Yet another star ground question

[wintermute]

Hi all, I'm sure this has been asked before but I searched and got swamped with results, and couldn't find what I was after.....

I'm making a p2p gainclone (but I'm cheating and using veroboard for the power supply).

I'm using a single dual 20V secondary transformer but I want to use two rectifiers and cap banks, one for each channel..... I've attached a pic.

What I'm not sure about is whether I:

1. do a separate PS board for each channel with a star ground on each, and then run a lead from the transformers 0V return on the terminal block to each star, or at least each pcb... Stars would be at B and C in the diagram.

2. have a single board for the ps with a common 0V line but two seperate rectifiers and cap banks, and have a single star point common to both channels, with the 0V return to the transformer terminated here too. Point A in the diagram

3. something else because both of the above are wrong/stupid

I've only ever done a single rectifier/single cap bank driving both channels before, and the star point was on the main amps pcb......

actually one thing I'm realy uncertain about is the return for the transformer, and whether it actually goes to the star point, I have a sneaking suspicion the answer to that is no....., I guess I could eliminate that problem by doing Two bridges per channel, but I was trying to cut cost/simplify

Tony.

[Nordic]

Here is the centretaped layout from Rod Elliot I used... works like a star... do tin the ground line well on the veroboard... had a discharge of caps due to wires touching during construction and it burned a hole through the trace.... where it was too thin around one hole

[wintermute]

Thanks Nordic I was planning on using three traces on the veroboard jumpered together for the 0V line, hopefully that will have enough current capacity. Also probably at least two traces for each +ve and -ve rail.

Tony.

[wintermute]

OK have made some progress (hopefully this GC isn't going to take as long as my speakers!!!).

Have made a PS board, picture attached. where the red cross is I'm going to put a bolt washer and nut and terminate the transformer center/common 0V lines, the speaker return lines and then run one wire to a second star point for the other ground connections ie decoupling grounds etc). I'm using phillips BYV32E 200V/10A ultra fast rectifier diodes, and 1 X 1000uf Panasonic FC per rail per channel. Tested one side just in case I had stuffed up, and got + and - 28.1V as expected (actually I was expecting a little higher with 20.9V secondaries not under load, but I guess the rectifier losses are a bit bigger than I thought.... anyway the transformer is 300VA so for two channels it probably won't droop anyway Still need to put in some bleeder resistors (but that requires a trip to the shop, and the car isn't going, so discharging with a 240V light globe is the method of choice at the moment

Tony.

[wintermute]

and a pic of the other side