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Class D Switching Power Amplifiers and Power D/A conversion

DSPed, portable/embeddable classD design advice
DSPed, portable/embeddable classD design advice
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Old 6th October 2019, 06:47 PM   #1
dimavb is offline dimavb
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Join Date: Sep 2018
Smile DSPed, portable/embeddable classD design advice

Hi!
I want to make a small, embeddable (and stand-alone capable also) amp, mainly for TWS speakers. Small speakers
It`s can be interesting for another people too, so I can make some things "as you say" =)

There are some hard desicions for me, so its interesting to see some thoughts from you.

My plan:
-Battery powered.
-Wireless (TWS preferred)
-Small
-Cheap
-DSPed, cortex-m7 (stm32F7/H7), audioweaver maybe?
-USB audio device.

Soooo.
Power.
PAs (2x TAS2770) will be powered from battery without DCDC. So 3S-4S li-ion. Charging via buck-boost charger bq25703a. Charging from USB-C, and any 5-24V source will be good.

Wireless.
Bluetooth + cc8520. CC8520 is for retransmition of received data to another speaker.

And questions
- Is there any reasons to integrate a battery balancer or any other battery management circuits? There are a lot of cheap solutions, and batteries with already integrated one. But I don`t trust them

-Is there any reasons to use a Bluetooth module and CC8520? I believe BT with aptx can be enough, but is there any good (and somehow configurable) BT modules with TWS support and I2S _input_ and output?
I need input as I want to retransmit data received by USB, and may be analog in also (or any other i2s source) but I found that TWS possible only for a2dp sources.
Usage of CC8520 is a bit hard mainly because of need of RF PCB design.
I`m also limited in i2s buses in case of stm32f7 (H7 is better, but there are another trade-offs)

-Is USB-C needed? universal charging solution for USB-BC and USB-PD is a bit expensive. 19v Barrel jack input is best one in question of implementation price) (Also buck-boost is not needed with 19V input)

soo... any thoughts?
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Old 7th October 2019, 01:30 AM   #2
Turbowatch2 is offline Turbowatch2  Germany
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Location: Northern germany
Yes. Im confused. Very...
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Old 7th October 2019, 07:47 AM   #3
lutkeveld is online now lutkeveld
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Join Date: May 2013
Have a look at the BTM625. It has APT-X, TWS and is reconfigurable
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Old 17th October 2019, 04:06 PM   #4
ButtCarcass is offline ButtCarcass  United States
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Join Date: Nov 2013
Location: Atlanta
Hi there, I've been lurking this forum for many years but I don't post often because usually I find answers without even asking.

I'm looking to do a similar thing, OP. (Assuming TWS means "two wireless speakers" or something else that means separate wireless speakers for left and right channels. I'm sure someone will fill me in on the actual acronym lol.) I also want most of the functionalities you've listed in the build I'm designing for.

I've wanted separate channel stereo portable bluetooth speakers for a couple years now. It seems no matter how well you make portable bluetooth speakers, the channels are really just coming from either side of a small box, so they end up sounding like anything else coming out of a small box.

With efficient amplifiers, efficient small drivers that can make decent bass (with proper enclosure, etc) and cheap class D boards, portable DIY audio has gotten way more affordable in recent years. Now it's possible to make it portable and high quality sound - but separating this into stereo channels still seems to be a bit of a dark area. (or maybe my search abilities are lacking?)

My friends gather often for outdoor stuff, at different places public and private - most of which could benefit from some music. Some of us have expensive portable bluetooth speakers, but they all suck because no matter what you do, the sound is coming from one place. There's a couple systems that you can do TWS with, but they are small and stupid expensive for what they do. So I was thinking it would be interesting to try building a two unit system with wheels to move them over grass and through doorways with low impact on surfaces. It would be an excuse for sawdust creation, welding and powder coating, and a bit of soldering - all of which I love to do.

Plus it would be badass at a round of beer bocce. I imagine the cabinets would have extra battery pack for each, something I could print parts for. Design will be fun. : )

So far I've found the modules lutkeveld mentioned:
Audio Receiver/Transmitter

Also, there's a more promising system by a company called "Acrylic" but technically, it's not cheap, as you would need two of these $50 boards:
Up2stream Pro WiFi&Bluetooth HiFi Audio Receiver Board
– arylic


There's content on YT about both of these product lines, but no implementation for TWS / multicast are proving stereo sync for two wireless channels to actually work.
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Old 17th October 2019, 04:19 PM   #5
ButtCarcass is offline ButtCarcass  United States
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Location: Atlanta
Here's a video of TWS setup with the cheaper TinySine board:
YouTube

EQ settings on TinySine boards:
YouTube

And the only decent video I can find regarding Up2Stream boards:
YouTube
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Old 19th October 2019, 06:25 PM   #6
ButtCarcass is offline ButtCarcass  United States
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Join Date: Nov 2013
Location: Atlanta
Mind if I bump this?

I honestly cannot believe nobody else wants to design/build a pair of portable separate channel BT speakers.
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Old 21st October 2019, 04:15 PM   #7
Boden is offline Boden  Netherlands
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Maybe a bit off topic, but as I understand the CSR 64xx series have a programmable equalizer onboard.

Does anyone here know whether this equalizer can be programmed as x/.over filter?
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Old 21st October 2019, 09:59 PM   #8
lutkeveld is online now lutkeveld
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Crossover implies that you need a separate filter for each channel. The equalizer is applied to both channels, so that's not possible
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Old Yesterday, 06:43 AM   #9
Boden is offline Boden  Netherlands
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Ah, I already feared that from the block diagram, but was hoping to have it wrong....
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