Loxjie A30 Amplifier Review

[Helicopter]

I think I am going to try this with my Focal Aria 948s for a while, and if it works, which I think it probably will, then run it for a few weeks like that... I wonder how much less power it will use than my class A SET 845 tube amp.

 

[JohnYang1997]

What about the distortion with different frequencies. There was false advertising from them saying 20khz has very low distortion.

 

[andreasmaaan]

@amirm nice little amp, thx for the review You didn’t happen to run a HD vs frequency sweep did you?

 

[bigjacko]

Why is digital input better than analog input? The power is quite low, the best use case is either low volume or active crossover. Can it be used as active crossover plus amp?

 

[Toku]

I can't understand that Toslink has better characteristics than RCA input.
Is this a disadvantage of using the RCA input and COAX as a common terminal?
I would like you to measure and compare the SMSL SA300 as well.

 

[infinitesymphony]

Why is digital input better than analog input? The power is quite low, the best use case is either low volume or active crossover. Can it be used as active crossover plus amp?

I can't understand that Toslink has better characteristics than RCA input.

Guessing all signals must be converted to digital before hitting the amplifier chip, so it sounds like there might be something going wrong with the ADC that occurs with analog input.

 

[pavuol]

Loxjie A30 Listening Tests
I decided to test the A30 in a typical desktop setup. So I grabbed the PSB Alpha P5 (84 dB sensitivity) and connected it to the A30. I was most impressed with power ability and lack of distortion! There was incredible bass and ability to drive the P5 hard. And loud. I could get ample loudness while staying below 50 on the volume control. Playing my deep bass tracks however caused distortion to show up above 50 (mild crackling). But really, that was quite hard and we are talking using just one speaker here.

Overall experience below limit was absolutely audiophile with no excuses to be made.

golf-panther amp + headless-panther speaker = balanced audiophile setup

Thanks again for a wonderful review. Topping/other competitors, I can hold your beer if you dare to

 

[pavuol]

Anyway, they advertise 80Wx2(4Ω)@ but the power/distortion graph in their measurements starts to rise rapidly at ~50W...?

And I'm curious, it has bluetooth 5.0 & AptX "only". Is the support for AptX HD "FW upgradeable" or is it rather HW limited?

 

[A Surfer]

This would make a great smaller room amp for a 2 channel setup like a dorm room, bedroom at home or small living room in an apartment where high SPL isn't needed. I would seriously consider this in a kitchen dinning room area as it is small and paired with some small speakers would still give you a nice system to cook and dine to.

 

[escape2]

This would make a great smaller room amp for a 2 channel setup like a dorm room, bedroom at home or small living room in an apartment where high SPL isn't needed. I would seriously consider this in a kitchen dinning room area as it is small and paired with some small speakers would still give you a nice system to cook and dine to.

Performance using analog input isn't all that impressive. I think I am still leaning toward Emotiva A-100, although it's a bit larger and has no remote.

 

[pavuol]

Ok.. $160.. Maybe I am not seeing this correctly - when I see:
- a DAC performance easily matched by many dongles
- a poor (useless?) headphone amp
- better Lepy-type power amp

So - for $9 we can get a better performing Apple DAC and what seems a no-worse 30mw HP amp to boot;

For $150 what most likely is a better performing bt speaker Amp:
https://www.crutchfield.com/p_022RS202/Yamaha-R-S202.html

Seems an easy choice to me...

Besides Amirs' points, spring terminals on a big "conventional hi-fi" Yamaha versus screw terminals on small Loxjie box.. the world is upside down!

 

[Toku]

Guessing all signals must be converted to digital before hitting the amplifier chip, so it sounds like there might be something going wrong with the ADC that occurs with analog input.

The MA12070 chip used in the A30 has an analog input.
Toslink, COAX, USB and BT are all converted from digital to analog, passed through an electronic volume and input to the MA12070 chip. Therefore, the RCA input is the purest input signal.

 

[DuncanTodd]

That's like six swinging panthers in a row. Good week.
I hope they improve the English wordings in a fw update. I'm not native English but "No Connect!" sounds off to me

 

[pavuol]

Some short videos on Infineon MERUS digital amp topic from their webpage:

vid1 / vid2 [+pdf]

 

[infinitesymphony]

The MA12070 chip used in the A30 has an analog input.
Toslink, COAX, USB and BT are all converted from digital to analog, passed through an electronic volume and input to the MA12070 chip. Therefore, the RCA input is the purest input signal.

In that case, the analog result is perplexing indeed.

 

[amirm]

Anyway, they advertise 80Wx2(4Ω)@ but the power/distortion graph in their measurements starts to rise rapidly at ~50W...?

They all just quote the chip spec which is at something like 10% THD.

 

[infinitesymphony]

This deep dive into the MA12070 is a little over my head, but this part was interesting:

"Absent some inductance to slow the switching slew rate across the load resistor, the amount of switching noise induced on the output is enormous and that makes measurement difficult. The solution, according to Infineon, is to use use 22 uH inductors in series with the output when making measurements. This will tame the fast edges, and make the signal more palatable to the signal analyzer. Of course, when driving into a real speaker, you'll get the inductance for free which helps to keep your EMI edges under control.

...

So, what does it look like if we make a noise measurement with the QA450 and QA401 with and without the 22uH inductors?

In the plot below, we can see the yellow (left) trace and the red (right) trace. The left channel has a -60 dBV signal going into the MA12070 board, and with the default 20 dB gain of the amp, the output is -40 dBV. The right channel is muted.

We can see the N+D measurement for both channels. This measurement is all of the energy from 20 to 20 kHz with the signal subtracted. For the left channel, that is -83.7 dBV (A-weighted). This is 65.3 uVrms.

For the right channel, this is -70.9 dBV (AW) which is 285 uVrms. Clearly, the inductor is making a big difference. The noise levels are almost unchanged for both 4 and 8 ohms. But the 13 dB gap is substantial."

Maybe just a coincidence, but those numbers don't seem too far away from the measured differences between analog and digital sources.

 

[amirm]

OK, ran some more test and analog input actually is fine. For consistency I set all integrated amps to gain of 29 dB. Here, doing so resulted in much higher noise level. If I turn the volume down and increase input to 1.9 volt, I get the same result as digital:

So the preamp is noisy.

 

[amirm]

This deep dive into the MA12070 is a little over my head, but this part was interesting:

Interesting indeed. Unlike that setup, I have the "expensive" AES-17 filter I use for class D amps. But seems like Infineon thinks that is not enough. Their solution of adding another inductor which mimicking real life, does distort the tests though by limiting bandwidth. That may be responsible for some oddness in these measurements:

 

[amirm]

@amirm Could you please measure distortion over frequency to see if it is well behaved on high frequencies?

Sure. See above.