The Naksa Amplifier

by Francis Morrin
pictures by Hugh Dean

Poor old Solid State. It just never will be as desireable or sexy as those big shiny glowing valves to the hordes of lusty-eyed audiophiles around the world. For so long the high price and rarified atmosphere of knowledge surrounding valve amplifiers has cast a shadow over the world of small-ish powered solid state amps. High distortion of 3% for a 3W SET amp – no problem they answer, it sounds beautiful!! But design a solid state amp with 1/10 of the distortion and all you will hear are terms like “mosfet mist” or “souless solid state”. It seems that designers of solid state amps are on a hiding to nothing.

Luckily, some of these designers are gentlemen not for turning. Not for them to be put off by disparaging comments or the lust in the masses eyes – no, luckily, they beaver away with ever improving circuits. Hugh Dean, an Australian, is just such a man. Hugh, who has served as military officer, IT consultant and science teacher, and holds a masters in IT, runs Aspen Amplifiers, which supplies amplifier modules to the DIY market. Each module is designed by Hugh, and follows an intense period of evaluation and research. Hugh’s latest offering, the Naksa, made it’s way to my door about 6 weeks ago.

The Naksa is a 70WPC solid state module – fully built, however the user must supply the case, connectors, transformer, and switch. This is probably the most cost effective way of supplying a kit – transformers and cases are heavy beasts, expensive to transport and are best bought locally. As the Naksa has the required heatsink already built in, finding a case for the amp is relatively simple. The Naksa module is also fully tested when it leaves Hugh’s lab, so the end user has little set up worries.

I’ll admit right off that I did not have high expectations. I do have some solid state amps – but only class A ones, and the last class AB one I heard was err, more B than A. So almost reluctantly, in a job-like fashion, I went about connecting the amp, moving cables and ICs in the bag of snakes that is the back of my hifi rack. All connected, I powered on the amp, got a good sized “thump” to let me know it was working and sat back to have my first listen. Mmmm, yes, thats what I remembered class AB to sound like. Soundstage a bit condensed, treble not that sweet, vocals a bit recessed, overall largely underwhelming. I moved off to attend to a few matters around the house while leaving the amp playing. After all, I had been warned that the amp took a little while to warm up, and that it was a new module, not previously burnt in. I’m nothing if not fair!

Well, I was glad I left it playing. I came back to the Naksa about an hour later – well wowee! What a difference! Back in the room was a clear sweet treble with no trace of harshness. Bass that was plentiful, well defined and tight. Vocals took two steps forward and now sat front and forward in the soundstage. Really, this was a major difference from an hour earlier!! As I used this amp again and again over the next month or so, I found that exact same phenomenon – basically it sounds a bit rough for about 20-30 minutes and then transforms gloriously.

The first and immediate frame of reference I used was my own Pass F5 amp – well renowned for its sonic qualities. The F5 performs highly, with sweet clear treble, well founded bass and midrange clarity to die for. The soundstage in particular is excellent. So the Naksa is pretty much up against it! How did it fare out? – well, actually extremely good! The Naksa has a fuller bass if anything, perhaps this is due to the 70WPC of the Naksa vs the 25WPC of the F5. The treble is very sweet – I tried loads of sibilant recordings (Nina Simone, Louis Armstrong, etc – I’m looking at you!) and in each case, they sibilance was somewhat muted. I don’t know how Hugh Dean has managed to hold onto the clarity and sweet treble while managing to keep the more unwelcome aspects of treble clarity under control, but he has. Likewise, the bass from this amp is quality, quality, quality all the way. Tuneful, full, not overblown or boomy, just right. I have subs to supplement the bass output of the horns in my main system ( yes I know, sensitive horns do not need 70WPC), and I did end up adjusting them downwards. I don’t think that this is unusual though – given the different output characteristics of the amps, its natural enough. However, the real gem in this amp is the midrange. It manages to render voices and most instruments with a beautiful liquidity that is rare outside of the world of the best valve amplifiers. Vocalists hover front and large (not overly so) and again, with a sense of palpability that is extraordinary. Was there any downside to this amp, I hear you ask? Well, the soundstage was not as wide as with my F5 – but then the F5 excels in that department. In depth both were equal though – and I would imagine that would be just fine with most people.

In just the last week I decided to give the Naksa a run in my second system. I normally power the Quad ESL57′s in this system with a smallish EL84 valve amp, and wary of the Quad’s reputation with small SS amps, I contacted Hugh about it. “ESL57s may be a tough load, not dead sure, so by all means give them a shot, quietly at first, then build up” was his answer. So I connected them up, again not expecting much given the awkward load the quads present. To be honest, my real motivation was to check out the treble with with quads. They present a load to the amp that is pretty much the reverse of a normal speaker, the load is much tougher with treble than with bass. Also, I wanted to hear how they fared in the soundstage department (again which the quads are pretty good at, even if the sweet spot is the size of your head!). Well, exactly as before, after the warm up period, the sound took off. The sound here really blew me away. This amp just seemed to love the quads. To all those users over the years who gloried in using Naim amps with quads – well watch out, there is a competitor for that slot – and at much less cost I might add. This really was a revelation – I couldn’t believe it. Maybe you could say I was preconditioned by my low expectations, but does not invalidate the results – this amp sounded fantastic with the quads.

So would I recommend the Naksa to a friend? Yes, with very little hesitation, even to a valve head. I suppose one thing is that I haven’t tested it with more conventional speakers. Another is that turn-on thump – it didn’t bother me although it was loud enough on the horns – but I could imagine some being bothered by it. If you are able to case an amp like this, chances are you will be also capable of inserting a time delay relay in the outputs if it bothers you. The fact that the module is ready built is a real boon – likewise the fact that the heatsink is supplied. Casework is the bane of the amp-builders life – but a module such as this is easily enough housed in an old CD chassis or similar. Throughout my time with the amp, the heatsinks never rose above barely warm, so I imagine you could even mount the module completely enclosed once there are adequate ventilation slots.

Further information on the Naksa amp is available from Hugh Dean at Aspen Amplifiers,

Test equipment:

“Shigaclone” DIY player based on the 47 labs Shigaraki transport
Pass D1 DIY dac
Twisted Pear Buffalo DAC with discrete output stages
Teres DIY TT with air-bearing linear arm, benz L2 cart and Pass pearl phonostage with lundahl step up transformers.
BNC cabling for digital, Silver plated copper ICs and speaker cables
Pass DIY symmetrical B1 buffer (DCB1)
Pass DIY F5 amp
Sachiko horns with modded FE206e drivers.
Quad ESL 57 speakers
Aikido Valve preamp
Lenco L75 in heavy plinth with Roksan Tabriz arm, Zyx R50 cart and phonoclone phono stage.