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Modded RPi4 (CM4+I/O Board) as Music Streamer


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Hello, i already made a similar thread over on DIYAudio (tho it didnt gather any results yet)

 

https://www.diyaudio.com/community/threads/modded-rpi4-board-for-better-sq.381877/#post-6917459

 

basicly the goal is to make a very light musicstreamer with as little noise and best SQ as possible :)

 

In short those are the ideas i had so far

 

1. replace the DC/DC Converters, one step further would be to provide the different voltages directly but i think thats a step too far, and someone also posting here said good dc/dc converter do make nearly the same effect (maybe add filter capacitors too?)

2. filter capacitors for usb, maybe as a sort of decoupling for all usb devices drawing power?

3. remove the BT/WIFI modul or disable it in some way, since even if disabled in config it still actively transmits

4. replace the clock(s) for better ones

5. remove the headphone amp circuitry and maybe other unneeded stuff?

 

6. add more filter/decoupling capacitors over all

 

7. underclock for less noise

 

8. adding shielding? something like the stationpi trys to accoumplish https://www.audiophonics.fr/en/raspberry-pi-and-other-sbc-accessories/ian-canada-stationpi-pre-assembled-adapter-pcb-for-raspberry-pi-and-audio-modules-p-14868.html , the i/o board has enough room to basicly do the exact same thing, ground plane under the CM4 and grounded heatsinks for the cm4 is probably also a good idea

 

9. using isolators to attached usb devices (bt and wlan dongle and maybe storage, tho my goal is to get a nas) and network

 

10. i had good expierence with diy chinch connectors/endcaps filled with turmaline, i had the idea todo the same for USB (and maybe other things but i will see)

 

i think the CM4+ I/O Board would be a very good alternative to the normal RPi4B since the CM4 modul can be bought without wlan/bt module and with inbuilt emmc (also a good thing is if i break something (cm4 or i/o board) its cheaper to get a replacement :D) thanks to tim curtis for the idea :)

https://www.reichelt.de/raspberry-pi-compute-modul-4-4gb-ram-32gb-emmc-rpi-cm4-4gb32gb-p290538.html

https://www.reichelt.de/raspberry-pi-compute-modul-4-io-board-rpi-cm4-io-board-p290556.html

(probably paired with this usb 3.0 https://www.waveshare.com/product/pcie-to-usb-3.2-gen1-b.htm)

i plan to use the pcie slot for usb 3.0, just like the RPi4B, so the usb 2.0 hub can be used only for a dac

 

one extension hat that got my attention was this one: https://www.thanksbuyer.com/ustars-audio-pi4-clock-system-clock-board-without-ocxo-for-raspberry-pi-4b-change-crystal-oscillator-73301?sort=p.model&order=DESC&limit=25 it basicly replaces the 3 clocks on the rpi4 with a single 10mhz high quality clock (and i think its probably a good thing all clock signals are derived from a single clock) tho im unsure if its also completly combatible with the CM4, since i dont find clock values on the web i have to wait till i get mine to check 

 

i should also say, i know about the allo signature but from my understand it mainly focuses on adding filter capacitors and not really more and the usb 2.0 output still shares the bus with network (because it uses the rpi3) and i wanna have a little modding/diy fun :)

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9 minutes ago, chauphuong said:

Buy an Allo Usbridge Signature, replace CM3+ with CM4, change clocks and it would be wonderful.

those adapter makes the cm4 combatible but i think the usbbridge signature would still be limited since most cm4 features wont be used (seperate usb and ethernet for example)

and i kinda dont wanna buy it that late in fear a updated version gets released soon, kinda wondering why they didnt come up with a better version yet 

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1 hour ago, the_bat said:

Mainly because the Pi4 and CM4 are pretty well unobtainable

are they? i hadnt problem finding them in stocks, tho it was like early 2020 unobtainable

 

12 hours ago, chauphuong said:

Usbridge sig has separate usb and Ethernet feature.

hmmm are you sure? maybe ethernet has a own chip but im pretty sure it and the usb chip end up in the same bus because the PI3 has not any buses to spare 

pretty sure it looks like this:

20021811.png

 

tho i guess they did a good job since noone is complaining about it but in the end i dont feel like spending 250€ on just the board and rather mod the 35€ i/o board myself including all cm4 features like:

 

1. emmc 

2. no inbuilt wlan/bt

3. acting kinda like a stationPi with a added shield

4. completely standalone usb2.0 bus

5. you can add a standalone usb 3.0 bus for storage/other usb devices or other pcie stuff if you feel like it

6. having all I/O on one side is kinda a big deal if you wanna put everything in a 1/2 HE rack case like me

 

i think those are the main advantages

 

(tho i really like having a usb 2.0 hub JUST for the dac, i actually kinda wondering if i could skip the usb chip completly and go directly into the Pi since i just need one port, this would also cut the need for a better clock for the usb hub chip, but then it depends on the Pi bus/clock

 

 

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One big advantage of the official I/O Board is also that schematics are available, i think with that additional filter capacitors are quite easy to add, specially because my electronic knowledge isnt that good (just add them where already "capacitor banks" exists in the schematics) (beside that i couldnt find any boards that fits my needs as good as the official i/o board anyway)

so i probably stay with the cm4+i/o board idea, i will keep you guys updated with pics etc once i have the stuff here :)

would still be nice to hear some opinions "on-topic" :)

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  • 9 months later...

i wanna dig this up again since i probably start soon! (like 1-3 months soon)

 

Since the Raspberry Pi 5 isnt in sight the plan hasnt really changed 

 

New things to consider:

The CM4 IO Board actually can skip the whole usb 2.0 controller in "otg mode" where a micro usb socket is directly connected to the CM4 usb 2.0 lanes instead of the USB 2.0 Controller, i will definetly try this out for the DAC (normally this is just used to flash the emmc flash)

 

I will probably rip out the complete power section of the CM4 I/O Board and power it directly with LT3045 Power regulators, 

there are 3 main voltages needed: 5V, 3,3V and 1,8V

normally the PCIE Express socket needs 12V too but i will use this USB Hub https://www.waveshare.com/pcie-to-usb-3.2-gen1-b.htm

which steps down the 12V to 5V anyway, so i will also skip the step down regulator and power it with 5V directly

the 1,8V are needed for the CM4 itself

 

So ideally i can make a 5V Input from a Linear power supply and step down the 5V to 3,3V and 1,8V which is probably the most efficient way of doing this

 

Thats it for now, i will keep you guys updated

Any Ideas are still very much appreciated! :)

 

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I thought about putting a JCAT USB card in the pci slot of one of these and using it as an NAA for HQPLayer. The problem I ran into was I would need to develop a case for it myself and I have other outstanding solutions already so I decided it wasn't worth it. It is a neat idea though.

No electron left behind.

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  • 1 month later...

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