[Foxyb]

I currently have a Hart audio 80W mosfet amp, with significantly upgraded feedback caps, and power supply including elna cerafine caps.

I was wondering if the power supply would be a good match with the aksa, as it can be adjusted to provide the required output, and uses sk56
sk176 pass mosfets in the high current regulator side to provide masses of peak current. As important, it uses a dc offset measurement, and short circuit sensor to shut down the power supply rails. This would replace the need for fuses.

In addition, what improvements would the aksa 55W Nirvana bring over this, when connected to my Ellis Audio 1801 speakers (which are fabulous)?

Many thanks,
John

[AKSA]

Hi John,

I should leave the comments about subjective improvements to those who have listened to the Hart Audio amps, and who perhaps either own or have heard an AKSA!!  On the face of it, however, I think you could expect greater resolution at low volume because of the well known mosfet short term self-oscillatory problem at the transition between on and off.

Regulated power supplies are a sophisticated luxury I have never indulged so I cannot say what improvements, if any, they would bring.

However, there are rules to follow.  The current demand of the AKSA, being a fast amplifier with no devices rated at under 30MHz, should never be constrained in current demand.  That is, the supply should be able to deliver large dollops of current with at least the speed of the amplifier.  This should not be a problem for a mosfet series element, but if the source impedance should increase with frequency, there might be a perceived effect on the sonics.  This is least likely to happen if the series pass element, a mosfet as you describe it, is connected in source follower mode - the fastest configuration.  If it is connected as common source, with output coming off the drain of the series element, then I would have serious reservations.

So, check the output of the regulated supply is connected to the SOURCE of the mosfet series pass element.  If it is, I see no problem.  Otherwise, I doubt you will perceive improvements over the very good unregulated supply caps and rectifiers which come with the AKSA kitset.

Hope this helps,

Cheers,

Hugh

[Foxyb]

Hi Hugh,
Thanks for the frank words. I need to check the circuit on the power supply. You don't think the dc offset protection the regulated power supply offers to the speakers is worth it then?

I have Ellis Audio 1801 speakers, which are great, and I am planning on getting either an Arcam CD192, or Cyrus CD8x cd player.

With this level of kit, would I be wasting my money on getting the Nirvana upgrade on a Standard 55W aksa, or should I go for the higher power aksa 100W, bearing in mind my investment in my existing power supply (Elna Cerafine 10000s, ug8 diodes, and Panasonic hfz electrolytic amp board decoupling caps). I have also upgraded the feedback capacitor on my hart audio 80W to a mucap tin foil capacitor. This was expensive but good.

Are your nivana kits priced with 2 sets of power supply components for dual mono operation or is that extra.

Also, what would I hear going from standard to Nirvana to nirvana plus versions.

Thanks,

John

[AKSA]

Hi John,

Weighty questions indeed!!

With this level of kit, would I be wasting my money on getting the Nirvana upgrade on a Standard 55W aksa, or should I go for the higher power aksa 100W, bearing in mind my investment in my existing power supply (Elna Cerafine 10000s, ug8 diodes, and Panasonic hfz electrolytic amp board decoupling caps).

No, the power supply upgrade comes with the N+ upgrade, so a Nirvana would not be at all out of place.  If the Ellis 1801 is 85dB/watt/meter or lower, then yes, the 100W is probably best here, but otherwise the 55W would be fine.  Of course, room size and preferred listening level is also important, but I'm assuming you're over 18 and not a Metallica fan!

I have also upgraded the feedback capacitor on my hart audio 80W to a mucap tin foil capacitor. This was expensive but good.

Yes, tin foils are VERY good, I too use them.

Are your nivana kits priced with 2 sets of power supply components for dual mono operation or is that extra.

Only the N+ changes the power supply, and in all variants the power supply is dual mono, right the way through, including two transformers.

Also, what would I hear going from standard to Nirvana to nirvana plus versions.

Stock is 7/10, Nirvana is 8/10, and Nirvana Plus is 9.2/10, give or take.  You can expect pretty much more of everything;  better resolution, more soundstage width and depth, deeper bass, crystalline top end and more transparent midrange.  These things defy language;  maybe ask a few guys on this forum for their view;  many here have taken the AKSA from stock through to N+ and can offer more credible comment than I can!

Anything which senses output offset beyond a certain point and shuts off the speaker is good, but if it switches the speaker through a relay there may be some sonic damage because relay contacts are like bad interconnects........  Nuttin' for nuttin'.......

Hope this is helpful,

Cheers,

Hugh

[andyr]

Hi, John,

Hugh says "Stock is 7/10, Nirvana is 8/10, and Nirvana Plus is 9.2/10, give or take."

Of course it depends what "10" means ... let's assume it is the maximum which an AKSA is capable of.

Now, Hugh is da maestro but he did say to ask some Forum members!  As an AKSA N+ upgrader, I would have thought it was more like:

*  Nirvana+ is 9.1 ... ie. yes, it may be possible to get more "beauty" out of an AKSA but I find it difficult to believe it will be more than 10%.  We've already used the highest quality parts where it's appropriate so all there can possibly be is some (minor?) circuit changes??

*  Nirvana is 7.8 ... ie. the N+ is a definite sonic upgrade (15%)!

* Stock is 6.3 ... ie. the N is a 25% upgrade.

Hugh also says "You can expect pretty much more of everything; better resolution, more soundstage width and depth, deeper bass, crystalline top end and more transparent midrange."

Absolutely!!  

Regards,

Andy

[Foxyb]

Thanks for your informative words regarding a choice of amp for my Ellis Audio 1801s.

Many posts, here and on the Ellis Audio circle mention that because the 1801s are 85-86dB/ W that the AKSA 100Ns are suitable.

However I barely listen to my current Hart 80W at more than a quarter the way up the volume dial.

Therefore the aksa 55 with the Nirvana plus upgrade sounds like better value for the lower volumes I am interested in, than the 100 with just the Nirvana upgrade.

Have you any comments?

Regards,
John

[DSK]

Therefore the aksa 55 with the Nirvana plus upgrade sounds like better value for the lower volumes I am interested in, than the 100 with just the Nirvana upgrade. Have you any comments?

John,
While the 55N+ will sound better than the 100N, you will have less headroom and may have problems if you later move into a bigger room, change to even less efficient speakers or want to crank up the volume now and then.

If you currently have insufficient funds for the 100N+, I would suggest going with the 100N for now and saving for the N+ upgrade. It isn't really much more and you will end up with better dynamics from inefficient speakers at any volume.

OTOH, if you are positive that you will never strike any of the scenarios I mentioned above, you will be very happy indeed with the 55N+.

Good Luck!

[AKSA]

John,

Couldna sed it better meself......  Darren (DSK) is right on the money!

Cheers,

Hugh

[Rhythm Willie]

"However I barely listen to my current Hart 80W at more than a quarter the way up the volume dial."

Of couse we know the Ohms/sensitivity of an amp's volume control has nothing to do with the amps actual power/current/loudness delivery capabilities or how it handles difficult  loads.

[Al Garay]

I have heard the Ellis 1801s with the AKSA 55W Nirvana and the power was not enough. That's why I went with the 100W Nirvana and it is enough for most music and home theater.

Some people who claim that the 1801b's don't have enough dynamics, control at  high volumes have not used enough power. Plug a Crown Macrotech series pro-amp and you'll see those speakers really come alive.

Al