AKSA amp kit

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AKSA schematic?


From my message on Audio Asylum -
"Posted by mlloyd1 (A) on November 28, 2001 at 14:13:19
For folks that either own or have played with the AKSA 55W amp...
I've been looking at the "conceptual" schematic at http://sound.westhost.com/project61.htm
Assuming the voltage gain stage bootstrap cap (electrolytic C4 in project 61 above) still exists in the current design, I'm curious about:
1. How good is the bass really?
2. How well does the amp behave in overload/clipping/recovery conditions.
3. Anybody taken any of the various kinds of distortion measurements? I'm not looking to have debates about whether 0.000001% is sonically preferable to 0.1%; I'm curious about how the curves look vs. frequency.

Comments anybody?


I saw responses from folks that indicated that this schematic was reasonably current.

I know about this site. But they have not given the device numbers and componenets values & ratings. Hence this schematics is totally useless for us. We can only try it if we buy it. Hence of no use. That's why i asked for detailed schematics.
Mahendra Palesha

I hear you! As I think about it, I guess that's kinda' where I'm comin' from too, with my original question to the asylum group. I remember seeing pretty much this same circuit in some books in high school (late 70's). Back then, I thought the bootstrap for the driver current source was clever. Certainly, Hugh has most likely done some great optimization and improvement has occured: R11 between the driver emitters, carefully selected operating points for the semiconductors, tweaking the PCB layout and the use of "sustained beta" output devices, as some examples. Maybe there is a lot of positive excitement about the AKSA because it is a good, trouble-free, first project for folks?

The schematic with component values was available on Rod Elliots page before Hugh Dean began to sell AKSA kits. I have that version of the schematic printed out at home somewhere. I don't know if the current AKSA is the same but I suppose it hasn't changed too much.

The other question is, if it would be moral of me to make it public although it was some time back publicly available. I suppose if anyone is interested I can dig it up and mail to you. Just let me know....
AKSA Schematics

Hi Palesha, Lohk,

While I can appreciate your desire to obtain the AKSA circuit diagram, I'd ask you politely to consider this:

1. www.printedelectronics.com is now my sole livelihood, and I protect my intellectual property by making it difficult to obtain the circuit diagram.

2. I fought quite a battle with Rod Elliot to prevent him putting up the complete AKSA schematic on his website. Like you, he felt it should be public domain. I refute this utterly because if it were public domain, the refinements I have made to an age old circuit would be worthless and I would not be able to sell a boutique, unique DIY kitset which performs outrageously well.

3. I do offer a comprehensive circuit diagram with every kitset sold. I ask each constructor to keep this to himself, and NEVER to post it on the net.

4. International patent offers only protection on a specific circuit, and changing just one resistor by a value not less than 10% avoids infrigeing the patent. Not much protection there..........

5. I defy any individual, DIY, engineer or audiophile, to make accurate connection between the circuit schematic and the sonics of the amplifier. There are obviously relationships there, but they are very difficult to spot.

6. My kitset sells for peanuts, particularly in North America. I have to doubt your bona fides if you seek out the schematic before you buy. You wish to build it? Why not buy the kit? There are large numbers of testimonials on my website, and in the various forums, particularly AA. It is fair to say not all these people are wrong.

Why not enter a dialogue with me? I will discuss my concepts in broad outline - always with an eye out for those who would copy - but I don't bite. Why not email me?



Hugh R. Dean
Research/Technical Director
If the circuit was posted against the designer's wishes, this could constitute copyright infringement. I'm not sure how Australian law reads on this; it would probably come under international law, anyway, given the nature of the net.
At least as far as US law, I automatically have copyright when I write a new story (technically without even having to file for it). If I choose to put the story out in the public domain, that's my decision. If someone else puts it in the public domain, then there's a problem.
I'm not a lawyer (thank goodness!). I'm an author. Copyright issues could easily be different for circuitry than they are for stories, but...I don't think they're <i>that</i> different.
If it's Hugh's circuit, and he doesn't want it to be public domain, then that's his decision.
Hugh, fragile though it might be, you might want to investigate filing for a formal copyright. Patent law is stronger, of course, but I didn't see anything new, so copyright would be your best bet.
For what it's worth, the circuit looks clean and simple (in the good sense, meaning lacking foolish bells and whistles). I haven't heard (nor built) the circuit, but see no reason why it shouldn't deliver good performance.


[Edited by GRollins on 12-02-2001 at 05:43 AM]
Hi Grey,

Thank you for sanguine advice; I'll look into it.

Yes, the original infringer did put it up against my advice, and had to be persuaded to pull it down sans a few significant refinements.

However, things have changed since to this circuit, and the quiescent stability and HF stability margin have both been improved still further. Anyone building that particular variant would doubtless notice those issues.



Dear Hugh R. Dean,
I fully respect ur right. My intention is not to harm u even in my dreams. I am from India. Here nothing is available of ur kit. Further the procedure to send u the money and call the kit is lenghthy. Then to receive it through the customs is also painful. And till the time i don't know anything about ur kit how can i proceed. This is like to send u the money blindly. U want to safeguard ur interest and what about the customer interest. We have got the right to know that the circuit is perfectly suitable for us. Even after knowing the circuit the layout part is a big trick. Here u come in the picture. We get all the componenets and pcb easily and without any problem from u. This is actually nice thing. Because most of the times diy project fails due to non avalability of proper components, proper layout and proper knowledge about the circuit. Here we also get technical backing from u. Hence it is good to buy kit from u provided we take the risk of calling it blindly.
Mahendra Palesha

To all,
The post with the schematic link was just brought to my attention, and I have sent an e-mail to lohk requesting that it be removed immediately.

As Hugh has pointed out, the one shown is an early version, but the ESP logo is a dead giveaway as to the source. I worked with Hugh to remove details that he thought would be detrimental to his intellectual property at his request (as pointed out above, I did want to publish the full schematic, and it _was_ on-line for a brief period - accidentally, I hasten to add :-(

The issue of copyright is quite clear - the image posted above has the ESP logo, and neither Hugh or I was ever asked for permission to re-publish it - therefore copyright has been infringed, both Hugh's and mine (since I drew that version of the schematic). The logo is also a registered trade mark, and there is no ambiguity about that!

I trust that lohk will do the right thing and remove the link forthwith.

Cheers, Rod

Rod Elliott
The best amplifier circuit in the world may not produce even reasonable performance if the PCB layout and wiring are not optimised. I keep reading on this forum of people who have got a schematic, off the web, planning to give it a go, sometimes as a first project. I don't want to put you off, but please realise that it might not work first time. Even if it does, it can take numerous alterations before you get the performance you desire, (but isn't that half the fun).

Even if you can get the AKSA circuit for free, without the correct PCB layout you may well end up with a pig, is that good value?

What I'm trying to say here is, if you want the performance you need the total design. It is usually best to BUY THE KIT, sorry. Maybe buy one and go from there, (sorry Hugh, you know they're thinking of it).

To put it another way, if you had a drawing of a formula one engine, and tried to build one from the drawing, you will fail. The metallurgy is just as important as the design and there are many other issues that you'll only find by trial and error, just as the designers did, (unless you think your better than them or very lucky).
I have repaired a number of DIY amplifiers that had failed purely because of poor layout. If you have read many threads on this site you will have come across builders who have had their amps self oscillate to destruction. This is not uncommon, just part of the learning curve and often easily cured. Even years of experience are no guarantee of immediate success, (how I wish). OK, so if some of them self-destruct, how many more will be producing poor performance from what is a good circuit? Listen, read, tinker, tune and listen again, OK, maybe measure every now and then. You can always ask for help here.

There are some designs that have few layout requirements in order to produce good results. I'm GUESSING that the Pass amps, due to their simplicity, would be a good example, there are many others. Maybe Nelson could elaborate here. A lot of designs are very fussy though.

I have not designed many amps, and have only built a handful, (maybe a dozen), I have spent over twenty years repairing other peoples, often DIY. Just so you know where I'm coming from.

It is great creating an amp, tweaking it and listening to it, enjoying it, do it. Just be aware what you're taking on and realise the advantages of a KIT.

Regards WALKER

PS I'm constantly amazed how helpful and understanding everyone is on this site.
Hi Mahendra,

Thank you for your post. You make some points I should answer.

First, you relate the sound qualities to the AKSA schematic. Even if you were that experienced (and if you were, you could design your own amplifier which was probably better!), you still need the right components and the correct pcb layout. These two aspects are crucial, as all three comprise a synergy.

Second, you are concerned you might be throwing your money away blindly, particularly as India is a high customs country, where importing is difficult. In this connection, you are no better or worse off than anyone else, and many countries other than yours carry high customs imposts, such as most of Central and Eastern Europe. You talk about sending me money blindly; well, here you need to understand something about US/Canadian/Australian business. This is often how it is done; there is this thing called trust, which most in these countries are prepared to accept. I am well aware that Indian business has many pitfalls, but I ask you to recognise that not all countries have the same risks and that there may be a lot less risk for you than you realise.

Third, perhaps you would like to build the amplifier from scratch even if you have no wish to deceive me. I can certainly understand that, but just how the schematic will tell you whether it is suitable for Indian folk is quite beyond me. You mention that I protect myself, but don't care about the customer. Rubbish. If you talk with any of my customers, and many are accessible to you on the net, you will find I care very much about my customers, and seek to build a long term business, with repeat orders. This means I must work hard to win their trust, and if you were one of my customers, you would be just the same.

Lastly, without the right components and the pcb, there can be no guarantee that you will get a good amplifier. It may be unstable, or hum badly, or be unreliable, or have terrible sound. With only the schematic, any or all these problems may occur, and as a consequence, my reputation is mud because, in your estimation, 'my amp design doesn't work'. Once again, I am not in business to destroy a reputation before it starts, so it is in my interests to field a complete kitset into the market, with prescriptive instructions on its assembly so that the amp works precisely as it should.

In closing, since no matter how many people explain the good sonics of the AKSA and my honesty, I can only conclude that you would prefer not to buy the kit. No problem at all, and no hard feelings. If you would like to talk about it privately, my email address is on the website, and I'd be delighted to further explain myself.

To all you DIY guys reading this, please excuse the heavy bandwidth used to date. I am not trying to use this forum to sell amplifiers, but rather to address a vitally important aspect of international trade - the protection of intellectual property. As usual, the law has not caught up with this business model, and where it is valid and enforceable remains extremely expensive. I am no genius, and all my good work is paid for with long hours, thousands of dollars, and genuine sweat. Anyone else in this position would seek, wherever possible, to recover some of this investment in a fair profit for a good product. I am not about to publish my findings for all in the public domain, because this is my life and passion, and I wish to build a viable business from it. Notwithstanding, my product is extremely inexpensive, and I hope for it to remain so. But if I have to spend thousands on protection from the occasional pirate, it won't be cheap, because I will shroud everything in secrecy, and offer only a built up module, probably with encapsulated componentry.

I would like to express my gratitude to Rod Elliot for his support of my position, and once again, I would ask LOHK to remove the early version AKSA schematic from his website immediately.

Something to ponder, have a great week!


Hugh R. Dean

I was not online at the weekend and today, reading the thread I feel that I too have to apologise to Hugh Dean as I created problems for him mentioning that there was a full schematic online. I assure you, that was not my intention at all. I respect Hugh's wishes and will not give the schematic that I have printed out (the old version) to anyone.

I have not built the AKSA myself. If I will some day I will surely buy the kit. At the moment I'm working on my own amp design and so I know and fully respect the work Hugh has done.

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