Emotiva XPA Gen3 two-channel power amplifier Measurements

Sidebar 3: Measurements

I measured the two-channel version of the Emotiva XPA Gen3 with my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Before performing any tests, I ran it at 100Wpc into 8 ohms for an hour. (With a class-AB or -B amplifier, one-third full power is when the heat dissipation in the output devices is at its maximum.) At the end of that time, the louvers on the top panel above the two circuit boards were hot, at 134.4°F (56.9°C), though the rest of the exterior case was cooler. This may be an inexpensive amplifier, but it has adequate heatsinking for its power rating, though this might be due to the fact that the case can hold up to seven amplification modules rather than the two of our review sample.

The gain at the loudspeaker terminals for both balanced and unbalanced inputs was 29.4dB, and while the output preserved absolute polarity (ie, was non-inverting) for the unbalanced input, the balanced input inverted polarity, suggesting that the XLR jacks are wired with pin 2 cold, the opposite of the modern convention. The balanced input impedance was moderately high, at 27.5k ohms; the unbalanced input impedance was 14.5k ohms at low and middle frequencies, dropping to 9.5k ohms at the top of the audioband.

The output impedance, including the series resistance of the speaker cables I used, was very low at 20Hz and 1kHz, at 0.09 ohm, and rose only slightly at 20kHz, to 0.125 ohm. As a result, the response with our standard simulated loudspeaker varied by just ±0.1dB (fig.1, gray trace). Fig.1 shows that the response into 8 ohms (blue and red traces) starts to roll off at the top of the audioband, with the output reaching –0.3dB at 20kHz and –3dB at 70kHz. The response rolled off only slightly earlier into lower impedances, reaching –0.5dB at 20kHz into 2 ohms (green trace). The Emotiva's reproduction of a 10kHz squarewave was very good (fig.2), with no overshoot or ringing.

817Emotivafig01.jpg

Fig.1 Emotiva XPA Gen3, 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) (0.5dB/vertical div.).

817Emotivafig02.jpg

Fig.2 Emotiva XPA Gen3, small-signal, 10kHz squarewave into 8 ohms.

Channel separation (not shown) was good rather than great, at 75dB or so from 20Hz to 5kHz, decreasing slightly to 67dB at the top of the audioband. The unweighted, wideband signal/noise ratio, taken with the unbalanced inputs shorted to ground, was good at 70.5dB left and 69.3dB right, both ratios ref. 1W into 8 ohms. Limiting the measurement bandwidth to the audioband improved these respective ratios to a superb 95 and 93.9dB, while an A-weighting filter offered further improvement, to 99 and 98dB. The spectrum of the XPA Gen3's low-frequency noise floor while it drove a 1kHz tone at 1W into 8 ohms is shown in fig.3. Other than some very low-level spuriae at 60Hz and its odd-order harmonics in the left channel, the XPA's noise floor is very clean.

817Emotivafig03.jpg

Fig.3 Emotiva XPA Gen3, spectrum of 1kHz sinewave, DC–1kHz, at 1W into 8 ohms (linear frequency scale).

Specified as delivering 300Wpc into 8 ohms (24.8dBW) or 550Wpc into 4 ohms (24.4dBW), the XPA Gen3 clipped at 315Wpc into 8 ohms (25dBW) (fig.4), and at 520Wpc into 4 ohms (24.15dBW) (fig.5), both readings taken with both channels driven. Looking at how the percentage of THD+noise varied with frequency at a moderately high level (20V, equivalent to 50W into 8 ohms and 100W into 4 ohms), the THD+N remained low at low and middle frequencies, and was even slightly lower in the low treble (fig.6). However, as can be seen in this graph, the percentage starts to rise in the mid-treble before climbing precipitously above 15kHz, exceeding 1% at 20kHz. All I can think of to explain this behavior is that the circuit has limited open-loop bandwidth, meaning that there is insufficient corrective negative feedback available at the top of the audioband.

817Emotivafig04.jpg

Fig.4 Emotiva XPA Gen3, distortion (%) vs 1kHz continuous output power into 8 ohms.

817Emotivafig05.jpg

Fig.5 Emotiva XPA Gen3, distortion (%) vs 1kHz continuous output power into 4 ohms.

817Emotivafig06.jpg

Fig.6 Emotiva XPA Gen3, THD+N (%) vs frequency at 20V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta).

At lower frequencies and moderate powers, the distortion signature is predominantly the third harmonic (fig.7). Though they can't be seen in the graph, there are small spikes surrounding each positive and negative waveform peak; ie, four per cycle, that could be seen on an analog 'scope. I have no idea where these spikes come from, unless they are related to the class-H voltage rail switching. At high powers, the third harmonic is joined by higher-order odd harmonics, as well as by the second and fourth harmonics (fig.8), though these are all very low in level.

817Emotivafig07.jpg

Fig.7 Emotiva XPA Gen3, 1kHz waveform at 50W into 8 ohms, 0.0082% THD+N (top); distortion and noise waveform with fundamental notched out (bottom, not to scale).

817Emotivafig08.jpg

Fig.8 Emotiva XPA Gen3, spectrum of 50Hz sinewave, DC–1kHz, at 200W into 4 ohms (linear frequency scale).

I usually test an amplifier for intermodulation distortion by driving it at a high power with an equal mix of 19 and 20kHz tones, which is very much the worst case. Given the dramatic rise in THD at the top of the audioband in fig.6, I was not surprised to find that the Emotiva XPA Gen3 did very poorly on this test. Fig.9 reveals a picket fence of intermodulation products, with the second-order difference product at 1kHz lying at –33dB (2%) ref. the waveform's peak level. Reducing the level to 1W (fig.10) eliminated the difference product, but many higher-order intermodulation products are still present, the highest in level lying at –66dB (0.06%). I repeated the 100W test with an equal mix of tones and octave lower (fig.11); though high-order intermodulation products can still be seen, these all now lie at or below –80dB (0.01%).

817Emotivafig09.jpg

Fig.9 Emotiva XPA Gen3, HF intermodulation spectrum, DC–24kHz, 19+20kHz at 100W peak into 8 ohms (linear frequency scale).

817Emotivafig10.jpg

Fig.10 Emotiva XPA Gen3, HF intermodulation spectrum, DC–24kHz, 19+20kHz at 1W peak into 8 ohms (linear frequency scale).

817Emotivafig11.jpg

Fig.11 Emotiva XPA Gen3, HF intermodulation spectrum, DC–24kHz, 9+10kHz at 100W peak into 8 ohms (linear frequency scale).

Emotiva's XPA Gen3 amplifier offers high powers with low levels of noise and distortion, at least at frequencies below 10kHz, at a very affordable price. But the amplifier's problems at the top of the audioband bother me. Predicting the subjective effect of this objective behavior is probably an exercise in futility, but I do wonder if it correlates with Herb's finding that the Emotiva sounded "hard and 100% masculine" through two of the speakers he tried with it.—John Atkinson

COMPANY INFO
Emotiva Audio Corporation
135 SE Parkway Court
Franklin, TN 37064
(877) 366-8324
ARTICLE CONTENTS

COMMENTS
mrkaic's picture

"I don't want to embarrass my friend, so in this story I will call him O., for Mr. Objectivity."

You should be proud of your friend. His is the correct way of assessing audio equipment. If measurements are bad, ditch the stuff!

rorie's picture

Audio equipment is for listening to dude. Measurements matter only when you measure the right stuff, and we haven't figured out all the right stuff to measure yet and likely the right tools haven't even been invented yet

Glotz's picture

Measurements only tell us what we want them to tell us.

I am sure there are measurements that will effectively tell the whole picture someday. Until then, they simply reward preconception and bias. I wonder what each of the reviewers would write knowing what the measurements were ahead of time. I surmise the most brave and honest would not flinch in the least (notably MF and AD).

I think if every review were given the small side-bar of writing space and the brunt of the article devoted to measurements, there would a fraction of the readership.

'Stereophiles' will never get excited about how a component measures- only how it sounds. 'Sterophile' as a lover a stereo is still the best definition, incidentally.

a.wayne's picture

Hello ,

That's a pretty ignorant position , listening and measuring occupies two distinct positions, both are required when making a decision .

Regards

Anton's picture

I love these discussions.

Interesting, to me, almost all the 'objectivists' I know shop by listening to gear. Do you just check the specs?

What comprises your system?

Probably most interesting would be how you choose speakers. I find I can only do it by listening, which, of course, renders me a pitiful subjectivist.

mrkaic's picture

Your second sentence is not an example of clear writing :)) But I'm doing my best to decode and answer it.

Yes, I mostly just check the specs. What else is to do there? Do studio engineers indulge in auditions to see what distortions they prefer or do they just go for the most accurate gear? You should do the same. I know I do.

I choose speakers based on measurements and budget (of course). Sometimes I listen to them, but find such "auditioning" to be an almost complete waste of time. Speakers sound different when you move them from the showroom to your listening room anyway. If you are serious, you will need to measure your room and reprocess the source music anyway. Start with speakers with a reasonably flat response curve and fix them with equalizers.

Anton's picture

I must have made a typo on shop and Spellcheck changed it to should!

Robin Landseadel's picture

"Do studio engineers indulge in auditions to see what distortions they prefer or do they just go for the most accurate gear?"

They go for the distortions they can live with. I recall a session at Skywalker, WATTS were on hand to demonstrate the inherent limitations of the 16 bit recordings we were making. The Head engineer decided on some British Mini-Monitors he was used to, the WATTS were distracting in comparison.

Les's picture

I hope then you are praying for JA's continued good health... Apart from a certain German magazine (that does a bit of measuring), I don't know a single other magazine that shows such a comprehensive set of measurements. I'm not an objectivist, but even I enjoy reading them.

These are the good ol' days...

mrkaic's picture

I am totally grateful for his measurements. For example, I traded in a pair of NEAT speakers after reading one of his his reviews. If a manufacturer produces even a single piece of gear that does not measure well, I refuse to buy ANYTHING from that manufacturer.

a.wayne's picture

+10

mrkaic's picture

1. Micromega M-One + Focal Aria 936
2. Quad VA-One + Quad S1 (BTW, this amplifier is great if you like to measure gear -- and you should give measuring gear a try. That way you will know that they have not snookered you with a bad output transformer.)
3. O2 Headphone Amplifier + Philips Fidelio X2

And yours?

Archimago's picture

"Probably most interesting would be how you choose speakers. I find I can only do it by listening, which, of course, renders me a pitiful subjectivist."

That's not true. You can certainly have an objective viewpoint without running your own measurements.

IMO objectivism is simply an acknowledgement that there are factors which can be elucidated and judged regardless of individual preferences and psychological mechanisms.

- Is a speaker capable of reproducing the frequency from 20Hz to 20kHz?
- Is a DAC truly hi-res and able of >16-bit dynamic range?
- How many watts can that amplifier produce cleanly?
- What is the nature of the time domain step response for that speaker?

An objectivist I think tries to understand this stuff and incorporates that understanding in determining whether the product is worth the money. Some things are hard to do - eg. frequency response flat to 20Hz so if objectively a speaker can do this well, then I'd be happy to spend more money for example...

This is why I appreciate the value of Stereophile - that despite the arguments and debates, as a magazine it does try to incorporate the subjective and objective elements in a review.

mrkaic's picture

I am still waiting for you to list your components...

Anton's picture

Open baffle Lowther-based horns. (I don't like box resonances nor crossovers.)

McIntosh 275 amps in mono configuration.

ModWright SWL 9.0 Anniversary Edition pre amp

ModWright PH 150 phone preamp.

Sony PS X800 turntable, rechipped (!) with Clearaudio Maestro 2 cartridges.

Michell Gyrodeck, 1985, Pabst motor, Zeta Van Den Hul arm and Shure V-15 5 MR 'needle.'

Technics SL 1200 GAE with Charisma Reference 2 cartridge (I like vinyls.)

Esoteric DV 50 S digital player thing.

(I am playing with an IFi Micro 2, I think it is, for the Michell table. man, it is amazing for the price.)

_

I other rooms, I like various things.

I like to listen to how different gear sounds, so I rotate things in and out.

Current joy in a very small loft is a pair of Infinity Intermezzo 2.6 speakers (300 bucks, used) driven by an SMSL 160 (99 bucks from Amazon) and an Oppo UDP 205. A pair of Audioquest silver interconnects (o.5 meters via HCM Audio) and some home brew speaker cables. It sings. I wish we could post pics.

My M-I-L lives with us and in her apartment is a Yamaha C-4 preamp, M-4 amp, and NS 1000 speakers, with a Marantz SACD player from about 7 years ago.

Lastly, family hang out room. Marantz CD-SACD changer, also about 7 years old and drawer motor is dying so soon to be replaced. To Krel KAV 300i integrated to Cerwin Vega XLS 215...which I adore.

When we finish our basement, I have some fun stuff ready to go, hopefully 2018!

Cheers, and apologies for not checking back.

mrkaic's picture

You have some very nice gear!

I am also thinking about getting the MC275, but would not use it in mono--too expensive, you need two.

No need to apologize, we all have other things to do, not just audio.

Best,

MM

mrkaic's picture

"Measurements matter only when you measure the right stuff, and we haven't figured out all the right stuff to measure yet and likely the right tools haven't even been invented yet"

How do you know this? Can you recommend any peer reviewed studies?

Anton's picture

For many things, an "N" of one is powerful enough to determine whether or not a hypothesis is valid.

Example: I hypothesize that stepping in front of an oncoming train is dangerous. How many trials are necessary before my data qualifies as valid?

So, if I listen to a piece of gear and say I like it, or not, why on earth would you want to insist I have a peer reviewed validation of my opinion?

You can't take my word for it that I prefer one thing over another?

With regard to Mr. O, did you notice how he reached his conclusions about all the different gear? Yup, subjectively. Inside every 'O' is an 'S' who is repressed.

Herb Reichert's picture

my reports for Stereophile ARE "peer reviewed studies"

Glotz's picture

in the start of your review, but then was annoyed when caught out in his own act of 'lying' to himself about the sound. (By 'lying', I mean trusting ones' own preferences, rather than challenging ones' audio value-system consistently.)

There were huge flaws that you heard, but only until you brought them to his attention, did he admit that this system was flawed.

His possible bias (about money dumped on the system and it's 'inherent' performance expectations) is much like a bias about measurements. It encouraged a bias that was proven wrong when one further defines and explores what one heard (and confounds as well... if this expensive system measures well, and was reviewed well, what gives?? Set-up, synergy and component matching...)

I have heard some really crappy $100,000 system demos (with very well reviewed components) in the past that my cohorts admit after challenging them; that it too, was a poorly-set up and performing system with major issues, after they got past the price-tag demanding such 'admiration' from the casual listener.

Proof that a review needs more than a few hours of listening, and how 'peer reviewed' input can assist in breaking bias. I think the same holds true for measurement assumptions.

One draws assumptions by analyzing measurements and only when the review and the data coincide do they provide meaningful insight into a component's sound. When they differ, head-scratching always follows (and doubt from those that don't trust their ears first).

(Yes, I heard you this month and I do agree about attention as a concept, and personally, I try to challenge my own attention 'requirements' at every critical listening opportunity possible for many years. Without that, how I am learning about my own system?)

(All audio purchases require a return policy from a trusted audio dealer that will allow the true nature of the component- in our own system- to shine through, and give us recourse when it does not fit our long-term attention.)

AD and Herb have brought the concept of 'Force' to the minds of many readers... and reviewers! Kudos again to both reviews. Very thought-provoking and extremely important to the study of our hobby.

mrkaic's picture

I think we have a different interpretations of "peer review". In science, your peers can ask you to update/improve your papers. They can also reject your submissions. I don't think that anyone has the courage or clout to reject your reviews :)

rorie's picture

@ mrkaic : Are you asking for specific peer reviewed studies that look at exactly what i wrote...or would pointing you to the IEEE site where you can for yourself search the number of new measurements techniques, methodologies and "tools" created over the last 5, 10, 15 , 20, 30, or 40 years be enough to extrapolate the very essence of my meaning. Alternatively if you are a member of the American Association for the Advancement of Science (AAAS), you could do the same there. The point being that if one has an applied science or science background one should know that research is continuous and furthermore these fields have advanced beyond what I would have imagined when I graduated in the 1980's. Spend some time perusing the fields of nanotechnology and spintronics to get an understanding of where we are headed. Good luck, its actually fun and fascinating.

mrkaic's picture

I can do the search, but you seem very knowledgeable about these things. If you can provide a few links, it would be great.

romath's picture

@mrkaic
"Measurements matter only when you measure the right stuff, and we haven't figured out all the right stuff to measure yet and likely the right tools haven't even been invented yet"

How do you know this? Can you recommend any peer reviewed studies?

----------

LOL! Nice one. Now, back to sanity...

mrkaic's picture

Assessing audio is not equivalent to stepping before a running train. Yours is a bad analogy.

ToeJam's picture

I like the idea that the person paying for the purchase determines the decision criteria. Humans are a highly subjective species.

Emotiva is about value. There are many among us who's budget is Class H, and to find Class B sound at Class H prices is a home run! Thanks for the review!

corrective_unconscious's picture

I believe Class B is considered to be inferior. Perhaps you meant Class AB. Maybe Emotiva would prefer to present its own value claims.... lol

ToeJam's picture

In this context, Class B and Class H refer to the classification within Stereophile's Recommended Components list. Meaning this Emotiva warrants a performance designation of Class B and a cost measurement of Class H. By definition, that's value!

corrective_unconscious's picture

There is no Class H in the "Stereophile" Recommended Components universe. There are Class H amplifier topologies - I believe it means one thing in the US and another in the UK. My wry comment stands.

ToeJam's picture

In all my prior comments I referenced Class H, but I meant Class K. So, what I literally said was rubbish as you wittily pointed out. I meant to say Class K - "keep an eye out" (my paraphrasing), which is not the best analogy either (Class B for Class K).

I only meant so say, Class B performance for not a lot of money, and I failed miserably!

corrective_unconscious's picture

It can be mildly amusing when people accidentally say the opposite of what they intended. Except when I do it. In those cases a neurologist should probably be summoned.

tonykaz's picture

Emotiva has been exciting.

Now, Schiit has it's 400W. Mono Amp for $699.

During my Retail Days, I ( we ) favored Electrocompaniet Mono Amps., back then I'd be paying $2,000 each.

Now, we can have the Emotiva for $1,000 ... or a pair of Schiit Mono's for $1,400. Phew.

Schiit has Audiophiles loving them ( like me ), Emotiva is Pro stuff finding it's way into living rooms.

I'm a Left Coast leaner rather than an Elephant leaning Tobacco Country loving person. ( I just quit Smoking so I'm now a Tobacco Apostate ! )

Still, Schiit has that Shitty Name. My Minister Wife won't tolerate potty naming stuff or potty humor. Schiit should be Stoddard & Moffat Inc.

Schiit has that 4 ea 6SN7 PreAmp for $699. ( aren't 6SN7s the Kings of PreAmp Tube-ology? )

The Full Schiits would be $2,100 with their Big DAC adding $2,500 making the total of $4,600.

Can a Trustworthy Stereophile person ( HR ) pllllllleeeezzzzzeeee tell us what to do?, which way to turn?, what to believe?

What HI-Fi?

Thanks,

Tony in Michigan

ps. With Baited Breaths, I wait, impatiently, for the story about the Manhattan DAC - I'm spitting out those dam worms, petueee!

mrkaic's picture

...and assemble a superb amplifier yourself.

tonykaz's picture

Thanks for the tip, Mrkaic.

I could agree with that type of thing except I seem to prefer Brand Name stuff to the junk I create with a soldering iron and a box of parts.

I don't even work on my Wife's Car.

I built Ham Radio Stations, back in the 1950s, till I could afford the Good Gear, then I owned Collins stuff.

I understand that the Recording Engineers will build and maintain their own electronics.

Now-a-days I like the shinny lights of CHORD stuff and the polished performance of well designed gear.

Thanks for mentioning Hypex.

Tony in Michigan

Anton's picture

I didn't know it was out and will try to find a way to hear it!

tonykaz's picture

Geez, we're able to have some pretty darn-good Music Systems for 1985 Era Money.

A CHORD Hugo2 + some Genelec 8020s w/Sub for $3,500

A Full Schiit System + some Magnapans for $6,500

A PrimaLuna System with nice Speakers for well under $10,000

Back in 1985, a Full Electrocompaniet System, a VPI Table/Arm/Koetsu + a Pair of Thiel CS3s w/MH750 Cables would Retail-out for $10,000.

I don't quite know if the Loudspeakers are any better now than 30 years ago but I'm feeling like the Electronics are better and lower priced, plus they don't have to cope with low signal sources like phono cartridges.

It's a great time to be an "Audiophile" or a "Stereophile" or simply a gear buying "Music Lover" ( like me ).

Tony in Michigan

adrianIII's picture

Stoddard & Moffat Inc. = S&M???

a.wayne's picture

Have you heard the Vidar ..... ?

Anton's picture

People, Herb is O!!!

Herb is Tyler Durden!

I reread the review and O stands out like Patty Lane, or is O Cathy Lane!?!?!

siouxiebuff's picture

Ofcourse listening impressions are the most important as the amps are for listening to music. Here the threshold of hearing v.s. distorsion is paramount.
Anyways, its remarkable that amps designed with todays tools and components are no better than amps from the eighties. Quality of design doesn't seem to be a priority nowadays.

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