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-   -   Aleph powersupply (http://www.diyaudio.com/forums/pass-labs/69191-aleph-powersupply.html)

Skorpio 6th December 2005 09:01 AM

Aleph powersupply
 
In my experience using resistors (CRC) in series with the powersupply will degrade the bass performance and dynamics. I have not tried CLC, but I suspect the same with an inductor in series with the supply.

On the other hand it gives good ripple/noise figures....

Also (my opinion), one larger cap (47.000uF) will sound better than 2x25.000uF in parallel. Also, in my opinion too much C is as bad as too little. Enough is when there is no audioble hum....thats it.

Therefore I will use the following PSU to my Aleph 3/30 version:

-1000VA 2x18VAC EI transformer
-Bridge
-One 47.000uF/40V per supply half

Does this seems to little? Has anybody tried this combo?

What is the positive and negative PSRR in the Aleph 3/30 circuit? My guestimates says -70dB on the negative and -75dB on the positive....

jeapel 6th December 2005 11:56 AM

hi

I am not a expert but i just finish my aleph overkill :-)

power supply:

68000uF +1.2mH +68000uF +1.2mH +68000uF

1.2mH internal ohm=0,15 ohm

and with the results a ok not topend aleph3 power would be:

1- 2x 21 vac not 2x18 to get +/- 25 volt one solution would
be to boost the 18 to 21 with a 24vac with center tap 10A
wired like a stepup transfo to boost the input 240vac to
250 or 260vac it s not ideal for noise but possible

2-my bridge are 2 x 35A 400v

3-just 47000uF too low for me 2x 47000uF ok or CLC better

jeapel 6th December 2005 01:06 PM

maybe more infos will be helpful

1-my overkill aleph 3 supply is for 2 channels and you ?

2-with output = +/- 24.9 v and 3.6 amp test resistor load

ripple with CLCLC : on cap1=500mV
cap2=50mV
cap3=not measureable with my scope

3-i don t change my design but cap3 is overkill

i hope it s help you to take a good decision :-)

Skorpio 6th December 2005 06:14 PM

I am not looking for overkill, just right will do nicely ;-)

Have you tried with "just" 47.000uF? And can you describe the changes in the different solutions?

On other class A amps (not Pass) I have found lack of punch in the bass with resistors in the psu.....

jeapel 6th December 2005 07:21 PM

with just one 68000uF all others cap and inductor disconnect

vout go from 24.9 to 26v

iout test go from 3.6 to 3.75A

the ripple is 500mV

maybe around 700mV with 47000uF

if you are afraid for the sound go to with just one 47000uF

and reserve space in your casing for 2 more caps

for aleph 3 from Mr.Pass document there is just one cap(4 x 22000uF)

for +v and another 88000uF for -v for 2 channels

Skorpio 7th December 2005 07:24 AM

No, just wondering if someone actually tried where the limit "too small" is....and also "too large" (sound wise, not calculated).

700mV on the supply will give 125-221uV ripple related noice on the output I don't think this will be a problem noisewise...and given the dynamic reduction with a series element, that will be my first version.

jeapel 7th December 2005 11:30 AM

sorry to bother you with my calculs :-)

maybe start another thread

Skorpio 7th December 2005 12:16 PM

No, it is interesting to know different veiwpoints :)

I am looking for different methods to adjust the Aleph performance.....and the powerpupply is an naturel start.


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