I upgraded my AKSA 55 power supply

Vinnie R. · « **on:** 22 Apr 2003, 11:30 pm »

All,

Well, I finally ordered those Panasonic TSHA caps and 10A, 200V International Rectifier Schottky diodes and built a new power supply board using 16ga OFC point-to-point wiring.

The caps are 5,600uF 63V TSHAs, replacing the 4,700uF 63V Nippon-Chemicon KMH's that I was using. I ordered both the caps and diodes from www.digikey.com

Results: EXCELLENT!

I find the bass to be tighter than before and there is plenty of grip and control of the woofers, even at higher volumes. The original KMH caps had plenty of bass, but it's the improved quality of bass (not quantity of bass) that makes the TSHA's better IMO.
The midrange hasn't changed much with the TSHA's, it's still just as good.
The highs are more detailed, slightly more pronounced, and have a better decay. There is no added harshness, even at higher volumes, but there is more treble emphasis than with the KMHs.

The bass improvement is something I think everyone would enjoy. The change in treble is something that you may or may not want. With my Vienna Acoustics Mozarts silk dome tweeters, and DACT CT-2 passive volume control instead of an active preamp, I really welcome the more detailed treble that I'm getting.

BTW, I built this power supply with the new caps and new diodes at the same time, so the improvements in sound may be also due to the 10A diodes

(I was using the 4A 200V schottkys before), but I have a feeling that the TSHAs have the dominant influence.

The 63V 5,600uF TSHA caps are ~$7.00 USD each
The 10A, 200V Schottky diodes are ~$1.00 USD each
The board to mount everything was $6.00 USD

(4 x $7) + (6 x $1) + $6 = $40 = Well worth the money to my ears!

-Vinnie

mb · « **Reply #1 on:** 23 Apr 2003, 01:23 am »

Thanks for the post. Interesting... I've been itching to change the Nippon Chemicons supplied by Hugh, not because they sound poor, but there is a source for Nichicon Gold Tunes at a reasonable price in town. Hope that I can find some of the right size.

I've been using Schottkys (100V/10A) from day 1, so I can't comment on how they sound on the AKSA, but here's an anecdote:

I upgraded my DAC rectifier (simple one-peice bridge) to SBYV27 soft recovery diodes. There were other upgrades at the same time, so I couldn't attribute precise improvements to the diodes, but there was nothing to complain about. Yesterday I received some IR 3.3A/100V schottkys. They look amazing -- big, fat axials with really thick leads. They look like they could carry 10A without a sweat. After swapping the soft recovery diodes out. I had a listen. The changes were very obvious -- to me it felt that some of the top end had disappeared, yet it was not rolled off. Bass had more 'growl' without boom. Transients were faste and more full-bodied. After more listening, it seems to me that the diodes have reduced perceived distortion. For the lack descriptors, it sounds like I've put is a very high quality tube output section, without sacrificing any of the current qualities.

Looking at the quality of the IR parts, I think that part of the improvement is not just the move from ultrafast to schottky, but the quality of the IR part. Some previously rough violin sonatas now sound pretty classy. Up to now, no CD sounds worse for the change.

Vinnie: I've used THSAs, which were replaced by Gold Tunes, albeit of much higher capacity. Fwiw, I suspect that most of the positives you've heard may be from the swap to schottkys, and the THSAs may not be passing you their full benefit.

AKSA · « **Reply #2 on:** 23 Apr 2003, 01:30 am »

Vinnie, Mervin,

Wonderful information! Thank you.......

I think this points up the compromises inherent in audio engineering.

I'm always chasing the highest bang for the buck. I've tried all sorts of power caps, and the Nippon Chemicons appeal as the best in this connection. However, for the next step, yes, mix and match.

You are limited to 30mm diameter, which may be a bind for the larger caps, but if the worst comes to the worst you can always hard wire.

Thank you both for adding to the AKSA experience.

Cheers,

Hugh

Vinnie R. · « **Reply #3 on:** 23 Apr 2003, 01:56 am »

Whoops! Forgot to send this link:

http://photos.yahoo.com/vinnie822

Note, the pictures of the Aksa are with the old power supply. The last picture shows the new one. I copied Hugh's layout with a same sized power supply board, but as you can see, the 35mm caps stick out slightly

So, mb, you think that the 10A diodes are the bigger contributor to the sound? Now that I think of it, I'm not sure if they are "ultrafast" or schottky!

Here is the link: http://www.irf.com/product-info/datasheets/data/mur1020ct.pdf

Guys, I don't think I ever changed D1 on the aksa board. What do you think would happen to the sound if I put in one of those 10A diodes that I use in the power supply? I have spares. Is this overkill?

Hugh, you did a fine job picking the Nippon Chemicons KMHs. For the most bang for the buck, they are the ones! I just wanted to branch out and try to hear the effects of different (a little more expensive) diodes and caps. Well, I feel lucky that my changes brought about a more pleasureable sound to me. It doesn't always work out that way

LONG LIVE HUGH DEAN AND ASPEN AMPLIFIERS!!!

-Vinnie

Vinnie R. · « **Reply #4 on:** 23 Apr 2003, 02:09 am »

All,

Sorry for the confusion here. The IR MUR1020 diodes that I am using are "UltraFast diodes" not schottky diodes

BUT...the diode that I was originally using were UG10DCT/BYQ28E,
which are also 10A ultrafast diodes. So it turns out that I really didn't upgrade the diodes, so it MUST be the Panasonic TSHA caps that are making the sound better to me

Okay, that clears things up a bit. Now I can go to bed and sleep well.

-Vinnie

eico1 · « **Reply #5 on:** 23 Apr 2003, 02:59 am »

What about buss bars for the ps. insread of 16ga. Is that possible?

steve

AKSA · « **Reply #6 on:** 23 Apr 2003, 03:23 am »

Sure Steve,

You can use busbars, but in my experience at this power it will make little or no difference to the sound.

Vinnie, you may be right. The difference is probably just the caps!

Cheers,

Hugh

Jonpike · « **Reply #7 on:** 23 Apr 2003, 07:33 am »

Good to see some experimenting going on..

I was wondering about diode types.. I've heard that soft recovery are supposedly the tip, idea being they don't snap off and generate high frequency RFI, which gets translated into noise and other effects..

Or, a ultra fast recovery, so fast as to minimize the ringing of a "sorta fast" diode, resulting in lower total noise?

Or all my thinking is out to lunch?

Seems like both would be opposites on the spectrum and one should be good and the other bad, but I'm not sure of the mechanisim of the noise being generated and which would perform the best..

It does sound like we have two votes for fast recovery sounding good, and one for fast sounding better than soft..

Jon

(curious since I have a friend with an old CD player with a possibly blown diode bridge, want to give him the best upgrade)

Jonpike · « **Reply #8 on:** 23 Apr 2003, 07:43 am »

Ah, forgot a question for mb.. got a part number on your IR 3A Schottky's?

I love poreing over datasheets..

Jon

mb · « **Reply #9 on:** 23 Apr 2003, 02:39 pm »

I've read pros & cons about both, and I'm NOT an expert...

AFAIK, Schottkys have no stored energy, hence by definition are super fast. The soft recovery diodes, on the other hand, try to minimize the effect of stored energy / reverse voltage by 'softening' the rebound. NOTE: not all ultrafast / hyperfast diodes have soft recovery properties. They should be avoided.

Most often, the recommendation is for schottkys in low voltage and digital equipment, because schottkys have not be available in high voltage valued. Now that 100V and higher are easily available, it would be interesting for someone to do some more thorough evaluation.

The IRs are 31DQ10 (31DQ = 3.3A series of schottkys).