[Larry]

I wonder if there is software that will design boards with gentle curves not sharp bends (a la Metaxis)?

Hi, mate, you are amazing. You have certainly passed even the stage of Valhalla! You are a very considerate man who looks after speeding electons that might fall over at a sharp turn. (I do slow down at all turns. Thank you.)

By the way, if Vahalla is no good, Nirvana means "death" in Buddhism influenced cultures, like saying "pass away" instead of "die".  In communist China, there is even a better way to mean that: "go to see Marx". (I hope this remark do not affect Nirvana sales. I don't mind what an amp is called as long as it sounds good.)

(for entertainment only. Don't fight back   )

[Malcolm Fear]

Hi Larry.
I still like following the Linn naming.
That would make mine a Cirkus!!!

[AKSA]

Folks,

I note with astonishment that this thread has over 3000 views!  WOW!!  It seems Valhalla is rather popular!  

Let me offer my thoughts on tweaking.

I say go for it.     It's important to you, and to Aspen, that we achieve the highest possible performance for the AKSA products, amps, preamps and speakers alike.  The fact that you built your own means you have few inhibitions about tackling component upgrades - it's not as though it's a fully built, retail product.  Along the way, you will discover that components all add their own sound, and that the final outcome is much like a recipe with ingredients of your choice.  The fact that the choices are now yours confers intellectual ownership and redoubles your efforts.  This is really interesting work, and shows how much of this craft is actually art, as you are effectively sculpturing the sound to suit your tastes.

However, different folks different strokes, and not everyone agrees on sound.  Some like it sharp and accurate, while others like it smooth and mellow - and some like to mix these qualities.  Needless to say, in some circles there is war between factions    (as Echidna sagely pointed out!)  But do this long enough and you find that some combinations don't work, and sound terrible.  This can be very disappointing, as you can easily throw away hundreds of dollars.

And there lies the rub.  What is terrible?  What is sublime?  How is this imaging thang manipulated?  Why did we just lose height in that recording?  And so on.....

When you tweak you discover a few factors which the designer must live with uncomfortably.  They are subjective (or 'perceived') quality, cost, and the spectrum of sonic taste in the listener, with the clear implication that you should aim for the middle ground to win over the most listeners.

I have chosen combinations of components in the AKSAs which deliver sonics adjudged by most to be superior at moderate cost.  Many people's ears must go into this judgement, not just my own.  For example, rather than use an expensive RTX 0.068uF 100V MultiCap for C19 in the GK-1, I use a quality axial foil polystyrene, which is almost as good but an order of magnitude cheaper because these are made as industrial products, not small-run audiophile components.  I do this because I have to keep the cost of the kit affordable, yet still make sufficient from the sale to stay in business.  I cannot do this if I supply RTX Multicaps right through the circuit, since you guys just would not buy.  This is simple psychology, since price matters hugely in the initial impulse to buy.  Nevertheless, I do include an Auricap at the output, because I found I just couldn't get the necessary sonics without it.  I would also say that a dollar spent at kit purchase is probably equivalent to several dollars spent on tweak components, since after the initial listening experience your audiophile virus will reinfect and you will be itching to start tweaking, lowering your price resistance!  

I guess this is the reason the Nirvana upgrades have been so very successful.  These days almost every new AKSA power amp kitset sells with the upgrade.  The 'Buy the software, pay for the upgrades' marketing ploy has been very successful because people are understandably wary, and like to test the water with their toe before diving in.  When you think about this carefully, it's sensible because it means that the initial commitment is moderate, even if the upgrade components might individually be very expensive, like RTX caps.  The fact that most sales now include the upgrade is testimony to increasing knowledge of the amplifier out there amongst DIYers, and trust is slowly rising.

Ultimately, when the dust settles and I actually have some time away from the GK-1 retail offering, I may offer a tweaker upgrade for the GK-1, also called the Nirvana.  In the meantime, Larry, Mal, Chris, and all of you carefully tweaking your GK-1s, please share your experiences with us!  It will make an even better product!

My thanks to all for their enthusiasm, participation, and continuing support.  

Cheers,

Hugh

[AKSA]

Steven,

I have just revisited this post and found a serious error on my part.

I'm very sorry.    

You asked about C3, the Diff pair/VAS decoupler.  It is operating at around 49 volts, and a Black Gate rated at 50V is NOT SUFFICIENT.  

My response referred to C4, the bootstrap cap, which can safely be a 50VW rating since it operates at around 30V, well within rating.

So, I'd have to say, DON'T USE A 50VW BLACK GATE FOR C3!  IT MUST BE RATED AT 100VW, THE NEXT SIZE UP FOR THESE CAPS.......  

Cheers,

Hugh

[PSP]

Has anyone tried (or have an opinion about) using a Black Gate at C7?

Thanks,
Peter

[stvnharr]

Hugh,
You supply caps rated at 63V, guess I should have looked.
Time to order some more Black Gates.

Steve

[stvnharr]

Peter,
I am currently using a BG Std 50V at C7.   Works well.   However the cap is a bit larger than space on the board, so have to bend the leads a bit and have cap above the board a bit.

Steve

[stvnharr]

Hugh,
Can a 50V cap safely be used in C10,12?  You supply 63V caps.

Steve

[AKSA]

Hi Peter, Steven,

C7 on BOTH AKSAs is a low voltage application.  In operation there is 2.3 volts across it, and at start up and switch off there is almost nothing across this cap.  Verdict:  the best cap for this application is the NX series Black Gate rated at just 6.3 volts.

Same arguments apply to C2, the feedback shunt cap, which actually has only about 100mV across it and can also benefit from the NX series.

C10 and C12 are rail caps, and should be rated to around 20% more than applied voltage.  On the 55W AKSA, this means they can be 50VW, but on the 100W AKSA, with its 50V rails, they should be 63VW.  Since Black Gate, Bless Their Socks, don't make a 63VW (now that's a smart commercial move!) you are forced to use their 100VW cap, which is MUCH more expensive, around $US6.95 on special at Parts Connexion.

Advice:  Don't change C8, the charge suckout.  Leave the one in which I supply for the Nirvana upgrade.  This is the BEST cap for this application;  I've tried them all.....

Hope this squares things away.  Please, guys, let me know your results.  It's more than likely you will find something I've not discovered, and I WANT TO KNOW!!  

Cheers,

Hugh

[eanee]

Anybody

[blizzard]

Hi Hugh,
  I have a question about your post on C4:

Steven,

I have just revisited this post and found a serious error on my part.

I'm very sorry.  

You asked about C3, the Diff pair/VAS decoupler. It is operating at around 49 volts, and a Black Gate rated at 50V is NOT SUFFICIENT.  

My response referred to C4, the bootstrap cap, which can safely be a 50VW rating since it operates at around 30V, well within rating.

So, I'd have to say, DON'T USE A 50VW BLACK GATE FOR C3! IT MUST BE RATED AT 100VW, THE NEXT SIZE UP FOR THESE CAPS.......  

Cheers,

Hugh

If the voltage rail is at +36V, how does C4 operate at 49 volts?
                      Thanks,
                           Steve

[stvnharr]

Hugh,
I too wondering how my 38V rail at the fuse gets raised to 49 after passing thru R10 @100R.
Are we getting the 55 rails confused with the 100 rails?

My 55 Twins show NO signs of stress and I've played them loud and hard.

BTW, what is the approximate power output of the 55 into 4 ohms?
I ask that as my dual woofer 2.5 ways @86.5 db. efficiency play louder than my 8 ohm 2 ways @ 88db. efficiency.   Just curious.

Thanks for the tip on C2,C7.   I might give that a go.   However, everything sounds so good that it's hard to really want to change anything.


Steve

[AKSA]

Hi Folks,

O Dear!  Sorry for the misunderstanding....

Yes.  For 55W AKSA, C4 operates at about 20V.  For the 100W AKSA, C4 operates at about 30V.

Cheers,

Hugh

[AKSA]

Steve,

My mistake;  fogot to add this!  A 55W AKSA into 4R should pull 90 watts, depending on the regulation of the power supply.

Close enough for government work.......  

Cheers,

Hugh

[blizzard]

Hi Hugh,
  I think it was C3 that was being questioned not C4.  What Voltage does C3 see?
  How does C3 see more than the 36 volt rail voltage?
                  Thanks,
                       Steve

[AKSA]

Steve,

C3 sees rail voltage in both amps.  That is, 36V on the 55W and 50V on the 100W.  Therefore, the 50V BG is NOT appropriate for C3 on the 100W AKSA.

Cheers,

Hugh

[blizzard]

Hi Hugh,
  That's what I thought.  So, 50V is ok for C3 in the AKSA 55.  I think we keep mixing up the 100 with the 55.
                Thanks,
                    Steve

[stvnharr]

This is better!
I think the confusion came when a question was posted on THIS thread about an Aksa 100, instead of posting it on the Nirvana 100 thread.

Also, nice to know that a 55 can give 90W to a 4R load.

[AKSA]

Folks,

Some words on my own modification of the 55W Nirvana AKSA using four Black Gate 100uF 50VW caps per channel bought for me kindly by E Type Phil.     I've been listening now for about ten days, so they should be run in.

In my opinion, and I'm not prepared to be too dogmatic about this because YMMV, here it is in a nutshell:

1.  A discernible improvement in clarity, notably mid and top end.
2.  Some 'air' on top of good recordings, formerly difficult to discern.
3.  No change to sound stage.
4.  No change to bass.
5.  No change to pace, rythym and timing (PRAT).

Verdict:

The previous caps in my AKSA were Elna Silmics, not a bad cap, which I had been trying for some time.  They were only a slight improvement over the Supertech I supply in the kitsets, certainly not worth the money considering the Supertech is quite an expensive cap by industry standards.

We are truly operating at the limits.  There is certainly a perceptible difference with the Black Gates, but I continue to be outraged by the absurd cost, and am now on a crusade to find a cap which is as good at a lower price.  I think my next port of call will be the Nichicon Muse.

I do not agree with Lou that the Black Gate is the only way to go.  I'm prepared to say that I have never seen an audio component whose price so grossly exceeds its value, and I will not be happy until I have investigated all other component options.     I think that if we are to use Black Gates, it should only be for C3, the diff pair/VAS decoupler.  The benefits using BGs in the other positions are much less.

I've said this before in other forums, but I feel compelled to say it again here.  I know many will disagree, but it's only the opinion of one man, so it's easily discounted.    The best gains to be had in audio come from good design with components of good industrial quality.  Exotica can add a little more, but nothing like as much as finessing the operating points or choosing a superior topology, particularly in the direct-coupled solid state environment.  Of course, these latter are a given in a kitset and/or retail amp, so I guess it's quite OK to add the best components you can find aftermarket.  But I would emphasize to all reading this that if I included BGs in the AKSA you wouldn't want to know the price of the kit! In fact, 80% of you very likely would not buy it...  

I will continue to look around for good caps.  I think the Hitano EXRs are VERY good, and absolutely exceptional for the money.  BGs are good too, but I feel there may be other caps in the market which almost match them, at least come within spitting distance.  If there are, I'll find 'em....

Cheers,

Hugh

[stvnharr]

Well said Hugh.  
And nice to know that my 55Twins are not on the edge of blowing up.
I cannot compare my 55's w/BG's to 55 wo/BG's.  It's clearly the design that makes them sound so good.  Perhaps the BG's help.  The 10-12 USD for them is not much for a single tweaker.   I've spent 10 times that on fancy caps for speaker crossovers that made NO difference.   Premium components never make things sound worse, but any improvement is rarely in proportion to the cost.   And often one just feels a little silly for having spent the money.
We are free to do this, and that's part of the hobby.
It's different in a business.