I'm taking apart an Onkyo amp from 2015. I'm breaking it into two projects. I'm building a 500W sub and a DAC with Amp for my HiFiman HE-5Se headphones. The amp has all the chips PCM, ARM processor, 128MB RAM etc. but no Bluetooth IC. I'm looking for a digital Bluetooth receiver IC, no built in DAC and pre-amp. Suggestions? I want my music to play from my phone and need to transmit and receive a PCM signal. Feedback welcome . . .
News to me, unless I missed something Silicon Labs are the only producers of Bluetooth technology. Though the WT32I-A-AI6-APTX chip is not recommended by SiL for new projects it remains their recommended product for audio purposes. Unlike its successors it isn't designed as a general-purpose microcontroller, however it does provide a built-in audio DAC and PCM throughput which the newer one doesn't. It has built in control for charging a battery, which for me will be some kind of a Samsung flat-pack. Everything I need.
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There are many good options. Just about any modern Bluetooth SOC will have a built-in DAC, but you don't have to use it--just use the I2S output, which is available on a lot of these modules.
What is most important is the CODEC used to encode the data over the A2DP transmission profile. A2DP specifies SBC (sub-band coding) as a minimum, but there are several variations on SBC and some newer CODEC's that can provide better audio quality than the minimum SBC implementation. Qualcomm purchased CSR and their SOC's are very good, with support for the aptX CODEC.
Look for a module with the QCC3008--they are about $10-$12 at aliexpress. The QCC3008 is a Bluetooth 5 SOC that has both differential analog output and I2S output. Here is a link: QCC3008 Bluetooth V5.0 Low Power Bluetooth o Module APTX LL Lossless Compression TWS I2S|Voice Recognition/Control Modules| - AliExpress. I ordered one on August 15 and it arrived today, so the delivery times aren't too bad.
What is most important is the CODEC used to encode the data over the A2DP transmission profile. A2DP specifies SBC (sub-band coding) as a minimum, but there are several variations on SBC and some newer CODEC's that can provide better audio quality than the minimum SBC implementation. Qualcomm purchased CSR and their SOC's are very good, with support for the aptX CODEC.
Look for a module with the QCC3008--they are about $10-$12 at aliexpress. The QCC3008 is a Bluetooth 5 SOC that has both differential analog output and I2S output. Here is a link: QCC3008 Bluetooth V5.0 Low Power Bluetooth o Module APTX LL Lossless Compression TWS I2S|Voice Recognition/Control Modules| - AliExpress. I ordered one on August 15 and it arrived today, so the delivery times aren't too bad.
Response to Indiglo
Indiglo. My bad, I may have used filters like audio. So there is more than one manufacturer, and there are varieties based on specific technologies included in one over another. A revised WT32I-A-AI6-APTX would be best TBH. Still going through the list Indiglo linked.
[EDIT]
I just became aware of the tunnel size of Bluetooth, so having a DSP kind of makes sense now. Looking at other tech, i.e. RF.
Indiglo. My bad, I may have used filters like audio. So there is more than one manufacturer, and there are varieties based on specific technologies included in one over another. A revised WT32I-A-AI6-APTX would be best TBH. Still going through the list Indiglo linked.
[EDIT]
I just became aware of the tunnel size of Bluetooth, so having a DSP kind of makes sense now. Looking at other tech, i.e. RF.
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PCM vs Compressed File
After long research into the topic I've arrived at some presumptions.
i) Unless I program my cellphone to do otherwise, all signals over I2S will be PCM and will not rely on compression algorithms like aptX or A2DP.
ii) The Cypress CYW20721 BT5.1 guarantees 3072kb/s transfer rate which produces both 48khz 24bit and 96khz 16bit stereo for choice.
iii) The I2S connection is actually faster than UART over Bluetooth HCI which seems to be 2Mb/s, so sending compressed audio over UART is pointless.
iv) Essentially I can't play lossless FLAC over Bluetooth, even if I programmed my own android media player and 'reworked' the signal. IMO unpacking a FLAC file and repacking it in aptX would still bring the quality down.
v) It looks like I can accept the 96khz 16bit stereo limit or I can write my player and send whatever I want over I2S or I can write my own player and use WiFi or RF . . . something like that.
thx all
After long research into the topic I've arrived at some presumptions.
i) Unless I program my cellphone to do otherwise, all signals over I2S will be PCM and will not rely on compression algorithms like aptX or A2DP.
ii) The Cypress CYW20721 BT5.1 guarantees 3072kb/s transfer rate which produces both 48khz 24bit and 96khz 16bit stereo for choice.
iii) The I2S connection is actually faster than UART over Bluetooth HCI which seems to be 2Mb/s, so sending compressed audio over UART is pointless.
iv) Essentially I can't play lossless FLAC over Bluetooth, even if I programmed my own android media player and 'reworked' the signal. IMO unpacking a FLAC file and repacking it in aptX would still bring the quality down.
v) It looks like I can accept the 96khz 16bit stereo limit or I can write my player and send whatever I want over I2S or I can write my own player and use WiFi or RF . . . something like that.
thx all
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The limiting factor is the wireless physical interface which if using EDR mode will give a nett data rate of around 1Mbps. This is the reason for the various types of audio codecs and why they are limited to around 900kbps or less.
Bluetooth is convenient for wireless headsets and mobile phones because of the ease of connectivity, just pair the devices and away you go.
If you want to stream uncompressed audio at high data rates then Wifi will need to be used.
Bluetooth is convenient for wireless headsets and mobile phones because of the ease of connectivity, just pair the devices and away you go.
If you want to stream uncompressed audio at high data rates then Wifi will need to be used.
The phrase "over I2S" is causing confusion here. I2S is a standard for interconnecting chips: it stands for inter-IC sound. It isn't a high-level protocol for sending data from one device to another--for that, you need to look at Bluetooth, WiFi, ethernet, etc.
But as Indigio points out and as you have discovered, Bluetooth doesn't provide the bandwidth for reliable transmission of uncompressed audio. However, WiFi does. And there are a lot of WiFi receivers available to the DIY community that would allow you to send FLAC files from your phone to your receiver. The most popular module is made by Linkplay (WiiMu), and you can get the Linkplay receivers embedded in many different brands of "smart speakers". Parts Express sells several Linkplay-based receivers that you could integrate into your project, and they even sell several "raw" modules that you could use. The module that has been around for several years but it still used in current products is the WiiMu A31. Do a search on that part on these pages to find more information.
But as Indigio points out and as you have discovered, Bluetooth doesn't provide the bandwidth for reliable transmission of uncompressed audio. However, WiFi does. And there are a lot of WiFi receivers available to the DIY community that would allow you to send FLAC files from your phone to your receiver. The most popular module is made by Linkplay (WiiMu), and you can get the Linkplay receivers embedded in many different brands of "smart speakers". Parts Express sells several Linkplay-based receivers that you could integrate into your project, and they even sell several "raw" modules that you could use. The module that has been around for several years but it still used in current products is the WiiMu A31. Do a search on that part on these pages to find more information.
As I've come across I2S can pipe anything you want i.e. mp3 as bi-wire serial bus provided you create the streams(Android.media AAudio) and sink them yourself just for fun right? I assumed I2S always played PCM which might be wrong. It seems it is compressed into SBC--gross--before transmitting, that's a problem. There must be a does not accept SBC enum. The problem I did come into was what is Bluetooth itself. The answer I came to is that Bluetooth is a high level protocol known as HCI or Host Controller Interface which operates over UART or USB 2.0. I am however looking at WiFi at this point.