AKSA 100 power capacitors

rimljan99 · « **on:** 5 Jun 2006, 08:39 pm »

Have anybody tested or try different companies capacitors like RIFA PEH, BHC, EPCOS or BC?

What would happen if we substitute two 4700uF capacitors with one 10000?

Thanks

aurelius · « **Reply #1 on:** 5 Jun 2006, 09:22 pm »

I have only ever used the capacitors that Hugh supplies with the N+ kits. I'm sure Hugh has probably tried a few though!

RE: substitution, irrespective of what you do with cap sizes, you can't reduce the number. The PS board supplies 2 channels x 2 rails (+ & -) per channel = 4 caps.

Regards,

Mark

AKSA · « **Reply #2 on:** 5 Jun 2006, 10:51 pm »

Two 4,700uF caps will generally have a lower ESR than one 10,000uF, and when I last checked the smaller cap was better value in terms of dollars/mF.

If you double the size of the filter reservoir, you will increase the pulse charge current from the transformer. This has two effects. Firstly, it will strain the UFSR diodes specified in the design, and some, usually at start up, will blow spectacularly. Secondly, the high pulse currents will heavily stress the transformer at the point in the waveform where it recharges the caps, and in turn produce more switching noise. There is a tradeoff, and the only way to push beyond this envelope is to go full regulation. Although a lot more expensive, this yields good results, IF the regulation is super fast.

Cheers,

Hugh

rimljan99 · « **Reply #3 on:** 6 Jun 2006, 07:47 pm »

Thank you for technical explanation.

If we go for complete regulation like Naim, how many amperes should this regulation provide ?

Thanks

AKSA · « **Reply #4 on:** 6 Jun 2006, 11:38 pm »

For a 55W amplifier with 30V peak output, it should be specced to 30/8 = 3.75A plus 30% for reactive load margin. This is 4.9A peak.

However, increasingly we see 4R speakers these days, and people will have an expectation that they work fine on a 55W amp. So, double this rating. That is, 9.8A, call it 10A peak.

This calls for a robust series pass regulator, with great speed, preferably about twice as fast as the fastest pulse through the amp. This means a flat response to 40KHz, which is easy to achieve, but 400KHz would be better in my view....... and it's worth noting the regulator becomes a mini amp all on its own, with series pass elements of equivalent size and rating to the output devices. In turn this calls for drivers, too.

Hmmm. Expensive...... Wonder how it sounds?? Probably pretty good.....

Cheers,

Hugh