AKSA 55 vs. ESP P3A vs. ?

[mb]

Originally posted by ABO

Fred,

Would you say that AKSA is better than Peter Daniel-style GC?

After all the ravings about GC, I am wondering if these things really are better than discrete amps? Of course, all amps are different, but what about it?
abo

I'm not Fred, but I have listened to Peter's amp and my AKSA 55N with the same speakers, in the same room. "All amps are different" is a nice way to summarize things. Speakers were VMPS RM2 and 626R, and the other amps were Ampzilla monoblocks.

The AudioZone GC didn't do very well with the VMPS, and clipped fairly easily. There just didn't seem to be the grip, even at low volumes. The AKSA did remarkably well compared to the Ampzilla -- very good speed, imaging, detail, but not the same bottom end control as the Ampzilla.

That's NOT the end of the story: the GC was tried on Meadowlark Kestrels. Voila! This combination worked very well. The Ampzillas was good, but not special with the Kestrels. Didn't have time to try my AKSAs on them.

Beautifully built GC v. humble 55W kit amp v. rock solid monoblock: which is "better"?? YMMV! I have tested my AKSA v. amps ranging from Krells (incl. FBP650cx) to Classe (monoblocks even), Accustic Arts, MF and others. It holds its own pretty well. For me, the key advantage is that I can tweak and tune it to my needs. Of course I can do the same with my Krell, but it would be a financially questionable venture.

Oh yes: I've also ventured into GC land, with a TDA7294A amp. Not pure 'GC' in construction, but with short signal paths, and components selected for sound. It offers great price/performance, but won't drive my main system speakers as well as my AKSA. For a smaller setup, with tuning (esp. a buffer after volume control), it's working very well.

[sonnya]

Hi!, i have received some AKSA 100W board, and you can't just compare the AKSA design with the P3A. So it is .. nothing more to say.

The are improved very much over the P3A. In the circuit and component selection.

Regards

Sonny

[sobazz]

Sonny, frankly speaking - I don't give a damn about "improved circuitry and better components". Does this translate into more desireable sonic caracteristics? If so, more specificly where does the AKSA better the P3A?

As I see it, you're complete right about the AKSA as a complete amp, where highly qualified component selection has been done by the designer. In other words you can be absolutly sure that the circuit has been maxed out component-wise.

But does that nescesseraly translate into AKSA being superior in every aspect? Is it impossible to build a P3A that actually outperfroms the standard AKSA (without Nirvana upgrade)? Have you compared the AKSA and a P3A sonically? And did you remember to some basic critiscism regarding component selection?

I don't doubt that the AKSA is indeed a very competent amplifier. Nor do I doubt that component selection has great influence on the final result. I recognize that the AKSA most surely betters typical P3As built by a reasonable margin.

[AKSA]

Interesting comment, Sonny. Thank you.

Sobazz, the AKSA uses a similar topology to the P3A. Very similar, but not the same. There are changes to the output stage, the voltage amplifier and the feedback network. These changes, together with very careful layout and meticulous component choice, really do make the difference. Stray capacitance is very important on an audio amplifier because it carries a global feedback loop, as I'm sure you realize. Board design on the AKSAs took literally hundreds of hours, with many prototype pcbs built and discarded.

Human aural perception is extremely discriminating. If the amp is 'voiced' or 'tuned' by ear, or better still, many ears, we will be taking a good engineering solution and progressing it that fundamental next step towards making the amplifier sympatico with the human organism, relaying the medium of music.

Our notion of musicality is critical here. As organic beings, not a single ethnic category of the human race seems to enjoy even minuscule levels of H5, H7, H9 and H11. Yet a poorly designed amplifier will produce almost immeasureable quantities of the higher, odd order harmonics. The essence of good amp design should aim to reduce these harmonics - commonly found in global negative feedback amplifiers - to imperceptible levels. The problem is, levels perceptible to the human ear are almost impossible to measure; even a quality Hewlett Packard 339 Distortion Analyser is struggling to pick up 0.005% of H5 at 10KHz. This corresponds to 86dB down; well within the dynamic range of the human ear, and the evidence would indicate this is subliminally audible, and leads to 'listener fatigue'.

Tube amplifiers have gradual switch on/off curves, and this produces far less artefacts, even in push/pull designs. Bipolar transistors are hugely disadvantaged with their horrific exponential transfer functions. Mosfets have problems of their own, too, as they also switch abruptly and gate capacitance complicates drive. Humans are remarkably capable of perceiving these subtleties; the organic 'feel' of so many tiny aspects of life is remarkably acute. Since music touches the soul, it should come as no surprise that we are fussy about how we perceive it.

The AKSA is almost trivially simple in implementation, but it belies a huge amount of R&D. I deliberately built it without using distortion analysers, and Robert Jones in California measured it only once the whole development cycle was complete. From a measured performance POV it came up smelling like roses. That it is so similar to the P3A topologically is one of life's ironies.

BTW, I hope this is not construed as an attempt to sell the AKSA, to you or anyone else. You asked a question, Sonny gave a slightly cryptic answer, I filled in the gaps. Actually, with some of the highly academic nonsense I've seen on this forum in recent times I'm beginning to ask myself why I spend so much time here!

Cheers,

Hugh

[sobazz]

Thank you for the answers, Hugh. As I said, I don't doubt the sonical performance of the AKSA.

[sonnya]

Originally posted by sobazz
Sonny, frankly speaking - I don't give a damn about "improved circuitry and better components". Does this translate into more desireable sonic caracteristics? If so, more specificly where does the AKSA better the P3A?

As I see it, you're complete right about the AKSA as a complete amp, where highly qualified component selection has been done by the designer. In other words you can be absolutly sure that the circuit has been maxed out component-wise.

But does that nescesseraly translate into AKSA being superior in every aspect? Is it impossible to build a P3A that actually outperfroms the standard AKSA (without Nirvana upgrade)? Have you compared the AKSA and a P3A sonically? And did you remember to some basic critiscism regarding component selection?

I don't doubt that the AKSA is indeed a very competent amplifier. Nor do I doubt that component selection has great influence on the final result. I recognize that the AKSA most surely betters typical P3As built by a reasonable margin.

I recieved those boards saturday and have not have tested them yet, i can only say that from the schematic point of view. It is refined a lot.
As Hugh says, in the output stage .. It is very much the same way i would do it.
Also the feedback path ensures good stability.

Of course a P3A is a good design too. But the last refinement done by hugh does make it a much better design.

He has done a lot of work in ensuring a good stability.

And the circuit uses a 1/4 of the components i do in my amp.

So it is easy to build.

There is many ways of getting the design right the way you wan't ... This makes the circuits so different. I am for current feedback as they work as they work as they work and work... For me the work every time i make them...

[sreten]

Originally posted by Paul Ebert

I'm really stretching to save money here. My thought is to build the amps into the bottom of the woofer cabinets. That way, I may save on casework, cables and connectors. My current pricing has the P3A route costing me less than $1200 and the ASKA route between $1100 and $1400.

Paul

so if I understand it correctly 3 or 4 channels built into each
wooofer cabinet.

What surprises me is a lack of discussion of the power supply
for the said 3/4 channels, and any "rationalisation" possible
here.

For example one big transformer is an option, for 4 channels
seperate rectifiers and smoothing capacitors ?

Using a common supply I'd be tempted to add a little RC
filtering to the mid amplifier and and a little more to the
treble amplifier PS's as the power lost would not be an
issue.

An amplifier with doubled up output devices and the
woofers in parallel should be as good as two seperate
amps ?

Or would they be built as seperate "monoblocks" ?

sreten.

[mikelm]

I would not put the amps in the speakers boxes

The vibration will affect the sound ( as it also does to the Xover )

better to put the amps in one big box with the X over aswell or even better have each amp and X-over it their own boxes fairly close to the speakers.

you may be suprised how much having the X-overs close to the amp improves the sound. It is much better that regular bi-wiring.

If you using one tranny this will unavoidably compromise your earthing scheme unless you have a tranny with multiple secondaries...

just a few thoughts

hope it helps

mike

[AKSA]

Sreten,

Power supplies. Ah, what a question!

An amplifier is a modulated power supply. Consequently the supply must be absolutely clean, no ripple, very low impedance, and completely free from intermodulation between channels. We are making malt whisky here; crystal clean, stream water is essential.

Therefore for any multichannel amplifier, as far as practicable, the power supplies should be independent. The AKSA has two completely independent power supplies, one for left channel, and one for right.

If you are making a five channel system, some economy is possible. You can use one supply for left front and left rear, and another for right front and right rear. The center channel should have a power supply of its own, since speech intelligibility is enhanced if there is absolutely no intermodulation with other channels.

Cheers,

Hugh