Hi All,
I have been developing a Bluetooth Amplifier board and have come across an issue. The BT audio module I was intending on using (BM64) has a pin out for right channel out (AOHPR) and a left channel out (AOHPL) which is odd as most BT audio modules have 4 pins a L-, L+, R-, R+. What would be the negative inputs in the case of the BM64 be. The datasheet is unclear. It seems that maybe AOHPM could provide ground for both but I thought the negatives were normally kept separate for each channel.
You may ask why use this module at all then but it offers BT 5.0, relatively easy programmable control and an aux in input. Unless anyone knows one similar with L-, L+, R-, R+ output pins.
Anyway here's the datasheet: http://ww1.microchip.com/downloads/...tereo-Audio-Module-Data-Sheet-DS60001403E.pdf
Any help on this would be much appreciated.
Thanks all!
Jonny
I have been developing a Bluetooth Amplifier board and have come across an issue. The BT audio module I was intending on using (BM64) has a pin out for right channel out (AOHPR) and a left channel out (AOHPL) which is odd as most BT audio modules have 4 pins a L-, L+, R-, R+. What would be the negative inputs in the case of the BM64 be. The datasheet is unclear. It seems that maybe AOHPM could provide ground for both but I thought the negatives were normally kept separate for each channel.
You may ask why use this module at all then but it offers BT 5.0, relatively easy programmable control and an aux in input. Unless anyone knows one similar with L-, L+, R-, R+ output pins.
Anyway here's the datasheet: http://ww1.microchip.com/downloads/...tereo-Audio-Module-Data-Sheet-DS60001403E.pdf
Any help on this would be much appreciated.
Thanks all!
Jonny
The headphone outputs are single ended. The data sheet states that you use left, right and "m" which might be for "middle" and is signal ground.
For such noise sensitive stuff like a Bluetooth thingy a bridged output would make sense, but this one does not have it. If you connect Headphones this is no problem, what you get with a high impedance amp input is yours to find out.
For such noise sensitive stuff like a Bluetooth thingy a bridged output would make sense, but this one does not have it. If you connect Headphones this is no problem, what you get with a high impedance amp input is yours to find out.
HI Jonny,
actually the audio out is configurable, what i mean to say is - it can be set as psuedo differential ( default shipped mode ) or single ende ( nned to use caps ) or sigle ended capless.
For the above setting you need to use the configuration tool. and there is one page where it configures the output type and also if you want the dac to be always on or on when it receives data, and what should be the attack time for the dac etc.
i have BM20 which is most economical one from the lot.
also just for further input OVC3680 modules also have similar psuedo differential output where the audio common terminal is not actually ground but its a 3 pin differential u can use a standard 2 opamp diff to single ended method to make it single ended. Best would be TI series OPA6XX which are line driver 2vpp or 3vpp and have internal -ve supply.
Yes Barry you can use it as stand alone, using a micro controller is just an option
Thanks for getting back to me on this. Yes I went for the RN-52 in the end even though the Bluetooth is a bit outdated. I will probably find a newer module soon. Any suggestions for modern ones with differential outputs?
Currently, due to the semiconductor manufacturing situation as there are many shortages I see 2 options.
1) BM 83 or BM62 or BM64 - in Pseudo-Differential mode. ( * FCC approved major advantage )
2) OEM / Chinese modules using Qualcomm (CSR ) chip module. ( would be a little tough to get FCC approved module )
3) BM64 module configuration tool documentation will show you how to do these BM modules as single-ended or pseudo diff.
if you have more questions you may PM, I will help out.
I would still prefer using pseudo-differential mode with an op-amp to do single-ended output though you could configure the BM module to work in Single Ended mode which is not possible in the CSR ( Qualcomm ) based Bluetooth module.
I m using one of the BM series modules for my amplifier but
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Thanks, I'll take a look at it again in the coming weeks. Chip shortages are causing crazy issues for my day job as well so imagine it's the same for audio hardware. I'd be interested to find out what the latest Dayton Audio boards are using these days. I had a look again recently and it's cool to see they have onboard DSP now.
When you say pseudo differential what is this? Is this some form of forced true differential and how does it compare to the RN-52 using the differential (L-, L+, R-, R+).
Thanks again!
Dayton is a mass consumer and as per my thoughts, what they use may be a little hard to get. they could be using OEM parts so those will not be easily available on the regular distribution sites like digikey or mouser or element 14.
you would need a large MOQ. If you want what Dayton uses.
Aliexpress does have a lot of Bluetooth modules but I personally have never bought from them.
recently I have come across ( seen online on some board ) some Mediatek chip based module. But than again what is oem manufactured their datasheet would be hard to get by.
Pseudo differential is L+ , (L- + R-), R +, therefore when you see the datasheet it says L - common - R.
to make it single ended you need to take the normal diff to single ended opamp confirmation and connect “common headphone” to the inverting input as if you has L - and R -