[hybride]

Aah - I see I need to upgrade my modules as they still have the square white cap! 

IMHO changing the input cap is not a 'must do' update to this amp, it's more like a personal taste and the effect depends on the character of the speakers and perhaps the impedance of your source. (i am driving directly from a Buffalo32 DAC) I read somewhere that big input caps also easily can pick up noise. When i put my finger close to the big one i hear i light hum. Allthough i think 0,47uf is a bit on the small side for a coupling cap. On the other side it's only a DC blocker. But Hugh must have it's reason!

Plz report your experiences here if you also try a bigger/other cap. You don't have to desolder the original one. i soldered it to the resistor near the earth connector.




 

[LM]

Plz report your experiences here if you also try a bigger/other cap.

Hi Hans,
Had Hugh fit 0.33uF Sonicap Platinum caps when I had your model (now have the Soraya 09).  Preferred the ultra clean presentation (compared with other caps) over any possible loss of base extension though never felt any serious loss existed due to the smaller size.  Very much personal preference for system balance as you say and my base was quite solid and tight.  The 1.00uF or 0.47uF VCap or Sonicap were just too expensive for me to get Hugh to try but would likely be the bees knees for transparency and extension.

[AKSA]

Hans,

The size of the input cap is of less importance than the quality.  The Sonicap, and particularly the Mundorf Silver/Oil, are very good in this role, but horrendously expensive and bulky, so they must be mounted off the pcb.

You've had some weeks listening now, Hans, would you like to make further comment on the presentation of your system with your very good DAC and speakers?

Hugh

[AudioTechs]

Hello All


I am new here, New to the AKSA amplifiers.

But not new to the audio listinening. since I installed high end audio system, speakers etc
like, Meridian, LINN

my questoin is fool, and many may dont like it!!

As I said, just heard about this amp.
I looked atspecs, people who heared it, impression results.

Now, i wonder how a simple amplifier will sound that way. while

1- using a low number of audio components
2- Very simple
3- Very normal electronics parts, nothing special

I mean, how to convince me pay that amount of money to buy that simple amplifier?

What is the secret in that design? i know no one will tell.

But convince me to buy it

the web is FULL of circuits for audio amplifiers


Thank you

[Johnny]

Just do it!
You won't regret it.
Looks can be deceiving and specs? Pha!
The ears will thank you
Jy

[Afterimage]

Hello All


I am new here, New to the AKSA amplifiers.

But not new to the audio listinening. since I installed high end audio system, speakers etc
like, Meridian, LINN

my questoin is fool, and many may dont like it!!

As I said, just heard about this amp.
I looked atspecs, people who heared it, impression results.

Now, i wonder how a simple amplifier will sound that way. while

1- using a low number of audio components
2- Very simple
3- Very normal electronics parts, nothing special

I mean, how to convince me pay that amount of money to buy that simple amplifier?

What is the secret in that design? i know no one will tell.

But convince me to buy it

the web is FULL of circuits for audio amplifiers


Thank you

So you want some one to twist your arm?  For starters research this forum.  Find out some of the things that are important to Hugh and see if that falls in line in what your are looking for as far how as how a component sounds.  For example, if you want a cold hard dry analytical sound, that would not fall in line with some of the things that are important to Hugh.  My example is extreme, but I was trying to illustrate a point.  Another thing, have you noticed any disappointed customers?  I am in the same boat as you, I am buying without ever hearing.  Have a little faith and good luck.

[hybride]

Hans,
You've had some weeks listening now, Hans, would you like to make further comment on the presentation of your system with your very good DAC and speakers?

Hugh

Hugh, i missed this question.. I will answer it and also pull 'AudioTechs' over the edge

I am playing for a while with the LF100 now. First i have to say that it's rock solid. Powering off and on is always quiet. Not tics or plop's. From all amp's i had before an Aspen amp is the first amp that could satisfy me. I would call it an amp with the best sum of properties. In all area's of what i expect from an amp it performs largely sufficient. That's unique imo. What's really magical with this amp are the beautiful roundings. NEVER heard that with another SS amp, only with tubes. I did some little modifications, like changing the input cap and i added some extra PS cap's. When listening to this amp i'll feel aware that this is not just a quick design with a few components, but a project with many years of R&D. And AudioTechs: be warned. After the LF100 i build the Vsonic's and sold my 8000 euro speakers. After that i bought the GK1 pre-amp. Ahum..became like an real Aspen fan! Together with my very, very sophisticated new 1541 NOS dac design from Ecdesigns (Dutch company) i am at a point now that i won't want to change anything anymore. That's odd after so many years of 'searching'. I have to learn to sit down, relax and listen to the music




               

[AKSA]

Hi Hans,

thanks for the critique, I think you are dead right, but then, I would, wouldn't I?   

The roundings (a tube term?) is the deliberate use of a bootstrap, which better accommodates the rather nasty back emf and phase shift coming off the speaker, which is effectively an active load for an amplifier.  There are also healthy base stoppers, which improve the musicality of the amp.  And there is a nested feedback loop, tricky to stabilise, but it reduces global feedback and makes the amp much more resistant to the kickback from the speaker voice coil.  The input stage is quite complex, designed to very accurately process the feedback.  This is very important, because the feedback loop really needs to be fast because of the tendency of a fb amp to intermodulate its error processing.

Because the topology is 'different', it sounds quite different too, much more like a tube amp with a bit more slam and resolution.  And the depth of image is better handled, and I've found that if you can locate the individual musical instruments in space, you can more closely follow just one.  This is what tube amps do so well, and I was striving to emulate this quality.

You are right about R&D.  It consumed years.  There is some original thinking in this design, quite a bit more than the AKSA.  It is not unique, however, and if you research the history of audio you find every circuit element covered prior to about 1980.  That's always a surprise, there is nothing new under the sun, sobering thought.

Kieran,  thank you for the vote of confidence, much appreciated!

I believe that there is far more work to be done to produce the ideal amplifier.  I suspect improvements will be consistent every year for the next ten years at least.  Unfortunately, my later amps are even better than the Lifeforce, for which I apologise   , but time brings progress slowly.  The Lifeforce remains my present best modular amp - until people hear the NAKSA.



Cheers,

Hugh

[andyr]

Hi Hans,

The roundings (a tube term?) is the deliberate use of a bootstrap, which better accommodates the rather nasty back emf and phase shift coming off the speaker, which is effectively an active load for an amplifier.

Cheers,

Hugh

Ah, Hugh, just picked up on this.    Some Qs:

1.  When you say "the rather nasty back emf and phase shift coming off the speaker" ... is this any speaker?  IE. is it possible to design a speaker which has no back-EMF?

2.  Is this back-EMF related to the inductance of the driver?  IE. do drivers that are almost entirely resistive - like Maggie drivers - produce less back-EMF?

3.  If back-EMF is related to inductance, do drivers which have Zobels produce less back-EMF?  (I were designed to "tame" driver inuctance?  )

4.  The Lifeforce amps employ a "bootstrap" ... so does this mean they cope well with back-EMF?

Regards,

Andy

[AKSA]

Andy,

When you send a current through a voice coil immersed in a magnetic field, a force results which moves the voice coil, former and cone of the speaker.  Broadly called a transducer, this changes electrical signals into comprressions and rarefactions in the air around the cone.

This assembly has mass, and thus inertia and when moving, momentum.

So, if you excite the speaker with a pulse, it moves.  It's extremely inefficient (around 0.25% typically) but it works well.

If now the pulse ends, the speaker voice coil, former and cone continue to move for a short time until they are brought to rest by the suspension of the cone assembly.

This overshoot produces a voltage across the voice coil, which obviously is impressed back upon the speaker terminals, and ultimately, to the feedback node of a global feedback amplifier.

A Magneplanar has a planar voice coil and 'cone', but the effect is the same.  This is a purely electromechanical phenomenon, and related to the principle of regenerative braking in an hybrid electric vehicle, where power is applied to the motor in the wheels to move the vehicle, and then extracted and fed back to the battery when the brakes are applied, with the motor used regeneratively as a generator.

The second effect is due to voice coil inductance, which causes phase shift between the applied voltage and the resulting current.  This phase shift is again impressed upon the amplifier, which has to deal with this as well as the back emf, which is much, much slower.

It is my contention that the amp has serious trouble with this task, because at audio frequencies the phase shifts in the amp are far less than in the speaker due to its inductance and the crossover reactances, and the application of a fb signal which is considerably delayed electromechanically or phase shifted will disturb the way in which fb functions, chiefly impacting on the stability of the amplifier feedback loop.  All this causes what is sometimes referred to as 'time smear distortion'.

For this reason, a zero global fb amp often sounds somehow more 'natural' than one with global feedback when both are used with a traditional electrodynamic speaker.  But these sorts of amps do have other problems, damping factor, for one.

I invite comment from others more qualified than I on this vexed issue.

Cheers,

Hugh

[daredevil_kk]

Hi guys,

May I add that a large part of the problem is not only caused by the drivers but the passive crossover as well. With all the cap, inductors and resistors. You will be suprised by how nasty some of them are.

KK