I'm thinking about building a clone LXmini or LXmini+2 LXmini+2. And, yes, I know that there are a lot of designs floating around, and I plan to learn from those.
I will use one of the ADAU1701 or ADAU1452 boards available on Aliexpress.
What I'm trying to figure out is the D-class amplification. Ideally I'd like to use a D-class amplifier with digital input. Since all my sources are digital anyway, it makes little sense to me to go from digital to a DSP, then analog to the input of a D-Class amplifier, which at the core is a digital device anyway.
The SSM3582A seems to be an ideal chip. I2S input and just enough power for my listening volumes (near field, low volume). Aliexpress sellers like this one 30W Class D Digital Power Amplifier Board (2 Channels) SSM3582|Transformers| - AliExpress have versions with 2, 6 and 8 channels. 6 channels would be ideal, since it would cover both the LXmini and LXmini+2.
The advantage of the 2 channel version, is that it offers full I2C control of the SMM3582A, while the 6 and 8 channel version do not break out the I2C pins
Has anyone used one of those boards and has any feedback, good or bad? Any other SMM3582 design available?
I have seen a few old posts on people designing their own SMM3582 boards, but none seems to have reached a "done" status. Given the low cost of the components, I would not mind having to assemble my own boards, but I'm not knowledgeable enough to create a schematics and design my own board (I have done it for digital electronics, but there are too many noise/EMI considerations for an amplifier). Does anyone know of any design that works?
Any other I2S input amplifier I should consider?
I will use one of the ADAU1701 or ADAU1452 boards available on Aliexpress.
What I'm trying to figure out is the D-class amplification. Ideally I'd like to use a D-class amplifier with digital input. Since all my sources are digital anyway, it makes little sense to me to go from digital to a DSP, then analog to the input of a D-Class amplifier, which at the core is a digital device anyway.
The SSM3582A seems to be an ideal chip. I2S input and just enough power for my listening volumes (near field, low volume). Aliexpress sellers like this one 30W Class D Digital Power Amplifier Board (2 Channels) SSM3582|Transformers| - AliExpress have versions with 2, 6 and 8 channels. 6 channels would be ideal, since it would cover both the LXmini and LXmini+2.
The advantage of the 2 channel version, is that it offers full I2C control of the SMM3582A, while the 6 and 8 channel version do not break out the I2C pins
Has anyone used one of those boards and has any feedback, good or bad? Any other SMM3582 design available?
I have seen a few old posts on people designing their own SMM3582 boards, but none seems to have reached a "done" status. Given the low cost of the components, I would not mind having to assemble my own boards, but I'm not knowledgeable enough to create a schematics and design my own board (I have done it for digital electronics, but there are too many noise/EMI considerations for an amplifier). Does anyone know of any design that works?
Any other I2S input amplifier I should consider?
You can consider this one too from our fellow member, uses the DSP from the TI power amp chip.
ZOUDIO AIO4CH: 4-channel amplifier with DSP and Bluetooth
BTW, it is misconception that the signal is directly converted to PWM in all the I2S chips. I can't generalize for all of them but I have come across quite a few with a built in DAC. Simple reason is the implementation of negative feedback requires two voltage level to be compared... so....
Oon
ZOUDIO AIO4CH: 4-channel amplifier with DSP and Bluetooth
BTW, it is misconception that the signal is directly converted to PWM in all the I2S chips. I can't generalize for all of them but I have come across quite a few with a built in DAC. Simple reason is the implementation of negative feedback requires two voltage level to be compared... so....
Oon
Thanks for the suggestion, I will read that thread. On first impression, I have 2 concerns, though:
1) it's only 4 channels, and if I want to add a subwoofer I would need two more
2) the crossover curve for the speaker is pretty complex (https://roon-community-uploads.s3.a.../0d0e2007e58090a39f5f3599664b4b7869e47ffb.png), and it's distributed in the miniDSP format, which is based on an ADAU1701, so relatively easy to port to another ADAU chip. The TI DSP works in a very different way, and would need to figure out if it's even possible to port vs re-building it from scratch, which might be challenging.And the software provided with the amp doesn't seem to allow something quite that complex (I might be wrong, only had a quick look)
1) it's only 4 channels, and if I want to add a subwoofer I would need two more
2) the crossover curve for the speaker is pretty complex (https://roon-community-uploads.s3.a.../0d0e2007e58090a39f5f3599664b4b7869e47ffb.png), and it's distributed in the miniDSP format, which is based on an ADAU1701, so relatively easy to port to another ADAU chip. The TI DSP works in a very different way, and would need to figure out if it's even possible to port vs re-building it from scratch, which might be challenging.And the software provided with the amp doesn't seem to allow something quite that complex (I might be wrong, only had a quick look)
You have seen from the block diagram that the chip has a DAC within it? as does the MA12070P.
The ZOUDIO AIO4CH is PCM to PWM, so no DAC.
Regards,
Andy
There is a lot to like in the ZOUDIO AIO4CH (especially since the person who built it is in this thread 
)
My concerns at the moment are that
)My concerns at the moment are that
- It's only 4 channels, and I might need 6. I see that the chip has an I2S output, so it might be possible to daisy chain a separate 2 CH amplifier just for the subwoofer
- From the datasheet, it's not clear if the I2S input is broken out (feedback for @lutkeveld, would be good to call that out). I'm sure it could be soldered using the BTh module output, but would need to understand the circuit to be sure I would not mess something else
- All the LXmini DSP information is for the DSPmini/ADAU family of DSP. There seems to be enough biquads and stages to implement an equalization as complex as the one for the LXmini, but would be completely new territory and I'd be on my own
I have been looking at options, and definitely the MA12070P looks like a very interesting option. Some well rated amplifiers (e.g. Loxjie A30) use the MA12070, the analog input version of the MA12070P. And it's interesting that the same module High Quality HIFI Digital CLASSD Amplifier Module MERUS MA12070 2X80W|Air Conditioner Parts| - AliExpress can be used as a 160W mono amplifier, 2x80W, 2x40W+1x80W or 4x40W simply changing a dip switch.
By buying two modules, could use one to have 4x40W for tweeters and mid-woofer in the LXmini+2, then another one for the 2x80W subwoofers of the LXmini+ version. And if the power is not enough, keep adding a ~$30 module as many times as needed
The more I read, the more I realized that a lot of my assumptions about class D and digital inputs were wrong. That's what so great about this forum 🙂
So, assuming I decide to go sources-ADAU1452 digitally, then have a DAC feeding an analog input class D amplifier, what DAC modules are good to consider?
I saw that the freeDSP uses an AK4458, while the ubiquitous ADAU1452 cheap Aliexpress/eBay boards the AD1938. The AK family DACs seem to have much better characteristics, but there are no AK-based boards readily available. I even considered building my own board, but the AK4458 is not in stock anywhere, with waiting times of 18 weeks 😱
Any other DAC else I should consider? Ideally 6 channels or more, to limit the number of parts I need to put in a box
So, assuming I decide to go sources-ADAU1452 digitally, then have a DAC feeding an analog input class D amplifier, what DAC modules are good to consider?
I saw that the freeDSP uses an AK4458, while the ubiquitous ADAU1452 cheap Aliexpress/eBay boards the AD1938. The AK family DACs seem to have much better characteristics, but there are no AK-based boards readily available. I even considered building my own board, but the AK4458 is not in stock anywhere, with waiting times of 18 weeks 😱
Any other DAC else I should consider? Ideally 6 channels or more, to limit the number of parts I need to put in a box