Read What Other Constructors Experienced!
Historically, testimonials are often contrived. However, these are genuine comments from genuine folk who have bought kitset on spec, built it, and listened critically. Minor editing has been carefully cleared with the writers. There are quite a few here, and they take some time to get through, but read on - these are amazing, and all reflect the astonishing sonic qualities of the Aspen products!!
Alan Oldale, Wellington, New Zealand - March 2006
You may be interested to know that I have at GREAT expense purchased a pair of Quad ESL 988 speakers. These run from the 55N+ through shielded leads which have a capacitance of 1580pF. No problems at all! The shielding keeps RF garbage from the very local radio tr`ansmitters out of the amplifier innards, and I have had to use shielded mains cable to keep the RF out of the speakers' power supplies. Although the speakers are highly capacitive I have absolutely no trouble with stability.
The sound is fantastic. Recently my wife and I had a visit from a relative who is a violinist in the Wellington Chamber Orchestra. I played a few CDs and she said that they sounded quite natural through the amp and speakers, just as she hears whilst playing in the orchestra. Good enough for me. I have had no signs of trouble whatsoever, the amp with ESL 988 speakers is more stable than Ayers Rock!
P. Pesheck, USA - October 2002
I was first drawn to the 55 watt AKSA amp (there was no 100 watt version at that time) by the combination of elegance, minimalist design, and early reports of awesome sonics. In addition, the price was attractive and Hugh Dean (designer and proprietor of Aspen Amplifiers) answered my initial e-mails with speed, grace, and good humor. It took about a week for the kit to arrive in the USA after I faxed my order and few more weeks to get all of the additional bits on hand. Construction and biasing went well, although I blew the output stage transistors on one channel... not careful enough attaching the multimeter clip leads I guess. Hugh replaced them quickly at a nominal charge.
When I first listened to the AKSA power amplifier I was immediately struck by its combined detail, power, musicality, sweet highs, and deep, controlled bass. Piano, large orchestral works, chamber music, vocals... all were "right," all were musical. In the following months I applied the Nirvana upgrade to the AKSA and replaced my Foreplay preamp with the TLP. Sonically, the Foreplay (mods are stepped attenuators in shunt mode, HV and filament snubbers, 5uf Auricap coupling caps, aluminum-lined enclosure) and TLP are quite close but I eventually found myself enjoying the music a bit more when listening to the TLP.
I listened to the 55w AKSA (Nirvana) and TLP for several months and loved every minute of it. Orchestral sounds were very much like the concert hall, violins sweet when they should be, the basses growly and biting when they should be too. Snare drums had real attack and rattle. I found this combination hugely pleasant to listen to. I was happy. Then I heard that Hugh was shipping the Nirvana upgrade for the TLP and two heartbeats later I fired off a fax to Melbourne to order one.
In my opinion, the Nirvana is a major, major upgrade to the TLP. If listening to the TLP is like dating the prettiest girl you know, then listening to the TLP/N is like having the supermodel of your dreams nuzzling your ear. The TLP/N is fast, really fast. The high end totally sparkles. Sound staging is spectacular... my listening room layout is sub optimal (just the way the furniture works in the room) and I have over the years given up on ever hearing a good sound stage. With the TLP Nirvana, listening to Vivaldi's Four Seasons, I could place every soloist and many of the members of the orchestra in real, stable positions. I was also struck by the musical impact as themes were passed around and within the orchestra... very, very nice. The effect of "speed" on instrumental attack is apparent on picked acoustic guitar and harpsichord (the sound is pinpointed in time in the same way that a star is a pinpoint of light on a cold, clear night). Speed also shows up as incredible clarity and layering in complex passages. More surprising to me was the way speed has the effect of "sharpening" (making more distinct) the beat frequencies heard when close harmonies are sung... once you hear this clearly you will never be satisfied with a more smeared, muddy presentation.
The TLP/N is extremely revealing. This means it will be happy to assist you in your growth toward Audio Truth by pointing out weak spots in your system. When I first installed the Nirvana upgrade to the TLP I found that about half of my CD collection suddenly sounded bright. The really well-recorded CDs sounded spectacular, but the rest were mediocre to bad, some verging on painful. Since I have long regarded my speakers (Energy exl:26) as the weak spot in my system, I replaced the caps in the XO with Axon and Auricaps and this made a huge improvement. Now, about 80% of my CDs sound very, very good and the rest are passable... and none sound bright. I tell this story because, in my opinion, deciding to put the TLP in your system is a no-brainer. Do it, it will sound good, very good. But if you do the Nirvana upgrade to the TLP you are making more of a commitment... if you aren't willing to track down the weak spots in your system that the TLP/N reveals, you may just want to stick with the stock TLP.
The music in my house now is simply incredible. I can hear Diana Krall's every breath, when she wets her lips, the fingers on the string bass. I can hear the musicians of the Saint Paul Chamber Orchestra (Appalachian Spring) squeak their chairs as they lean into an attack, the air around the flute, the piano hammers strike, the pianist's foot on the pedal... all this detail is there if I want to listen for it. But most of the time, there is only the music, the musicians, and lucky me... sometimes reading my work stuff, sometimes a good book, and sometimes snoozing for a few minutes, clear evidence that there is no listener fatigue with the AKSA and TLP/N, none at all.
John Banas, North Carolina, USA - January 2004
Both AKSA amps are now up and running! So far they sound fantastic after just a few minutes of running in. I have used a lot of high end gear like ARC 100MKII, BATVK200 & VK60, Conrad, Hybrids, ASL, and the list goes on. I must say that the AKSA is one of the best I have heard. Smooth and detailed without any solid state glare. Soundstage to die for. My next project will be to build either two more 55 W stereo amps or one 100 W stereo amp to run the base of the Orion dual bass drivers.
Mike Clapperton, Durban South Africa - August 2004
I started investigating the AKSA amps towards the end of 2002, but finances mitigated against a purchase then. Just before Christmas 2003, I bit, and purchased an AKSA 55 Nirvana kit. It is very much to Hugh's credit that he recognised me immediately from more than a year previously. Hugh was a pleasure to deal with, and I was soon the proud owner of a box of neatly packaged little electronic pieces, plus one big heat sink.
A few weeks later, my AKSA was born. I had no problem in assembly – the instructions were very clear and well illustrated. I over-ran my initial estimate of time required to complete due to having to set up and clear away for each building session. To paraphrase Hugh, it can be built on a kitchen table, but you will work better and quicker if you can set aside a dedicated work area.
I initially bought the kit with the idea that I would learn something, and if the amp wasn't that great, I could use it to run a future second system, or use it for PC sound. With this in mind, I didn't spend money on a decent case, but built the amp into a pine box. After setting the initial bias, I disconnected my Proceed Amp-2 and connected the AKSA. I was actually very happy that nothing blew up, and that it appeared to play music. I followed the instructions to run it hard and check the bias, but wasn't overly impressed initially - it sounded quite congested. After checking the bias, and not noticing any flames, I left a CD playing and went outside. Half an hour later, I was listening to a different beast entirely, and the amp improved considerably over the next week. The Proceed has seen maybe 10 hours use since then, mostly when I upgraded the AKSA to the Nirvana Plus level, and is now for sale.
In Nirvana Plus guise, the AKSA 55 only loses out to the best amps I have heard in ultimate power capacity. With my speakers (Lynn Olsen Ariels) this is not an issue. In its ability to communicate the emotional impact of the music, it is unequalled in my system and only two hugely expensive systems I have heard have come close overall. I believe this is due to the dropping of the subliminal noise floor to levels where minute detail is no longer obscured. There is a sense of calm to the musical presentation. I am now hearing things in familiar recordings that must always have been there, but are just more apparent now, without having the etched quality that much "high end" equipment exhibits. Most importantly, really poorly recorded stuff (like most commercial recordings) now sounds a lot more enjoyable than previously. Well recorded material sounds spectacularly "right", with ambience, instrument decay and small vocal inflections clearly delineated and contributing to the emotional experience of the music. It is a very special amplifier, and an absolute bargain at the price.
I have no experience with the stock AKSA, but there is a definite benefit in the upgrade from the Nirvana to Nirvana Plus, and I would recommend it to any potential buyers. However, the lower pricing for entry level is far less intimidating for anyone unfamiliar with the sound potential of the amp, and the upgrade is relatively simple and painless, apart from having to live without your AKSA until completed. Do note however, that the Nirvana Plus break-in period is nowhere near as painless as that for the standard Nirvana. This is not a criticism, just a consequence of the components used.
Although I assembled the kit with no real problems, the extended Nirvana Plus break-in period prompted several e-mails from me to Hugh. In this time, I found Hugh extremely patient, courteous, and absolutely committed to his amps and getting the best out of them. I have no doubt that I would have had his complete attention if I had run into problems during the building of the kit. I have no hesitation in recommending the AKSA amplifiers to anyone who can wield a soldering iron.
run the base of the Orion dual bass drivers.
Haron Abrahimi, California, USA - July 2004
After much internet research and careful thought I finally decided to order an AKSA 55 Nirvana Plus amplifier kit from Mr. Hugh R. Dean from Downunder. For almost a year I had been skeptical of the design, component and documentation quality, but I need not have worried....
I have always wanted to say "I built it", but to be truly proud, any DIY amp would have to best the sonics of my current amp. Although I have owned my dream amp for some time now there was that niggling, missing musical note and a lack of engagement. I will not mention names of course but I can say my dream amp was designed by former space technology engineers and boasts an extremely fast presentation.
When I ordered the Nirvana plus kit Hugh was unable to supply the premium quality power supply caps. When they arrived Downunder he kindly sent them on to me at his own expense. I scrupulously followed all kit instructions, and even read through them twice before commencing just as Hugh suggested!! This was the single most crucial step since it cut down considerably on rework times and greatly spared my patience.
The instructions were clear and concise, conveying the strong impression that Mr. Dean had really done his homework well. During assembly (which was fun by the way!) I had a couple of questions:
HA: Hugh, I have looked through the manuals and I can't find the instructions for the power supply?
HRD: Well, good day to you Sir, the power supply instructions are there towards the end. Please have another gander.
HA: I don't think so! Oh, there they are! Thank you! Oh, and how do you assemble those caps again?
HRD: I have attached a picture to this e-mail, hope it helps.
HA: Thanks again
So there you have it, requests for support were acknowledged and received almost immediately.
After two months I finally assembled my AKSA 55 N+. It sounded wonderful immediately, and seems to be getting better with each passing day. I have to say that the high and low extensions are extremely smooth and bass is awesome with lots of 'meat on the bone' as they say.
I will avoid all the fancy words and just say that the AKSA makes music beautifully and at this price the kit delivers performance costing five or six times more than current retail prices.
Thank you Hugh for the great AKSA kit, the best possible support and your obvious love for DIY Audio.
Steven Harrison, Wyoming USA October 2003
In April 2003 I decided to construct an AKSA 55 Nirvana amplifier. I was somewhat experienced at DIY speaker building, but had not constructed any audio electronics since building a Dynaco integrated amplifier in the '70s. However, I was quite comfortable with a soldering iron, and reasonably familiar with many things electrical.
I am also quite experienced in the finer aspects of audio sound reproduction. Through the '90s I was able to assemble a rather nice, and very expensive, audio system. All components of the system, amp, preamp, cd player, speakers, had individual retail prices of $US5000.
My musical listening preferences tend to run to classical music. My experience has been that only a very fine music system can reproduce the details and musical nuances intrinsic in classical and acoustic music and tease out the most enjoyment.
My desire to construct an amplifier was for a variety of reasons, but in part out of a sense of adventure that had been fueled by my success at DIY speaker building. I chose the AKSA amp because I had read some good reviews and reports, and also because at the time I was in close proximity to Melbourne.
Price was also a big consideration. The price of the AKSA kit was small, about the same as a good audio cable. But when venturing somewhat into the unknown, as diy electronics was at the time, it's nice to not spend too much money at first.
I had a couple little difficulties in constructing the amp, mostly just from my lack of polished techniques. Having Hugh only an hour away was a real blessing!!!
My expectations for this little amplifier were not all that high. As long as it amplified and made music I was happy. A product of less than modest cost cannot possibly be expected to perform with the audio world's finest products. After all, audio products are rated and evaluated as much on their retail price as they are on performance!
Be that as it may, I was simply not prepared for what I heard from this amplifier. I was simply stunned by the performance of the AKSA. I had a rather simple system with just a Sony portable cd player, and a pair of Greg Osborn's Titan Reference speakers (a $5K USD retail set of speakers), all installed into a somewhat cluttered listening environment.
I heard music that WOWED me. Here was bass that was deep and low and controlled. Highs were like no other, though due in part to the Audiom TLR tweeter in the speaker. The music was all around with a clarity that only the finest and expensive musical systems can achieve. The driver control was so good that volume could be turned up with no ill effects, and sound was excellent even when very quiet.
I have listened to most of the audio world's best and most expensive amplifiers, mostly in fancy audio salons, but I've also owned a couple fine amplifiers, and currently own a BAT VK-60. My first impression of the AKSA 55 Nirvana was that this little amplifier could perform with the best amplifiers in the audio world! It may not be powerful enough to fill a large room with concert hall volume, but certainly in any regular sized room in a house it would do fine.
I was so impressed with the amp that I immediately purchased a GK-1 preamp, which I will write about later. Amp/preamp synergy is important. I like to keep them of same manufacturer/designer, if possible, though I have not always done so. But it was a real no-brainer once I heard the amp.
This past August I proceeded to construct another AKSA 55. This was to be for the main audio system, the all BAT system, with my own, self-designed speakers. My desire was for monobloc construction to have each amplifier close to the speaker to keep all cables short. This was also to see if the AKSA 55 really was as good as one of the audio world's acclaimed amplifiers, the BAT VK-60.
I tweaked the amp up with some Black Gate capacitors and Riken Ohm resistors. I wired the signal paths with the same Chimera wire that I had used for interconnects, speaker cable, and internal speaker wiring. I was going to really go for it!
Once I had the amps fully constructed and tested I installed them into the audio system for a test run with the music, and set the VK-60 over off to the side temporarily. I'll just simply say that the VK-60 was NEVER reinstalled into the system. It sits off to the side collecting dust and will now be sold.
The full musical spectrum performance of the AKSA is simply stunning. The bass is so low and controlled. The highs are never harsh, shrill, or hard on the ears. The music has a clarity that other amps can only hope to achieve. I have also used these amps with speakers that were not my own. The musical clarity that was brought to the midrange is usually something more associated with high quality solid state amps in the $10K category.
I have found that the AKSAs give music a very clean, clear sound, never thin and dry like so many solid state amplifiers, and never colored like so many tube amplifiers. One can listen for hours without the slightest notion of fatigue, no matter what volume level the music, loud for a symphony, soft for late night jazz.
I would never want another amp in my musical system!!!!
Darren K, Melbourne Australia - July 2003
Over 18 months ago, a respected friend in the hifi industry suggested I take a good look at the products being offered by a Melbourne based company called Aspen Amplifiers. With mild interest I took a look at the website and read about Hugh Dean, his philosophies and products, and the rave reviews from his customers. Having no DIY skills myself, the notion of buying kits and building them myself was quite daunting. Besides, these kits were ridiculously inexpensive (less than many of my "tweaks"). Surely they were only good performers "for the price" and not serious contenders, let alone upgrades, to expensive audiophile brand components that come complete with rave reviews from professional audiophile magazine reviewers? Interesting, but I think I'll pass.
That is where things stayed until early 2002 when the same friend was in town and visiting Hugh. I tagged along for the ride. I guess I expected to hear "reasonable" sounding equipment that would impress non-audiophiles or suit hobbyists who couldn't (or weren't prepared to) pay for "real" high-end gear. After all, we all know that we more or less get what we pay for don't we? As much as I hate to admit to being a victim of audiophile snobbery, I guess I was until that day.
Needless to say, I was completely knocked off my audiophile perch. My head kept telling me that Supermarket priced gear couldn't sound any good, but my ears and tapping foot were telling me otherwise. Here was a system without special power cables, interconnects, speaker cables, dedicated lines, footers, anti-resonant bases, room treatments, fairy dust and so on, that sounded more lifelike and emotional than many "audiophile priced" systems I had heard before or since. What was going on? Although I knew the writing was on the wall, I wasn't prepared to accept the obvious easily.
I fetched my trusty audiophile pre-amp (US$3500) complete with NOS tubes, my favourite test music, and headed back to Hugh's for a showdown. Now we'll see what's what! Well, Hugh and my friend were very gentle, but the proverbial egg was all over my face. In several areas, the TLP was clearly better than my reference pre-amp. If it were not for the fact that the GK-1 was under development, I may have signed up for a TLP right then.
After many months of anticipation, the GK-1 was finally released. Back to Hugh's for an audition. Wow! As good as the TLP is, the GK-1 is in another league. It clearly surpassed my reference pre-amp in every technical area. But more importantly (or perhaps because of this) it was more musical, lifelike and emotional than any pre-amp I have ever heard regardless of price. You don't hear "solid state" sound or "tube" sound, just real vocals and real instruments in real space. With Hugh's invaluable help, I have built my GK-1 with a few simple modifications and, with the addition of a modified TKD stepped attenuator (as used on the US$12k+ CTC Blowtorch & US$14k Lamm L2 Reference) last week, it has gone to yet another level. Unbelievably, it is getting even better as this attenuator goes through its lengthy break-in process. Yes, it is serious money for an attenuator, but the GK-1's circuitry rewards it and even deserves it ….it is that good. I actually doubt that there are many pre-amps under US$10k that could embarrass a thoughtfully assembled GK-1 (depending on your choice of internal wire, layout, attenuator, etc).
Having lived with the GK-1 for 6 months now, I feel that as good as the Plinius SA100/3 (US$4500) power amp is, the GK-1 may shine even brighter with an even better amp. Hmmmm, perhaps passive bi-amping with an AKSA 55w Nirvana on top and a 100w Nirvana below ….now there's an idea. Another AKSAphile has already achieved better mids and highs by doing just that and relegating his Plinius SA100/3 to subwoofer duty.
It is a huge leap of faith for an audiophile to choose an inexpensive kit pre-amplifier over much more expensive and well-known models from the "big boys" of hifi. It is very doubtful I would have done it had I not lived within driving distance of Hugh and been able to audition the GK-1 first hand. After that, I couldn't swap my designer label bragging rights for far better sound quality quickly enough (or without grinning stupidly). My friend also bought one to replace another very highly regarded Australian tube pre-amp.
The prices included above are simply to give readers some idea of the price/performance of Hugh's products and those with which they rank. My sincere thanks go to Hugh for his time, patience, and wonderful sounding products at ridiculously low prices. Bravo!
Ian Miller, Adelaide, South Australia, August 2002
For many years I have seen reviews and articles making the claim that for truly wonderful sound you can not better a valve amplifier. Two years ago I decided to put this to the test and built a 12W a channel Class AB1 Ultralinear Push Pull Amp using 6BQ5s [EL84]. The result was everything claimed about valve amps - emotion, warmth and a stunning 'live' sound. The difference is striking, not just some marginal thing that will be noticed by those with 'magic ears'. The result of this is that every solid state amp I have tried since has sounded sterile, cold and unlistenable in comparison - that is, up until I built the AKSA! It has all that emotion, warmth, airiness and stage prescence that I get from my valve amp.
So how does it stack up in A/B listening tests against the valve amp? Very well indeed! The 'standard' AKSA has a slightly more agressive edge which detracted a little from my listening pleasure. I have since fitted Polycarbonate Capacitors (the best quality capacitors I had in stock) in place of the Ceramic 'charge suck out' capacitors and this minor modification cured the agressive edge and made the sound even more "Valve like". While I still have a marginal preference for the valve amp there is now very little to pick between it and the AKSA. I would recommend that you make at least this change if not go the whole Nirvana Kit road when you build your AKSA.
[Ed: Since this review was written Ian has now upgraded his AKSA to Nirvana Plus, and tells me he prefers it to his latest tube amp, an 845 SET.]
My Conclusion: If you want the ultimate audiophile experience, have an unlimited budget and don't mind having to replace valves every few years, then get yourself a valve amp. If you'd rather be listening than tinkering but want 'THAT VALVE SOUND' at 20% or less of the cost, get yourself an AKSA - you won't be dissappointed.
Andy Redwood, Melbourne, Australia - September 2002
Six months of work and a giant leap of faith in a kitset amp from - of all things - an Aussie designer! - has finally paid of ….. in spades!!
I now have a system which is a leap ahead of my previous setup! A little more in the way of bass but a whole lot more in terms of the "life force" in the music … all I want to do now is sit back in my couch and smile as I go through my record collection again (forget going to work!!).
My system uses an active crossover and Magneplanar IIIa speakers. This means I need 3 stereo power amps to drive the Maggies. For many years I have been running 1st generation Naim 250 amps … these have always delivered the musical line but I felt I was missing out somewhere (well, the amps are 15 years old!). But, buying 3 x better replacements meant huge cost - hence I began looking around for something I could put some "sweat equity" into, making it a more affordable proposition.
The result of my research was the Aspen Amplifiers AKSA kit. The AKSA is available in two versions - a 55w module and a 100w module. However, the 55w version can be "downgraded" to a 25w version … which delivers enhanced fidelity to compensate for its reduced power rating. So I have ended up with 2 x 3-channel amps, each side incorporating a 25w, 55w and 100w module. These feed, respectively, the ribbon, mid and bass drivers.
If you are after a seriously good amplifier, I unreservedly recommend the AKSA! All you need is a small amount of money, a fair bit of time and an orderly approach to building things!
The instructions which come with the kit are extensive and I found them very easy to follow. The designer, Hugh Dean, was always ready with an answer to any emailed question I had during the construction process.
Felipe Sa, Portugal - October 2002
I have just finished construction of a 100W version, and am very, very impressed.
When I received my AKSA package I was a little unsure if I could build something that would give genuine high fidelity performance. I wrote this to Hugh, and with patient, careful explanation he gave me every confidence, always providing excellent feedback,motivating me to move forward. My fears disappeared when I began construction, as the instructions were clear and Hugh gave marvellous, patient email backup all along the way.
On completion and switch-on, the first impression was STRONG, CLEAR and FAST! Ultra Fast! I have never heard any amplifier this fast sound so sweet. The AKSA is definitely much faster than my previous amps - a Cyrus2+PSX, and an AV Onkyo 898. The Cyrus was sweet and the Onkyo strong, but the AKSA is both, and even stronger than the Onkyo.
The AKSA also has many other wonderful qualities. After a burn in period these began to reveal themselves.
It began to sound beautiful, harmonically rich, with no trace of listener fatigue. I use Silver cables throughout my system, and if any component sounds bright it is immediately apparent. My speakers are Proac 2s, which I consider the most transparent I have ever heard. While these speakers are not as dynamic or powerful as some floorstanders in the market, they certainly reveal all.
Nonetheless, there is room for improvement here, because I would like more bass to fill my huge room.
The AKSA soon revealed a very large soundstage, with precise imaging and wonderful clarity. I have little experience with tube amplifiers, but I know that the AKSA has their wings. It might be a heavy solid state amplifier, but it flies like a valve amplifier!
This solid state amplifier fulfils my every audiophile dream, and Hugh's willingness to help with constant email support made it a pleasure to construct. I still find it hard to believe that I made this amplifier with my own hands, and I sincerely thank the designer, seller, and supporter of this incredible product, Hugh R. Dean.
Yury Stepanenko, Victoria, Canada, July 2001
I did not really expect much by purchasing an amplifier kit. I was greatly surprised when I assembled the AKSA. The clarity and musicality of the AKSA was immediately noticeable. Therefore, I decided to test the AKSA against some professional amplifiers.
The 3-way test system consisted of a Professional Tascam CD player (CD-RW2000) connected via a digital (AES/EBU) cable to XTA Digital Signal Processor (DP226). The processor provided digital crossovers (Linkwitz-Riley, 24dB/octave) at 200Hz and 2000Hz. Six DP266 outputs were directly connected to inputs of power amplifiers.
The acoustic system was assembled from high quality drivers: Scan-Speak 25W/8565-01 and 18W/8545-00 for sub and midrange respectively, and Newform 45" Ribbons for the high-range. The drivers were mounted on two open panels in order to eliminate any resonance effects from acoustic cabinets. With this system, I tested the AKSAs against two professional rack-mounted amplifiers. These were the Symetrix 420, and the QSC2000.
The AKSAs performed superbly, with real depth in the sound and a lot of air and space. Clarity, especially in the range below 150Hz (a difficult range to control), was remarkable - strings were heard with warmth and weight. The AKSAs were notably better than the above-mentioned amps. I also noted that the AKSAs provided a musical softness which made you forget the digital source.
The AKSA design is very robust and well thought out. The amplifiers require practically no tuning and worked immediately after assembly. They are not critical concerning their power supply. I run my AKSAs from a standard lab DC unit that provides only 31V. The amplifiers still perform very well, better than the others in fact. Using the recommended power supply brought a notable improvement, but unless your entire system and acoustic drivers are high-end, you may not note these differences.
I did find, however, that the AKSAs are sensitive to transistor selection. I tried various substitutions for BD377 transistors (T4, the Vbe multiplier which controls bias), but the sound quality was nowhere near as good as with the genuine devices supplied in the kit. [This portion of the circuit has now been altered to use a more common transistor, the BD139. Ed.]
After a few months experimenting with the AKSAs, I am constantly stunned by their imaging and clarity. The AKSA is a truly high-end amp and one of the most musical amplifiers on the market today (and for an unbelievably low price).
Stan Chew, California, September 2001
Nice little amp, the AKSA. I had the opportunity to build a version of Nelson Pass' Aleph, but after hearing my friend George's newly constructed amp, my attention immediately turned towards this Hugh Dean creation. George was so enamoured by its sound that the AKSA quickly replaced his EAR tube amplifier, which now sits comfortably in his closet. Surprisingly, and somewhat to George's chagrin, this little giant slayer weighed in at only l/10th (the cost) of an "EAR".
After completing my kitset in merely 2 l/2 weeks, I had no misgivings. Best sounding amp, yet? George and I have had the pleasure of living with a variety of distinguished amplifiers. Our collective ears have been graced by such historical standards as the modified (Joe Curcio) Dynaco ST-70, the Borberly DC100, Mark Levinson, B&K, Adcom, Douglas Self Class B amp, and vintage MacIntosh. So, how does the AKSA compare? Quite frankly, we don't miss the old stuff.
Some may be asking, what's an AKSA and who is Hugh Dean?
AKSA, or Aspen kitset amplifier, was a design challenge to create a 'tube amplifier' using semiconductors with minimalist topology. After months of research and many more months of listening tests [leading to significant modifications], has Hugh Dean succeeded where others have failed?
To my assessment, the AKSA is extremely detailed, but without harshness, even less than many tube amplifiers. The low end does not suffer from a lack of bass management, extension or detail, characteristic of tube circuitry due to transformer coupling. The mid range is seductive..... sweet, smooth, sexy. Tonal balance is natural. It lacks the edginess so typical of semiconductors, and a frequent cause of listener fatigue. The information retrieval is startling. Imaging is not as expansive as with some tubes, but indeed, there is real depth and dimensionality.
All in all, what Hugh Dean has accomplished is quite remarkable. He has displaced a number of myths, including the common notion that one must spend thousands of dollars to bring home a reference amp. Having communicated with Hugh on several occasions, I can attest, he is both a gentleman and a scholar.
So, how happy am I with the AKSA? As happy as a clam. At its affordable price, I plan to build two more copies to triamp my system. (The 100W version will be ideal to power the subwoofer.) The monies saved will go towards a SACD player to fully take advantage of the amplifier's retrieval of detail. The circuit's simplicity also invites experimentation, and if you are like me, curiosity is a prerequisite for this hobby. Realistically, I seriously doubt Hugh Dean has left any fun for the rest of us. He leaves no stone unturned.
Jeff S, Arizona, November 2001
I now have the AKSA amp up and running. Let's just say that it is everything you claimed it was and much more. I've never had the dynamics, frequency extremes, and imaging of the AKSA with my tube units. This amp will replace my ARC VT50 and my Cary 300se Signature amps.
Everything I wanted is here....cool running.... dynamic exciting presentation..... and no listening fatigue. I wish I'd taken the chance a while back and bought your amp when I first heard about it. I am regretting the time I have wasted listening to my tube stuff.
I'm going to set up a stepped attenuator on the front end, and get rid of my "preamp" (line amp?) in the bargain. You could save people thousands of dollars on equipment if they could only just listen. I'll send you a picture of the "integrated amp" when I get it in a case.
All I can say is - WOW!!
Thank you for designing this amp! Through an ocean of murky water-a light shines through!
Chuck Little, USA, May 2001
Attached is a picture of my finished AKSA Amplifier. I decided to keep the front of the enclosure very simple; there are two blue LED's (lower right) to indicate power in each channel (I like lights!!), and nothing else. The power switch is on the back panel in the upper right of the picture. The line input and speaker outputs are on the other side of the heat sink in the upper left of the picture. Of course, there is a black slotted top panel which is removed for the picture. I thoroughly enjoyed building your kit and found it only slightly more challenging than the old Heathkits I have built in the past; it was a refreshing mental challenge not to have the extreme "hand holding" instructions that Heath used. I really enjoyed your humorous touches ("pat the dog, take up a glass of port")!
The amplifier worked perfectly the first time with only a couple minor changes. Our line voltage is very high here for some reason (right now it is slightly over 123Vac) so I changed out resistor R12b for 68 Ohm parts since my bias measurements were a tad high; my rails are running around 39 Volts with two Avel Lindberg Y23 series 25-0-25 transformers. One very positive observation is that the heatsink has not yet ever become even slightly warm, even after several hours of playing; right now the heatsink is only 4C above ambient after about 4 hours of playing. The only other thing I had to do was to ground the case of our CD player with a separate ground wire since it was injecting some hum into the inputs.
I have one suggestion for anyone who builds an AKSA: try to borrow a second digital VOM, (Volt-Ohm Meter), if the builder doesn't already have one. I have two VOM's and it was extremely handy to be able to leave one connected to each amplifier board when making the bias adjustments.
One of our favorite recordings is Tchaikovsky's 1812 Overtureby Erich Kunzel and the Cincinnati Symphony. My wife had a wonderful observation that the bells towards the end actually have dimension to them when played through the AKSA. Each individual instrument is more clearly discernable and the percussion instruments have much greater presence than with other amp's. The cannon fire actually sounds like cannons rather than just a loud "boom". Drums have a much sharper attack that sounds like a live performance. The overall sound is extremely well balanced with no excesses in any range; it has an almost soothing sound which is not tiring at any volume.
The AKSA boards just do not look like they have enough parts on them to create the sound levels easily achievable; the amplifier will effortlessly play at any volume desired and not even warm the huge heatsink appreciably. And, the amplifier is absolutely silent when there is no input.
Overall, we are extremely pleased with our AKSA. Thanks again!
Shane Ceglar, Adelaide, Australia, August 2000
I want to share with you my impressions of the AKSA power amp. The amp is available in kit form, from Printed Electronics in Melbourne, and is a 55W push-pull solid-state amp, and sells for A$430 with power supply caps, diodes, and custom pcb. The kit is supplied with high quality components and is easy to assemble. The design is simplicity itself and the PCB for each channel is the size of a cigarette pack.
This amp was designed by an engineer who respects the virtues of valves, a person who understands that good figures on the test bench do not guarantee good sonics. You can read more about the design philosophy and a description of the various stages of development in his documentation in the kit.
I bought the kit and all the components for a power supply. Assembly was straightforward and well documented. In these times we should always take what we read with a pinch of salt, and some of you who have spent big $$ on amp's may well be sceptical, so I'll get to the point.
The sound is very un-solid-state-like. For years I have used a valve line-stage with a valve power amp because it simply sounded more real. It produced the kind of sound you just cannot achieve with solid-state amp's, not even with my 'once upon a time ME850'. The AKSA, with its modest a-la cheap price tag blew me away. So much for so little, how did they do it? In truth the AKSA does just what solid-state generally does not do; it is fast, transparent, detailed, dynamic and smooth, with an unbelievable sense of depth.
Bart Shepherd, Sydney June 2001
I took delivery of my pre-assembled 55W AKSA module just two days ago. After extensive listening tests using a quality CD player, good quality DAC, stepped attenuator, 55W AKSA, new speaker cable and Diatones alone (without a sub-woofer), I must admit it. I'm STAGGERED!!!
I should mention that I love tube amplifiers, and own a pair of 211 monoblock SETs and a D115 ARC tube amp.
The AKSA delivers transient response and dynamics playing Jazz/Rock at very loud levels like I HAVE NEVER HEARD BEFORE!!
Image depth and coherence are amazing, together with an astonishing ability to hold it all together during loud, complex musical passages.
Some of my CDs I can finally listen to; before they sounded muddled and too extreme.
Detail and resolution is amazing. This system, with a SS amplifier, ruthlessly reveals any suspect source material.
The AKSA is in no way soft. Without being harsh, it is hard-edged, and transients just hit you. FAAAST!! On electronic Jazz/Rock, well, just ELECTRIFYING!
The AKSA must place its speakers in a vice-like grip and demand they perform or else!! The amplifier makes sense of very complex extreme music as intended by the performers!!
Cymbals.... talk about shimmer! Sound stage... you are almost there. Live concerts a specialty.
The AKSA is absolutely astonishing for a solid state amplifier and betters ANY type of amplifier that I have heard at anywhere near its price point, tube, solid state, kit or otherwise.
Timo Christ, University of Bremen, Germany, September 2000.
When compared to a Class A 'Aleph' amp I recently built, the AKSA has better drive in the bass range. It is more fun to listen to without a sub-woofer. Bass notes seem to have more impact; after more listening it does indeed seem to me as though AKSA produces more bass than the previous amp, (and maybe any amp I have used before). Bass output without the sub is phenomenal, and E-Bass and E-Guitar come across very well.
There is no hum at all. I would certainly notice any hum with 99dB+ sensitive bass speakers.
I have already described AKSA's phenomenal control and bass ease. I switched it with the Aleph amplifier which was handling the midrange, with the Aleph now playing the bass and AKSA the midrange. The AKSA does it very well -clean, powerful and with the right dose of slam. Maybe a bit thinner than the Aleph and not aggressive at all. Really a lot of fun to listen to!
With the Alpeh taking over the bass again it was apparent just what kind of an outstanding job the AKSA does. Overall I think the AKSA is the better amp, because of its better bass handling. And as an efficient Class AB it wastes less energy!
The music used to compare the two amplifiers was "Brothers in Arms" by Dire Straits and "The Electric V" by Thomas Wilbrandt, (a most excellent new interpretation of "The Four Seasons" by Vivaldi, wholeheartedly recommended), both on CD.
John H., California, February 2001
The first time I heard my AKSA stereo amplifier, I couldn't help thinking to myself, "Thank God, I'm finally a high end audiophile".
The sound of the AKSA is really outstanding. The detail and clarity of the sound is excellent and is delivered very smoothly and, seemingly, effortlessly at any listening level. It is a very musical, sweet and natural-sounding amplifier. String and wind instruments particularly have a beautiful natural timbre which I had never heard before, as had both male and female vocals. Cymbals shimmered. Transients were very good indeed.
Interestingly, the AKSA amplifier has only half the number of components of the amplifier that it has replaced but the difference in sonic qualities is like night and day. A strong case of less being more as a result of what must be a very sophisticated design.
Musically, I can think of no criticism to make. Constructing the amplifier was not difficult but, like all kits, you need to be careful and not in a hurry. I checked each component before installation which I think is good practice; all checked good, and the amplifier worked properly the first time it was connected.
Chris T., Melbourne, Australia, March 2001
After first hearing the AKSA amplifier while setting up the bias I thought to myself this amp sounds mighty good. I rapidly assembled the other module. Once completed I soon replaced my Heathkit Tube amp's with the AKSA and was astonished at the increased resolution and wonderful deep bass that I had not previously heard in my system.
The AKSA is a true audiophile amplifier capable of a wide, deep sound stage with plenty of air between each instrument. It is very fast and revealing to the point where you can hear a singer take breath as well as other small nuances in the mix that were once muffled in the background noise.
I have since auditioned the AKSA on a friend’s true high end system comprising Marantz 5 mono tube amps, a Krell preamp and a $3000+ vinyl front end. I can assure you the AKSA was up to the task , playing all types of music with the speed and dynamics one would expect of much higher priced brand-named amplifier.
I cannot over-emphasise the ability of the AKSA to play music. It does so with ease, never sounding strained, and with some of the best midbass slam I have ever heard. I found the kit easy to assemble and it worked first time. If I had any questions Hugh e-mailed with the answer in less than one day on more than one occasion.
Thanks Hugh for a brilliant amplifier.
Roger G., Melbourne, Australia, February 2001
After listening to the first piece of music through the AKSA amplifier, I was captivated. It held my attention, and it was as though listening to a real performance, not just a recording.
Real depth was immediately apparent, not imagined, with a solid soundstage I thought not possible through my speakers. I am now selling my popular Japanese amplifier that cost many times more than the AKSA, and I will not miss the bells & whistles. So do not be fooled by this relatively simple and inexpensive kit, it really performs!!