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Earthquake XJ-300ST Stereo Amplifier Review

amirm

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This is a review and detailed measurements of the Earthquake XJ-300ST stereo amplifier. It was kindly donated by a member for testing. It costs US $462.83 from the company website.
Earthquake XJ-300ST Stereo Amplifier Review.jpg


I like the compact packaging and old school but solid feeling switchgear. Likewise, having a low-pass filter (no doubt to drive subs for which they are famous), filter corner frequency and phase come in handy. And of course the integrated volume control. Back panel is typical with the exception of crossing terminals (for bridging):
Earthquake XJ-300ST Stereo Amplifier Trigger subwoofer lowpass  Review.jpg

12 volt trigger is icing on the cake.

Unit runs is a "class J" amplifier and was cool and comfortable during testing.

Amplifier Measurements
Here is our usual dashboard:

Earthquake XJ-300ST Stereo Amplifier Measurements.png


We have massive mains spike which I could hardly reduce no matter what I did. I am assuming it is internal leakage. Can't figure out why one channel is so much more distorted than the other. Averaging the two, the amp falls in "poor" category of all tested with a SINAD of 59:
Best subwoofer amplifier review 2022.png


Frequency response showed strong roll off at both ends of the spectrum:

Earthquake XJ-300ST Stereo Amplifier frequency response Measurements.png


There is a note about a 15 Hz high pass but nothing about the top end. I tested the programmable lowpass by more or less setting it to 80 Hz and got this:
Earthquake XJ-300ST Stereo Amplifier Low Pass frequency response Measurements.png


Crosstalk is very poor:
Earthquake XJ-300ST Stereo Amplifier Crosstalk Measurements.png


SNR was poor likely due to high levels of power supply/mains noise:
Earthquake XJ-300ST Stereo Amplifier SNR Measurements.png


Power is modest:
Earthquake XJ-300ST Stereo Amplifier Power 4 ohm Measurements.png


I have no idea how they have arrived at their power spec:

Earthquake XJ-300ST Stereo Amplifier Max and Peak Power 4 ohm Measurements.png


Finally, here is the 8 ohm performance:

Earthquake XJ-300ST Stereo Amplifier Power 8 ohm Measurements.png


Conclusions
Not much to hang your head on here other than the compact size and functionality. Not sure how it is suitable for subwoofer duty when it has so little power. Can't recommend it.

------------
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/
 

XaVierDK

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Well with this and my experience with Earthquake's FF-12 subwoofer, which they incidentally claim is a 400W sub with frequency response down to 25 Hz, which turned out to be categorically wrong, I think I'll just write off the manufacturer in general going forwards.
 

fordiebianco

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Blimey.
 

Phantomuser

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Didn't earthquake start out years ago making knockoff copies of early Hifonics amps?
 

JSmith

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Thanks for the review Amir.

See this kind of this annoys me... it's just a waste of the planet's resources to make such substandard products, when it could be done well for little further cost. The fact it doesn't match the quoted specifications is bordering on misleading as well.

As for "class J";
Class-J amplifier that provides the same efficiency and linearity as Class-AB or Class-B amplifiers across a broad frequency range due to absence of the resonant impedance condition, such as short-circuit or open-circuit. The Class-J PA increases the fun-damental voltage component assisted by the second-harmonic voltage by employing a capacitive harmonic load [10]– [12]. However, a complex load impedance at the fundamental frequency is required to shape the voltage waveform. As a result, the performance of the Class-J PA is degraded due to the phase mismatch, making it comparable to that of a harmonic tuned linear PA, such as a Class-AB or a Class-B, but the reported Class-J PA provides better efficiency than the theoretical expectation.


JSmith
 

Vladimir Filevski

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As for "class J";
Earthquake's "class J" must be something different (intentionally mislabeled, maybe?), because real class J amplifiers work exclusively at radio frequencies.
 

AudioSceptic

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This is a review and detailed measurements of the Earthquake XJ-300ST stereo amplifier. It was kindly donated by a member for testing. It costs US $462.83 from the company website.
View attachment 211915

I like the compact packaging and old school but solid feeling switchgear. Likewise, having a low-pass filter (no doubt to drive subs for which they are famous), filter corner frequency and phase come in handy. And of course the integrated volume control. Back panel is typical with the exception of crossing terminals (for bridging):
View attachment 211917
12 volt trigger is icing on the cake.

Unit runs is a "class J" amplifier and was cool and comfortable during testing.

Amplifier Measurements
Here is our usual dashboard:

View attachment 211918

We have massive mains spike which I could hardly reduce no matter what I did. I am assuming it is internal leakage. Can't figure out why one channel is so much more distorted than the other. Averaging the two, the amp falls in "poor" category of all tested with a SINAD of 59:
View attachment 211919

Frequency response showed strong roll off at both ends of the spectrum:

View attachment 211920

There is a note about a 15 Hz high pass but nothing about the top end. I tested the programmable lowpass by more or less setting it to 80 Hz and got this:
View attachment 211921

Crosstalk is very poor:
View attachment 211926

SNR was poor likely due to high levels of power supply/mains noise:
View attachment 211922

Power is modest:
View attachment 211923

I have no idea how they have arrived at their power spec:

View attachment 211924

Finally, here is the 8 ohm performance:

View attachment 211925

Conclusions
Not much to hang your head on here other than the compact size and functionality. Not sure how it is suitable for subwoofer duty when it has so little power. Can't recommend it.

------------
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/
This would be poor at any price, but for $463 is outrageously bad. WTF are they thinking?
 

CedarX

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Earthquake's "class J" must be something different (intentionally mislabeled, maybe?), because real class J amplifiers work exclusively at radio frequencies.
From the XJ-300R user manual (different model):

“What is a class J?
Class J is a monitoring circuit that optimize class D amplifiers. The class J is a class D amplifier which has a microprocessor Algorithm that trades in high efficiency for high quality throughout the audio spectrum. So in simple terms, the class J gives you the highest efficiency possible without compromising the quality.
The XJ amplifiers possess an oversized power supply: 8 ohms, 4 ohms and even 2 ohms. These amplifiers will deliver clean accurate sound with massive damping factor.”


A clever Class-D implementation or Marketing BS? (I vote for the later!)
 

sarumbear

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The fact it doesn't match the quoted specifications is bordering on misleading as well.
If this is bordering on misleading, what is a plain lie in your opinion?
 

Vladimir Filevski

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From the XJ-300R user manual (different model):
“What is a class J?
Class J is a monitoring circuit that optimize class D amplifiers. The class J is a class D amplifier which has a microprocessor Algorithm that trades in high efficiency for high quality throughout the audio spectrum. So in simple terms, the class J gives you the highest efficiency possible without compromising the quality....


A clever Class-D implementation or Marketing BS? (I vote for the later!)
Yup, that is.
 

tomtoo

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Or is this thing build for bassshakers and shows more power at low impedance?
 

sarumbear

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Or is this thing build for bassshakers and shows more power at low impedance?
The product page has no mention of power capability at all. (I wonder if that happened after @amirm's test?)

The user manual has the following specification where it clearly, in bold, says it is not suitable for low impedance loads.

2 x 110 Watts RMS @ 8-Ohm
2 x 170 Watts RMS @ 4-Ohm
1 x x 170 Watts RMS @ 8-Ohm Mono
1 x 300 Watts RMS @ 4-Ohm Mono
(Do not use this amplifier in 2-Ohm)

The difference between what is promised to the buyer and what is delivered is almost two-fold. A big fat lie. That is what it is.

It is pretty funny that they have no engineering knowledge at all. They say do not use this amplifier in 2-Ohm but specify both per channel and the bridged operation at 4-Ohm...
 
Last edited:

JDS

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Apr 21, 2021
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This is a review and detailed measurements of the Earthquake XJ-300ST stereo amplifier. It was kindly donated by a member for testing. It costs US $462.83 from the company website.
View attachment 211915

I like the compact packaging and old school but solid feeling switchgear. Likewise, having a low-pass filter (no doubt to drive subs for which they are famous), filter corner frequency and phase come in handy. And of course the integrated volume control. Back panel is typical with the exception of crossing terminals (for bridging):
View attachment 211917
12 volt trigger is icing on the cake.

Unit runs is a "class J" amplifier and was cool and comfortable during testing.

Amplifier Measurements
Here is our usual dashboard:

View attachment 211918

We have massive mains spike which I could hardly reduce no matter what I did. I am assuming it is internal leakage. Can't figure out why one channel is so much more distorted than the other. Averaging the two, the amp falls in "poor" category of all tested with a SINAD of 59:
View attachment 211919

Frequency response showed strong roll off at both ends of the spectrum:

View attachment 211920

There is a note about a 15 Hz high pass but nothing about the top end. I tested the programmable lowpass by more or less setting it to 80 Hz and got this:
View attachment 211921

Crosstalk is very poor:
View attachment 211926

SNR was poor likely due to high levels of power supply/mains noise:
View attachment 211922

Power is modest:
View attachment 211923

I have no idea how they have arrived at their power spec:

View attachment 211924

Finally, here is the 8 ohm performance:

View attachment 211925

Conclusions
Not much to hang your head on here other than the compact size and functionality. Not sure how it is suitable for subwoofer duty when it has so little power. Can't recommend it.

------------
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/
In addition to the power issue, a subwoofer amp that's down 3dB at 30Hz is rather ill-conceived.
 
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