Hi there,
I'm planning to build a (frugal) Aleph-X and am wondering
about some details of the power supply.
I'm hoping to use two 300VA 2x12VAC transformers in a
single stereo unit. The secondaries of each transformer
will be tied in parallel and will generate one rail. The
two channels will share this single power supply.
Would this work, or should I build a separate PS for each
channel?
Also, my local surplus store has some 25VDC 220000 uF
Phillips caps. The price is right, but I'm a bit worried
about using caps with that high a capacitance value.
Aside from inrush current, which I hope to control with
thermistors, are there any problems I should worry about
if I want to use these large caps? Will the transformers
be able to handle them?
Sorry for these incoherent newbie questions.
Dennis
I'm planning to build a (frugal) Aleph-X and am wondering
about some details of the power supply.
I'm hoping to use two 300VA 2x12VAC transformers in a
single stereo unit. The secondaries of each transformer
will be tied in parallel and will generate one rail. The
two channels will share this single power supply.
Would this work, or should I build a separate PS for each
channel?
Also, my local surplus store has some 25VDC 220000 uF
Phillips caps. The price is right, but I'm a bit worried
about using caps with that high a capacitance value.
Aside from inrush current, which I hope to control with
thermistors, are there any problems I should worry about
if I want to use these large caps? Will the transformers
be able to handle them?
Sorry for these incoherent newbie questions.
Dennis
Ok, first of all "frugal" 
! Frugal sounds to me like sanyo boom box. Frugal and alephX don't belong in the same sentence!
What board are you going to use? The Grataku/Chad board it's particularyl well suited for dual mono. Even if we didn't intend to @ $5/each it came out to be dirt cheap. Since you have the luxury of having two transformers you might as well make use of it. I am going to do just that and use Nelson's trick of joining the grounds via the bridge. 300VA transformers are really OK for a 4.5-5 amp bias x channel. If you can buy 8 of those 220000 you could do a two chn. PS with C-R-C or a C-T-C with anywhere from .3 to 1 ohm R or T (under load). The PS voltage would be anywhere from 14 to 11 V with ripple between 15 and 2 mV. A thermistor in series to the primary should be good to safeguard the transformer primary. The rectifier may need a little more care. I would use two bridges one for the positive and one for the negative rail, 2 is better than 1.
! Frugal sounds to me like sanyo boom box. Frugal and alephX don't belong in the same sentence!What board are you going to use? The Grataku/Chad board it's particularyl well suited for dual mono. Even if we didn't intend to @ $5/each it came out to be dirt cheap. Since you have the luxury of having two transformers you might as well make use of it. I am going to do just that and use Nelson's trick of joining the grounds via the bridge. 300VA transformers are really OK for a 4.5-5 amp bias x channel. If you can buy 8 of those 220000 you could do a two chn. PS with C-R-C or a C-T-C with anywhere from .3 to 1 ohm R or T (under load). The PS voltage would be anywhere from 14 to 11 V with ripple between 15 and 2 mV. A thermistor in series to the primary should be good to safeguard the transformer primary. The rectifier may need a little more care. I would use two bridges one for the positive and one for the negative rail, 2 is better than 1.
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