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-   -   rectifying....what would be prefered (aleph PS) (http://www.diyaudio.com/forums/pass-labs/907-rectifying-what-would-prefered-aleph-ps.html)

hifi 9th October 2001 11:52 PM

What would be the best option in rectifier diodes...im a bit sceptical thatr i will hear any differende...(against ordinary diodes in paralell with a small cap to slow the down) but since im doing this amp overly seriosly i think it would be propper to atleast look in to the diod bull**it...;-)

any recomendations ?

/micke

Pete Fleming 10th October 2001 03:07 AM

I've used soft recovery diodes in DACs before and was very pleased with the results. I'm with you on this one however in that I really don't feel it would make a huge difference in an amplifier situation (DACs are particularly noise sensitive). Then again, hang the expense, why not use them anyway.

Cheers,

Pete Fleming

Petter 10th October 2001 11:24 AM

Consider using Schottky diodes. They are cheaper than say HexFred's or QuietFred's but only come in about 100V rating. I will use Schottky for the driver stage and probably HexFred's for the power section.

This is a majority carrier diode, and there is thus no reverse recovery.

The Fred's mentioned have soft (reverse) recovery).

Petter

Pete Fleming 10th October 2001 03:58 PM

Yes indeed, to be more precise it was also Schottky diodes that I used too.

Cheers,

Pete

promitheus 13th October 2001 12:54 PM

I agree with NP on fast diodes for high power amps. They donīt offer much in amplifiers. Just use good normal diodes and also take care of the typical precautions in using the correct caps where needed. You will have excellent results.

Nelson Pass 15th October 2001 06:56 PM

On the other hand, Schottky diodes are way cool.

Damon Hill 15th October 2001 10:58 PM

Given Schottky's lower forward voltage drop, I'd say they
>are< pretty cool! ;)

I've held off using them in power amplifiers because the
100 PIV rating of the units I can easily get is a bit marginal. But I gather that's about to change as new
semiconductor materials become available.

But the ultimate in "cool" are probably syncronous rectifiers. Dunno how they rate for noise characteristics.

(In case you're wondering, this is just a power transistor
with its base/gate wired to a low voltage winding that forces it into saturation--it thus acts like a rectifier.
A bit too busy for our purposes, but an interesting idea that might be worth exploring some day.)

hifi 16th October 2001 01:05 PM

but isnt 100V enough safty margin? ...in my aleph they will never se more than 48v and that is peak to peak value..

Is there any preferable brand among Schottskys? and what spec are inportant when used in rectyfiers?

/micke

Jakeh 16th October 2001 02:21 PM

Irf have some 150V devices for a bit more margin. Try 30CPQ150, for example.

Jake

hifi 16th October 2001 04:30 PM

nice...but those suckers are about 10$ a piece here in sweden...and that is in 25pcs quantites...(farnell.com)


any cheaper advice?

/micke


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