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Power Amplifier

NAKSA 100

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NAKSA 100


The Naksa 100 was developed over the three months immediately following development of the NAKSA 70, and uses a closely related topology. Like the 70, it is a solid state, Class AB push-pull stereo power amplifier module, one channel to each heatsink, delivering 100watts RMS into an 8 ohm load and 180 watts into a 4R load, depending marginally on the regulation of the single 400VA 35-0-35ac power transformer. It is sold as two (2) completely independent single channel modules, constructed on a 300mm (12") long 0.25C/Watt heatsink. Both channels are fully built and tested, requiring only that you connect up two secondaries of a suitable transformer to each module, the signal inputs, and the speaker outputs. Input sensitivity for 100W output into 8R is 993mV rms into a Zin of 30K. A purpose built enclosure is now available as an option for the NAKSA 100.

 

The 2011 replacement module for the Lifeforce 100, the NAKSA 100, employs an unconventional topology and design principle to create a power amplifier with very high resolution, powerful, clear bass, an extremely low noise peformance, and a rich, vivid sound. Each channel of the amplifier including all power supply circuitry is built onto a single, double-sided pcb of 230mm x 70mm mounted on a single 300mm x 75mm 0.37C/W heatsink. The NAKSA 100 offers power with glory, an almost tube-like sound, and represents the ideal option for people with less efficient speakers, a large sized listening room, and demanding musical tastes. The sound quality of this amplifier is genuine high end, and shames many amplifiers several times its cost!

Distortion measurements for the NAKSA 100 best measurements made with the NAKSA 70. Spice simulations are superior to the NAKSA 70, indicating a THD of 0.008% at +20dBU 1KHz into 8R. The profile of this distortion is linearly decreasing with higher order. The NAKSA 100 exhibits a musically benign harmonic residual which fosters involvement with the music without penalty to the resolution. In turn this creates musical engagement, the holy grail of all audiophiles.

The NAKSA 100 circuit board is compact and elegant, fully integrating a single amplifier channel with a twin bridge, bipolar power supply. Output devices and drivers are mounted beneath the board directly to a large, 0.37C/watt heatsink. This construction is both mechanically robust and compact, and ensures that in even the hottest climate both amplifier channels will always remain well cooled.

A powder coated case with all metalwork and drilling complete is available at additional cost for those constructors who do not have the facilities or skills to fabricate their own. This box permits full dual mono construction, but does not include binding posts, IEC power entry module, or high rated toggle power switch on the front panel (these items are available at small additional cost). The 385W x 320D x 80H enclosure is fabricated of mild steel, fully ventilates the two internal modules and their heatsinks, and is both robust and elegant.

Here is an example of a NAKSA100 mounted in a special case with a four secondary EI transformer using heavy shielding. This is the best NAKSA we at Aspen have yet heard; the sound is simply out of this world.

Black Art NAKSA 100

The NAKSA design brief embraced vivid, warm presentation, refined top end and midrange, strong bass, deep soundstage, low noise and effortless dynamics. The design employs an elegant and reliable circuit topology to offer stunning sound quality genuinely rivalling the best audiophile grade amplifiers in the world. The NAKSA 100 wins praise for its vice-like grip at low frequencies on drivers of all types, including ribbon and electrostatic speakers. This remarkable achievement has been realised in a module which, through meticulous industrial and engineering design, is dimensionally compact and may yet create its very own category of high end power amplifier in the years to come.

SPECIFICATIONS:


Frequency Response:

1dB points at 20Hz and 38KHz for 10w into 8 ohms

Harmonic Distortion:

Distortion measured at 14.14Vrms (20Vp) or 25W into 8R at 1KHz:

H2 -74dB H3 -81dB H4 -79.5dB
H5 -85dB H6 -87dB H7 -95dB
H8 -86dB H9 -89dB H10 -85dB

THD of 0.008%, 95% comprising H2, H3 and H4
At 1W output, measured THD is 0.008% at 1KHz

Signal to
Noise ratio:

280uV peak with input shorted and output connected to 8R load. Referred to the rated 100W output, this represents 105dB weighted.

Topology:

Modified HC Lin singleton design, with single ended voltage
amplifier and asymmetric output stage with nested feedback.

Quiescent Current:

90mA output pair bias, +/-10mA, with ambient thermal feedback.

Stability:

1KHz Square Wave, 25W into 8R in parallel with 470nF.

Square Wave:

Triangulates at 65KHz.


The above results were obtained by Graham Huon of Waverley, Victoria Australia, using a Clio distortion analysis system from Audiomatica on a stock NAKSA 100 fitted with power supply as specified in the instructions. They are quoted here with his kind permission.

The NAKSA amplifier was developed to offer a warm, involving musical presentation, and to overcome most of the sonic problems of SS push pull technology. It incorporates innovative thinking, not just dictated by the engineering (which is crucial) but also by the subjective musical experience.  Mindful of the engineering issues, the design cycle has also been focused on the audiophile listening experience, and the inspired desire of every audiophile to experience emotion via the musical artform.  The rationale behind this is simple;  people listen to music to be moved, not to marvel at the elegance of the amplifier design or the paper specification. While the technical aspects are important, they are a means to an end, and not the end in itself.

While engineering has been crucial in achieving the goal of the NAKSA, the primary focus has been to facilitate the palpable transfer of emotion.  In no way does this indicate that distortion measurements, linearity and slew rates are not important, but rather that there is more to this technology than first appears.  The missing dimension is, in fact, psychoacoustics - the way in which sound is perceived by the human hearing system, encompassing the brain as well as the ear.

The NAKSA 100 creates a presentation comparable to a quality tube amplifier, whilst delivering astonishing resolution and a pure, sweet, musical sound.  This has been achieved at low cost in an attempt to balance the pricing policies of high end audio against the principles of DIY audio.   Like many tube amplifiers, the NAKSA 100 amplifier shines with just about any loudspeaker system, including electrostatics, ribbons and horns, regardless of efficiency.

Key features of the NAKSA are the almost supernatural silence, the cavernous low frequency grip, a strong emotional communication, startling transients, crystalline clarity, and palpable depth of image.   The warmth and image depth are most unusual for solid-state amplifiers, reflecting single ended design where possible and an unusual feedback regime.

The amplifier is very simple to set up.  All electronics, including the power supply, are pre-assembled on two separate, double sided 230mm x 70mm printed circuit boards, one for each channel.  Each pcb is mounted on a single, flat backed 300mm x 75mm heatsink with a thermal capacity of 0.37C/watt, ensuring both channels remain cool at full power in even the hottest climates.

The NAKSA 100 is powered from a single 400VA toroidal (or EI) transformer with two 35Vac secondary windings. This creates two isolated 52V rails for each amplifier module, one positive and one negative. Each channel has its own power supply onboard, effectively four separate power supplies, each with its own bridge rectifier and two large storage capacitors. The best toroid to use for the power supply (the transformer is NOT supplied in the kit) will have 8% regulation or better. Good choices are supplied by Plitron, based in Canada. The transformer has little sonic impact, so no specific brand is recommended; most of the power supply benefits accrue from the integrated filter caps and rectifiers. The NAKSA 100 runs very efficiently in Class AB with a quiescent output stage current of 80mA, and delivers imaging, slam and clarity to rival the best Class A designs with none of the troublesome thermal problems. NAKSAs are part of the green revolution - they are VERY efficient!

This amplifier is winning plaudits around the globe for its astonishing sonics, especially in North America and Europe. The NAKSA truly represents the pinnacle of development of modern day analogue amplification. The elegance and compactness of this jewel gives it stunning looks as well as performance, and the low cost guarantees it will be a top seller for years to come.

The designer, Hugh R. Dean, an Australian with an eclectic background in science education, computing, and language training, stands behind his product with a 12 month conditional warranty and unsurpassed email backup.

Build this amplifier, and join the growing cadre of blissful NAKSA owners, many of whom go on to buy more amplifiers from Aspen for multi-amp Home Theatre installations.

If you have any questions about the NAKSA and are considering purchase, ask one of the owners! You can find them in the Aspen Amplifiers section at: www.audiocircle.com

BUILDING THE NAKSA:

WHAT'S INCLUDED?

The NAKSA 100 product shipment includes:

Two pcb modules, both with integrated power supplies for each rail.
Modules are attached to a 300 x 75mm MF30-75 Conrad heatsink, machined and tapped
Star earth wire
Chassis wire
Two speaker hot leads
Two speaker cold leads
NAKSA 100 badge (as above)
Two RCA input connectors (red, black)
Four 6.3mm (1/4") crimp spade connectors (female)
Coaxial input cable (figure eight pattern) 25cms
2mm heatshrink tubing 12cms
LED green 5mm
18K resistor, half watt metal film
M4 x 8mm Philips head heatsink attaching bolts
Two green LEDs for power indication with associated 18K resistor

You will be supplied with extensive and detailed instructions (with many photographs and diagrams), and full email support and backup. You will require only a single 400VA transformer with two secondaries each of 35 volts AC, an IEC power entry socket, a suitable mains switch, speaker binding posts, rubber feet for the case, and an enclosure. That's it!

 

WHAT YOU NEED TO SOURCE:

There are a a few essential components you will need to acquire. Mostly these are the large, heavy components that are impractical to ship around the world!

YOU WILL NEED:

A case to mount the components in, some wire, a mains switch and IEC power entry module, a 400VA power supply transformer (ONE required with two independent secondaries, each of 35Vac), rubber feet for the case, speaker binding posts, and several small fasteners.

Tools and facilities:

A Workbench of some sort, A fine Soldering Iron, Long Nosed Pliers, fine Side Cutters, Multimeter, Reading Lamp, Philips Screwdriver, Moist Sponge, Sharp Razor, Jeweller's screwdriver, Superglue sachet, School compass.

SOURCES for other components can be found at CONTACT/SUPPLIERS

 

A FEW TESTIMONIALS FROM CUSTOMERS:

'The sound.....detail is amazing, every instrument clearly defined in such a musical way and vocals, my God! I was listening to the backing vocalist on a track the other day and really couldn't believe how easy it was to follow her, no mumble in the back ground. No tinnyness , just rich full sounding music.' Lindsay, NZ

 

'The biggest surprise was the comparison with a top end 300B amp on 94dB speakers, Audio Note AN/E. A great surprise for all listeners was that the NAKSA produced exactly the same character as the 300B across the whole spectrum. It was also clear to everyone that the NAKSA was better in control. On one area the 300B was slightly superior and that was its airy flow. That's a feature of tubes that's hard to beat. But hey, what a surprise that a SS amp is able to compete with a famous 300B and that with more than ten times more output power! We all were impressed. In the light of this review the NAKSA is a real bargain. The tube amp was in the 5000 euro area.'
Hans, Netherlands

 

'The Naksa performed flawlessly over the weekend for some musicians, and left them shaking their heads. They played some of their instruments through the amp and were very impressed with the detail, bass response and overall clarity. I think we converted some old "Tube Heads" to solid state. In fact they wanted me to leave the amp with them but that wasn't going to happen.'
Sam, Arkansaw USA

 

'This amplifier is in a different universe than the one it replaces. I am not a frequent upgrader and it takes something special to prompt me to move!

'On first listen with less than 4 hours on the amp it is detailed beyond anything else I have heard, but amazingly not at the expense of musicality and smoothness. There is stomping bass, magnitudes above what the Lifeforce is capable of; deep and musical. Vocal highs are unstressed and presented so separate and forward it is uncanny. The thing is, from some prior listening comparisons of this amp, I was expecting to sacrifice some detail given the smooth analogue slightly tube sounding presentation, but it is not the case, the presentation is revealing and detailed while remaining eminently listenable and relaxing.'
Russ, Melbourne Austalia

 

'My audition period with the new Naksa ended a couple of days ago and I now feel that I have recovered from the audio equivalent of a hangover, sufficiently recovered, that is, to make some hopefully helpful observations on Hugh's latest and greatest. I say greatest because I firmly believe it to be the best amp that I've had in my lounge room.

In no particular order some of the Naksa wins are as follows:

  • Bass - deeper, punchier and more tuneful. Quite shocking and addictive really;

  • Detail - greater retrieval and more analogue in presentation;

  • Background noise - much blacker and commented upon by my wife at the end of a track;

  • Realism - much greater. Piano, especially, sounds more bell-like.

Martin, Melbourne Australia

 

'Good God, I really wasn't fullsome enough in my praise of this amp - the more I play it & listen the more astounding it sounds. I don't know if this is a burning-in or if I'm playing for long periods & it's reaching a nice thermal equilibrium (no heat coming from the heatsink vanes) - but it's incredible.

I'm trying to put my finger on its sonic secrets and all I can come up with is that it is so quiet & THD is so low that the instrument tails are clearly revealed giving a true foot-tapping & engaging sound to it. I'm in the process of finishing a Sabre DAC & can't wait to hear what an improvement in the front end will reveal. Problem is I just don't want to stop listening to music with this amp.

I brought the Naksa to a friend's house yesterday & he was madly impressed with it. I won't give the details of the amp we compared it to or the rest of the system but I made the comment which I think seems apt here in light of the gorgonzola cheese - the amp had " delicacy with balls".

Hugh, my hat off to you - I knew you were a good designer but this is truly exceptional.'
John, Dublin

 

'I've now had one of my NAKSAs up and running for about a week and have listened a fair bit to it.

I have to say right up front that this is the best amp I've ever had! I liked my LifeForce 55 very much for its musicality, but the NAKSA 100 bests it with a wide margin

I am using the NAKSA in conjunction with my GK-1R, and even though the NAKSA may sound very good indeed driven directly from a source, I can vouch for the GK-1/NAKSA combo - very impressive pair. And very silent. With the LF55 I had a slight bit of hum, which is gone now. The noise floor in my system is now very low, even though I have speakers that are 94-95 dB/m efficient!'
Jens, Copenhagen

 

 

 

 

PRICES:

The prices for all our products can be found at: BUYING/PRICELIST