power supply for source follower.

[AudioGeek]

I need to build a power supply.

I need about 20 to 25vdc on the output mosfet.

currently I have 4 68mF 50vdc caps (quite large). bridge rectifier (what type should I use?)

I just need a power transformer.

any ideas?

[peranders]

15-18 V AC ?

[Fuling]

Put a choke in there too for ripple rejection.

[AudioGeek]

even with a 6A draw... still 18vac???

i should d/l PSUD II again.

[Fuling]

A 18VAC transformer that can handle the current, yes.
I guess this is for your choke loaded follower project, right?
I´d suggest a 2x18VAC >300VA toroid transformer.
Use one secondary per channel, 2x3A is easier to handle than 1x6A.

[AudioGeek]

ok 2x18vac it is then. 10A winding for each???

rectifier... which should I use??? regular bridge?

68,000 cap / choke / 68,000 cap. per channel.

10-30mH choke, low DCR. does digikey or parts express have one?

[Fuling]

Yes, two 18V 10A windings will be fine. If you want 27V rails (as mentioned in the thread about the amp) you´ll need slightly higher voltage, say 20-22VAC.

A regular but big bridge. 35A is fine.

I´ve read somewhere that one always should have more capacitance after the choke than before it. Ringnings and stuff I guess.

I guess Hammond has suitable ones.

[MarekM]

Hi Audio Geek,

Do not resign from soft-start circuit if you plan to use toroid trafo and large capacity. This simple circuit will reduce big curents charging capacitors on start-up and avoid from accidential fuses blow.

Regards,

Marek

[AudioGeek]

which should I do????

recommendations for the choke either way?? part numbers etc...

Thanks!!

[Fuling]

You might not want to mess around with choke input filters.
Works fine electrically, but finding a choke that doesn´t buzz is not easy. They need to be big (as in BIG), too.
Been there, done that.

A suitable choke for LCL filters might be this one:
159ZG 15mH 4A


Say, 2 x 22000uF - 159ZJ - 4 x 22000uF. Per channel.
If you want to run two channels on the same rail, double up the capacitance and use a 159ZL choke instead.

Make sure that the caps (at least the ones prior to the choke) can handle some heavy ripple currents.
Dirt cheap? Nope, but if this is a serious project you won´t regret spending some hard cash on the caps.

Speaking of caps, put some film caps (1-10uF) across the `lytics.
A 10nF/10R serial network across each diode in the rectifiers is nice, too.