Loxjie A30 Amplifier Review

[Helicopter]

Perhaps I am misunderstanding the goal here. Are you suggesting the sub play all the way up to 500hz to fill the gap from the speakers?

If your subwoofer has say, a 60-80Hz filter built in, then a 500Hz rolloff in the subwoofer signal from the A30 (If that chart is actually right) isn't going to be a problem anyway. You're only going to see the end result of the much lower pass frequency that is built into the subwoofer. It is pretty unusual for a subwoofer not to have such a filter built in. Even my passive subs have them, and I have never used an active sub that didn't.

 

[mattzildjian]

If your subwoofer has say, a 60-80Hz filter built in, then a 500Hz rolloff in the subwoofer signal from the A30 (If that chart is actually right) isn't going to be a problem anyway. You're only going to see the end result of the much lower pass frequency that is built into the subwoofer. It is pretty unusual for a subwoofer not to have such a filter built in. Even my passive subs have them, and I have never used an active sub that didn't.

The comment I am referring to was talking about turning the bass control -10db to the speakers as a makeshift high pass so the SW can do the rest (assuming the SW output is untouched by tone controls). At least that's how I interpreted the post, he wasn't completely specific in his goal.

 

[Helicopter]

The comment I am referring to was talking about turning the bass control -10db to the speakers as a makeshift high pass so the SW can do the rest (assuming the SW output is untouched by tone controls). At least that's how I interpreted the post, he wasn't completely specific in his goal.

Gotcha. I thought you were talking about this mind-boggling graphic from Loxjie:

 

[infinitesymphony]

Gotcha. I thought you were talking about this mind-boggling graphic from Loxjie:
View attachment 94162

Somehow in my search for info I managed to look everywhere but Loxjie's product page for the A30. Thanks for posting the SW OUT graph.

Not sure how useful that LPF is, but there you have it. Easy connection, enjoy easily.

 

[Shadow12347]

Woooow... This is the kinda device I've been looking for! At the moment in our living room TV setup, I am using our TV's optical out to an Aune X1s, which is going into a passive pre-amp (not much volume range without it), which then goes into a garage sale bought analog input only AVR (Pioneer VSX-406), which then goes into 2 floors-standing speakers, and an active sub.

The speakers are 4 ohm, and given I needed to throw in a passive pre-amp (turned down about halfway from full output) to get more usable volume range out of this setup, I would tend to think I can get away with something that has far less power than my current setup... Not only that, but I'm almost certain this has far better noise and distortion performance than this old analog AVR I got at a garage sale...

That said, my only concern is would this be enough power? If so, this would be amazing as I could replace literally every piece of equipment I have in this setup with this one little device...

 

[MattG]

Any chance of a picture of the internal circuitry of this unit?

Amir, do you have any way of measuring radiated EMF from audio sources?

The questions are related: I'm curious if the amp's output goes through a true LC filter, or simpler (and cheaper!) ferrite bead filter?

I've been reading about this chip. All of the cheaper DIY boards I've seen, and even the reference evaluation board, do not include a true LC filter. In class D amps, the output signal has a lot of high frequency noise that needs to be filtered. This high frequency noise is well above the range of human hearing, so even if not filtered at the circuit, the speaker will not reproduce it. However, the problem is, if not filtered near the actual amp IC, the speaker wires become EMF broadcast antennas. The MA12070(P) technical documentation recommends using a true LC filter if speaker cable length exceeds 60mm.

Also, FWIW, there are actually two versions of this chip: the MA12070, and the MA12070P. The former is an analog-input class D amplifier, which is what the Loxjie A30 appears to use. The latter (note the trailing "P" at the end of the part number) is a digital input (I2S) class D amplifier. Comparing the datasheets, the "P" version (digital input) has slightly worse measured performance.

Another interesting factoid about this chip: the datasheet goes into detail its different "power management profiles". That is, the chip can be configured (on the fly, via serial commands) to essentially trade some performance for power savings. IIRC, the default behavior is to dynamically change the power management profile depending on certain operation conditions. But you can force it into one profile, and even define custom profiles!

It's a pretty cool chip! I'm actually planning to use the "P" version to build a DIY "sound server" for my office. In a single fairly small enclosure, I'll have a power supply, Raspberry Pi, and MA12070P board. I can send audio over the network to the RPI (e.g. from my PC) via PulseAudio, and the RPI can send audio data via I2S straight to the MA12070P chip. I can also do digital volume control, change power management profiles, and some other fun stuff via I2C serial command from the RPI to the chip. Still waiting for all the parts to arrive, so only at the planning stage, but I expect to get something working fairly quickly.

 

[The Capstan]

I've been reading about this chip. All of the cheaper DIY boards I've seen, and even the reference evaluation board, do not include a true LC filter. In class D amps, the output signal has a lot of high frequency noise that needs to be filtered. This high frequency noise is well above the range of human hearing, so even if not filtered at the circuit, the speaker will not reproduce it. However, the problem is, if not filtered near the actual amp IC, the speaker wires become EMF broadcast antennas. The MA12070(P) technical documentation recommends using a true LC filter if speaker cable length exceeds 60mm.

the device carries FCC mark on back panel, so I assume the unit has undergone proper certification tests including EMI.

Ale.

 

[Helicopter]

Woooow... This is the kinda device I've been looking for! At the moment in our living room TV setup, I am using our TV's optical out to an Aune X1s, which is going into a passive pre-amp (not much volume range without it), which then goes into a garage sale bought analog input only AVR (Pioneer VSX-406), which then goes into 2 floors-standing speakers, and an active sub.

The speakers are 4 ohm, and given I needed to throw in a passive pre-amp (turned down about halfway from full output) to get more usable volume range out of this setup, I would tend to think I can get away with something that has far less power than my current setup... Not only that, but I'm almost certain this has far better noise and distortion performance than this old analog AVR I got at a garage sale...

That said, my only concern is would this be enough power? If so, this would be amazing as I could replace literally every piece of equipment I have in this setup with this one little device...

How this will work for you depends on the sensitivity of your speakers, how big your room is, how far you sit from the speakers, and how loud you want the system to get. If you provide this information, we can probably give you a pretty good guess. Chances are you'll be OK.

Any chance of a picture of the internal circuitry of this unit?

Amir, do you have any way of measuring radiated EMF from audio sources?

I told him he could open it up, but it's already on the way back to me. If I don't have to remove any adhesive, I can take some pictures when it gets here. They won't be as good as the pictures Amir takes.

 

[pjug]

the device carries FCC mark on back panel, so I assume the unit has undergone proper certification tests including EMI.

Ale.

I wonder about that though. As @MattG said Infineon recommends a filter for some applications. Maybe a manufacturer would get around FCC by testing with short or twisted wire, or no cable at all just plugging in a resistor?

 

[amirm]

If the DA-8S is reviewed and does as well as the Loxjie then hopefully my rash purchase will have been a good one!

I have had a DA-8S here for a while. I will try to testing soon.

 

[Shadow12347]

How this will work for you depends on the sensitivity of your speakers, how big your room is, how far you sit from the speakers, and how loud you want the system to get. If you provide this information, we can probably give you a pretty good guess. Chances are you'll be OK.

I had to do some digging as they're also old, and were also purchased from a garage sale . I found out it was originally sold as part of a full system with an amplifier and all. What I purchased only included the Front L/R, Rear L/R, and Center Channel speakers, however, the center channel was blown out, so I settled on only using the Front L/R with a separately purchased active sub. I looked up the tech specs from the manual, and it doesn't give any sensitivity figures. That said, it does give the power ratings of the amplifier that originally came with the system:

I'm only using the Front L/R speakers, and the original amp it came with output 75W at 4 ohm. It also states that the output power of the Front L/R speakers was 50W for each. This makes it seem like the A30 would be enough?

We generally sit from about 10 feet away (on the couch) to about 16 feet away (dining room table), and the room only extends a few feet past the table. Of course we normally turn it up higher at the table, but my VSX-406 has enough power currently to keep it's volume at about the 12 o'clock position, with the pre-amp's volume down about halfway at the same time to get plenty of volume from the furthest point. The VSX-406's specs look something like this:

This has quite a bit more power than the amp the speakers originally came with, as well as the A30, but again, without the pre-amp, the volume would really only be bearable up to the 9 o'clock position on the VSX-406.

So putting this all together, to me it would seem that the A30 would be enough?

 

[Helicopter]

I had to do some digging as they're also old, and were also purchased from a garage sale . I found out it was originally sold as part of a full system with an amplifier and all. What I purchased only included the Front L/R, Rear L/R, and Center Channel speakers, however, the center channel was blown out, so I settled on only using the Front L/R with a separately purchased active sub. I looked up the tech specs from the manual, and it doesn't give any sensitivity figures. That said, it does give the power ratings of the amplifier that originally came with the system:

View attachment 94381

I'm only using the Front L/R speakers, and the original amp it came with output 75W at 4 ohm. It also states that the output power of the Front L/R speakers was 50W for each. This makes it seem like the A30 would be enough?

We generally sit from about 10 feet away (on the couch) to about 16 feet away (dining room table), and the room only extends a few feet past the table. Of course we normally turn it up higher at the table, but my VSX-406 has enough power currently to keep it's volume at about the 12 o'clock position, with the pre-amp's volume down about halfway at the same time to get plenty of volume from the furthest point. The VSX-406's specs look something like this:

View attachment 94382

This has quite a bit more power than the amp the speakers originally came with, as well as the A30, but again, without the pre-amp, the volume would really only be bearable up to the 9 o'clock position on the VSX-406.

So putting this all together, to me it would seem that the A30 would be enough?

I agree. At 10 to 15 feet, with speakers designed to work with a 50 watt multi channel amp, you should be happy. You should keep in mind half setting on your current units is likely way less than half sound pressure level due to the way electronics are scaled to match our perception, i.e. dB is logarithmic. This product should be fine for your setup.

 

[Hiilari]

I got interested about this nice little amp because it says to have EQ. In my room and my home-brew speakers I need some. But seems it has different bass/treble adjustments, not a proper parametric one. Need to invest more serious cash into that RME ADI I presume...

 

[milus]

...
It's a pretty cool chip! I'm actually planning to use the "P" version to build a DIY "sound server" for my office. In a single fairly small enclosure, I'll have a power supply, Raspberry Pi, and MA12070P board. I can send audio over the network to the RPI (e.g. from my PC) via PulseAudio, and the RPI can send audio data via I2S straight to the MA12070P chip. I can also do digital volume control, change power management profiles, and some other fun stuff via I2C serial command from the RPI to the chip. Still waiting for all the parts to arrive, so only at the planning stage, but I expect to get something working fairly quickly.

@MattG

This could be quite an interesting project!
Do you plan to document it in any way? Opening a new thread here or in any other forum (DYIAudio, etc.)?
Please, keep us informed!

Thank you!

 

[Helicopter]

I got interested about this nice little amp because it says to have EQ. In my room and my home-brew speakers I need some. But seems it has different bass/treble adjustments, not a proper parametric one. Need to invest more serious cash into that RME ADI I presume...

If you like this but want to add PEQ, you could buy an all digital miniDSP processor to put before it.

 

[RikB]

I have had a DA-8S here for a while. I will try to testing soon.

Nice, thank you Sir, I look forward to it!

 

[The Capstan]

If we assume a product is made 50% by actual product and 50% by support, well I have to complain that after 4 days I have not received any answer to a request I have sent via email to Loxjie support for clarifying sample rate capabilities of the USB input.
Ok it‘s Chi-fi, it’s low cost, but not a good sign IMHO.

 

[Toku]

If we assume a product is made 50% by actual product and 50% by support, well I have to complain that after 4 days I have not received any answer to a request I have sent via email to Loxjie support for clarifying sample rate capabilities of the USB input.
Ok it‘s Chi-fi, it’s low cost, but not a good sign IMHO.

The correspondence of the SMSL group is always unfriendly.

 

[The Capstan]

The correspondence of the SMSL group is always unfriendly.

Are you sure of this statement? I remember direct participation of an SMSL representative on the thread of the SMSL M500 a while ago, something that testifies a different approach. I also equired them couple of times and got responses in reasonable time frame. Not the same with Loxjie, I see.

 

[dougi]

I have had a DA-8S here for a while. I will try to testing soon.

On measuring Amir, how did you measure the Loxjie? It is a filterless amp right? I know TI for their versions say you need to then use an RC filter in the front of the test gear in order to do so. Is that what you did? I tried to measure a cheap chip amp I had (with a RME) but despite putting in a filter it still oscillates uncontrollably when measuring. It works into a speaker load though.