The Naksa 70 is a recently developed (August 2010) solid state, push-pull stereo power amplifier module delivering 72 watts RMS into an 8 ohm load and 110 watts into a 4R load, depending marginally on the regulation of the single power transformer. It is fully built and tested, requiring only that you connect up two secondaries of a suitable transformer, the signal inputs, and the speaker outputs. Input sensitivity for 72W output into 8R is 841mV rms into a Zin of 30K.
The 2010 replacement module for the Lifeforce 55, the NAKSA 70, employs an unconventional topology and design principle to create a power amplifier with very high resolution, extremely low noise peformance, and a rich, vivid sound, but at much higher power than the LF55 it replaces. The entire stereo amplifier including all power supply circuitry is built onto a single, double-sided pcb of 280mm x 70mm mounted on a single 300mm x 75mm 0.37C/W heatsink. The NAKSA 70 offers power with glory, an almost tube-like sound, and represents the ideal option for people with moderately efficient speakers, an average sized listening room, and demanding musical tastes. The sound quality of this amplifier is true high end, and shames many amplifiers many times its cost!
The following distortion measurements for the NAKSA were taken at 14.14Vrms, 20Vp, or 25W into 8R at 1KHz using the Clio Audiomatica system:
H2 -72dB, H3 -79dB, H4 -79.5dB
This sums to a THD of 0.0404%, 91% comprising H2, H3 and H4.
At just 1W output, 2.83Vrms, THD is 0.008%, of which H2, H3 and H4
The NAKSA circuit board is extremely compact, fully
integrating both amplifier channels and a bifurcated, 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.
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.
The NAKSA 70 creates a presentation comparable to a quality tube amplifier, whilst delivering stunning 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 70 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 extraordinary 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 NAKSA 70 is powered from a single 300VA toroidal (or EI)
transformer with two 30Vac secondary windings. This creates two
isolated 42V rails for each amplifier module, one positive and one
negative. The power supply is bifurcated, effectively a dual mono
configuration. 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 filter caps and rectifiers which are all integrated into the
pcb layout. The NAKSA 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
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.
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.
BUILDING THE NAKSA:
The NAKSA 70 product shipment includes:
Module pcb, with both power amplifier modules and an
integrated power supply
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 300VA transformer with two secondaries each of 30 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 300VA power supply transformer (ONE required with two independent secondaries, each of 30Vac), rubber feet for the case, speaker binding posts, and several small fasteners.
Tools and facilities:
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.'
'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.'
'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.'
'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:
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.'
'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 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!'
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