F4 power amplifier

nelson - i wired it like the diagram in post 2314-but instead of a star it is a short wire with power supply on one end and signal grounds on the other,next to the thermistor-which goes to the chassis along with the power plug earth .here is a pic of the bottom of peter's supply board.the two traces in the middle are the grounds which i jumpered together in 2 places in the middle-top half holds the crc and the bottom half holds the other 2 caps and i have a jumper wire on the bottom side going from + to + on the caps on each side of the resistors for the positive supply. negative supply is the same but caps reversed. what improvements could be made???????
 

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Nelson Pass said:
I looked at the photos and I couldn't clearly see how the
grounding is arranged, and for that matter, I can't tell how
the two power supply boards are used.
Yeah, I wondered that too. I used PD's power supply boards just like those with two Plitron 18vac x 2 transformers. To get the 36vct it uses two FW bridges per channel. With some jumpers it can use just a FW, but I'm not sure why you'd do that. I would just start with a single power supply board with two FW bridges assuming the transformer there has dual 18vac windings. This should yield the +/-24vdc and you can decide if it's the PS or the signal boards that cause the problem.

Tom
 
so the F4 has been on the bench turned on for 8 hours hooked up to some small rat shack speakers and i could swear the hum is less now that the amp is warmed up--weirdness #2 i went to hook up a pair of ev horn speakers to the amp and when i plugged one channel in with both speakers being driven by the same channel the hum increased--almost double the volume in the rat shack speakers!!! stumped in missouri
 
bubba177 said:
if i used one board for the whole supply i would have to use 30,000 uf caps --- i am using 15,000uf caps and the other half of each board is just holding the other 2 caps
Not sure I quite understand that, but do you have a good +/-24vdc to both boards?

Can you move the ps boards, bridges, ac wiring away from the input wiring temporarily to see what happens?
 
it is the bleeder resistor-those two jumpers hook the two ground rails together and the wire at the end of the board is the ground wire to the star ground.i didn't know i was doing anything new--do you guys just use 1 board and 4-- 30,000 uf caps??? two boards for 8 --15,000uf caps is what i did-just like the ps diagram showed that i have. no cold joints that i know of, was very careful with that.
 
well this amp has been on for 12 hours, believe it or not the hum is less and in my main system the F4 just drives the lowthers and ribbons in my basszilla's which is 150 hz and up so the hum is even less- i can just hear it from my listening seat. been listening to patricia barber-taste of honey-black magic woman... and just about slid out of my chair!!!!! detail- nuance-detail-lack of any coloration(compared to what i had before) and a soundstage that was 10ft by 16ft in a 8x12 room!!!!!!!!!!
thankspapa thankspapa thankspapa
i'm spending my stimulus check on an F5!!!!!!!!!!!!!!!!!
 
bubba177 said:
it is the bleeder resistor-those two jumpers hook the two ground rails together and the wire at the end of the board is the ground wire to the star ground.i didn't know i was doing anything new--do you guys just use 1 board and 4-- 30,000 uf caps??? two boards for 8 --15,000uf caps is what i did-just like the ps diagram showed that i have. no cold joints that i know of, was very careful with that.

Take a look at my picture on post #2128. I agree with Carpenter and would stick to the Peter Daniels plan for the PS. +/- rails per board. The caps don't need to be exact. I think I used 15,000 x 4 for mine. I tested it with one trafo and PS board first, then just decided to overkill it with two later. Mine is absolutely dead quiet into 100db drivers, such that it's hard to tell it is even on.
 
Andrzej,

Bubba is using one secondary of the transformer to generate the minus voltage, the other for positive.
The PS board on the right side of the picture feeds the positive rails of both channels, 2 red wires.
The one of the left handles the minus rails, 2 Grey wires going left and right.

(setting them up as dual rail CRC boards, what the layout of the boards was intended for, would have been more rational. Symmetrical looks nicer, imio, only requires different resistor values in the CRC's. Rotating the PS boards 90 degrees and moving the rectifiers closer to eachother also would have saved a few feet of wiring.)
 
jacco vermeulen said:
Or disconnect the labyrinth boards and try a simple lytic bank with a few wires to see if the CRC mumbo-jumbo is causing the hardships.

(might have been wiser to jumper the CRC boards at the front and the back instead of playing crossroads. Tom Waits in the Fisher King : Whoop, Whoop, now boarding for the Ground Loop Express)

like dis, master jacco?
 

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