[Vinnie R.]

All,

Has anyone experimented with replacing each power supply cap for two (or more) smaller ones?  For an example, replacing the 4,700uF cap for two 2,200uF caps.  In theory, this should bring about a lower ESR, but has anyone actually tried doing this.  Space is not an issue in my case, but a new power supply board would be needed.

I suspect this may be worth the trouble and added complexity (not really much though) for even better dynamics.  I can understand why Hugh recommends the 4,700 caps though, decreased parts and complexity and still very good sound.

Thanks,

Vinnie

[jesserparker]

i was thinking of implementing something like this once i build my AKSA.  if you're thinking of modding the PSU i'd recommend (if you haven't already) taking a look at this article.

http://tnt-audio.com/clinica/ssps1_e.html

later,
jesse

[Vinnie R.]

i was thinking of implementing something like this once i build my AKSA.  if you're thinking of modding the PSU i'd recommend (if you haven't already) taking a look at this article.

http://tnt-audio.com/clinica/ssps1_e.html

later,
jesse

Jesse,

I know that article, and here is another great one for download that
is similar: www.zero-distortion.com and then click on "build your own
power supply."

There were a few good points mentioned, like usinging 2 full-wave rectifier bridges (one for the + rail, and one for the - rail) per channel!  
Snubbers on the diodes were also shown, along with bleeder resistors,
and a cool tweak on the rail that uses and capacitor with a series resistor
to ground.

I LOVE the aksa 55, and I am using the stock Nippon-Chemicon
caps (4,700 uF per rail as Hugh recommends), and I always wondered
how much better it can get if the power supply was improved (still keeping
it unregulated though).  Using two smaller caps for every 4,700uF cap
is something that I might try out.  Has anyone researched this, or using
two rectifier bridges per power supply, as shown in the link above?
In theory, the ESR will decrease, and there should be an improvement
in punch and dynamics.  Panasonic TSHA caps from digikey will be the
caps of choice because I've used them before on other projects and
they are a terrific value!  

I'd enjoy if this topic is revisited by others on the board because most will
agree that the power supply is very important in the audio chain, especially in a good design like Hugh's Aksa 55.

Best Regards,

Vinnie

[tropicalcb]

gday,  what you can do to accomplish the same end result ie lower ESR, is use the Nippon Chemicon KMF -Low Z/105 5,000hrs  or LXF - Low Z/long life 105 3,000-15,000hrs or SXE - Low Z 105/ 1,000-2,000hrs.....in fact you'll get a lot more hrs than the ratings but IMO all electros should be replaced after 5 yrs/5,000hrs or so...The ones which Hugh supplies stock with the kit are a very good KMH Series General Purpose 105 degreeC 2,000hrs+R cap. If you can source the above High Frequency Series Nippon Chemicons or their 2003 equivalents at a reasonable price, and can hear a definable sonic improvement, as against a different sonic flavor, I would be interested to hear your impressions. In the meantime a valid option would be to bypass the existing caps with a 63-100v 220-470uf low Z electro + 0.1uf PP film and check the difference.
     cb

[Jens]

I can vouch for the beneficial effect of bypass caps. A little while ago I added four audiophile .22 uF Mundorf Extreme caps (highly estimated European brand) to the power supply of my AKSA Nirvana 55 watt. They definitely made a difference, improving soundstage and highs.

A week ago I did some rewiring during the finishing of the enclosure for the AKSA, and at the same time I moved the four caps onto the power amp boards themselves. I was surprised to hear another improvement, although of lesser magnitude than when I originally installed the caps.

Try it out, it may be worth it!

Cheers,

Jens

[cmscott6]

Any opinions on this, Hugh?

[AKSA]

Lots, Chris,

But I prefer to keep my baleful influence off the forum from time to time to give others the opportunity of putting in their 2c........  

I have to admit that I've not tried everything, hell no, and there are always combinations and permutations which AKSA builders try which I've not heard.     Added to that, Australia is at the bottom of the SE Asian supply chain, and our choice of components is often restricted.  Knowing also that I am the son of a pragmatic farmer from an isolated community, you might ruefully observe that I shy away from exotica, because it is just not my style to approach snakes too close.     I strive to design circuits so clean and pure that even inexpensive components will sound good, so, aside from the Nirvana (which I admit to researching exhaustively!) I don't often go there.

Power supplies.  First, anything which militates against rapid, clean switch off of the rectifier diodes is verbotten.  Hence I do NOT recommend caps across these diodes, and deliberately designed the ps pcb so adding them would be difficult.

Second, anything which improves the ESR at 20KHz plus is a GOOD thing.  To this end a coterie of film caps across the power capacitors should make a difference, and indeed I'm reliably informed by Lewis Muratori who wrote the cable article on the website that it certainly does.  He recommends quality film caps around 47uF per rail, but, but warned, they are BIG and VERY EXPENSIVE!!  

Lastly, in engineering as in life, more of this ALWAYS means less of that.  Consequently, when you roll a few filter caps you find that more top end is invariably at the expense of bass;  and vice versa.  So, the best option is to select one which does midrange well, because that's where most of our listening is done.  Extension of the top end can then be achieved with film caps on bypass;  to me, this is akin to avoiding race cams in commuter cars;  if the engine spends 80% of its time idling, you don't want it to be rough......  

Nuff said.....

Hugh

[Jonpike]

All,

Has anyone experimented with replacing each power supply cap for two (or more) smaller ones?  For an example, replacing the 4,700uF cap for two 2,200uF caps.  In theory, this should bring about a lower ESR, but has anyone actually tried doing this.  Space is not an issue in my case, but a new power supply board would be needed.

Hi Vinnie and all..

I was going to respond to this one,  got sidetracked,  and tempus has fugited..

This could give you a lower ESR..  you would want to have all your caps close together and wired with short and heavy leads for best effect, so you don't loose your ESR benifit in wiring and connector resistance!

You should get the manufacturer's data sheets on the caps you're working with (available at their sites)  and see how they rate..  usually you get lower ESR in a single, larger cap,  but most of the time you might do better with two higher ones in paralell..  Higher voltage same value versions are different as well..   Checking it out will show what the best combination  (theoretically!) should be..

As for different types of caps..  I'd been interested in Nichicon's "audiophile" version caps,  and had tried to find a source where I could get some samples for auditoning (have no AKSA yet, but a 20 year old Yamaha amp) or even get some to Hugh or the other main players..  and see if they'd be worth their extra cost.  Well,  long story shorter..  I located a limited batch for $10 ea USD for orders of 10,  or 4 for $20 ea!!  Yikes!!  

Needless to say,  this was a little steeper than my original expectations..
The vendor said that the factory would produce a run of these parts for a minimum of 50 parts (amazingly small) for about $3.85 ea (fairly reasonable)  Of course the catch is, we won't know if they are worth ordering without spending lots for the samples.

At this point,  I stopped pursuing it.  Recently, I happened to look into Michael Percy's audio parts website (http://www.percyaudio.com) and darned if he didn't have some Nichicon KG Gold caps, 4700uf @ 63 and 80 volts,  for $5.95 and $7.95 respectively.

So, if anyone out there is interested in testing the KG vs the stock KMH caps,  I point you in this direction..    Who knows,  they just might be worth the extra price for a decent tweak...  or for Hugh to contemplate as part of a Nirvana kit..

[PSP]

Hi Vinnie, et,. al.,
I've used the Nichicon KG Gold 4700uf 63v caps in my power supply since day one on the single 55w AKSA that I've had time to build.  Never compared them to Hugh's stock caps though.  

BTW, these caps are larger than the stock caps (30 mm for the 63v, 35 mm for the 80v) and won't directly mount to the power supply PCB... I ran short (1cm maybe) flying leads of 2x 20awg magnet wire to connect the caps.  

Peter

[Vinnie R.]

All,

Thanks for your posts.  I am most likely going to be ordering Panasonic
TSHA caps from www.digikey.com, but if the Nichicon's have better
specs I'll order those.  

I was also toying with the idea of using two full-wave rectifier bridges per power supply instead of one bridge.  Take a look at www.zero-distortion.com and download the "designing your own power supply"
article, and you'll find that the last topologies uses this design and
it is supposed to provide higher current and offers more isolation
from the transformer.  Of course, double the schottkys are needed
but if it improves the sound, then it's worth the extra cost to me.  

Does anyone know if www.digikey.com has the proper schottky diodes
that Hugh recommends for the aksa 55  

Take a look at that article for more info. on this idea, it looks interesting.
I'll post my results when I finally build a new PS.

-Vinnie

[jesserparker]

hugh,
any thoughts on doubling up the rectifiers?

[AKSA]

Hi Jesse,

No advantage here; the ratings are entirely adequate.

This is often done for higher voltage rating;  back to back.  If you double up for increased current capacity, you need to use equalizing resistors;  complicates thing enormously and adds to the series impedance.

Cheers,

Hugh

[jesserparker]

thanks,

[PSP]

Hi guys,
This is to correct an error in my post above regarding Nichicon KG caps in the AKSA power supply.

Last night I mounted four 4700uf 63v Nichicon KG caps onto the power supply board and they fit perfectly.  

In my previous work, I usrd 4700uf 80v caps; these are 35mm in diameter and don't fit without fitting flying leads.

Peter