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Old 26th March 2014, 08:21 PM   #11
Bigun is online now Bigun  Canada
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I think it's easy to underestimate how vast a change there is between AKSA and NAKSA. It's only an "N" but I would expect anybody comparing the two will be very pleasantly surprised with what they see and what they hear
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Old 26th March 2014, 11:59 PM   #12
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Thank you Gareth, have you figured out the NAKSA topology? I know you are constantly chasing the amp topologies, and you are one of the most builders and testers on this forum..... strength to you, Sir.
I'm waiting on my first patch of N125s. Like the N80 it's a completely different topology. Singleton input, mosfet outputs with trick drive system, unusual VAS arrangement, it sounds very, very different to the old AKSA, which was an old, standard Bailey design tweaked for best possible performance, ported and polished. The NAKSA, trying to exploit the good AKSA name, takes all my lessons over 20 years into a different, svelte beast. I do wonder how long the AB technology will persist; Class D is runner up at present but will likely overtake very soon.
I am quite sure that harmonic profiling is attracting attention. I'm convinced this is the only we can resurrect the analog ways. I have been working on a high quality headphone amp, and this technique has completely demonstrated it can reduce development time by perhaps 80%. With good software a good virtual analysis can predict sound quality within minutes.
Hiraga was right. The French pointed the way in this area as far back as the sixties; google Eric Juaneda and you will see more proof of this. His circuits are almost eccentric, but when you examine them in LTSpice the results are astonishing.

Cheers,

Hugh
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Old 28th March 2014, 05:27 PM   #13
Bigun is online now Bigun  Canada
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If the old AKSA was ported and polished, I'd say the new one is likely adding some super-charging (with local feedback)
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Old 29th March 2014, 06:28 PM   #14
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Hi Hugh,to get the most out of the NAKSA125 is it best to use another PS? If yes, what is the price of the PS for the NAKSA125... thanks Click the image to open in full size.
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Old 29th March 2014, 11:19 PM   #15
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Hi PP,

Ah, the power supplies are built onto the N125 module, one for each rail, so the question is not quite correct; all you need for the N125 module is a transformer with two separate secondary windings!
I designed integrated power supplies onto the module so I could control the power supply, particularly earthing which is a perennial problem with audio amplifiers. Furthermore, the heat output of a 124W amp at full power is considerable, and I was obliged to separate the output devices to equally heat across a 300mm heatsink, so the module was necessarily long and therefore installing the power supplies was easily accommodated.
Much of the cost of an audio amplifier is invested into the power supply filter caps. This approach means that while the module is expensive to buy, you now only need a transformer and an enclosure. I had designed a very clever case, and I can sell this with the modules too - with heatsinks fitted, drilled, tapped - at a very competitive cost.
Since I sell from one of the most expensive countries in the world at the most remote area of the planet I can only compete with exceptional performance and design, as the reference cost of a commodity product across the world now is peanuts from China.

Kapitz?

Cheers,

Hugh
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Old 30th March 2014, 12:00 AM   #16
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Hi Hugh,what size transformer and type do you recommend for the NAKSA125 and what price is the very clever case that can be sold with the NAKSA125 modules fitted to drilled and tapped heatsinks... thanks

Last edited by PingPing; 30th March 2014 at 12:02 AM.
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Old 30th March 2014, 09:23 AM   #17
AKSA is offline AKSA  Australia
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Hi PP,
Transformers needed are 2 x 300VA toroids each with two 35Vac secondaries - see website. Standard toroids are fine earlier used with the AKSA 100 is just fine.
Altronics, Harbuch and Tortech all make them in Oz, easily sourced. They cost around $75 each.
The case is $165 plus GST, with complete holes, cuts, folds, and semi-gloss powder case. Makes building the amp a snap. See attachment!

Cheers,

Hugh
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File Type: jpg N100prodComplete5S.jpg (158.0 KB, 88 views)
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Old 31st March 2014, 07:04 PM   #18
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On the subject of power supplies, a few individuals sell upgraded expensive power supplies for turntables, preamps and power amps. Can these upgraded power supplies improve the NAKSA 125?
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Old 31st March 2014, 10:23 PM   #19
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Hi AS,

Not sure, maybe yes, maybe no! Design of a power supply for any audio product is tricky because there are many competing issues in the functionality. For example, most think that when you use very large capacitor banks the sound is better; I refute this from my tests. To me, the subjective assessment is that while bass is tighter, the sound becomes 'leaden', slower. I suspect this is because the surge charges become very large from the rectifiers, and these charges overcome the very small earth return currents from the speaker voice coils. The effect is intermodulation, which slows and coarsens the sound presentation.

There are a few regulated power supplies for audio amps. Again, my feeling is that there is no headroom in the supply; that is, a very short, high amplitude signal has a few extra volts from a filter reservoir with an unreg ps; a regulated approach means that the undistorted output is set at a lower limit, attracting clip.

Finally, the PSRR of the amp is critical. If you can proof the amp from peturbations from the supplies, then it will be quieter and generally deliver cleaner sound.

Perhaps not what you wanted, but my thoughts on this....... I have spent a long time on the power. One of my tricks is to be used a full wave rectifier on EACH rail, not one for both. That improves the sound quality too.

Cheers,

Hugh
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Last edited by AKSA; 31st March 2014 at 10:25 PM.
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Old 8th April 2014, 08:51 PM   #20
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Hi Hugh,

Does the NAKSA 125 use a linear regulated power supply or unregulated power supply?
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