[AKSA]

You got it, Chris!!

I still vividly remember your kindness to me at Denver in 2007, I use your Reference CD almost every day, and I'm delighted to see you still here and very active, Chris.  How are those dirty windows on Manhattan?  You must be quite a guy to work at those heights, you haven't got Navajo background, have you?

Did you know the veins in Gorganzola are the penicillin mould?

I love that cheese, maybe it's good for audiophiles too!   

Ciao,

Hugh

[lonewolfny42]

I need to update your Reference Cd Hugh....think your missing 2008 and 2009.

We had a nice time at RMAF....great to meet both you and Marty.

How are those dirty windows on Manhattan?  You must be quite a guy to work at those heights, you haven't got Navajo background, have you?

No Navajo.....just a good work ethic...always busy...dirt doesn't take a holiday.

Did you know the veins in Gorganzola are the penicillin mould?

I did....so...eat it in good health...just not TOO much...

Keep posting your impressions - I enjoy reading them....and hope to hear the Naksa at a future date...

Good luck Hugh !!!!

[jkeny]

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"  .

[Joe Rasmussen]

Neils Bohrs definition of an expert "An expert is a person who has made all the mistakes that can be made in a very narrow field."  

Yes, John - but not wanting to be picky but I know of no other name that gets misspelt more ofthen than Niels and Nielsen (son of Niels). Almost as bad as recieve..

Another Niels Bohr story/quote that comes to mind. Taking a visitor home, the visitor noticed a horseshoe for good luck over his door. He was taken a little back by that, surely the great professor was not superstitious? Bohr noted it and replied that he wasn't superstitious but added "I am told they work even if you don't believe in them."

Cheers, Joe

[bhobba]

Another Niels Bohr story/quote that comes to mind. Taking a visitor home, the visitor noticed a horseshoe for good luck over his door. He was taken a little back by that, surely the great professor was not superstitious? Bohr noted it and replied that he wasn't superstitious but added "I am told they work even if you don't believe in them."

My favorite Bohr father and son story comes from when they worked on the Manhattan project and the person they most liked to discuss their ideas with was the young Richard Feynman.  He was generally recognized as the best young physicist there and of course he later became one of the greats fully in the same class as the Bohr's.  Everyone thought that's why they sought him out because they recognized how good he was.  But Feynman later let out it was not that at all - everyone deferred to their opinion - Feynman was the only one that had guts to tell them - hey that's silly.  Trouble with being famous no one wants to upset you.

Thanks
Bill

[Joe Rasmussen]

Bill, your EL34 amp needs to come back... need to arrange something.

Hugh, sorry, should have gotten back to you earlier re the phase/stability margin you mentioned. With SS <2dB PFF and with tubes <1dB PFF - and no NFB or GNFB, not a problem as under those circumstances, with open loop gain linearised and rather stable by nature, dialling in that much, or that little, is not likely to be a problem, but yet be careful. What I don't know is what happens with both NFB and PFF (I prefer PFF to PFB when there are no other loops) are employed, at the same time. Maybe not wise. PFF sums upwards, hence its action is also forward. NFB is never.

I am also in a discussion with conrad-johnson's ex Chief Designer (all current c-j tube amps is his based on his philosophy) via VoIP, over the last month. The idea that this is an electronic equvalent of inertia, especially where in the circuit the current, the active current, is highest, is something that we can both grasp. This hones in on output stages. One thing he observed is that it certainly affects the impression of speed in the amp - and it certainly ups the PRAT factor, in a very realistic sense. It also enhances a lot of low level detail, opens up the soundstage. Elson Silva of Cymer Audio has also dabbled with this, said so when we had lunch together last week. This topic has legs...

With Bill's EL34 I need to dial in 0.55dB and then for him, and Mike, to hear it. The difference, to the same identical amp I did this to last weekend, was quite dramatic.

Peculiarly, if one reads Hawksford's paper on feed forward it applies to Bi-polars (power transistors in particular) and utilises two amps a la Peter Walker's current dumping, but Hawkford's was applied to a Unity Gain output stage (into speaker/load) and no NFB. But I am seeing serious signs that a second amp is not needed to create a similar type of error correction. So somewhere you may enter that possibility into your arsenal for use in the future - it was after all an SS thing to start with. This could be useful  to you later...?

There is a particular device that uses a Diamond transistor front-end followed by a Unity Gain output stage, no NFB at all. I put a resistor of a couple of hundred Ohm from the "Collector" of the diamond transistor and the output pin of the UGS stage. It ought to do nothing as there is no gain, and yet I swear I saw the output go up and eventually settled on 100 Ohm and the UGS had a gain of 1.6dB, yes gain.

If anybody can explain that, please I ask and I will listen.

Who said everything in audio that has to be learnt has been learned. Some guy in Hi-Fi World wrote that about a year ago. 

Cheers, Joe

[bhobba]

Bill, your EL34 amp needs to come back... need to arrange something.

No problem Joe it is down at Mikes right now.  Simply give him a tingle - I am sure you can arrange for him to send it down and return it to him for a listen.  I will be seeing him tomorrow about another matter and will mention it to him.

Thanks
Bill

[AKSA]

Bill,

I've finished your amp, now addressing the logo issue!!  I've been running it in for two days now, very pleased with it.

Joe,

Feedforward really appeals to me because properly done, IFF that's possible, there should be no spray of artefacts generated to the 40th harmonic, a serious issue with conventional gnfb.

I have noted that a beefy diamond buffer output stage sounds fabulous without feedback across it, so I am convinced that global feedback degrades as much as it improves.  To me, a huge problem is the serious levels of lag compensation required to calm the savage beast;  I have always noticed a profound effect on the sonics from lag compensation, yet other means, such as two pole, or shunt, also seem to have their sonic problems.

As I see it a natural roll off is desireable for RFI reasons, so a low pass filter on the input should be all that is required.  But the non-linearities of the amp as a whole could only be compensated by their conjugates as an error FF regime, and creating these without additional distortions could be very tricky.

Of course, without global feedback, stability issues are no more, and that's a huge advantage.....

Cheers,

Hugh

[bhobba]

I've finished your amp, now addressing the logo issue!!  I've been running it in for two days now, very pleased with it.

Great to hear Hugh.  Let me know when you want payment and how much. I will get it delivered to Mike's where I will do a comparison with Joes amp.  I will be leaving it at Mikes for at least 4 weeks so anyone that wants to can pop around for a listen.

Thanks
Bill

[ginger]

More listening on the new NAKSA.

John stated above that the amp just gets better and better as it "runs in".

Anybody who does not believe in amp "break in" or "run in" will be converted to a believer by the NAKSA.

When first fired up it had something (a slight edge) I'm not quite sure how to describe, were it a tube amp I would have described it as "pentode glare". This (happily) has totally disappeared with a few days run in.

Cheers,
Ian

[Jens]

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!

It should be noted that my system is currently bi-amped. The NAKSA is driving the treble/mid section only, whereas the bass section is currently being powered by a hefty Behringer PA amp. Room/system correction is being used on the bass section, and the system is linear (in-room, measured in the listening position) more or less down to 20-25 Hz.

As I said, the NAKSA is the best amp I've ever had. It does so many things so very right - in fact I find it difficult hear any real shortcomings. Also, I can only say that I agree with everything that has been said in this thread about the sound

The things that have impressed me most about the NAKSA are its exorbitant clarity, its musicality, and the soundstage. Add to that a beautiful, well extended top and a very articulate midrange - well, then you have a world-class amp!

Apart from the above, I find that instrument positioning within the soundstage is vastly improved over the LF55. Also, instruments have a plasticity to them that I've only rarely heard on any system.

On recordings with a good soundstage, the soundstage is rendered beautifully, both in height/width, as well as back to front depth. However, with the NAKSA the size of the soundstage always seems to be accurate - unlike with some amps that tend to 'bloat' the soundstage, which sounds artificial.

For me it is difficult to grasp how an amplifier at this cost can do all this. I have certainly heard amps at ten times the price that fail at several of the above mentioned disciplines.

Hugh, this is one hell of a job you've done! You have created a musical beauty

My deepest respect, Sir!

I can hardly wait to implement my second NAKSA so I can go fully active on my system (with electronic x-overs).

It will be very interesting to see what you come up with next - apart from the NAKSA 100, of course!

Cheers,

Jens

[AKSA]

Hi Jens,

I'd only sent you an email an hour ago asking how things were with the NAKSA, well, I've received my answer - in spades, thank you Sir!

I've just watched a particularly depressing documentary on people smugglers operating in Indonesia - a country I know well and which I actually really love - and the problems of Australia seeing its foreign aid to the country being subverted by korupsi, and your post arrived, cheering me up immensely!!   

A good friend of John Kenny's in Dublin is presently writing a review on the NAKSA which eventually will be published in StereoMojo - sincere thanks to John for the sensory deprivation this must be causing -  and so things are moving along well and I have good reason to be very pleased.  Ahem.   

Jens, I'm so pleased about your description, I really am.  I ask myself how this design came around;  it has all dissolved in a mist of coffee, confusion, determination and blind faith.  There certainly was not much in it I would describe as scientific...  and I listened to LOTS of people, Jon Pippard and Richard MacDonald in particular, both on different pages, but with more in common than they realised.

Cheers,

Hugh

[Jens]

Hi Jens,

I'd only sent you an email an hour ago asking how things were with the NAKSA, well, I've received my answer - in spades, thank you Sir!

I've just watched a particularly depressing documentary on people smugglers operating in Indonesia - a country I know well and which I actually really love - and the problems of Australia seeing its foreign aid to the country being subverted by korupsi, and your post arrived, cheering me up immensely!!   

A good friend of John Kenny's in Dublin is presently writing a review on the NAKSA which eventually will be published in StereoMojo - sincere thanks to John for the sensory deprivation this must be causing -  and so things are moving along well and I have good reason to be very pleased.  Ahem.   

Jens, I'm so pleased about your description, I really am.  I ask myself how this design came around;  it has all dissolved in a mist of coffee, confusion, determination and blind faith.  There certainly was not much in it I would describe as scientific...  and I listened to LOTS of people, Jon Pippard and Richard MacDonald in particular, both on different pages, but with more in common than they realised.

Cheers,

Hugh

Hi Hugh,

Well, truth be told, I was already in the process of writing up my impressions when your email arrived 

But I am very pleased to have been taking your mind off sad going-ons in Indonesia! And I am very, very pleased to hear that the NAKSA will get a review in StereoMojo! Looking forward to reading that

Keep up the good work!

Cheers,

Jens

[gaetan8888]

A good friend of John Kenny's in Dublin is presently writing a review on the NAKSA which eventually will be published in StereoMojo - sincere thanks to John for the sensory deprivation this must be causing -  and so things are moving along well and I have good reason to be very pleased.  Ahem.   

Cheers,

Hugh

Hello Hugh

Yeaaa, very good, a review in StereoMojo

The more I read listening impressions texts, the more I think that the Naksa will become a legend like the Aksa.

Bye

Gaetan

[Jens]

Hugh & everyone,

I'm sorry to say that my initial review of the NAKSA was incomplete. My only excuse is that this little beauty keeps revealing new sides of itself, as I go through more and more of my favourite tracks (and there are a lot of those!).

What happens is that on good classical recordings, the walls of my room simply disappear, and I am suddenly benched in my favourite seat in the concert hall.

This is not just matter of soundstage rendition, but more the ability to render accurately the simmer in the air that you only experience in a real concert hall. Well, that was until now. To date, I have never heard this rendered in such clarity and realness by any amp! However, the NAKSA does with complete ease and no strain at all, with naturalness. Wauw!

I go to classical concerts regularly, and with the right material, this comes close to the real thing ...

This is phenomenal

Cheers,

Jens

[Joe Rasmussen]

Feedforward really appeals to me because properly done, IF that's possible, there should be no spray of artefacts generated to the 40th harmonic, a serious issue with conventional gnfb.

I have noted that a beefy diamond buffer output stage sounds fabulous without feedback across it, so I am convinced that global feedback degrades as much as it improves... I have always noticed a profound effect on the sonics from lag compensation, yet other means, such as two pole, or shunt, also seem to have their sonic problems.

As I see it a natural roll off is desireable for RFI reasons..But the non-linearities of the amp as a whole could only be compensated by their conjugates as an error FF regime, and creating these without additional distortions could be very tricky.

Of course, without global feedback, stability issues are no more, and that's a huge advantage.....

Cheers,

Hugh

Hugh, I think this has a lot off aspects that will be sorts itself out over time, provided we work with it. Personally surprised that I am not the only one out there thinking about it. But I feel that PFF should be used in a fairly local loop rather than global when possible. But certainly having both negative and positive globally makes no sense and I am inclined to use one or the other - not both. BTW, I use diamond transistor for I/V converters in digital players with "current" DACs. They are a natural and no GNFB required. Huge bandwidth, totally immune to extreme RF noise. Didn't know you have dabbled with them too.

Bill, the comparison between the NAKSA and JLTi EL34 PFF version is not something I am pushing as a contest of sorts. This is after all a NAKSA forum. But it is rather the before and after PFF application that I am interested in and what you guys up there will think. If positive reaction is made public, then the fact this has SS application as well and... well, we all are interested in new things that may lead to productive ways in the future. It's all about options and then a bit like Allen Wright who thinks of these thinks as part of the designer's Cookbook. A new ingredient to play with?

Hugh, the low output Z and low GNFB you said - I seem to recall in an earlier post - the the amp's output Z is higher than normal or possibly lower than your earlier designs? The reaction and obviously favourable early reviews, and as a comment I have found that amps, SS or tubes, invariable sound better, even if on on paper they has poor 'damping factor' and provided coupling with unproblematic speakers. There is an ease of delivery. Not the only parameter I know, but reading between the lines by early NAKSA users, you seem to have achieved that. I put this down, at least in part, to greater immunity from the reactive load, the speaker. I say this as this is very much part of my own philosophy. I call amps with greater than 1 Ohm output Z non-Voltage amplifiers. Does the NAKSA approach this? Some may think this as a minus, I don't.

Cheers, Joe


Cheers, Joe


 

[AKSA]

Hi Joe,

Both the LF and NAKSA use nested fb, which of course controls loop gain by default.  The former had 16dB, was highly immune to reactive loads, had moderately high Zout (around a third an ohm), where the NAKSA has a full 31dB of loop gain.  It will still drive an ESL63 with aplomb, however.

My thoughts are that PFF is the future, if it can deliver that concert hall palpability which is the hallmark of very good, if somewhat conventional, designs.  Aspen (that's me and my pal in Vancouver) has had very good success with an adaptive bias diamond buffer operating open loop.  It delivers the most natural sound I've heard yet, up there with a very well done 300B SET but without the colouration.   If the DB output stage could employ PFF - very much on the cards - I feel it would deliver the holy grail.  I'm getting closer, and clearly so are you!!  I know that Terry Demol is also pushing back the limits here;  he is also a very bright man, one of the cleverest.

OTOH, Joe, from my interest in various technologies over the years it is always true that the best technology is the one just rendered obsolete!

Cheers,

Hugh

[Joe Rasmussen]

OTOH, Joe, from my interest in various technologies over the years it is always true that the best technology is the one just rendered obsolete!

At least it shows you have an open mind.

Cheers, Joe

[bhobba]

Bill, the comparison between the NAKSA and JLTi EL34 PFF version is not something I am pushing as a contest of sorts. This is after all a NAKSA forum. But it is rather the before and after PFF application that I am interested in and what you guys up there will think. If positive reaction is made public, then the fact this has SS application as well and... well, we all are interested in new things that may lead to productive ways in the future. It's all about options and then a bit like Allen Wright who thinks of these thinks as part of the designer's Cookbook. A new ingredient to play with?

Its not a contest to me either.  It's just the two amps I have and I have found when reviewing audio equipment it is a good idea to compare and contrast it to other equipment.  You can't always do that of course but when you can its something I like to do. 

I mentioned to Mike you have a tweak you wanted to try out so he may have a chat to you about it.  Of course I am happy for you to try it on my amp.

Thanks
Bill

[AKSA]

Jens,

Thank you for your kind words, you are indeed fullsome in your praise.    

The day I first heard the NAKSA with Jon Pippard we both felt it was unique, there was a sonic quality immediately evident!  Keep on listening, I believe it does improve with age, just as Ginger and John suggested.

Next stop will be a bigger version, but as it will involved three pcbs, two modules on their own heatsinks and a separate dual supply, it will be quite a bit more expensive, so it will not directly compete.  The idea is to replace both the LF55 and the LF100.

Thank you again, keep the comments rolling!

Hugh