Tone board : external powering

It’s easy to connect 5V power to pins 1 and 21. The usb c input still works. This way I can use my phone to play music to the Khadas dac over usb c. Without 5V to the pins my phone and Khadas won’t work together.

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You can plug a “Y” split on TB and use a USB type C data (only) cable between your RPi and the TB and a USB type C power cable between your external PSU and the TB.

If you don’t have data cable you can create yours, just cut power wire.

Power mod :slight_smile:

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Trying to follow this thread and after reading manual, I’m still confused if powering the board through pins 1/21 allows it to operate from that power while connected to source (such as phone) through USB connection.

It does with my phone. Else it would not make sense to power it seperately.

Agreed. So you still have power on the usb cable coming from your phone?

Yes, still the Khadas dac sounds better with additional 5V from power pack.

@JaapDeventer,
Have you tried to connect with PC by USB and send the signal from there and use the additional power supply?
I was thinking to make the same mod, but some people here wrote that in that case the board will receive electricity from two different sources each of which with 5V, and that will harm the board.
Other than that, I was thinking to power the board via USB and bring the signal via coax, but can’t find 500 mA power adapter. So will 5V 1A adapter harm the tone board or it won’t?

Don’t worry on this, 5V 1A works.

Just ensure the external power is clean & purity for a better sound.

Yes, that’s what I’m doing.

An additional power supply of the same voltage is usually not a problem with electronics.

A 5V 1A supply is not a problem. It has to be at least 0,5A (not more than 5V though).

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I use an Y-kabel.
https://www.tnt-audio.com/clinica/221_diy_usb_e.html

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@getdadams okay just asked @Gouwa one more time to be sure:

“If you connect an external power supply to pins 1 and 21 on the GPIO, the electrical power arriving via the USB-C port will be cut-off. So any noise arriving via USB-C power would also be silenced.” :smile:

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Hi to all!
I am new here!
I have received KTB the day before and I can say that it’s quite a DAC for the price!
OK flagship killers don’t exist IMO but KTB is goood!!

I tried it from my RPi3B+ running piCoreplayer and from my old Mac mini running JRiver25/Audirvana.
I also use ifi’s iDefender that gives the option to use an external power from it’s micro USB in.
So I used iFi iPower (supposed to be a low noise SPS) and another DIY Linear Power Supply, made from a local diyer, based on a TI chip that reduces noise, that i normally use to power my RPi.
From past experience with DACs I know that a good power supply can make quite a big positive difference to the sound of the DAC. Anyway the way(s) I did it the difference was not that big. Yes i think there was a slight improvement (sometimes with the diy LPS I had distorted sound … don’t know why) but not as big as I heard before with other DACs.

I can have a diyer friend make me a great newly designed LPS which I want to connect to the GPIO. If done right will there be a greater diffrence than the way I described above? From your experience powering through gpio is the improvement worht the effort and the cost? The LPS I am talking about is quite expensive just for the parts (almost as KTB) so I want to hear some thought if the whole project will worth!!

Thank you in advance!
Michael

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I did two different tests with separate power supply, but the sonic improvement was very very small that did not justify the investment in time and money.
I truly believe that the TB has been very well engineered that is almost “immune” to other power supply, which obviously with other DAC’s the difference was remarkable.
At the end, I choose to use the standard USB wire from the TB to my Intel Nuc.

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Mywalsh thank you for your reply!
Me and my diyer friend we might try a temporary gpio connection to an existing LPS just for test and we will see…
I suppose it won’t take much effort and time!

Any one else on the matter?
Thnx!!

DomieMic65 Your welcome!
Pls keep me posted.
Have fun!

If you’ve a mobile battery pack laying around you could give it a go. I like using mine as external psu for the Tone Board.

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@Mywalsh,
I hear audiuble noise when I turn all the way up the amp (without sound).
With my Creative ZxR (yes, internal sound card) I don’t have this noise!
That is why I’m searching another way to power the KTB.
I still haven’t tryed JaapDeventer mod.
But I’ll surely try Solveit proposal.

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You might interesting in this blog:
https://www.khadas.com/post/khadas-tone-board

Have fun!

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I will thnx!
You too!!