Quick Intro:
In another thread I posted a picture my RME ADI-2 DAC running off of a powerbank. I received a PM asking for more details about how It worked so I though I'd type up something a little more comprehensive.
This should hopefully be useful to complete noobs and not require any tools besides a multimeter, a wire stripper, and a glasses screwdriver. I've tried to include explicit mentions of various safety checks which would to obvious to someone more experienced but hopefully others can read though it and point out anything I may have missed.
If anyone is interested in doing this for themselves but a little unsure please reply to the thread and ask for help. Onto the show...
The first thing to understand is USB C Power Delivery. It's a spec for a variable charging system which can output between 5 and 20 volts at up to 5 amps. The device to be charged can negotiate with the charger to pick what available voltage and current it would like. This makes one charger or powerbank could be capable of powering various devices with different power requirements.
The only "downside" to this is that it's new so plenty of things which could support it don't.
I got excited when I first heard about the spec since the higher voltages could provide a way to power all sorts of home/desktop gear away from mains power or rolling your own battery pack. I looked into the spec and hoped it would something simple I could DIY with a couple of resistors or something to set the voltages, but alas it required a microcontroller. After a lot of searching and eventually discovering the magic search terms I came across the PD Buddy Sink, which did exactly what I needed. The PD Buddy Sink is a bare board with a USB C socket, a programmable microcontroller, and power takeoff. I ordered one with screw terminals for ease of connection since I don't like soldering at such a tiny pitch.
To program it, hold in the setup button while plugging it into you computer. It will connect as a virtual serial device to enable programming. I had to patch mine through to a Windows 10 VM because Windows 7 doesn't include the right virtual serial driver. Then you can send configuration commands with a console program such as PuTTy. Select serial as the connection type, type in the name of it's com port, (It will probably be COM3 but you can check in the device manager), leave the speed as is and hit open.
Now we're ready to pick our settings. This will depend on the device you want to power. Piecing together specs from a couple different places in the manual the ADI-2 DAC needs 12W of power and can accept voltages between 9.5 and 15. Documentation for the config console is here. The standard is pretty new and chargers and powerbanks don't always support a given current capacity or even specific voltages within the allowable range so I programmed mine with the same broad range I found in the manual. Here are the commands.
Note that it uses milliwatts, milliamps, and millivolts. This sets the preferred voltage to 12, the allowable range between 9.5 and 15, the total required power to 12W, and then writes that information to the flash. You can then use
Next you'll need to test it with a multimeter and your powerbank or charger. The terminal nearest the setup button is the ground, and it may be easier to measure with a multimeter if you hook up some short lengths of wires to the spring terminals. If you hooked up wires, make sure they aren't shorted, plug the PD Buddy into your charger or powerbank, and measure the voltage to see if it's capable of delivering it. Measure quickly because a powerbank will probably shut off after 20-30 seconds if the current drawn from the port is too low.
Different chargers and powerbanks will give different results as support for any given voltage seems to be all over the map. With the above settings my RAVPower powerbank will output 12V but my Anker wall charger won't do 12V at all. With the above settings it will output 15V. If I remove the range specification and just ask for 12V and 1A I don't get any power at all. That's why specifying the range is helpful. Since this isn't the intended use, it's also a good idea to measure what voltage you get from any new charger before connecting it to an expensive piece of electronics. Many SMPS's I've measured are a few percent higher than nominal rated voltage, even under load, so that should be expected from chargers and powerbanks as well. 2-5% seems typical IME. Any higher and you may not want to use it
Also keep in mind that a charger with a USB C port doesn't necessarily support power delivery. It may only support the USB 3/3.1 standards of 5V but with higher current. It should state that it is a "PD" or power delivery charger and give couple different specs detailing current capacity at a few different voltages.
If all that's worked out you're ready to try and power something from it. For my ADI-2 DAC I cut a barrel plug off an old, broken wall wart. Despite the locking plug it comes with standard 5MM/2.something barrel plugs will fit. If you don't already have a suitable plug and don't want to spend $7 on shipping for one part from a domestic seller or wait 3+ weeks for one to come from China for 99¢ you should have no trouble finding a charger or wall wart with a suitable plug for a dollar or two at a local Goodwill or other thrift/second hand shop.
Test fit the barrel with the wall wart unplugged and chop it off the charger. Strip a 1/4 inch or so from the ends and twist them very tightly so that a stray strand doesn't make a short circuit. Use the continuity checker on a multimeter to find which wire is connected to the inside of the barrel and which to the outside. For the ADI-2 the inside should be positive and the outside should be negative. Then feed the bare tips into the PD Buddy's screw terminals and tighten them down with a very small flathead screwdriver. The negative terminal is the one closest to the setup button. Don't plug it into the ADI-2 DAC yet.
Test that the positive and negative lines aren't shorted with continuity tester of the multimeter. Touch one probe to the outside of the barrel and stick the other inside the barrel. If the meter beeps at you, they're shorted. Remove them from the screw terminals, twist them up and try again. If you can't get it to stop showing continuity there may be something wrong with the wire or plug. Plug the PD Buddy in to the charger and confirm the voltage and polarity one more time. Place the positive probe (usually red) into barrel and hold the negative probe (usually black) against the side. You should see a positive voltage in the range of 9.5 to 15, depending on the abilities of your charger. If it shows a negative voltage unplug the PD Buddy from the charger, reverse the wires, and then plug it back in to retest.
If all that goes well you're ready to power your ADI-2 DAC from a power bank. Plug it in and see if can actually deliver enough current to keep it working. With the power bank mentioned above, my most current hungry headphones (modded Fostex T50 RP), and most of the DSP options on it has no trouble keeping up. About as loud as I would ever want to listen with those headphones is -10dB on high power and setting them on my desk and cranking it to +6 didn't trigger the low power error state mentioned in the manual.
I'm planning to pack my ADI-2 DAC, the powerbank, and a tablet into a hardcase for wandering around the headphone tables at AXPONA next year. Anyone else as nuts?
In another thread I posted a picture my RME ADI-2 DAC running off of a powerbank. I received a PM asking for more details about how It worked so I though I'd type up something a little more comprehensive.
This should hopefully be useful to complete noobs and not require any tools besides a multimeter, a wire stripper, and a glasses screwdriver. I've tried to include explicit mentions of various safety checks which would to obvious to someone more experienced but hopefully others can read though it and point out anything I may have missed.
If anyone is interested in doing this for themselves but a little unsure please reply to the thread and ask for help. Onto the show...
The first thing to understand is USB C Power Delivery. It's a spec for a variable charging system which can output between 5 and 20 volts at up to 5 amps. The device to be charged can negotiate with the charger to pick what available voltage and current it would like. This makes one charger or powerbank could be capable of powering various devices with different power requirements.
The only "downside" to this is that it's new so plenty of things which could support it don't.
I got excited when I first heard about the spec since the higher voltages could provide a way to power all sorts of home/desktop gear away from mains power or rolling your own battery pack. I looked into the spec and hoped it would something simple I could DIY with a couple of resistors or something to set the voltages, but alas it required a microcontroller. After a lot of searching and eventually discovering the magic search terms I came across the PD Buddy Sink, which did exactly what I needed. The PD Buddy Sink is a bare board with a USB C socket, a programmable microcontroller, and power takeoff. I ordered one with screw terminals for ease of connection since I don't like soldering at such a tiny pitch.
To program it, hold in the setup button while plugging it into you computer. It will connect as a virtual serial device to enable programming. I had to patch mine through to a Windows 10 VM because Windows 7 doesn't include the right virtual serial driver. Then you can send configuration commands with a console program such as PuTTy. Select serial as the connection type, type in the name of it's com port, (It will probably be COM3 but you can check in the device manager), leave the speed as is and hit open.
Now we're ready to pick our settings. This will depend on the device you want to power. Piecing together specs from a couple different places in the manual the ADI-2 DAC needs 12W of power and can accept voltages between 9.5 and 15. Documentation for the config console is here. The standard is pretty new and chargers and powerbanks don't always support a given current capacity or even specific voltages within the allowable range so I programmed mine with the same broad range I found in the manual. Here are the commands.
Code:
set_v 12000
set_vrange 9500 15000
set_p 12000
writeNote that it uses milliwatts, milliamps, and millivolts. This sets the preferred voltage to 12, the allowable range between 9.5 and 15, the total required power to 12W, and then writes that information to the flash. You can then use
get_cfg to verify the settings.Next you'll need to test it with a multimeter and your powerbank or charger. The terminal nearest the setup button is the ground, and it may be easier to measure with a multimeter if you hook up some short lengths of wires to the spring terminals. If you hooked up wires, make sure they aren't shorted, plug the PD Buddy into your charger or powerbank, and measure the voltage to see if it's capable of delivering it. Measure quickly because a powerbank will probably shut off after 20-30 seconds if the current drawn from the port is too low.
Different chargers and powerbanks will give different results as support for any given voltage seems to be all over the map. With the above settings my RAVPower powerbank will output 12V but my Anker wall charger won't do 12V at all. With the above settings it will output 15V. If I remove the range specification and just ask for 12V and 1A I don't get any power at all. That's why specifying the range is helpful. Since this isn't the intended use, it's also a good idea to measure what voltage you get from any new charger before connecting it to an expensive piece of electronics. Many SMPS's I've measured are a few percent higher than nominal rated voltage, even under load, so that should be expected from chargers and powerbanks as well. 2-5% seems typical IME. Any higher and you may not want to use it
Also keep in mind that a charger with a USB C port doesn't necessarily support power delivery. It may only support the USB 3/3.1 standards of 5V but with higher current. It should state that it is a "PD" or power delivery charger and give couple different specs detailing current capacity at a few different voltages.
If all that's worked out you're ready to try and power something from it. For my ADI-2 DAC I cut a barrel plug off an old, broken wall wart. Despite the locking plug it comes with standard 5MM/2.something barrel plugs will fit. If you don't already have a suitable plug and don't want to spend $7 on shipping for one part from a domestic seller or wait 3+ weeks for one to come from China for 99¢ you should have no trouble finding a charger or wall wart with a suitable plug for a dollar or two at a local Goodwill or other thrift/second hand shop.
Test fit the barrel with the wall wart unplugged and chop it off the charger. Strip a 1/4 inch or so from the ends and twist them very tightly so that a stray strand doesn't make a short circuit. Use the continuity checker on a multimeter to find which wire is connected to the inside of the barrel and which to the outside. For the ADI-2 the inside should be positive and the outside should be negative. Then feed the bare tips into the PD Buddy's screw terminals and tighten them down with a very small flathead screwdriver. The negative terminal is the one closest to the setup button. Don't plug it into the ADI-2 DAC yet.
Test that the positive and negative lines aren't shorted with continuity tester of the multimeter. Touch one probe to the outside of the barrel and stick the other inside the barrel. If the meter beeps at you, they're shorted. Remove them from the screw terminals, twist them up and try again. If you can't get it to stop showing continuity there may be something wrong with the wire or plug. Plug the PD Buddy in to the charger and confirm the voltage and polarity one more time. Place the positive probe (usually red) into barrel and hold the negative probe (usually black) against the side. You should see a positive voltage in the range of 9.5 to 15, depending on the abilities of your charger. If it shows a negative voltage unplug the PD Buddy from the charger, reverse the wires, and then plug it back in to retest.
If all that goes well you're ready to power your ADI-2 DAC from a power bank. Plug it in and see if can actually deliver enough current to keep it working. With the power bank mentioned above, my most current hungry headphones (modded Fostex T50 RP), and most of the DSP options on it has no trouble keeping up. About as loud as I would ever want to listen with those headphones is -10dB on high power and setting them on my desk and cranking it to +6 didn't trigger the low power error state mentioned in the manual.
I'm planning to pack my ADI-2 DAC, the powerbank, and a tablet into a hardcase for wandering around the headphone tables at AXPONA next year. Anyone else as nuts?
