Hello,
I designed an USB Headphone Amplifier in KiCad, inspired by this tutorial USB Headphone Amplifier Design Walkthrough - Phil's Lab #101, inspired Douglas Self.
The PCB works (I fixed some minor errors in the uploaded Schematic), maybe it is helpful for someone 🙂
Nevertheless I have some questions:
Without Headphones connected/music playing the board draws around 270mA from the USB power supply. When R8 (20R) is removed, current draw is ~0. In this state the voltages for the "+16V" and "+15V" net are ok (measured 15,9V and 15,1V), but with R8 connected, voltages drop to 14,7V and 14,5V, so only 200mV drop over the linear regulator :/ Decreasing R5 did not help, even if the "idle" voltage of the boost converter is set to >>16V it breaks down when R8 is connected (there is a 1,4V drop over this 20Ohm-->70mA). The USB power supply could deliver 2A@5V.
Any ideas how to fix this? This also makes the device not really usable on a phone because it draws a lot of current from the battery.
The sound in general is quite good, maybe a little bit too "bright" for my taste, it could be some distortion in the higher frequency range (frequency response is completely flat), but I dont have access to a spectrum analyzer to evaluate this. The gain could be a bit more for 600Ohm Beyer DT880, I am mostly using the 250Ohm Version and for me it is more than enough.
The DAC (PCM2902) is quite old (but easy to implement), I will probably switch to ES9039Q2M and add SPDIF --> analogue conversion which is missing here (SPDIF goes only to USB atm).
Any suggestion how to improve here? 🙂
I designed an USB Headphone Amplifier in KiCad, inspired by this tutorial USB Headphone Amplifier Design Walkthrough - Phil's Lab #101, inspired Douglas Self.
The PCB works (I fixed some minor errors in the uploaded Schematic), maybe it is helpful for someone 🙂
Nevertheless I have some questions:
Without Headphones connected/music playing the board draws around 270mA from the USB power supply. When R8 (20R) is removed, current draw is ~0. In this state the voltages for the "+16V" and "+15V" net are ok (measured 15,9V and 15,1V), but with R8 connected, voltages drop to 14,7V and 14,5V, so only 200mV drop over the linear regulator :/ Decreasing R5 did not help, even if the "idle" voltage of the boost converter is set to >>16V it breaks down when R8 is connected (there is a 1,4V drop over this 20Ohm-->70mA). The USB power supply could deliver 2A@5V.
Any ideas how to fix this? This also makes the device not really usable on a phone because it draws a lot of current from the battery.
The sound in general is quite good, maybe a little bit too "bright" for my taste, it could be some distortion in the higher frequency range (frequency response is completely flat), but I dont have access to a spectrum analyzer to evaluate this. The gain could be a bit more for 600Ohm Beyer DT880, I am mostly using the 250Ohm Version and for me it is more than enough.
The DAC (PCM2902) is quite old (but easy to implement), I will probably switch to ES9039Q2M and add SPDIF --> analogue conversion which is missing here (SPDIF goes only to USB atm).
Any suggestion how to improve here? 🙂