I have built a few PTP tube preamps and I would like to learn more about PCB design with tube circuits.
I am starting with a very simple two stage preamp (vintage RCA BA-2C schematic) using two 6J7s connected as triodes.
I have attached a schematic of this circuit and the layout I have come up with. I have a few doubts regarding the following :
- Ground planes : I have been doing some online research on the subject and from what I could understand the high impedance of tube circuits can be problematic if using ground planes because the parasitic capacitances can cause oscillations and loss of treble. Can this be avoided by considerate spacing of the ground plane from the traces and pads ? What would be the recommended isolation of the ground plane ? (I have set it at 0.035" at the moment)
- I have chosen to use DC heaters to simplify wiring and perhaps reduce noise.
I have routed the heater traces on the top layer, along with the ground plane, and on the bottom layer I have all the signal traces and B+power supply lines.
Would it be preferable to place the ground plane on the same side as the signal traces ?
I am starting with a very simple two stage preamp (vintage RCA BA-2C schematic) using two 6J7s connected as triodes.
I have attached a schematic of this circuit and the layout I have come up with. I have a few doubts regarding the following :
- Ground planes : I have been doing some online research on the subject and from what I could understand the high impedance of tube circuits can be problematic if using ground planes because the parasitic capacitances can cause oscillations and loss of treble. Can this be avoided by considerate spacing of the ground plane from the traces and pads ? What would be the recommended isolation of the ground plane ? (I have set it at 0.035" at the moment)
- I have chosen to use DC heaters to simplify wiring and perhaps reduce noise.
I have routed the heater traces on the top layer, along with the ground plane, and on the bottom layer I have all the signal traces and B+power supply lines.
Would it be preferable to place the ground plane on the same side as the signal traces ?
