Dear Community,
I need some help and your advice will be very appreciated.
At the moment, I am using the RPI 4 as end point. The Khadas tone board is connect with the RPI 4 by USB Khadas cable found in the box. In order to improve the sound (actually I am happy with the RPI + DAC but I would like to make some experiment), I want to power the KTB using the GPIO connection. My question are:
1) If I use the GPIO to power the KTB, can I sill use the USB-C just (link to RPI) to input the signal?
2) If I use the GPIO to power the KTB and the USB-C (link to RPI) just to input the signal, should the USB cable be without +5V connection (red wire cut) in order to avoid a double power supply or useless connection (which can introduce noise)?
3) Could you suggest a power supply you know is good in your experience, without sell the house? Is the IFI Ipower 5V a good solution? Do you have a better one?
4) Please could you suggest a good USB cable in your experience? without sell the car..
5) Do you know if USB cable has to have demanding 90ohm +-15%? Or less is better?
Thank you so much in advance. Thank you for the attention.
Kind Regards,
Francesco
I need some help and your advice will be very appreciated.
At the moment, I am using the RPI 4 as end point. The Khadas tone board is connect with the RPI 4 by USB Khadas cable found in the box. In order to improve the sound (actually I am happy with the RPI + DAC but I would like to make some experiment), I want to power the KTB using the GPIO connection. My question are:
1) If I use the GPIO to power the KTB, can I sill use the USB-C just (link to RPI) to input the signal?
2) If I use the GPIO to power the KTB and the USB-C (link to RPI) just to input the signal, should the USB cable be without +5V connection (red wire cut) in order to avoid a double power supply or useless connection (which can introduce noise)?
3) Could you suggest a power supply you know is good in your experience, without sell the house? Is the IFI Ipower 5V a good solution? Do you have a better one?
4) Please could you suggest a good USB cable in your experience? without sell the car..
5) Do you know if USB cable has to have demanding 90ohm +-15%? Or less is better?
Thank you so much in advance. Thank you for the attention.
Kind Regards,
Francesco
Its probably best to have the dac and the RPi powered separately. RPi is pretty noisy in terms of conducted and radiated EMI. Its power rails are noisy along with other parts of it.
However, iFi ipower is not too bad for a SMPS. However, IMHO its not as good as a good linear supply. I have used ifi for RPi with okay results. Personally, I would not use it for a dac.
However, iFi ipower is not too bad for a SMPS. However, IMHO its not as good as a good linear supply. I have used ifi for RPi with okay results. Personally, I would not use it for a dac.
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Hi Markw4,
Thank you so much for your answer. All right IFI power is good enough for RPI. Are you using different power supply for RPI than Ifi power? And for the DAC what do you suggest? What do you mean exactly with " IMHO its not as good as a good linear supply"? My apologies but I am not sure I understood what IMHO means.
Thank you so much again!!
Francesco
Thank you so much for your answer. All right IFI power is good enough for RPI. Are you using different power supply for RPI than Ifi power? And for the DAC what do you suggest? What do you mean exactly with " IMHO its not as good as a good linear supply"? My apologies but I am not sure I understood what IMHO means.
Thank you so much again!!
Francesco
I use a sliver of tape over the USB connector's + pin, else you'll have two power sources interacting with each other. The power can be fed through KTB's GPIO, or you could use an off-board injector. Either works and the route into the KTB's circuitry is exactly the same. Soldering a full GPIO just for two pins seems a lot of effort.
Note that the XMOS receiver can act very funny when powered this way, detection reliability is quite poor. Many DACs leave the XMOS on the USB supply and use other means to power the rest of the circuitry.
Note that the XMOS receiver can act very funny when powered this way, detection reliability is quite poor. Many DACs leave the XMOS on the USB supply and use other means to power the rest of the circuitry.
I use a DIY linear supply for the most critical applications unless space is tight, in which case I use an iPhone charger (I don't own an iPhone, the supply is pretty good 
) Pi4 is actually quite high current and you do need a supply with good transient performance. When I don't care too much (which is bout 50% of my devices), I stick an old mobile charger into the Pi
I've also successfully used a Meanwell LRS50-5 which is enough to power a Pi4 and a few hard drives running off a powered USB hub. You do have to hack a few cables, but it works great.
For the DAC I have mostly stuck to linear supplies, usually series regulators with a cap multiplier following it. For very low current applications (<100mA) I also use a shunt regulator. I rarely use a switched supply to power a DAC unless it's a very casual setup.
) Pi4 is actually quite high current and you do need a supply with good transient performance. When I don't care too much (which is bout 50% of my devices), I stick an old mobile charger into the PiI've also successfully used a Meanwell LRS50-5 which is enough to power a Pi4 and a few hard drives running off a powered USB hub. You do have to hack a few cables, but it works great.
For the DAC I have mostly stuck to linear supplies, usually series regulators with a cap multiplier following it. For very low current applications (<100mA) I also use a shunt regulator. I rarely use a switched supply to power a DAC unless it's a very casual setup.
Please could you give me some further info regarding "For the DAC I have mostly stuck to linear supplies, usually series regulators with a cap multiplier following it. For very low current applications (<100mA) I also use a shunt regulator. I rarely use a switched supply to power a DAC unless it's a very casual setup.". I am not an expert but I like diy if I can follow guide.
Many thanks in advance!!!
Many thanks in advance!!!
Francesco,
Khadas Tone Board is a very nice measuring dac for the price. However, whether or not it is a very good sounding dac is probably more a matter of opinion. Some people may like it and others may be looking for something they like better. May I ask, how to you like the sound so far, and what is your purpose in asking about power supplies? To get better sound?
Khadas Tone Board is a very nice measuring dac for the price. However, whether or not it is a very good sounding dac is probably more a matter of opinion. Some people may like it and others may be looking for something they like better. May I ask, how to you like the sound so far, and what is your purpose in asking about power supplies? To get better sound?
