Based on Hugh Dean's AKSA 55

Even if Hugh reveals the original AKSA schematic. It is always the parts he selected that plays a major role in the well known excellent performance of AKSA, not to forget the layout as well. Hugh will not be able to reveal the schematic to public, we all know that. Greg is trying to create the Child of AKSA, and I hope he succeeds, it is important for the forum that Greg succeeds, at least we will have something that we can call, pla pla pla AKSA for the DIYers. We all know Greg's version will not as good as the original AKSA, still this doesn't mean it is going to be bad, it might surpass many existing amplifiers in this forum, and this is a good thing.

I don't know if Greg is going to emphasize on components selection to the extent Hugh did, and the amplifier layout or even try to be as close to the original AKSA layout, I don't know if this is possible, but there are constraints that can't be discussed in public, it is always better to leave them to Hugh and Greg to discuss in private when it comes to what has to be put in the schematic, what selections of components to be adapted and the layout hints that Hugh will allow Greg to put in his PCB on the forum.


Omar
 
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I would like NOT to see Hugh secrets in public...as he made enormous efforts

to keep these secrets, even selecting the ones he sell amplifiers....people that has Aksa kits, or aksa amplifiers, knows cannot show board in close up...cannot let people borrow as they can inspect and copy, cannot give or show schematic, cannot even keep schematic inside the hard drive..this is a gentleman agreement...and as you could see...we are all gentlemen..no one failed to protect this.

Even when Hugh changed policy, his politics about Kits or assembled amplifiers..not selling board for kits anymore, what made me not happy about his decision..even this way.... we keept his secrets.

I do not think Greg will help or stimulate non decent things, as he is a decent man... and also he is Hugh's friend.... this is not his intention..he is just playing with boards the way he likes.... an exercise using Eagle.

I have my own forum, and there, this conversation is forbiden... we do not talk about Aksa there....i do not even answer when someone ask some details.

Dx amplifier and more 9 amplifiers in this forum where inspired in the Aksa 55, into this same schematic Greg is using...and no one could make it so good as Hugh did...without use the subcircuits, all them...and together...no way.

The most interesting thing is that, reading forum, since 2004, you will see that hugh has explained all his features, and people was so arrogant that have not even perceived.... because i had the amplifier
i could see he gave, his tips and tricks, in small portions...some of them already used here or there...but never all them together.

I have not used any of his features, from that "nude" amplifier i have developed mine listening, tweaking and listening..and if one of mine tweaks that result fine was alike Hugh did..then i give up to use.

My currents are different, the long tail is feeded in a different way, also the VAS current and many things..also i do not use diodes in the rails...and other subcircuits and parts Hugh uses i am not using..this was an effort to respect his job.

In my point of view, i have made the best possible (my own ears and subjective opinion) without the use of Hugh tips and tricks, subcircuits and parts... i do not even use power emitter resistances and output coil..also i reduce the power on thump and increase a lot the bass level and presence.

It is a good exercise..but seems we are marching in the same place, as so many guys have explored this circuit, and if you join all them, putting them together in a cooperative way, including features from all them together..even this way, will not match Hugh Aksa 55.

Threads to explore modifications, or to call, invite or stimulate folks to make it better..for sure will not succeed....because we have "that" feeling that is decent to protect and honor our good designers, our important members, the creative ones that, at the end, work for our communitty producing excelent audio amplifiers...the ones have Hugh units, respect them and knows they have an excelent piece of audio equipment.

The result of his ideas published will be chinese non authorized kits...and really... i would not feel good to have one of that, because it is a piece of stollen thing...not even fair to the ones have paid decent ammount of money for Aksa boards, kits or assembled amplifiers.

If we let this happens, we gonna create the exception that may become a rule..and no one will be respected anymore and the whole thing will turn into a mess..without lack of respect and decense.

regards,

Carlos
 
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Well said, DX

Greg, for curiosity, what are you using for a power supply and how do you plan to test all 3 amps. Would you use the same supply - voltage, etc. and just rotary switch the outputs or inputs or whatever?

Hi Ian,

As it would happen, I'm using my first AKSA PSU. Nothing fancy, some nice diodes and 4700uF per 35V rail. I have my own PSU PCBs 80% designed but not manufactured yet.

At the moment, I am using spades (fastons) so it is easy to disconnect/reconnect each amp. I was thinking about relays and a switch on the front panel or remote control. There will be 6 amps in 2 boxes, so automatic switching would be good for ABC testing.

The only problem with switches or relays is you are adding stuff to the audio chain so you are adding more variables to the equation.

regards
 
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Peter, would the KZ's work as well as the FG's in the non-bootstrap locations. I would work out a little cheaper for quantity discounts if I got one type.

regards

The KZ cap is supposed to be better than the FG and I think is the premium Nichicon Muse cap. It should perform well in the other locations as well. If you find a supplier of the KZ let us know as mine no longer sells them.
 
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I was thinking about relays and a switch on the front panel or remote control. [/QUOTE said:
Remote control? Nah, a long stick with soft HD foam wrap to grip the control. Settle back, relax, twiddle. It sounds a bit like design, build...etc.

Double, single or venetian blind tests are to rattle the competition, not become a financial burden to humble, honest designers IMO.
 
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If i were to design a +50kn high speed vessel i'd have to choose the hull type (topology), the type of propulsion and materials used (parts), and tweak the hull geometry with model tank testing (layout).
Each of those components has an equal share in the final outcome.
Even the best commercial grade steel is useless compared to sealium alloy or carbon/aramid fiber composites.
Even the lowest kg/kW modern diesel engine is inferior compared to a 0.2kg/kW Vericor marine gas turbine.
Next parts step, above 30 knots speed nothing outperforms efficiency numbers of water jet propulsion systems.
The chosen hull topology often inherently determines the choice of parts.

Picking good quality general commercial parts may get you to the finish line more cost efficiently, but you will not have pole position and not finish first either.
Dismissing any part that is not generic commercial grade by labelling it as "boutique" is the equivalent to deciding not to compete for the design performance target from the onset.
About as pointless as the opposite approach : hoping to finish 1st with unsubstantiated, no one does voodoo like you do, boutique parlor items solely. :clown:

you seem to be up with your boats, whose going to win the next americas cup?
 
Luke,

It's a pleasure, got lots of opinions like most people.....
However, anyone perceived to be below your ability is fair game. Witness the tech wars of yore when a couple of the world's rudest people left the forum.

Jacco,

The reason reciprocating engines are still used on ships is not because of weight, it's efficiency. How many turbines boast 45-50% thermodynamic efficiency? But you knew this anyway.
 
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The KZ cap is supposed to be better than the FG and I think is the premium Nichicon Muse cap. It should perform well in the other locations as well. If you find a supplier of the KZ let us know as mine no longer sells them.

Hi Rabbitz, you might want to try parts connexion. $1.00 each for 100uF 100V KZ caps. if you are only ordering a small number, and choose the postal service rather than courier, I think the freight would be under $10 US. you will probably be looking at at least $50 US for a courier.

I bought 8 10,000uF 100V KG's and a bunch of other stuff and it cost $62 US for freight (which was a fair whack on top of the $380 odd worth of parts I ordered), but it would have been closer to $75 for postal. They told me postal would have been in two packets the small one I think they said would have been about $9.00... However they only told me this after I asked the question post shipping. That is the main thing I don't like, they will not give you a shipping estimate, you don't know the shipping cost until they have packed the order.

I'm actually still waiting for my 1000uF Silmic II's they are on back order have been for over a month, and no idea when they will come in :( Note also that they charge additional shipping for the back ordered items!! if you don't want to double up make sure you specify to not ship until backordered parts are available!!

Greg, I think that the answer to what amp I would build next (when I finally get around to it) has been answered :) I will follow with interest!

Tony.
 
it's efficiency.


Hybrid propulsion systems will be the next step for yachts as well imo, i've been thinking of constructing a lightweight +100 footer that does +40kn on water jet drive and consumes less than 15 gal/hr on diesel-electric drive in 10kn long range mode.
The latest electric drive solutions developed overhere, combined with oversized diesel generators and the latest PWM converters, offer up to 25% increased overal efficiency compared to a traditional propulsion system.
A former school mate(hydro dynamics PhD) works for the company that manufactures the composite propellor blades of the electric drives.

Higher complexity usually places a lesser demand on the individual components, for decreased complexity it's commonly the other way round.
Same deal for audio electronics, imo, but i likely rank to the crudest of the rudest.

Larry racing can likely spare a few billion bucks more, know the joke of how Mr Ellison's yacht Izanami is spelled backwards ?
(and the prompt name change to Ronin, the samurai)
 
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Here's a PDF of the PCB. I have chosen to use a separate Zobel/inductor PCB. There is room for the zobel on the amp PCB if required, but the inductor will have to be external in the output line.

I have allowed space for 13mm caps in all locations which should allow for bit of experimentation. It should be noted again, that the PCB layout is for BD139/BD140 drivers (ecb) so if you use other drivers you may need to reverse the orientation of the transistors.

After building a few of these now I have found a few minor things. The holes for the spades are a little large making squaring them up not as easy as it could be and the pins for the inputs are a little close together when using alligator (crocodile in Oz) clips. :D

regards
 

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Hi Greg
The proximity of the zobel to O/P stage affects it's function. I wouldn't speculate on sonics (please).

Hi Ian,

I will be in a position to test this out.

My understanding (possible wrong) is that the zobels/inductors are endeavouring to fix issues related to the load (cable, xover and speakers) and as such should be located close to the sockets on the case to prevent ingress.

Over the years, when I have played around with zobels, I never heard any advantage in having a zobel, so moving it from the amp board will not hurt in my opinion. Of course, I have very limited experience and believe there could well be situations where this is not the case. I may find out the hard way. :flame: :D

regards
 
Ian,

If I might step in here.... I understand the Zobel imposes a load on the amp at very high (ultrasonic frequencies) to compensate for the rising impedance of most speakers and cables, which are typically inductive (not all of course, ESLs are different).

I've found that if you place the output inductor, however, near the input stage, you set up inductive coupling into the input stage, which can cause severe oscillation and self destruction, particularly if the input cap is close.

I haven't noticed any effect on sonics, however. You might be saying this all along, however, difficult to tell from your post!

Hugh
 
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Well, I can't recall the influence of even the EA, SC design philosophy of unconditional stability. i.e. 6.8 uH/ 150nF with 12 & 10 ohm R values respectively for the Zobel and LC. Plenty claim otherwise, however.

No, the Zobel is solely intended as a load and "damper" of HF oscillation, should it occur. The inductor, more obviously, protects LS. RF protection? Fortuitously yes. Amps without make great high SPL scanners for CB, Cops, Fire brigade etc. So much much for Hi-end audio intentions. The values and hence corner frequency of these networks are usually independent of the amplifier design so you are in the right frame of thinking by having a common, separate circuit at least.

Anyways, it's just not going to happen here is it? It's all looking too good!

Sorry Hugh, didn't see your post there but this clarifies my intent if it only repeats, I hope
 
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