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Old 12th April 2002, 03:58 AM   #21
AKSA is offline AKSA  Australia
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Default Amplifier Design & Reality Checks

In response to inquiries from Griff and Mrfeedback, let me offer a few comments about the technology from where I sit.

1. Pro-audio is about filling large spaces with good sound, sound reinforcement is about filling huge spaces with OK sound, and Hifi is about music. These are different engineering requirements, and they attract quite different solutions. Just for starters, output stage and speaker protection is mandatory in the first two, and often deleted for sonic reasons with hifi amplifiers. And remember that word 'MUSIC'. We like music because it tickles our soul; there is a huge emotional impact in music, and that's what we like about it. So any amp used for this purpose must be capable of communicating emotion. How do we measure that?

2. Within hifi there are huge differences. Tube, SS, hybrids, digital topologies - all are often radically different. And each has a sonic trademark; OTLs and SETs are different, SE mosfets and PP bipolar are different, etc. This closely parallels many technologies, particularly the auto industry.

3. Within each category it is possible to do it right, or badly. You are the consumer; you make your judgments, then you choose. If you want power, push-pull offers more possibilities than single ended, for example. Commensurately, PP introduces intractable problems at the crossover disjunction, which should be addressed and often are not, or at least incompletely.

4. Regardless of topology, the same building blocks are used over and over, and each has its strengths and weaknesses. If you want huge power and great speed, be aware that to some extent these requirements are mutually exclusive. As in all technologies, the design which identifies the best compromises is often the winner.

5. The consumer is often unrealistic about complex technologies because he doesn't know the compromises intimately. That's cool; it's the reason he's in the marketplace to begin with. If we all knew all about autos, we'd design and build our own. We don't, but we are still very discerning about these products.

6. Good sonics and high power are very difficult to do, because, in general, the larger the transistor, the slower it becomes. Speed is important for good sonics; I can use a 30MHz voltage amp in place of a 100MHz voltage amp and the difference is night and day. So for high power we use multiple, smaller devices, say 150W rating, and run them in parallel. Then we face that perennial problem; how to turn them on and off at the same instant. This is the matching issue, which is expensive and inconvenient, and has taxed some of the best minds in electronic design, including John Linsley Hood, Nelson Pass, and Doug Self.

7. In closing, there is eternal debate about specifications, which don't say too much about how the amp will sound. Gross figures such as power, FR, and current capacity are useful; distortion totals are probably not very predictive.

That's the reason the market is so large, so varied, and so full of hype. In truth, the sonics of an amplifier have even the engineers who design them confused!

Of course, none of this is very conclusive. But it shows one important thing: 'LISTEN BEFORE YOU BUY, AND KNOW WHAT TO LISTEN FOR'.

Sincerely,

Hugh R. Dean

[url]www.printedelectronics.com
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Old 12th April 2002, 07:54 AM   #22
griff is offline griff  Australia
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Quote:
griff and mrfeedback
sorry to hear that the AKSA is not stable to 0.05 ohms and clips just like any other SS amp. I bet you won't be buying it anymore, will you?
When you are done shopping around, and putzing around, make sure you let us know. For the moment, you should be thankful that Hugh is a nice enough guy to dignify your highly pointless and annoying requests with an answer.
If it's a sales pitch you want to hear I suggest you leave this site and visit your local Subaru dealer.
grataku

thanks for your input, ill put this fire out before you start pouring petrol on it. I have no trouble admiting that i havent as much knowledge on this subject as i would like, but we all start somewhere, as im sure u did urself.

I appreciate Mr Dean's responses, as i equally appreciate the expertise of others on this forum, Nelson Pass, Grey, AudioFreak, Navin, Sandro, mrfeedback, pmkap, H.H and Jocko just to name a few that have my upmost respect and appreciation for all that they bring to this excellent website (and Jason too ). Im sure he is busy, as is everyone else here, but has taken the time out to attempt to put some of my concerns to rest, part of good business i feel, as a consumer i have as much right to ask a question as anyone else, and it is for him to decide whether it is worth responding too, and questions that you see as pointless may be entirely relevant to some one else. Im not in any way concerned with the Ohm readings, or clipping, i havent mentioned it, i merely gave a manufacturer an opportunity to further depict an apparantly great product. A DIY amp kit is a common theme throughout this website and i would have anticipated that it would be understood that this would help to enlighten us about the working of the AKSA amp, to understand the engineering of the amp more fully, so that a rational judgement can be made on it and to improve all of our skills through listening to those with more knowledge then ourselves.

It is nice to hear from people with experiences that you havent, ie, building an aleph/aksa, and i would prefer to know any pitfalls, problems before i commence so as to avoid unnecessary pain.

I have but 3 questions, i know that they have a point TO ME, and will help me to decide on what way to go when i am spending thousands of dollars

1) Has there been an example of some one using 5 of these modules as either a one box 5 channel power amp, or monoblock configuration?

2) What is the cost of the Nirvana?

3) Where in Melbourne are appropriate chassis available?
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Old 12th April 2002, 08:51 AM   #23
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Hi Griff,

I have only build an old version of the 55W ASKA, but I beieve that the mounting to the heatsink is much the same concept for the 100W version, just a bigger PCB and double the output devices.

If you are happy with a standard rack mount style case, I think you should be able to get a case at any local electronics stores (i.e. Jaycar/DSE/Altronics/Radio Parts). I used a 3 RU case from DSE that they were disconinuing, cost only $35AU.
Also on the forum mentioned earlier (http://www.harmonicdiscord.com/forum...p?forum=42&828) there was an aticle with a guy who build the 100W version into a case from Jaycar (http://www.harmonicdiscord.com/forum...81&forum=42&12).

Regards,
Tim.
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Old 12th April 2002, 02:52 PM   #24
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Default wrong vibes

Hey grataku, did you miss out this morning ...?,.... and last night ...? .

C'mon, this is a friendly happy place here and the whole point of this diyAudio forum is to enable us like minded
curious and experimentalist, sound reproduction interested group of boffins to gather and share positive
experiences and knowlege in order to better the state of the art and enjoyment for all.
So, please recant and apologise " before the gods strike you down with merciless fire and vengeance ! " .

Peace, Love and All That Stuff, man,
Eric.

BTW - your profile says nothing of you - I'm sure that there is much more to say than that !.

"PLATS" is the name of a Perth band - really good 70's, 80's, 90's covers.

Hugh, Griff and all, thanks for your inputs, I'll get back.
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Old 13th April 2002, 10:14 AM   #25
AKSA is offline AKSA  Australia
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Hi Griff,

Pardon the delay; it's Saturday night and at last I have some time.

You ask:

1) Has there been an example of some one using 5 of these modules as either a one box 5 channel power amp, or monoblock configuration?

ANSWER: Not in Australia, but in the States, yes, and there are at least two others I know of, one in Holland and another in Norway. Because of the dynamics of the sonics with the AKSA, it is actually highly suited to the Home Theatre situation where transient reproduction is extremely important.

There are a number of monoblocks, a couple in Australia (not Melbourne, unfortunately) and two more in NZ, and many in the States and Europe. They work very well, reputedly, and this configuration is actually easy to assemble since the power supply is fully dual mono anyway.


2) What is the cost of the Nirvana?

ANSWER: For the 55W AKSA, $US60. For the 100W AKSA, $US80.

3) Where in Melbourne are appropriate chassis available?

ANSWER: Altronics sell a good one; a 2U is fine for the 55W, while a 3U is suggested for the 100W. Cost is around $AUD75 and $AUD95 respectively.


Hope this helps!

Sincerely,

Hugh R. Dean
Research/Technical Director
Aspen Amplifiers P/L
Melbourne AUSTRALIA
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Old 13th April 2002, 04:15 PM   #26
griff is offline griff  Australia
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thanks Hugh! thats exactly what i needed to know.look for my order in the mail
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