceeded by the actual measurements at the test bench.

tonykaz's picture

doesn't that phrase have to do with a "Bubble-Gum" daughter of a "Captain of Industry" describing the desirability of a $5,000 Fendi Purse?

Isn't our age group already too close to Oakwood Cemetery's Waiting List to consider our next Amp as one to "die for" ? Phew, maybe I should hunt down a vintage conrad-johnson MV-45a whilst hoping for another 3 Decades.


maybe we should consider this Amp's imaging as something: To Live For !!!

Dear Editor JA,

Your wonderful yet quirky reviewing twins have discovered 16 ohm output resistors. It seems that Nelson Pass has been informing your Staff. Steve & Herb are "to live for" .

Tony in Michigan

dalethorn's picture

No, it has to do with the hypocrisy of selling expensive gear and then decrying others who also like to enjoy the finer things of life.

Bogolu Haranath's picture

They tried twice and still couldn't get the measurements right ......... Let us wait another year or two and they may come out with Centaur III with better measurements :-) ...........

dalethorn's picture

Maybe we're missing the real quality here, blinded by "measurement". For example, what if the amp has a secret technology that reduces the power value in direct proportion to how it produces a purer cleaner more musical signal, but does so in such a way that the sense of dynamics is even more breathtaking than indicated in the review? That, or I just wrote the best ad copy this year.

Bogolu Haranath's picture

Constellation Audio thanks you for your support and free promotion. Centaur III is gonna be even better (sounding). They want repeat buyers :-) ..........

Anton's picture

Perhaps we are simply seeing the current paradigm of making up "alternative facts" and people being OK with that, and it's leaking into Hi Fi.

Constellation should call it a 2,000 watt per channel amp, the most powerful amplifier, ever. It is such a winning amp that audiophiles will get tired from all the sonic winning it does?

Bogolu Haranath's picture

Thank you JA for the measurements .......... Stereophile is the only hi-end magazine providing comprehensive measurements for audio equipment (so far) :-) ............

Axiom05's picture

A $55K amp and they can't warrant it for more than 3 years? Bryston gives a 20 year warranty, should be an industry standard.

tonykaz's picture

... Schiit outfit in California that makes all their gear in the USA! Phew!!

Tony in Michigan

ps. Zippo lighters all have a "Lifetime" warranty ( for gods sake ) and they seem to appreciate in Value as they get older.

Bogolu Haranath's picture

Those lighter guys know that those smokers don't live for long ......... So, no problem :-) ............

dalethorn's picture

I think Koss has a lifetime warranty on their headphones, and the plan seems to be that you eventually get tired of sending them in and just buy a replacement.

dalethorn's picture

Here the longest person who ever lived (to 122) smoked until she was 117. The reason she lived so long smoking is because she smoked Centaur cigarettes (rebranded Chesterfields actually), although due to copyright issues, Guinness doesn't mention the brand.

Herb Reichert's picture

In the 1990s, when I represented Kondo/AN Japan, their amps came with a lifetime parts and labor warranty - except tubes. We usually sold these amps with a back up set of NOS tubes. After 20 years, most owners have not touched the back up tubes.

steverman's picture

I wonder if those making the remarks have actually heard this amp. I heard it at a friends place and it sounded absolutely sublime. It didn't run hot actually. I thought it sounded like a Class A amp, but it never got hot. He was using it with a tube preamp, but it was the best amp I have heard at his home, and he's owned alot!

Anton's picture

It may sound great, so why lie?

allhifi's picture

I can't imagine I haven't replied to this abomination of a high-school tech project gone bad.

Constellation 'hack's' (including "supporter's" Harley & company) have absolutely no shame, dignity, design/construction capability, honesty, any sense of minimum quality standards nor craftsmanship, whatsoever.

This beyond laughable POS high-school failure of an excuse design- construction project is an unmistakable, unfathomable rip-off "project" that surely must have been designed as a joke to do nothing but 'poke-fun' at anyone who either raves of its "quality" -or god forbid, purchases it.

It's a piece-of-junk. Nothing more. Nothing less.

Comparing it to 'Lamm', 'Levinson', SimAudio, etc. should be detested by all readers and/or listener's who value engineering 'chops' and precision manufacture -both of which 'Crapellation' fails miserably. And shamelessly.

Unconscionable. UGLY. Figuratively. Literally.