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Emotiva BasX A-500 5-ch Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Emotiva BasX series A-500 five channel home theater amplifier. It is on kind loan from a member. The A-500 costs US $529 which seems reasonable given the functionality and ratings.

I can't say that I find the A-500 attractive but is not ugly either:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Audio Review.jpg

Here is the connectivity which sadly does not include balanced XLR connections:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Back Panel Audio Review.png
This is a Class AB amplifier with a rather larger toroidal transformer. It is not overly heavy though which my back appreciated.

The heatsinks end well below the top of the case so it was hard to judge how warm it got by touching the case. A quick test with IR temperature sensor showed the heatsinks running around 50 degrees C.

In use the A-500 never complained, shut down or go into thermal protection. This is nice benefit over the delicate amplifiers in AVRs which if you look at them wrong, they go into protection/shut down. Clearly this is much more robust solution.

Amplifier Audio Measurements
As usual, we start with our dashboard of 1 kHz tone into 4 ohm load at 5 watts output:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Audio Measurements.png


I was surprised by two things: large channel disparity with respect to distortion (SINAD) and very high mains hum at 60 Hz. No amount of playing with grounding fixed the latter which tells me the 60 Hz is probably induced from the transformer into the amplifier section. The former, channel distortion parity varied with which channel you used. Channels 1, 2 and 4 were very close and good. Channels 3 and 5 lagged way behind.

The "good channels" had their SINAD actually dominated by that mains hum and power supply noise, not distortion (red channel). The situation was reversed for the "bad channels."

Averaging all the channels we get a middle of the road score:

Best Home Theater Multi Channel Amplifier.png


Signal to noise ratio reflected the above issue with a-weighting resulting in substantial improvement of SNR:
Emotiva BasX A-500 Five Channel Home Theater SNR Amplifier Audio Measurements.png


Our threshold of heaving in low frequencies is quite high so this is not as big of a problem audibly as it is in measurements.

Frequency response was very good, almost ruler flat in audible band and going beyond 100 kHz at -3 dB:

Emotiva BasX A-500 Five Channel Home Theater Amplifier Regulated Power into 4 ohm Audio Measur...png


Crosstalk between channels 1 and 4 were rather disappointing:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Crosstalk Audio Measurements.png


It is closer to a $29 amplifier than our state of the art Benchmark AHB2.

The meat of the review is power measurements versus distortion. So let's get into that at 8 ohms:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Power into 8 ohm Audio Measurements.png


Nice to see the massive improvement relative to a higher end AVR (NAD T758) but as soon as distortion takes over, that advantage is sadly lost. We do get a few more watts though than our AVR.

Here is the same measurement with 4 ohm load:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Power into 4 ohm Audio Measurements.png


Let's sweep from 20 kHz to 20 Hz and see how much power we get with THD+N set to 0.1% (barely or not audible distortion):
Emotiva BasX A-500 Five Channel Home Theater Amplifier Regulated Power into 4 ohm Audio Measur...png


We see a small drop in power at the extremes which is good.

Some of you have been demanding that I work harder and measure performance with more than two channels. So here you go:
Emotiva BasX A-500 Five Channel Home Theater Amplifier Regulated Power into 4 ohm 2 to 4 chann...png


I could not get the amplifier to distort less than 0.1% with 4 channels regardless of output level. So I stepped that up to 0.2% to get the third graph. I could have been watching a movie instead of running these extra tests so I hope you are happy!

Conclusions
The Emotiva BasX A-500 seems to be a decent shot at building a 5 channel amplifier for a very decent price. Yes, it is a bit of a gamble how good each channel is, and how audible that mains hum can become. Other than that, it is a definite step up very amplifiers in AVRs.

Overall I can recommend the A-500 if you are on a budget and have a bad back stopping you from lifting something heavier.

--------
As always, questions, comments, corrections, etc. are welcome.

Do you work on weekends? I didn't think so. As you see, I am working, having produced two reviews instead of enjoying the last bit of sunshine we are having. So please, reach deep in your pocket and empty every dollar you have in my coffers using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

amirm

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#2
Ah, just realized there are two little fans in there:



There is no safety ground in the IEC socket. I measure 10 ohms between the chassis and RCA shield. That may allow some mains current to travel in the case and couple into the amps.
 

Tks

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#3
Hey bossman, what's up with companies using so many parts that always contribute to such bad mains performance? Do they even measure this stuff? I know companies will sometimes make their own custom amps and such, but why are so many complimented with such meh power supplies?

Also what's up with some of these pretty bad grounding practices? Are the methods simply not taught to people in electrical engineering?
 

amirm

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#4
Well, architecturally unbalanced/RCA is a broken system. That connection was invented by RCA to be in the same cabinet, not between two pieces of gear externally. Can't believe so many decades later we are still using it.

Beyond the RCA, some companies cheat and use floating AC supplies and such to get around mains leakage. I don't do that but do play around to see if I can reduce the impact.

Worst part of this is that what you get may not match what I get.

As to your final question, no, it is not taught at all in engineering school. Engineering students learn the basics (Maxwell equations) but promptly forget them as they have no connection to real life circuit then. The number of people who know these issues is a small fraction of designers out there. You are dealing with what you don't see, rather than what you see.
 

digicidal

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#6
Seems consistent with most Emotiva products I've used... decent build quality, mediocre (but acceptable) performance, but a great price-per-watt/channel for tried and true designs. I don't really see anything wrong with that, in fact - it's sorely lacking in the amplifier market IMO. Unless it's from their highest-bracket gear, I don't see myself looking to them for my main system again... but for occasional use (office, guest room, vacation home setup, etc.) it's pretty great stuff for not much money at all. Other than Outlaw, few alternatives exist within these budget constraints.

Push it up a few hundred dollars per channel though, and there would be very little to get excited about here.
 

Rja4000

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#7
There is no safety ground in the IEC socket.
Is that box CE compliant?
No chassis grounding look like a safety risk, isn't it?
Dumb question: is it possible to just replace the mains connector by one with ground, then connect ground to chassis and would that improve anything?
 

digicidal

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#8
Is that box CE compliant?
No chassis grounding look like a safety risk, isn't it?
Dumb question: is it possible to just connect ground to chassis and would that improve anything?
It's a 2 pin connection (see the IEC socket on the back in the photo) - like most of their stuff. So there's not an actual connection to ground to attach in the first place.
 
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Rja4000

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#9
It's a 2 pin connection (see the IEC socket on the back in the photo) - like most of there stuff. So there's not an actual connection to ground to attach in the first place.
Just seen that. I changed my post.

Over here in EU, most amps have grounded plug.
Typically, you find C6-C7 for low power (no ground, 2.5A max) and C13-C14 for any serious amp (grounded). (CEI 60320-1)
 
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amirm

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#10
Is that box CE compliant?
It has the mark on the back and Emotiva is big enough fish that they won't risk being out of compliance.

No chassis grounding look like a safety risk, isn't it?
It is the same as other Emotiva products I have examined. In my book it is not safe. A hot lead could come loose and touch the case. Then, anodization is the only thing protecting you. It doesn't look to me that it is compliant with Class II for double insulation. Yet that is the symbol it has (a square inside another) on the back.
 

digicidal

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#11
I've often wondered about that. I know that it technically can be done (vacuums and hair dryers are high-wattage applications that are rarely grounded either) but it seems to be a rather odd choice. Almost as if their engineers don't know how (or don't want) to design for it? :confused:
 
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#12
The innards look identical to the UPA-500s I use to power my Linkwitz LX521.4s. We did drive these into thermal shutdown when testing how loud the LX521.4s could play. The SPL level was extremely high and did not represent normal listening conditions. Presumably the fans were running but inaudible!

I'm in the closing stages of building replacement amplifiers using a mixture of Neurochrome and Hypex modules which will provide better performance.
 
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#13
There is no safety ground in the IEC socket. I measure 10 ohms between the chassis and RCA shield. That may allow some mains current to travel in the case and couple into the amps.
It seems to me that retrofitting an IEC socket with RF/EMI filter and a ground cable is fairly straightforward. The sockets go for around $3.50 and it's a relatively low-risk operation. I wonder if there's anything to be gained from that.

I think as far as amplifier quality goes, it's ok at ~$100.-/channel, especially if you have some sensitive speakers and mostly run around 10W. But if you already own an AVR, I'd rather spend $500.- on a stereo amplifier for the fronts and music and leave the smaller effect-channels to the AVR.
 

somebodyelse

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#14
Is that box CE compliant?
No chassis grounding look like a safety risk, isn't it?
Dumb question: is it possible to just replace the mains connector by one with ground, then connect ground to chassis and would that improve anything?
It'll be double insulated (IEC Class II) and the label will have a symbol for it (square inside a square). The idea is that you'd need 2 separate insulation failures in the same place before the case became live. Some countries don't (or didn't) require earth at their mains outlets, so you couldn't always rely on earthing the case.
 
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#16
Interesting! It's not a step up from the Denon AVR X3500 amplification! If it wasn't for the poor DAC...
In the same price range of this Emotiva, what is a good preprocessor?

P.S.: in Europe Emotiva stuff costs much more! Ouch!
 

garbulky

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#18
Thanks for the review. Glad to see some Emotiva gear being reviewed.
I noticed a lot of gear with torroids appear to exhibit hum on your test. Have you tested your own power and are you willing to show the measurements?
Anyway, it looks about what I expected for the A-300. (note: No dbt tests, subjective impressions) I've heard it numerous times on various speakers. The sound (to me) is nothing objectionable but it's also not something to write home about. I didn't hear any hiss or hum or anything. I found myself preferring my old Emotiva UPA-2 over this one which was its immediate replacement. On the positive side, I thought this one sounded more natural than their XPA-2 gen 3 amp.
I would pick the Emotiva PA-1 and my current amp (XPPA-1 gen 2) over this any day in terms of how it sounds.
@amirm you're right about it being hard to distort. I remember accidentally plugging in my UPA-2 directly in to a line output - no attenuation, max volume. The amp bought the house down as I struggled to turn it down. However it did not show noticeable clippiong distortion and my speakers were unharmed.
 
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#19
Some of you have been demanding that I work harder and measure performance with more than two channels. So here you go:
View attachment 40177

I could not get the amplifier to distort less than 0.1% with 4 channels regardless of output level. So I stepped that up to 0.2% to get the third graph. I could have been watching a movie instead of running these extra tests so I hope you are happy!
Guilty as charged, m'lud! :D

Thanks for doing this Amir, much appreciated.

Is this latest version of what I think is Emotiva's entry level 5 channel amp a much cheaper version (build wise, not price wise) than their original entry level model the UPA-5. Although power wise there seems to be little difference. The new one is certainly much lighter!

emotiva-upa-5-power-amplifier-inside-chassis-large.jpg

I have several 7-8 channel power amps from different manufacturer's and the large toroids all make some mechanical noise - but no hum through the speakers. In contrast my Hypex based multi-channel amp is dead quiet. It would be interesting to see how a Hypex (or Ice-power based) multi-channel amp would compare, especially when it comes to heat generation, crosstalk or any other potential channel to channel issues.
 

Matias

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#20
"Ultra Low Noise" transformer... Imagine how it would measure with a noisy one. ;)
 
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