Aleph 5 Power Supply

[martinschki]

Hello Forum!

First of all please do not kill me for this question. But i'm not that expert and i want to be sure that my Aleph 5 will work.

For the Power Supply for ONE Mono i will use:

- 2 x Toroid: 2 x 29V, 260VA
- 4 x C: 47.000/40V (RIFA, PEH169, 85°C)

When I look at the Voltage after the Diodes i will have about 41V.
Can I use the 40V Cap.?? Or do I have to face some Problems when the Amps are on for hours?

The reason why I want to use Cap. with 40V is, that i got them very cheap.

Thank You very much
Martin

[Nelson Pass]

Yeah, it'll be OK on the 40V.

[PedroPO]

Nelson,

Do you use 40 V caps on 41 V rails after the bridge?

I personally use a little more.

for 38V(after the rectifications and caps) rails I used 50V caps, but I that only for extra safety.

I don't know elecronics to say that it must be 50V.

(in my bridge decks designs I use 1.5 safety factor, and they don't fall with the cars over, so I use the same principle to other stuff that I don't really know)

But Nelson does

[PedroPO]

regarding the caps, I used 2x47000uF on my aleph 5 and the turn on thump is quite large, so if you are using 4x47000uF I would get a soft start circuit or a switch for the loudspeakers.

[hifi]

The Rifa:s is quality caps but running them above the voltage limit will atleast reduce there lifespan, i guess they got safety vents so they don´t explode ;-)

you should atleast get some voltages of safty margin, (what if the AC mains swings up a bit)

Maybe you can unwrapp some of the Transforemer windings to lower the voltage a bit?

btw, I think Nelson was refering to the Aleph living of ~41V not the caps??

/micke

[martinschki]

Im not shure how much i should use.
I could use 4 x 47.000uF AND 4 x 22.000uF per Channel because I have them at home.
But I think thats too much, isn't it?

Martin

[hifi]

You can never have to much capacitance...but you do want some safty margin, if the 22mf caps are higher voltage, them you might want to use a LC filter to reduce the voltage a bit and then use the Rifas, (btw you will also decrease the inrush current a bit)

/micke

[martinschki]

to bad, the 22.000 are the same type and also 40V.
Do caps have a "tolerance"?
I read the Datasheet of the RIFA's but I couldt find anything.

Martin

[hifi]

Tolerance for caps is mainly +-20% or so but on the speced capacitance not on the voltage!....

The transformer is a bit small (IMHO) althoug not to small, i would use a 2x25V 600VA or so for the monoblocks...

Btw, you dosen´t seem to have any load voltage drop (29*1,414=41v) it should be lower considering the 3A voltage draw from the aleph and diod losses and the small toroid.

/micke

[martinschki]

Thats the reason why i use two toroids for one Monoblock. (2 x 260VA --> 520VA)
I've to look a little bit on my budget so I think, I will try it that way.

Last Question:
HOW much capacity should I use for one Mono???
(I could use 4 x 47.000 and 4 x 22.000)

Martin