Made some Dual rail ultra low noise power boards for the preamps and audio drivers.
Ultra low noise dual rail power using an LT Umodule for the +-5v for PGA2500's
LTM8049 with TI ultra low noise TPS73701 series regulators that will hopfuly get the noise down to under 10 microvolts on both + & - 5v rails.
I want to use this board to power the differntial audio drivers for line level outputs from the mixer also at +-15v
The Umodules from LT are 20$ a go ! so not really cheap. and the TPS regulators from TI I managed to find for 3$ each.
I can just change resistor values to select +-5v +-12v or +-15v
I made the board at pcbway.com as ussual. I actually recieved 14 boards so 4 extra above my order ! bonus :)
This board is my first 3 layer board with a center layer as the ground plane. I used smaller vias than ussual and they look good.
I'm not really sure I made the BGA footprint perfectly. some of the pads look smaller than the vias and I'm not that happy with the large via on the supply rail being so close to the BGA vias, although I don't think it matters since they are also suppply + rail.
Still if the board works well well I will just make another revision.
I used larger traces where I could on both + and - rails thoughout the board design.
I should be using smaller componants that 1206 ! yes its true , but I just find it easier to try out differnt componants on the same boards with larger pads.
R1 & R2 in the picture should really be nearer the BGA pins.
Anyway , I'll post more pics here once i populate the board ans test it.
I'll attach some pics from the oscilloscope of the noise on output of both rails.