pc power supply to symetric output (need help)

[El-even]

thanks a lot ciaran, i will trying that tomorow and post test results

[Ciaran Haslett]

Sweet.  Looking forward to hearing how it goes.

Good luck

[El-even]

i repost my question from the last page
I don't understand how they have +15/-15 from 18Vac; i was thinking the circuit need double voltage transformer (36vac for +18/-18)
18Vac means it is 18-0-18?

[Ciaran Haslett]

Look up voltage rectifier doubler.  That looks like whats going on in that PCB

[El-even]

with ground terminal and 18V terminal from the Vac the circuit double and convert it to +36/-36 and after, regulating to +15/-15? simple like that?.... so this is what i need

[Ciaran Haslett]

Well....converted to +36v DC.  You then need to create the +/- voltage divider then regulate.  But yeah that'll work too

[El-even]

nothing better...
i've just rebuild a single channel pcb with one lvlark's 1N4001 bipolar converter (with one 7809 before) and have ~17v symetric outs (so nearest 18v than the 15v announced but anyway)
but, once wired to the preamp the voltmeter gives me +1.5v & -2.6v at pins O_o'
with my first version preamp i have ~12v symetric at pins, with the same converter
i have checked all connections, routing etc and my circuit seems correct
ics are all from banzai on the two version
the only differences are, one is on veroboard, the other on diy pcb (1mm width trace and 2mm pads; default clearance) i can't imagine this is the problem;
mica caps (5pf & 200pf) switched for ceramic (tayda) because of the size (maybe that...?), and i can't verify them cause i don't know how and i don't have the tool
and some resistors are from a chinese 2000 pack (very thin and fragile legs plus BIG tolerance...last build with these shits)
so i don't know why the circuit doesn't work... resistors, caps, grilled ICs....? F***k

I must build some simple component testers

[El-even]

ok, it works
chinese rc4558 guilty
now i'm going to sleep 3 days in a row
good night...

[El-even]

Back,

new problem,
individually, the two preamps and the two power supplies (Mark's bipolar converter with 1n4001) works almost good (~+11/-11 at ICs pins)
not the "correct" voltage but the preamp drives brutal and better than i have expected.

when i daisy chain the two converters, i have +16/-16 at the twos
it seems perfect for the job and don't see why not.
so,
i plug each pre separate with their own individual converter
and boom, i read +5/-5 at pins now
i don't understand the cause

9v + conv1 + preamp1 > work

9v + conv2 + preamp2 > work

9v + conv1/conv2 > work

9v + conv1/conv2+preamp1or2 > work

9v + conv1+pre1/conv2+pre2 > fail

and logically, the two converters/preamps works fine with two separate 9vpsu



i've tryed ur method ciaran (with resistors) and have +8/-8 at wires end and, +15/-7 at pins