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Emotiva BasX A-100 Review (stereo amplifier)

amirm

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#1
This is a review and detailed measurements of BasX A-100 Class AB amplifier. It was kindly purchased by a member and drop shipped to me for testing. The A-100 costs US $229 from the company direct.

I must stay, this is one gorgeous looking and nicely feeling amplifier:

Emotiva BasX A-100 Review Amplifier.jpg


This is a deep cabinet ending in the terminals in the back:

Emotiva BasX A-100 Review class AB Amplifier.jpg


As you see it has trigger capability. Not a fan of the figure 8 AC mains cable as I have very few of them. Best to not lose it.

There is a fan on top but I did not hear it come on. The unit does get quite warm though so allow ample cooling/space above it.

Emotiva BasX A-100 Measurements
Another member had contacted me asking me if I could test if the unit was distorted while cold. I had stopped testing for this since the warm up effect has been so minimal. Not so here:

Emotiva BasX A-100 Measurements Amplifier Warm up.png


You see what I am seeing? 12 dB improvement in distortion after 5 minutes??? I am assuming bias is not optimal while cold but why? Temperature compensation is quite cheap and has been part of design of amplifiers forever.

Anyway, here is our usual dashboard:
Emotiva BasX A-100 Measurements Amplifier.png


Not happy about the channel gain difference. As it is, performance is a bit below average:
best budget amplifier review 2021.png


I like to see a dynamic range at 5 watt approaching 96 dB and we are fair bit short of that:
Emotiva BasX A-100 Measurements Amplifier SNR.png


Frequency response is flat enough:

Emotiva BasX A-100 Measurements Amplifier Frequency Response.png


Crosstalk is pretty good for a budget amp:
Emotiva BasX A-100 Measurements Amplifier Crosstalk.png


Here is the multitone:
Emotiva BasX A-100 Measurements Multitone Amplifier.png


Power versus distortion+noise is good:
Emotiva BasX A-100 Measurements Power into 4 ohm Amplifier.png


Emotiva BasX A-100 Measurements Power into 8 ohm Amplifier.png


If we allow 1% THD, we get the power spec from the company:

Emotiva BasX A-100 Measurements Peak and Max Power into 4 ohm Amplifier.png


Distortion characteristic has a simple relationship with frequency and that is it:

Emotiva BasX A-100 Measurements Power into 4 ohm vs frequency and distortion Amplifier.png


Conclusion
I really like the packaging and price of this amplifier. While overall performance is good, having to wait 6 minutes before it stabilizes is just not acceptable. I would be tempted to buy this and mod it to make it temperature stable.

As is, I can't recommend the Emotiva BasX A-100 amplifier.

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

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Blumlein 88

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#2
Hoped you would also test the headphone output. This is like old school receivers that just tap the output for the headphone thru some resistors. Not that such a thing is great, but for some perspective into how such an arrangement performs as a headphone amp.

They also have a jumper to allow direct Power amp output to headphone without the resistors in place which might be even more interesting. I know the peformance otherwise isn't much to right home about, but you really only test half of what some people buy this amp for in general.

Also the lack of temperature compensation in this day and age, just makes me think it is another half-a** design from Emotiva. They really seem to always take advantage of people cheaping out on some aspect everyone takes for granted in designs.
 
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#4
stupid but serious question, coming from headphones and now exploring loudspeakers.

with this kind of amplifier, how do I connect a sub. both passive and active?
 

respice finem

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#5
If you have a passive sub with hi-pass sat speaker outs (rare these days), quite simply to the speaker outputs of the amp, and the sat speakers to the sub's sat outs. An active sub can be connected (depending on its design) with either a Y-cable or L+R RCA to the RCA output. Having an active sub and passive sat speakers, you will get some delay on the sub side. That said, I wouldn't be getting this one ;)
 

bigjacko

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#7
Thanks for the review Amir. Did you measure headphone output and output impedence? The default headphone output has two resistors to reduce the power, there are two jumpers that can short and bypass those resistors. Give the output impedence a measure, lets have some fun!
 
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#8
If you have a passive sub with hi-pass sat speaker outs (rare these days), quite simply to the speaker outputs of the amp, and the sat speakers to the sub's sat outs. An active sub can be connected (depending on its design) with either a Y-cable or L+R RCA to the RCA output. Having an active sub and passive sat speakers, you will get some delay on the sub side. That said, I wouldn't be getting this one ;)
Thanks, man. I would assume a dedicate output for a sub like the Loxjie A30 would be a better option.
 

Matias

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#9

capslock

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#10
So if it wasn't for the poor bias control, you would even give it a happy panther? The bias is no deal breaker for me even if annoying.

I am surprised at the power supply noise. Plenty of harmonics from the rectifier, plenty of intermodulation with the 1 kHz carrier. Some of this may be radiated due to the close proximity of components in that case. Maybe they also economized the current source of the input LTP, resulting in poor PSRR? Loop gain also runs out of steam quickly, as evidenced by the decline in THD+N in the 5 kHz measurement.

Overall, I feel class AB in both dedicated stereo amps as well as AVRs has regressed over the past 10 or so years. It is instructive to look at the service manuals of a progression of Onkyo, Yamaha and Denon amps in a market bracket. Current mirror in the input disappears from one generation to the next, enhanced VAS goes the way of the Dodo, triple darlingtons, why bother with that? On the other hand, once that DACs became a solved problem, they managed to screw up the volume control circuits and the digital signal handling with the introduction of HDMI, so that lowered the bar for poor power stages. Competition from poorly implemented class D didn't help either.

Denon has used integrated darlington power transistors all the way to their top models for years. While that saves money, it precludes the use of a shared emitter resistor in the drivers which helps to lower switching distortion.
 

voodooless

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#12
"Ultra Low Noise Transformer", yeah right...
Actually, transformers can make quite a bit of noise. My amp occasionally hums quite loudly depending if there is some DC on the mains (which occasionally seems to happen). Often you see the transformers being potted in some goo for this. This one however is not by the looks of it. As for mains noise, that's probably not the transformers fault: They probably skimped on snubbering the rectifier and have an amp design with low PSRR. They do seem to have some kind of mains filtering though (right where the fuse is on the left side).
 

ThatM1key

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#13
I was almost thinking about getting one to replace my Sansui 2000A. I realized an old sporty mustang is truly a better value than a new chevy spark.
 

abdo123

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#14
is it me or for 220$ this is a bargain? you get a warranty and similar performance to DIY Class D at this price range. The only devestating fault is the gain difference between channels, but again i doubt it's audible if it's below 1 dB.
 

Veri

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#17
Hoped you would also test the headphone output. This is like old school receivers that just tap the output for the headphone thru some resistors. Not that such a thing is great, but for some perspective into how such an arrangement performs as a headphone amp.

They also have a jumper to allow direct Power amp output to headphone without the resistors in place which might be even more interesting. I know the peformance otherwise isn't much to right home about, but you really only test half of what some people buy this amp for in general.
Thanks for the review Amir. Did you measure headphone output and output impedence? The default headphone output has two resistors to reduce the power, there are two jumpers that can short and bypass those resistors. Give the output impedence a measure, lets have some fun!
+1 for testing the headphone out, mainly with jumpers. As they allow the full power of the amp in exchange for poor resistance (50W into 8ohm, 12W into 33ohm, 1.2W into 300ohm).
Any chance of that @amirm ? That's what a lot of people buy this BasX amp for, headphone function with the jumper in place.
It's probably same low-ish performance, but it'd be interesting to see headphone output impedance and power.. :)
I personally used it like this for a little bit, until I moved on to cleaner solid state. But for ~$200 I'd think it's not bad.
 

GGroch

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#19
......Having an active sub and passive sat speakers, you will get some delay on the sub side....
(re: connecting the BasX line out to an active subwoofer).

Is this connection any different from the sub out of a Loxjie A30 or any other stereo amp in this regard? I assumed that all amps that lack a mic / autocalibration circuit could have timing issues that are dependent on sub and speaker positioning. These are generally solved through the sub's phase switch or pot, right? A dedicated sub out often adds a low pass filter...but that is not necessarily a benefit.

I agree that based on measurements it is not the best choice, for anything really. I have never owned one of these but have always been irrationally attracted to them based on their substantial physical build, class A/B circuitry, and retro look. I bet the BasX 100 is Emotiva's biggest seller in units by far.

The ability to send the amps full output to its headphone jack is theoretically an attractive option...but even without measuring the headphone out it is clear that its noise/ channel imbalance are far worst than most dedicated $100-$150 headphone amps.
 
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#20
Thanks for the technical review @amirm

In Europe this costs as much as a buying a Audiophonics Hypex Ncore NC122MP amp. Sure, this one has a headphone amp and an output for bass but looking at the performance of this I know where I'd rather spend my money.
 
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