CM6631A decoder and TPLink wireless adapter

Audio Gear DACs
1

This is indeed a great project, a wonderful way to use the Raspberrypi and an amazing way to listen and enjot music from high resolution files.

Bravo!

I have used a Tenor based USB decoder to play the high resolution files without any problems or difficulties. However when I used a CM6631A USB decoder there is no sound output. Is this because the drivers for the CM6631A are not yet provided in the OS?

I would also wish to request for assistance in using a TPLINK TL-WN321G USB Wireless adapter instead od the ethernet connection. Is this provided for in the OS?

Thank you,
Maestroji

2

Have you tried connecting connecting your raspberry to a wired network connection?

While researching for a wifi dongle for my raspberry, i came across this list.

elinux.org/RPi_USB_Wi-Fi_Adapters

TL-WN321G (Ralink RT2501/RT2573, rt73_usb) Works out of the box when plugged in before boot. Plugging in after boot only with powered USB hub. RasPi Model B, Rev. 2.0

I’m using a TL-WN727N and it works out of the box. I’m also getting a CM6631a board in a few day. Will let you know if it works.

Hope this helps.

3

Thanks dippy. I will await the results of using the CM6631A with high hopes.

4

Hi, I just got my CM6631a board today and its also not working for me. The board was only recognized when I used a 2A power supply. Even though the board was detected it wasn’t able to send an optical or coaxial signal to my DAC.

Any luck on yours? Any help would be appreciated!

Some notes

  1. Alsamixer detects it as High speed True HD Audio
  2. Using the command cat /proc/asound//stream0 gives the following
CMEDIA USB2.0 High-Speed True HD Audio at usb-bcm2708_usb-1.3, high speed : USB Audio

Playback:
  Status: Stop
  Interface 1
    Altset 1
    Format: S16_LE
    Channels: 2
    Endpoint: 5 OUT (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
  Interface 1
    Altset 2
    Format: S24_3LE
    Channels: 2
    Endpoint: 5 OUT (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us

Capture:
  Status: Stop
  Interface 6
    Altset 1
    Format: S16_LE
    Channels: 2
    Endpoint: 10 IN (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
  Interface 6
    Altset 2
    Format: S24_3LE
    Channels: 2
    Endpoint: 10 IN (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
5

Try to enable the C-Media Fix and let me know (menu -> system)

6

Hi Michelangelo,

Thanks for your prompt reply. Yes I have already tried the C-Media fix and still nothing.
This is the card I have

ebay.com/itm/CM6631A-USB-to- … 35cf3d4c4a

Seems that Alsamixer does not detect SPDIF Out for this board.

7

After some research and tweaking, I was able to get it to work. I had to change the firmware on my board to get the SPDIF out to work.

From 0108 VID 0x0D8C PID 0x0314 to 0101 VID 0x0D8C PID 0x0319

Description of the difference in firmware

Instructions from to change the firmware #211 (not sure if it works for your board, use at own risk)

Hope this information is helpful!

8

Dippy,

The link to Diyaudio you referred to had referred to the CM6631a not being able to output any frequency higher than 48KHz after being flashed with the new firmware.

Would you confirm that the firmware 101 that you utilised to get the CM6631A working with volumio, is able to output 24/192?

Thanks

9

Hi mllum88,

Yes i just downloaded a couple of 24bit 192k files and it plays fine…BUT there is stuttering. There is stuttering also on 96k files. Tried putting the file on RAMplay but still stuttered.

10

Hello Dippy,

Would this stuttering have anything to do with the low power of the Raspberry CPU and the small amount of RAM on the Raspberry board.

Thanks.

11

Hi maestroji,

You are exactly right, I overclocked my raspberry to 850mhz and there was a great improvement. Thanks!

12

I am happy to know this Dippy.

13

Good to know! Could you guys report if the overclocking creates some issues? Maybe tell me if after a week the system is already working, if you see some errors while booting etc…
We can make this default…

14

Hello guys.
I wish to raise a small issue pertaining to audio output.
I happen to use the CM6631A USB Decoder with a AK4396 DAC.
With the Raspberry/Volumio sample rate setting at 24B96K all files with sample rate of 24B96K or lower play smoothly without any stutter or any problem.
However files with sample rate of 24B176K and 24B192K and 32B192K stutter badly.
On the other hand when the sample rate setting is 24B192K all files with sample rates of 24B192K and 32B192K play smoothly and without any problems, however files with lower sample rates like 24B96K to 16B44K stutter badly.
I would be greatly pleased for your views on this apparent paradox.
Thank you.

15

Hi Michelangelo,

Did you mean CS8416? I might be wrong but I think it does 192K.

My system = Raspberry Pi USB -> CM6631a -> Coaxial -> DAC (CS8416 + PCM1798)

24b192k files work OK for me on an overclocked Raspberry playing from USB storage (some random glitches)

Not possible to stream get glitch free stream from my NAS. I still get occasional glitches for even for 16b44.1k FLAC. I suspect the USB bus is struggling to cope with both audio and WiFi data at the same time.

16

I am currently using a Rev B Raspberry Pi, overclocked to 900Mhz, USB connection to a CM6631A, to my StageDAC. I am using a NAS storage, via a (ID 0bda:817b) Realtek wireless dongle. I also have an external USB drive attached too. I was concerned about noise, so I used an external power supplied, USB hub, attached is the wireless dongle and a USB drive. I wanted to isolate the power supply noise, so used a short USB cable between the Pi and the hub, were only connected with the +D and -D terminals, the 5Vdc is cut.

  1. Even with the power isolation of the Hub, I had many pops and clicks. With and without the CM6631 work around on or off.
    Two things had resolved this.
    A. Overclocking to at least 800Mhz
    B. Update to rev 1.2Beta

  2. To reduce SSD wear, I copied the root file system to a partition on the USB disk and grew it to 16GB. Then edited the cmdline.txt on the boot partition to point to the new partition, over the root partition on the SSD.

  3. I like bit perfect, so never change any bit rates.

  4. Buffer is set to 4096 and preload 30%

  5. Do not need to use the CM6631 fix

  6. Use the default Kernel, but have not seen any issues changing it either

  7. I installed Fuse exFAT, for my Music partition is an exFAT. (The disk has two partitions, exFAT and a ex4.

I do not get any pops, or clicks, it plays very well, via, NAS, and USB. The library consists of 16-32bit 44-192Khz recordings. I am going to replace the pi with a Cube-i soon, for a diskless configuration, using only a NAS based library.