Here's a single 35lb Emotiva XPA-1L "Gen 1" monoblock which I bought back in 2013, a few months after it was released. Far from the most expensive monoblock amplifier out there, costing a "mere" MSRP US$699 each:
Over the years, I have seen a couple of (p)reviews from Audioholics and The Poor Audiophile, but have not seen any independent measurements of the output quality.
From late 2014 until they discontinued this model (not sure when), Emotiva also made the "Gen 2" model which cosmetically looked slightly different with black instead of silver side trims. I believe internally they also made some changes which were more about cost-cutting than affecting the sound quality.
Remember that running in Class A makes the amplifier significantly more power hungry, hotter due to reduced efficiency with most of the energy dissipated as heat (~25% Class A efficiency vs. ~50% for Class AB). Consumers however have been told that Class A sounds "better" due to higher linearity without crossover distortion. We'll try to quantify that with this device.
I. Basic Amplifier CharacteristicsAmplifier Gain was measured as +35.1dB through the RCA input and 6dB lower at +29.1dB with the balanced XLR input. The manual states +29dB gain which must be referring to the balanced input.
Across the audible spectrum, the damping factor is at least 40x with an average of >80x across the 7 frequencies examined. Note that by the time one reaches a level of 100x+, slight variation on the voltage meter will result in huge swings (I've been using the oscilloscope to measure average RMS voltage). The high damping in the bass range will provide excellent control of woofers. Notice the drop after 1kHz. With this amount of damping, we should see excellent control of frequency response even with low-impedance speakers.
Here is the Frequency Response of the amplifier comparing a 4Ω load and the Sony SS-H1600 speaker I've been using as a comparator - range on the Y axis of this graph is only 4dB:
As expected, with the high damping factor, we see quite a smooth Sony bookshelf speaker curve. Notice that this amplifier tends to roll-off the high end (-2dB at 20kHz for 4Ω load) a bit more than the Onkyo receiver a couple weeks back. There's also a -0.2dB roll-off in the bass as well by 20Hz.
Here's what the Phase Response looks like compared to the frequency response across 4Ω:
II. Single-Tone Harmonic Distortion and Noise
As I mentioned above, this is a high power amplifier and indeed, at 31.6V/250W the amplifier is still producing output with better than -85dB/0.0056% THD+N. While not shown here, for those who might be curious, the 5W into 4Ω SINAD is 85dB.
So far, all of this is with the Class AB setting... What if we flip the switch into "Class A" mode as well for the THD+N vs. Voltage curve?
As you can see, I've overlaid a yellow curve (Class A) over the orange line (Class AB). We actually don't know with the Class AB setting at what point it transitions away from pure Class A - perhaps at most a handful of watts?
There's really little difference in THD+N whether it's in Class AB or the high bias Class A mode. Though small, somewhere around 6Vrms (~9W into 4Ω) seems to be the most notable THD+N difference.
Remember though, this is THD+N and the noise component can be getting in the way of the difference between the two settings; what if we just had a look at the harmonics themselves? Here are some Class AB vs. Class A mode THD+N spectra:
On the left, we see the 1kHz tone and spectrum at 5, 10, and 25W when the switch is set to "AB" mode and on the right is the "A" setting. Immediately I think we can appreciate that indeed harmonics are lower at 5W and 10W particularly but not much difference by 25W into 4Ω.
Despite this overall lowering of harmonics in Class A mode, which by the way is primarily a reduced 2nd harmonic, there is a price to pay. Notice how the 60Hz power-line hum and its harmonics have worsened at the "Class A" setting. Class A mode puts a significant demand on the power supply and this can be appreciated with the Kill-A-Watt meter - in Class AB mode, power draw is ~100W when idle while Class A mode sucks up much more power, about 220W when idle!
The bottom line is that "Class A" mode, despite claims which to some extent can be verified objectively as showing "improved" distortion results, creates other issues. In fact, we could argue that the power-related 60Hz harmonics take away any benefits one might hear. Furthermore, it's mainly just the 2nd order harmonic that is reduce while the 3rd order harmonic appears almost untouched.
In general, over the years I have not heard of any owners of this amp claim the ability to hear a large difference between AB and A mode. As far as I can tell, the "first watt" was always Class A already. Over the years of listening to this amp, I've been suspicious that this is what I'd find as I never really heard a difference either... Nice to be able to get the results and report on this after all these years; Class AB mode is IMO excellent already.
III. Multi-Tone Testing: Intermodulation Distortion and Triple-Tone TD+N
And here are the same IMD signals, 10V into 4Ω:
With a 2V signal, across the board with the IMD tones, we're seeing a low -80 to -86dB distortion and with 10V, the distortion is higher, ranging from -68 to -80dB. As a point of comparison, remember that the Onkyo TX-NR1009 "WRAT" AV receiver scored -60 to -80dB at 2V for these three IMD signals.
Here's the result from the "transient intermodulation" (TIM) distortion test looking at sidebands forming around a 12kHz sine tone situated within a 1kHz square wave. We can see that by 10V output level, there are a couple of sidebands sitting above -100dB. There's a bit more distortion here than what I found with the Onkyo receiver a few weeks back even at 14V. Comparatively, the Onkyo had more power-related spuriae down in the noise floor at 2V however.
As I discussed before, I'm just not convinced that the TIM result necessarily correlates to audible distortion given how extreme these test tones are compared to real music! Nonetheless this still is an interesting measurement to look at as a proxy for an amplifier's slew rate and potential "accuracy" of transients.
Finally, for the Triple-Tone Distortion and Noise measurement used in my AMOAR scoring system (in the Conclusion section), here's the TD+N at 2V and 10V into 4Ω:
2V TD+N result of -80.6dB. The TD+N increases to -76dB at 10V output.
As I demonstrated above in Section II, turning the switch over to "Class A" does have an effect with lowering THD. Here's the difference between "Class AB" and "Class A" for the TD+N at 6.32V into 4Ω:
An improvement in TD+N of -2dB for the Class A setting with lower distortion although there again seems to be a bit more low-level power supply related noise.
IV. Square Wave and Wideband Noise
Yup, we can easily see the double peaks at 5kHz and 93kHz (notice the roll-off of the 93kHz vs. 5kHz). Otherwise, nice and clean all the way up to 1.5MHz. Nothing to see here folks...
V. Impressions and Conclusions
|Updated... Made a mistake with the text colors and frequency response previously and shifted up to show more of the roll-off. Also, because I used the Douk Audio passive pre-amp to control volume, slight droop in bass and treble compensation added.|
If there is one acoustic characteristic I would have liked to be more "ideal", it would be the frequency response. Notice that this amplifier starts rolling off the high frequencies around 2kHz and by 20kHz, we're down at -2dB with a 4Ω load. While not ideal, this should still not be a problem in real-life listening and might even be desirable especially if you have tweeters that are a bit harsh above 10kHz or to tame metallic tweeters with resonance peaks. On this blog over the years, I've already seen this amp's tendency to roll off the treble years ago when I compared this amplifier against the Vitus Audio SS-010 in 2016; note that for those measurements, I had used an 8Ω power resistor.
The Class AB/A front switch is an example of an interesting feature that looks good for advertising material. It certainly differentiates this amplifier from others even within the Emotiva lineup. In practice, the amplifier already is excellent in Class AB mode (mature solid state technology after all!) and the difference, while measurable, is small and as far as I am concerned, inaudible. The only noticeable difference is the inefficiency in Class A mode with a hotter-running amp and about twice the power draw when idle - great for this time of the year when the basement is cool and Class A mode can help serve to warm up the room :-). It's also worth reminding everyone that even with that Vitus Audio amplifier mentioned above, turning the amp to Class A mode also made a slight improvement in distortion level but just like with this amplifier, nothing significant and IMO inaudible.
Subjectively, as they say, beauty is in the eyes of the beholder. She's rather flat, squat, isn't adorned with the prettiest face, but her voice is beautiful and she can belt out the tunes when needed :-). This amplifier sounds great especially if you have potentially harsh speakers, I suspect. Plenty of "microdynamic" details on account of low distortion and lots of "slam" when you need the oomph to drive louder passages. I was certainly impressed when I first got them noticing that I was able to turn the volume up louder than usual and not feel fatigued compared to a Denon AV receiver I was using for a number of years before. If I had heard anything objectionable, I would have changed the amps out years ago.
The Emotiva XPA-1L is a competent "hi-fi" monoblock power amplifier. At US$700 x 2 MSRP for a stereo pair when first released, performance wise, it's a nice example of a good modern high-power solid state Class AB amplifier. While it may look utilitarian, I know that the performance is clearly superior to some more expensive "audiophile" boutique brands (like the Vitus Audio SS-010).
To end off, let's talk about brand names for a second. I am also very happy with the performance of my Emotiva XSP-1 preamp by the way, and I see no reason to doubt the subjective and objective sound quality especially of their higher tier products. Over the years, I have run into audiophiles who seem to have negative impressions about the Emotiva brand name despite never having heard the products or have an impression that these are just meant to be for home theater use. An amplifier is an amplifier regardless of what the advertised target audience might be. The lower prices and good value certainly places Emotiva in the "budget brand" category and hence the lack of "snob value" will not appeal to certain magazines and writers more affected by the non-utilitarian aspects of luxury products than actual sound quality. I think it's important to consider the assumptions inherent among circles of traditional audiophile culture. There's nothing wrong with being discerning when one chooses a product, but it's important to consider if one is simply expressing undue discrimination without objective facts or a genuine attempt at unbiased subjective experience.
Inevitably, cultures change as younger participants enter the hobby and I think the relative value of brand names will shift with the different perspectives of the changing participants with their take on technology and economic sensibilities.
Not seeing much going on in the audiophile world this week; just the usual "best of" lists and more consumerism. End-of-year and people preparing to go off on holidays soon, I suppose.
A friend showed me some cool "trailer" music from Two Steps From Hell the other day, a production team that has created many interesting clips that one may have heard especially in the background of movie trailers but unaware of the source. Anyhow, it has been fun listening to stuff on Invincible (2010), and Archangel (2011) this past week. Recommended for a listen if you find this kind of music exciting, majestic and "inspiring". That's of course interspersed with some Christmas albums playing around the house like the gleeful Lea Michele's Christmas In The City (2019) which my wife likes and my pick - A Blackheart Christmas - depending on mood and company ;-).
Hope you're enjoying the month and the music!