The Linear PSU https://collybia.com/collybia-linear-power-supply/ gives no technical informations, such as schematic, layout, scope output signal measures…
From what I read, they use Ti TPS7A84A ldo (low drop out) chip.
It’s a very good regulator indeed, BUT, PCB layout is crucial, especially for this part.
I’ve commited some regs with them, hand soldered, I know a little about.
OTO, consider 139€ for a boxed single linear PSU…
You’ll find documented threads about DIY Linear PSU design.
Most geeksboxes requires 5V single PSU.
As TB requires about 120mA (5V), you’ll find better documented kits for this purpose.
Have a look at https://www.diyaudio.com/
Power Supplies section shows a lot of very good single linear PSU…
Unfortunately I can’t give more info about the Collybia lp supply because I simply do not know.
I am not a diyer so, although I visit diyaudio I can’t build anything.
I have some diyer friends though.
When we make any other tests with KTB I will post here. Along with some info about the second LPS.
I would like to make the second LPS work too because I am very curious if there will be any difference between the two.
Can anyone explain WHY when I connect the power cable directly on the power supply I get distorted sound but then I put in the chain the ifi iDefender without connecting it to the rpi it works just fine???
false alarm… it worked ONCE as I described above!
If i recall right it kept working even i unhooked the idefender from the rpi without shutting down or rebooting.
then after reboot … NO!
also with the LPS it doesn’t work with Y cable to the usb-c input of the DAC with switching ps it works!
One last update for now!
I did the following trick:
I hooked the usb-c cable of the KTB to the rpi through the Y cable but without connecting the power to it. Instead I used all the power supplies I had, linear or not, connected to the GPIO.
The result was that the TB didn’t work with none of them.
So this tells me that one way or another the dac needs some kind of power from the usb to work properly. Regardless the supply to the GPIO.
So with all the respect to the Khadas people and their product may be it isn’t so much “clever” as they stated in a previous post.
After the above I connected the usb-c cable directly to the KTB and used a simple LPS I remembered I had laying around (shown in the pic) and it worked just fine.
Now why it isn’t working properly in the exact same way but with the more sophisticated LPSes remains a mystery!!
Look at the TB schematic for answers. Power from the USB-C socket (DCIN_VBUS) is used as a signal by U12 to switch the USB data connection to the XMOS between the USB-C socket and the GPIO header input. You need 5V on the USB-C for its data connection to be used. Diodes D1 and D2 prevent either ‘5V’ supply backfeeding into the other, but there’s no formal switching - whichever is the higher voltage ‘wins’. In your case the easiest option is to get a USB B connector to wire to the GPIO header USB data connection, while supplying power from your linear supply to the GPIO power pins.
Incidentally I just noticed there are no resistors on the USB-C CC1 and CC2 pins. This will probably prevent a USB C to C connection working because there’s no indication to the host that a device is connected.
I made my own connector between phone and TB. With power on pins 1 and 21 the USB +5V wire is still needed, the 0 wire is not needed. So only three of the USB wires need to be connected for USB input with external power.
Thank you!!!
I can not implement what you are saying by myself but I hope I’ll get some help to try it!
I guess that now it makes sense to me! From what I can understand!!
I was communicating with one of our Tone Board users on Facebook. He took the extreme method of powering his Tone Board using a power bank. I did not put this into the original blog post, because it seemed to me that (a) poorly-designed power bank circuits could be noisier, or (b) it would be inconvenient to use a power bank for long periods of time.
I am investigating how to power the generic tone board from a good power supply directly on the card and keep up as bridge from RPI (not through Y cable which I already manage).
I am confused on what to do to feed power. I understand it is through pin 1 and 21 as presented in this thread, here and on examples on picture here.
However, here it is also mention that a ship needs to be to de-soldered.
What is the exact method? Need to de-solder? Actually what is the purpose of this ship.
I made this circuit and it works extremely well. Its not exactly what i use (I use more filtering) but this is the basic principle. And it is powered by external linear transformer with LM 5v ultra low noise regulator.
Problem i have is whenever the inductive loads in home like fan, grinder etc turned off, khadas will disconnect from pc. I know it is very sensitive to voltage fluctuations but never thought it would be on this scale. With khadas connected directly to pc, this problem never occurred. Can Someone from khadas shed some light? Adding more caps is not solving the problem. Is there any other way around? Thanks
