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AKSA Builders of market proven kits and modules at sound quality to rival the best in high end

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Old 27th September 2018, 03:04 PM   #131
meanman1964 is offline meanman1964  Belgium
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Peer (Limburg) , Belgium
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Old 27th September 2018, 03:23 PM   #132
Mark Verhoeven is offline Mark Verhoeven  Netherlands
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Will send you PM
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Old 28th September 2018, 12:29 AM   #133
AKSA is offline AKSA  Australia
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Mark,

I can listen to it you will understand how it 'sound' and a hugely important aspect of buying any audio product.

I am very grateful to Patrick, very kind of him. Thanks Patrick!

Mark, I owe you an email........ expect today.

Hugh
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Old 28th September 2018, 08:06 AM   #134
Mark Verhoeven is offline Mark Verhoeven  Netherlands
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Thanks for your Email Hugh. I will try to listen at Patricks to the Maya. We are in contact.

Mark
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Old 3rd December 2018, 06:41 AM   #135
AKSA is offline AKSA  Australia
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Mark,

Did you visit Patrick at Peer and have a good listen to a Maya?

I'm very curious about your experience!

Hugh
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Old 8th April 2020, 04:45 AM   #136
audiostar is offline audiostar  United States
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Hugh,

For the Maya200, how many watts is enough? Why 200 watts and not 400 watts? Is 400 watts overkill? The more watts the more the cost goes up? Does more watts give you a better sound. Would a 100 watt Maya with the best parts be better? Is there a disadvantage with an amp geater than 100 watts? By the way, how many pounds is the Maya200?
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Old 8th April 2020, 06:03 AM   #137
AKSA is offline AKSA  Australia
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Hi AS,
Aha, good questions.
When I produced the AKSA 55 (36V rails), people clamoured for the 100W (50V rails) and most were happy. But many in the US (and a few in Oz) wanted a 200W, and one or two wanted 300W (74V rails).
I scratched my chin and decided to do a 200W, which would use 65V rails.
Then I had to decide about bipolar or mosfet. After a few years with the 100W AKSA and then the 125W NAKSA, I came to see that two or even three pairs of bipolars outputs was a considerable issue because to ensure low distortion and suitable reliable operation you had to match them. Now, matching bipolars should be done in two steps; first for equal Vbe voltage at the quiescent current, and then, second for equal beta. With 100 transistors of the same batch, you'd generally get about 15 perfect matches of pairs, and about 5 of the triples. I was using 2SC5200/2SA1943 Toshiba, and this is a very good hit. But it's tedious, and soon I began to see that large mosfets might be the go.
So I studied the mosfet market and noticed that Fairchild offered very good 280W mosfets like FQA series for three or four bucks, and if you used a complementary pair you did not have to match as only two large devices do the job very nicely.
I found you could buy single TO264 complementary pairs of mosfet up to 960W, and this gave me the opportunity to build a 200W amplifier at moderate cost with just two mosfets.
The next issue was to try to get good sound from these large mosfets. It is not straightforward; there is a pitfall as some mosfets do have limitations in SOAR, just like bipolar. It took me a little more experimenting to find that you have to avoid Trench mosfets, as they do not work well in linear (linear operation is in between on and off - many trench mosfets are used in PWM use in traction control electric motors and they are either ON or OFF but not inbetween). And driving mosfets with their large gate Ciss is tricky, even with slow audio. But I found that with FQA series I could pull more than 200W from 65V rails and deliver outstanding sonic performance with reliability.
As a general rule, it is difficult to get wonderful clarity and low distortion from large AB power amplifiers. Smaller amps tend to sound better, and this of course favors Class A.
For very power amps, I will use IXYS devices, but I drive them with bipolar drivers, and I use the Polar devices, not the Trench devices.
And I still use a single pair........ and this keeps weight down. A full on Maya with enclosure, heatsinks (350x100x50) and two 3Kg toroids is 13Kg and fully packaged it almost 18Kg.

Cheers,

Hugh
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Old 8th April 2020, 06:53 AM   #138
andyr is offline andyr  Australia
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Quote:
Originally Posted by audiostar View Post
Does more watts give you a better sound.
That's a deep philosophical question, audiostar!

And I guess there are diametrically opposing answers - as in many things in life!

There are those who firmly believe that a 5w SET gives you audio nirvana - so you need nothing else! But of course, you need to couple the SET with 105dB speakers! By definition such speakers must use a single "full-range" driver - ie. no XOs - so immediately you are up against 2 issues:

1. a so-called "full-range" driver has a range which lacks high extension ... and low extension. Which is fine if your preferred music is, say, a female singer with a guitar.

But no good if you like Bach organ music ... or jazz with cymbals.

2. a SET imparts its own unique harmonic profile to the music. Some people love this presentation - others (like me) prefer something a bit more accurate.

Quote:
Originally Posted by audiostar View Post
Would a 100 watt Maya with the best parts be better?
I presume, here, you mean "Would a 100 watt Maya with the best parts be better than a 200w Maya with normal parts?"

The answer is, AFAIAC ... it depends on: a) your room, b) your speakers, c) how loud you listen and d) the type of music you listen to!

If you never get anywhere near clipping with your choice of a, c and d - and your speakers are an easy load to drive - then I would suggest, yes ... a 100w Maya built with esoteric parts would sound better than a 200w Maya built with standard parts.

But if:
* you listen loud
* in a large room
* or your speakers present a difficult load

... then, without a doubt, the 200w Maya will sound better.

Quote:
Originally Posted by audiostar View Post
Is there a disadvantage with an amp geater than 100 watts? By the way, how many pounds is the Maya200?
Hugh has provided detailed answers to these Qs.

Regards,
Andy
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Old 9th April 2020, 06:42 AM   #139
stvnharr is offline stvnharr  Australia
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I have some useful information to add, beyond what Hugh and Andy have already posted. I did much of the prototype work for the original Maya, as well as much experimental work on the design afterwards. I constructed Maya's of differing power outputs, and I used an array of differing parts in a few places in the circuit.

Power Outputs: 60W, 120W, 200W, 300W. These all varied by transformer secondary voltage and output devices.
The original Maya is 200W and the output devices are Fairchild FDA69N30P and IXYS48P20P. I used these same output devices in the lower power units, as well as some others. I really did not detect any noticeable differences in the lower power units, as long as I used the standard Maya devices.
The higher power 300W unit required higher power output devices as well as larger electrolytic capacitors for the 75V voltage rails. It also requires much more expensive transformers. I did not really detect any improvement from the 300W unit as compared to the 200W or 120W units.

As to the use of "premium" parts, well, the original Maya uses premium parts. The original Maya used an Auricap input cap. I used a Mundorf Evo cap in this position, because I had them, but noted no difference. I also used a stacked Wima cap in this position, again noted no difference.
Sure, one could replace the 1% resistors with 0.1% resistors at considerable cost. This is more in the line of something a diy person would/could do if building up a bare board. But the Maya is a production unit, and designed for the parts specified.

Also, many times there were comparative listens to Hugh's Maya and my own variations of the Maya. The original Maya is as good as it gets for this circuit design.

Hope this helps.
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Old 9th April 2020, 09:25 AM   #140
AKSA is offline AKSA  Australia
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Thank you Steve!
This is the most impartial analysis one could get.......
Your input to the Maya was huge, along with outstanding ideas from Paul. I think that any complex product there are always many different minds behind the reality; one person cannot do it all. It is not a Renoir masterpiece; it is a team effort of huge diverse compromises......

Hugh
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