[ShinOBIWAN]

I've now had my AKSA 55N+ assembled for over a month now and I feel I'm ready to comment on the sound now I'm fully sure its broken in.

I must admit, I thought Hugh was something of a crackpot when I first read about the burn in time on the 55N+. However I'd generally agree that there were changes, the amp starts out fairly blurred and generally sounds unimpressive. I was so unimpressed that I resorted to connecting the amplifier upto a dummy load of resistors and driving it hard for nearly a whole week. I kept my patience as I'd read of others experiencing the same things and I hoped and prayed it would improve considerably.

After around 140 hours of burn in using the dummy load I left it to cool down for around 20 minutes, I then rechecked the bias, tweeked it very slightly to get the 55mv required and then reconnected the amplifier to my pair of ATC SCM7's. Boy, what a difference a week makes! It now sounded like a real high end amp, its almost impossible to convey in words what the AKSA sounds like but I can try.

I tried a large genre of music, from paino solo to orchestral to dance and many others. I've got a wide taste in music and if I like the sound its good music to me.
One thing that is inescapable is the fact the AKSA is a very controlled performer, everything is in its place and a place for everything is very apt here. The sound stage is very well layered and completely believable, its almost but not quite three dimensional, I feel the reason why it falls short here is because the imaging is a fraction blurred compared to the best I've heard but still good, if only Hugh could tidy this imaging part up it could very well be one of the best SS designs available.
Dymamics are good and you get the sense that things swell out of complete silence making the presentation clean, controlled and a just a general feeling of correctness to the sound.
Speed and fluidity are possibly the best I've heard yet from any design. Its massively fast and I suspect the feeling that the amp is always in control aids this. Fluidity or how naturally the acoustics are formed are again unsurpassed IMO.

The only downsides for me are the bass and imaging. I so wish Hugh could do something to tighten up imaging just a notch more. Another thing that isn't stella compared to the very best is the bass. Its just not quite tight enough and the definition whilst good sometimes slips with complex bass lines. Compared to the other world class attributes, these two points seem to have taken a slight back seat. I'd personally trade off a small amount of the awesome soundstage layering for a tad more imaging and bass definition.

On another note:

I'll be comparing the 55N+ to the UcD700AD this weekend and will report back here with my thoughts on that.

I've also ordered some SKA's from Greg to compare to the AKSA with the intention of using the preferred amplifiers for tri-amping my mains.

[ShinOBIWAN]

Hugh,

The amp is really amazing, if you didn't gather that from what I've already said.

Definitely in my top 5 regardless of cost.

One thing that confuses me or rather impresses me is just how did you manage to get the amp to sound so very fast? Its uncanny and rather addictive.

[Joules]

Definitely in my top 5 regardless of cost.

Pretty lofty for a 700 dollars (or there abouts) amp.

[ctviggen]

You also have to realize what Shinobiwan is going to do:  he's going to have three of the Aksa in order to drive one pair of speakers.  He's set up his own computer system(s) with independent crossovers for each driver, and digital room correction.  Very impressive, and using the Aksas for that purpose should rock (though I'd think about maybe a bigger Aksa for the bass).

[ShinOBIWAN]

Pics of the AKSA's under testing:

[ShinOBIWAN]

You also have to realize what Shinobiwan is going to do:  he's going to have three of the Aksa in order to drive one pair of speakers.  He's set up his own computer system(s) with independent crossovers for each driver, and digital room correction.  Very impressive, and using the Aksas for that purpose should rock (though I'd think about maybe a bigger Aksa for the bass).

Thanks ct,

As you've pointed out I'm at the point were I'm selected amplifiers for use in these (excuse the bachelor pad layout, ahem, scruffy):











As you can see they're still in the preping and priming stage for spraying. Not shown is the base which is also finished and the cabinet are now fully finished which isn't the case in that shot. I was chatting with Hugh about it and the British weather is holding me back on spraying but hopefully in the next couple of months I can continue with the spraying and finishing.

[AKSA]

Hi Anthony,

Thank you for your generous review - I'm delighted with the report card!

It's difficult to know what to say about the imaging and the bass.  Imaging is already good;  your standards are pretty high, of course (which is fine), but the only way I've found to enhance it more is either to use the GK1 or to take a portion of the feedback signal from the voltage amplifier.  The latter course costs impact and slam, regrettably, you don't seem to be able to have it all.

Bass comes back to the output stage and the filter capacitor bank.  I've tried all the other parameters in the circuit affecting bass, but attempts to increase it remove some of the fluidity and warmth of the amp.  The best way is simply to ratchet up to the 100W AKSA;  this has much more bass, precisely as you'd expect, and significantly it uses twice the filter capacitance.  Your power supply is a little different;  I understand it uses 16 x 220uF caps?  Is this right?  If so, the combined capacitance is 3,520uF, which might be a little light on, particularly as each cap is interlaced with small resistors.  As a trial, you might cobble in another 2,200uF across each rail to see if this improves things.

There are a myriad of compromises in amp design, like any other technology, so you are often damned if you do, and damned if you don't.  Apropos your comment on speed;  this is achieved by using lightning fast voltage amp and driver/outputs, and by very careful attention to layout so there are no parasitics to compromise design.  Lag compensation is important, too.

If I can get up there with the best with a humble kit amplifier, I consider I've done something pretty good;  this is not exactly top dollar hardware like a Krell or Halcro, yet there are people who much prefer the sound.

Thank you again, your rig is just amazing, and hats off for such a detailed, visionary crossover regime.  And your speakers, WOW!!

Cheers,

Hugh

[ShinOBIWAN]

Your power supply is a little different; I understand it uses 16 x 220uF caps? Is this right? If so, the combined capacitance is 3,520uF, which might be a little light on, particularly as each cap is interlaced with small resistors. As a trial, you might cobble in another 2,200uF across each rail to see if this improves things.

Hugh,

Each monoblock PSU has 18 x 4,700uf caps or 84,600uf per channel Kinda overkill for 55w class A/B but I really like the low ripple ten-fold RC filter, bleeder resistors and low ESR so I used it with the ASKA. Its almost like having a regulated supply.

[ShinOBIWAN]

Hi Anthony,

Thank you for your generous review - I'm delighted with the report card!

Your welcome Hugh.

If I can get up there with the best with a humble kit amplifier, I consider I've done something pretty good; this is not exactly top dollar hardware like a Krell or Halcro, yet there are people who much prefer the sound.

I heard Halcro's in the B&W suite powering one of Nautilus range at the Bristol Hifi show, absolutely awesome and that's probably my dream amp. But when you look at the cost the AKSA 55N+ is around 80% of that sound.

Thank you again, your rig is just amazing, and hats off for such a detailed, visionary crossover regime. And your speakers, WOW!!

No thankyou Hugh, you've given a great many folks a chance to hear a remarkable amplifier for the money. I'd personally say it sounds like £3k's worth to me and it cost me roughly £600 all in for the electronics.

[natemil]

ShinOBIWAN,

In viewing your AKSAs, which manufacturer's toroids are those with the covers?

Thanks,
Doug

[ShinOBIWAN]

ShinOBIWAN,

In viewing your AKSAs, which manufacturer's toroids are those with the covers?

Thanks,
Doug

They are Noratel encapsulated toroids. Secondaries are 25-0-25v 160VA with 230v primary.

http://www.noratel.com/

[ShinOBIWAN]

The UcD700AD will be round this evening and I'll have it over the weekend until Monday!

I'll be sure to post pics of Dave's(the owner of the UcD) excellent case work as well as my full and frank thoughts.

[netaron]

I have noticed better bass performance from different preamps. I am trying a conterpoint pre at the moment and the bass is the best I have heard from my system and I have tried Spectral, PS audio, Adcom, EAR, and a few other preamps. Just a thought.

Haron

[ShinOBIWAN]

I have noticed better bass performance from different preamps. I am trying a conterpoint pre at the moment and the bass is the best I have heard from my system and I have tried Spectral, PS audio, Adcom, EAR, and a few other preamps. Just a thought.

Haron

I'd agree normally but I'm using an all digital system right up to the amps, very clean, very linear. The pre-amp, if you can call it that, is an RME Fireface 800 interface/convertor with an Apogee DA16x doing the master clock thing and all this is connected up to a PC transport via firewire 800. The DAC's in this machine are spec'd at 119dBA measured in real world use and not theoretical data sheet specs, the current state of the art is around 120dBA. Other specs follow a similar pattern. Clocking is again exemplary resulting in very low jitter of around 4pps. Basically what I put in comes out virtually untouched. Its heartless and ruthlessly revealing, with good recordings it sound incredible with less good ones it sounds OK and poor ones sound completely unlistenable. I primarily choose AKSA and the 55N+ as a foil to this nature.

One thing that's clear is it allows you to audition speakers and amps in a completely neutral manner. You can play music and be sure that the source isn't adding or taking anything away. It really does allow you to hear the differences.

The AKSA 55N+ and the source make an intoxicating combination. Clarity, detail and massive speed.

Its not a lack of bass that's the problem with the AKSA, merely its interpretation of how it should sound. I've had other amps that were more true in that regard.

I've been listening to the UcD700AD for a couple of hours tonight - its a mix of very good and dissapointing but I'm not sure how that exactly relates to the AKSA until I've done a side by side tommorow.

[gonefishin]

I've been listening to the UcD700AD for a couple of hours tonight - its a mix of very good and dissapointing but I'm not sure how that exactly relates to the AKSA until I've done a side by side tommorow.

   I'll be interested to read your thoughts.  I own a 25n+, 100n+ and have another 55n+ to build for my brother, so I'm familiar with the AKSA sound.  But I've only heard the UcD's one time with unfamiliar speakers, so it wouldn't be fair to attach my impressions to the amps alone.  It would have been nice to have some loaners for a proper evaluation...but then again...I haven't the time for that either right now    


     take care,
     dan

[ShinOBIWAN]

Photo's of the UcD700AD enclosure:







This monster holds 4 x UcD700's, 2 x UcD700 power Supplies and two 1200VA transformers!

Its not quite finished yet as Dave needs to add the power switch and indicator to the front panel. There's also a couple of softstart's that really need to be added too as when you turn this thing on you hear it vibrate slighty with the energy pulled through the toroids. I've been assured its normal and in operation its completely silent. What did surprise me is how very slightly warm the heatsinks get when you've been listening at loud levels for some time.

Also note that I have not been bi-amping for any critical listening tests and comparisons but I have tried it just for the hell of it.

[ShinOBIWAN]

Its now nearly 6:00 in the evening here in the UK and I've been listening to both amps all day with a wide range of music. I thought I'd got the amp until Monday but it looks like I'll be out all tommorow so I'll have to cut my comparison short I feel confident I have a good idea of the sound of each though. It doesn't take days and days to form an opinion. These are also just opinions based on comparing each amplifier in my system and room so please don't be offended if they don't neccessarily agree with your own experience's, chances are you don't own the same kit, don't have a room dimensioned and constructed the same as mine and your preferences are also probably different.

My comments about the AKSA posted at the very beginning of this thread stand.

When this amplifier is used with very revealing electronics it sounds cold and removed from the performance compared to the AKSA even with the best recordings I have - Chesky et al. Extremely accurate for sure and you always feel that your not missing a thing no matter how loud you play. But when I swapped back to the AKSA a lovely sense of musical pace, layering, smoothness and rhythm was very obvious that the UcD simply didn't have. I should note that it never sounded harsh nor grainy even when driven very hard.

Dynamics on the UcD are great, massive attack, good speed (not the equal of the AKSA though) and a general feeling of control right through the frequency range. The AKSA on the other hand is smoother but equally dynamic *provided* the volume is kept to sensible levels.

Bass on the UcD is much better than the little 55N+ but as Hugh already pointed out its 400w into 8ohm vs. 55w and that's nearly 8 times more power on tap. Elaborating futher on the bass; its got a real sense of power, punch and definition. I'm using ATC SCM7's which are only 83dB sensitivity although they are 8ohm. I know from experience these like power and lots of it 150-250 is recommended by ATC. The UcD has absolute control over these speakers at all times. If you read back to the first post on this thread my thought's on the AKSA bass is there, suffice to say it isn't a UcD700!

Soundstaging on the UcD is average to good. The presentation tries a little too hard though and it comes off as unatural and synthetic compared to a direct comparison with the AKSA. When listening to music recorded in a venue with natural acoustic's the AKSA absolutely destroys the UcD in everyway, much more natural and the reverberation, decay and layering are so real as to be palpable on the AKSA - you feel like you are there and not just listening to a facsimile. You hear all this on the UcD but its presented in a less believable way.

Imaging on the UcD is a big WOW! Soundstaging and imaging are often confused and maybe I'm guilty of that but for me soundstaging is the ability to relay the event, acoustics and overall space of the sound whereas imaging is how well defined and dimensioned individual aspects are within this soundstage. The UcD may suck a little with soundstaging but boy does it know how to image! Even with the most complex of mixes you can follow an individual sound and it remains stable, focused and coherent in respect to the rest of the performance. The AKSA on the other hand is a tad blurred in comparison on very complex material and you have to listen harder to make out what seems to come naturally and without strain from the UcD.

Detail on the UcD and AKSA are around about the same but again I'd definitely give the edge to the AKSA in providing those details with more 'electricity' whilst maintaining a sense of absolute calm and smoothness that the UcD doesn't quite do in the same manner. Its just a difference of presentation and someone's favourite could be easily swayed by preference - I prefer the AKSA here but I do rather like the UcD also. Overall I'd say its down to personal preference rather than absolute superiority of one machine of the other.

The speed/pace of an amplifier is a rather daft idea on the face value. Afterall how can one amplifier be quicker than another? Its all down to presentation, system synergy and tonal balance which really defines how fast an amplifier sounds and the AKSA is perhaps the ultimate amp on the planet in this regard. Its massive speed allied with an effortless smoothness is a huge paradox but one that is utterly alluring and not easily forgotten. There's no way the UcD can even hope to hold a candle to this.

To sum up:

First off, the UcD700AD is a good amplifier and anyone who owns one should be proud. In the right system I imagine it can sound fantastic (my friends for example). However in my system it just doesn't work as well as the AKSA. Maybe the combination of extremely revealing frontend, studio monitoring speakers and the matter-of-fact delivery from the UcD just doesn't gel well for musical enjoyment. I imagine for monitoring and mastering its a doozy though since you can hear everything and know exactly what is going on and what's wrong with a mix.

The AKSA is an audiophile product, proud to be coloured and all the better for it when it comes to actually enjoying music rather than just listening to music.
Whats clear is Hugh has masterfully crafted these colourations into something that bridges the gap between the recording and the original live venue. Is it accurate? Not in respect to the recording no but it does bring you closer to the original spectacle and surely this is what enjoying music is about?

This little test has been great fun and its only cemented my opinion of the AKSA. I suspect that when I do the comparison to Greg's SKA things maybe somewhat closer but as far as 55N+ vs. UcD700AD, I'd take the AKSA for my system any day.

Now to order an 100N+ Hugh are you listening? I want an 100N+, like, yesterday.

[gonefishin]

Nice write up...thanks.

    I think you'll be pleasantly surprised with the 100n+.  I really think the AKSA amps do bridge a gap that many amps miss all together.  Personally...I do like soundstaging.  But I think the current audiophile market has become too concentrated on staging and its effects.  You enter into the realm of holographic and entertaining...but not all that real or convincing.  But this is coming down to preference issues.  In which case I'd rather look to my preferences for tone, dynamics, presentation and imaging over a nice holographic presentation.

   I also think the AKSA amps lend a good hand for evaluation of sources as well.  So many times you listen to a speaker/room/system that gives you tonal changes and a seeming change in detail with one player over another.  But what you've actual gotten is a large change in presentation and dynamics.  It's hard to generalize about a system because one system may need certain qualities (from a CD modder) that clean up the sound a bit...aiding in the draw of detail.  While another system with the same player in will sound lifless, as if the system isn't playing up to it's capabilities in regard to dynamics.  

    I do think of the AKSA amps as a work of art.  More like a picture...or perhaps an interpetation of a picture (who knows).  But it's nice that they're able to color the sound yet allow you to listen to other parts of your system as well.  But then again...I'm not sure if I'd say there was any component that wasn't colored.

   take care all>>>
   dan

[ShinOBIWAN]

Nice write up...thanks.
But then again...I'm not sure if I'd say there was any component that wasn't colored.

The most fundamental part of the playback system is flawed and that is the recording. All else after this is therefor compromised and deemed coloured even if its true to the recording and the more true to the recording it gets the more coloured it can seem with less than perfect recordings, its kinda like building a house without a foundation - the house is compromised right from the start. The other major contributors to colouration is speaker and then room. Only when you've surmounted those two is it worth pursuing higher end electronics IMO.

Amplifiers like the AKSA help to restore something that is lost in the recording process.

[gonefishin]

I almost forgot to add...

   For some very nice recordings you could get a hold of the ISOmic demo CD's.  He's got everything from blues, orchestra, choral and instument examples of his recordings on here.  The presentation is just soooo natural.  It's far from the normal close mic'd stuff you hear...or the over compressed pieces.

    At first...it's not as impressive or in your face as some other recording out there.  But all the elements are in the recording.  Tone, dynamics, detail and a realistic natural presentation.  When I think of neutral (and natural) this recording comes to mind before scores of audio components out there.

   Sorry t go on and on...but I have been impressed by it.  Although my largest complaint is that the CD's simply hold examples of the recording technique.  Many of the songs/pieces are cut off long before they're done.  This could be quite aggrevating when your trying to listen to the music.
   
Ray Kimbers ISOMic recordings


   If anyone has a chance...check it out.  You won't be out much if you aren't as impressed as I was.


     take care,
  dan