New Aksa Amplifier build pics - Naksa

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I recently bought this new amplifier offering from Hugh dean at Aksa because I liked the philosophy behind it's design & also the initial reports of the sound impressed me immensely striking many bells (forgive the pun) & ringing through with my experiences along my own audio journey. here's the main thread on this : New Naksa Amplifier! Quick Initial Impression......

This is a 70W per channel amplifier designed with sonics in mind. It's design is single ended where possible & it has a unique THD spectrum which intrigues me & I'm hoping will prove itself to be exemplary in the area of sonics. The design philosophy that Hugh has followed is to reduce the sonically offending higher odd order harmonics at the expense of some extra even order harmonics - a philosophy that I see adopted by well respected designers such as Gary Pimm in his SS Tabor amplifier "There is more second harmonic but the higher order distortion is way down. This is a case where I would glady take an increase in second harmonic distortion in trade for virtually getting rid of high order harmonics."

The pcb arrived in about a week from Oz to Ireland and they look stunning - two channels & the PS on one board - just supply a 30-0-30 transformer & a 300mm long heatsink (I ordered mine without heatsink to save on postage).

Now I happened to have a perfect donor amplifier case to house this Naksa - it's a Samson servo 550 studio amplifier. Heatsink is 300mm long & was serving a 275 watt per channel amp so suitable for this 70watt amplifier.

I've only started the fitting of this pcb into the case but here are some pics of my progress so far.

Inside of Samson amp & Naksa pcb in the background
An externally hosted image should be here but it was not working when we last tested it.


Pcb mounted on heatsink & outputs wired to speaker connections - inputs (at the top) wired but not yet connected to vol pot (I'll be using some lightspeed vol units)
An externally hosted image should be here but it was not working when we last tested it.
 
...because I liked the philosophy behind it's design...

This is a 70W per channel amplifier designed with sonics in mind. It's design is single ended where possible & it has a unique THD spectrum which intrigues me & I'm hoping will prove itself to be exemplary in the area of sonics. The design philosophy that Hugh has followed is to reduce the sonically offending higher odd order harmonics at the expense of some extra even order harmonics - a philosophy that I see adopted by well respected designers such as Gary Pimm in his SS Tabor amplifier "There is more second harmonic but the higher order distortion is way down. This is a case where I would glady take an increase in second harmonic distortion in trade for virtually getting rid of high order harmonics."

The philosophy is not the best one (There is better philosophy). The most important thing is that the designer can differentiate a subjectively good sound from a subjectively bad sound. This is a skill that I found correlate highly with "tweaker"-type designers than the theoretically oriented designers.

I believe that the best amp should have low distortion, both high order and second order, no exception. And because single ended topology always correlate highly with second order harmonics, it is hardly the best topology either.

The problem is, can anybody show me an amp that is low in distortion (including the second order of course) but sound subjectively good/better? (I know it will be hard to build without oscilloscope at minimum)

The problem IMHO is not simply about low order or high order harmonics, there must be something else. When you try hard pushing the (second order) harmonics down, you seem to mess up with something else.

The perfect or better amp is possible, but where is the circuit? Somebody may have designed it for his own personal use, but if it is not approved by the majority (hopefully the golden eared audiophiles), no need to debate that his is the better one ;)
 
Jay, if I can understand your post you are saying that this is not the best design philosophy but are voting for a low distortion as a better sounding amp? Have you not followed the numerous discussions along these lines - there are plenty of examples that show that vanishingly low distortion has no correlation with an amp sounding good!

You do realise that we like the distortions that emanate from musical instruments, don't you?

Have you looked at the distortion spectrum of the Naksa & have specific points to make about it?

I don't wish to get into a debate about distortion spectra at this time - the amp will either survive or not my best instrument that I have in my lab - my ears/brain as this is what I use to listen to music & this is the reason I bought this amp!

I hope you understand my predilection to this habit I have of listening to music rather than looking at THD spectra but if the spectra & the sound both make sense then I'm doubly happy. I haven't fired it up yet so it could sound like rubbish & if so, I'll say so, with apologies to Hugh
 
I hope I haven't picked you up wrong but you seem to be dismissing the approach rather too quickly rather than spending some time reading the links & analysing the spectra. AFAIK, Hugh is a designer who uses both measurements & his ears - he's no slave (or stranger) to measurements but tries to also correlate what he sees in his measurements with what he hears - a very difficult investigation & one that intrigues me!
 
Jay, if I can understand your post you are saying that this is not the best design philosophy but are voting for a low distortion as a better sounding amp? Have you not followed the numerous discussions along these lines - there are plenty of examples that show that vanishingly low distortion has no correlation with an amp sounding good!

You do realise that we like the distortions that emanate from musical instruments, don't you?

Have you looked at the distortion spectrum of the Naksa & have specific points to make about it?

I don't wish to get into a debate about distortion spectra at this time - the amp will either survive or not my best instrument that I have in my lab - my ears/brain as this is what I use to listen to music & this is the reason I bought this amp!

I hope you understand my predilection to this habit I have of listening to music rather than looking at THD spectra but if the spectra & the sound both make sense then I'm doubly happy. I haven't fired it up yet so it could sound like rubbish & if so, I'll say so, with apologies to Hugh

Nooo, actually I'm agree with you ;) If later, IF, you found that this amp sound like rubbish, don't forget to tell me which one doesn't.

Actually, I want those whose ears I can trust (I think I can believe Hugh and may be you) can show me the best sounding lateral mosfet amp he/you has ever heard. I'm ready to expect that those people will have bipolar as better reference. Surprised me though, that Rod Elliot uses his mosfet P101 as his "reference". That is if he is "honest" enough about it.
 
I hope I haven't picked you up wrong but you seem to be dismissing the approach rather too quickly rather than spending some time reading the links & analysing the spectra.

I only looked at the first page of that thread you linked, but in that its only simmed distortion figures which are quoted. Is there anywhere some measurements?

Also you said:

The design philosophy that Hugh has followed is to reduce the sonically offending higher odd order harmonics at the expense of some extra even order harmonics

Is there anywhere a technical treatment of how this trade-off occurs? The only place I've seen it is in the argument against using low levels of NFB, so is this a 'no feedback' design?
 
I hope I haven't picked you up wrong but you seem to be dismissing the approach rather too quickly rather than spending some time reading the links & analysing the spectra. AFAIK, Hugh is a designer who uses both measurements & his ears - he's no slave (or stranger) to measurements but tries to also correlate what he sees in his measurements with what he hears - a very difficult investigation & one that intrigues me!

I think you have picked up me wrong, because of my poor English.

I don't know about Hugh electronics background, but he is intelligent and I suppose has very good ears. But there are others with better electronic knowledge, BUT, often with poorer ears (usually related to poor hands-on experience), and worse, less intelligent :p

What I'm saying is, there is better philosophy than you mentioned. Single ended is probably not the best if you want to get rid of those second harmonics. But I believe that to get a good result sound wise from that theoretical concept requires good ears, not EE degree.

I feel lucky that to enjoy the music I have a high dependency with the speaker, and only little with the amplifier. If I have to build Hugh's amp for my reference system, I will use Sanken 2SC2922 for it's output (tho the amp is not designed specifically for that transistor). But because I have plenty of lateral mosfets (and I like them) I'm not interested with the best bipolar amp, but I'm interested with the best lateral mosfet amp. And because Hugh encouraged me to build the Mooly Amp, then that is what I built and listened :D
 
Yes, keep reading..... actual measured distortion has been presented.

Thanks.:D

What would you expect, my friend?

No one expects the Spanish Inquisition:D As it happens I live without expectations - no expectation means no disappointment and definitely no expectation bias. Now, that turns out to be quite valuable when listening to modifications of audio kit...:p
 
I only looked at the first page of that thread you linked, but in that its only simmed distortion figures which are quoted. Is there anywhere some measurements?

Also you said:

The design philosophy that Hugh has followed is to reduce the sonically offending higher odd order harmonics at the expense of some extra even order harmonics

Is there anywhere a technical treatment of how this trade-off occurs? The only place I've seen it is in the argument against using low levels of NFB, so is this a 'no feedback' design?


Hugh's philosophy is right on for a better sounding amp. In my reverse engineering of the symasym , I have found that the loading of the VAS , while increasing total THD , will give that "magical sound" . Investigating further , I saw that the 2nd increases with load while 3rd-5th decreased. You do pay a price with increased heat (dissipation) and distortion in the VAS , but the heck with .003% if it does not sound better than .02% with the "right" harmonic content.

Another factor is speed , some compensate for amazing slew rates and 100khz perfect square waves. My amps can do this , but we listen to audio , not 100khz SW's. I have found that careful attention to the different compensations (the main Cdom , lead ) and the right compensation for different devices also determines amp "character". Another is bias... MJW21193/4's not only sound different than 2SA1943/2SC5200's but need a hotter bias. There is no "perfect amp" ,all is just a big trade-off . Now that I am building a new amp , I will allow for all these tweaks to be done without any redesign , worst case with separate Current /voltage boards is just another board swap. Is not DIY great !!! :)
OS
 
But I believe that to get a good result sound wise from that theoretical concept requires good ears, not EE degree.

I agree that good ears are more valuable than an EE degree. But with both, the designer is able to get to a good sounding solution more quickly I think. Merely a good pair of ears won't allow the designer to have a feel for what works to improve the sound. A long experience can easily surpass what's taught in EE these days, particularly so in regard to audio. Although I'm a teacher myself I concur with Shaw when he says 'Those who can, do. Those who can't, teach.'.
 
Hugh's philosophy is right on for a better sounding amp.

So you say, but in my experience, THD is not at the top of the list for better sound. Grounding is.

In my reverse engineering of the symasym , I have found that the loading of the VAS , while increasing total THD , will give that "magical sound" . Investigating further , I saw that the 2nd increases with load while 3rd-5th decreased. You do pay a price with increased heat (dissipation) and distortion in the VAS , but the heck with .003% if it does not sound better than .02% with the "right" harmonic content.

Have you ever heard the phrase 'correlation is not causation' ? You choose to measure the harmonic profile, but what leads you to believe that's the cause of better sound? You do not hear harmonics, you hear sounds - which are a system level perception.

Another factor is speed , some compensate for amazing slew rates and 100khz perfect square waves. My amps can do this , but we listen to audio , not 100khz SW's.

Good point there. It applies to my arguments above too - we listen to audio, not harmonics.

There is no "perfect amp" ,all is just a big trade-off .

How true. So when a person says an amp sounds better, isn't the rest of the system they used when they got that sound very important? I'd prefer to say 'this amp sounds better in this system' - its more consistent.

Is not DIY great !!! :)

Couldn't agree more:D
 
Yes, keep reading.....

I found the page you must have been hinting at. But I stopped before getting the figures when I found this statement:

The vast majority of modern solid state amplifiers produce
a harmonic spectrum where, after the often prominent
second harmonic (musical), the odd order artefacts dominate,
usually 5-10dB above the evens. This results in the oft described
‘sterile, mechanical’ rendition.


What are you basing this claim on?
 
THD is not at the top of the list for better sound. Grounding is.

Grounding is part of implementation. I don't have sufficient electronics knowledge but I use my tweaking experience to implement a good sounding amp. I pick one good circuit/topology and execute a favorable implementation, most often by tweaking.

I select a better brand of cap for on-board decoupling, I select better value. Often I simply carry the result from one system to another system. For example, I often use Black Gate F 680uF on each rail, and a Solen 330n or 220n (the Black one not the white one) from +v to -v.

But the kind of implementation that I haven't seen executed by others is the use of extreme point-to-point wiring. One signal ground return, one output return in star topology. I glue together small transistors that suppose to have equal temperature drift. IME, this approach is always superior than using a much bigger size PCB. Very unfortunately tho, that I don't have oscilloscope for even better implementation :(
 
Grounding is part of implementation.

Yes, for sure. But it can also be part of design too - for example if a design is fully balanced then some grounding issues don't come up.

I select a better brand of cap for on-board decoupling, I select better value.

I'm curious - how do you find out which brands of caps are 'better' ? ISTM there are two ways to do this - by measurements and by reputation. Call me a skeptic but brand reputation in other areas doesn't serve very well (think Bose as one example) so I'm not going to choose components by reputation alone.

Often I simply carry the result from one system to another system. For example, I often use Black Gate F 680uF on each rail, and a Solen 330n or 220n (the Black one not the white one) from +v to -v.

I know almost nothing about these brands of caps, what makes them 'better' in your estimation?

But the kind of implementation that I haven't seen executed by others is the use of extreme point-to-point wiring. One signal ground return, one output return in star topology.

Have a look at my blog - I describe this kind of approach but haven't put up any pictures yet. I haven't found yet that by unsharing a ground with another component that the sound has gotten worse. Often it does get better, sometimes I can't tell a difference. As far as I know, valve amps are built in this way, they have a good reputation for sound.

Very unfortunately tho, that I don't have oscilloscope for even better implementation :(

I agree, I think a scope is essential.
 
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Hi jkeny,

Nice build so far. Can't wait for the feedback. :)

I had the opportunity to listen to one of the demo NAKSA a few weeks ago and was very impressed. The system I heard also included Vsonics speakers and a GK1 preamp and it was probably one of the most detailed systems I have ever heard. Lots of detail and very good bass control. A definite step up from my AKSA 55 N+. :mad:

IMHO what surprised me the most was the NAKSA still has the "AKSA" (or should that be Aspen) sound even though the topologies are completely different. Food for thought. :2c:

regards
 
Yes, for sure. But it can also be part of design too - for example if a design is fully balanced then some grounding issues don't come up.
Yes, but fully balanced topology should not be chosen simply to remove the grounding issues when you know that you can still solve the problem

I'm curious - how do you find out which brands of caps are 'better' ? ISTM there are two ways to do this - by measurements and by reputation. Call me a skeptic but brand reputation in other areas doesn't serve very well (think Bose as one example) so I'm not going to choose components by reputation alone.

I know almost nothing about these brands of caps, what makes them 'better' in your estimation?

When I said "tweaking", it means plug and play and LISTEN. It takes tedious effort yes, but sometimes the result is surprising. For example, how can you say that Amp A is better than Amp B when you don't put each amp in their best implementation state? Often, by only changing the diode brand, the sound is surprisingly improved. I have tested/compared many diodes, I have tested many current sources.

If you ask me why a cap can sound better than the other, especially in power supply, I think it is related with ESR. I don't know electronics, but I indeed pay extreme attention to components specs and it's correlation to the resulting sound that I experience, so I can expect/predict that "this transistor will sound better here than that transistor".

Caps in power supply are important. Bigger capacitance usually give worse sound, so to have enough capacitance I prefer to parallel smaller caps. That's already a widely accepted implementation practice.

If you have 680uF cap, it is usually better to parallel with smaller cap. How small? I guess it depends on the capability of the bigger cap to do what it should do. But "overlap" seems to give bad result, so there must be a correct value. For a Black Gate F 680uF I predict it is closer to 220n than 330n but I don't want to waste my time on comparing things like that.

Again, I have many caps and I believe I have good ears. It is just a matter of time and willingness to compare them all. Unfortunately, this kind of tweaking can be considered "stupid" if you have proper electronics skill and knowledge. That's why I'm pessimistic that those clever experts have enough chance to develop good ears to build a better sounding amp.

This is true when you notice in the old time some designers still use 78/79XX regulators. They didn't know like I did, that if they throw away those regulators they will have much better sounding gear.

Another example is how my experiment with choke based power supply for tube heater can change my view for a tube line stage. I'm skeptical about the use of tube amp due to it's "slow" bass. I was skeptical about the use of preamp especially tube one especially because the horrible distortion and insufficient damping for solid state amp. Only after I found the effect of the choke based power supply on the tube heater I wanted to build an Aikido Chatode Follower. The supply balance will cancel the distortion to an acceptable degree, so the last thing I need is the tube and setup that produce the lowest Zout (12AT7 and 6SN7 is what I have on hand)
 
What are you basing this claim on

My theoretical, simulation, and listening experiences taken over half a lifetime of building, designing, and listening.

Tragically, I have little else to go on.... but then, if you listen to everyone and implement everyone else's ideas, you achieve nothing.

But, don't take it too seriously, it's only one man's view, and if yours differs, no doubt it's right for you too... the only time people are taken on face value is if they are dictators, or credentialled experts, and then people go too far the other way.
 
IMHO what surprised me the most was the NAKSA still has the "AKSA" (or should that be Aspen) sound even though the topologies are completely different. Food for thought. :2c:

I have a believe that a good sound should have a long life impression. That's why I always pay attention to amp that has satisfied an audiophile for many years of service. This is including the classics. I have tried to find the classics from each brand and tried to find out the topology. Sadly, they are all single ended, worse they are class-A or with small wattage. And they do sound similar even if the circuit is different (including use of transformer coupling).

I also have read a few first posts in the link to Hegemony's post and I read about Hugh saying about basing his amp on a certain NAD product. As far as I know NAD produced crappy amps (in audiophile standard) except for the classics 3020. It seems that this is how Hugh has chosen a base for his amp design and topology. Then no wonder if the NAKSA sound similar to AKSA, and if they become an everlasting good sounding amps.

I have no problem to stick with these classics British topology. The challenge is now how to expand the wattage (or expand them into class B) as some problems may arise in the VAS section. I'm happy that Karl/Mooly can do this to JLH 30W with his 60W lateral fet amp. Graham Maynard didn't seem to be successful with his GEM imo (may be because I don't like bipolar).
 
Many great posts while I have been catching my beauty sleep - thank you Hugh (I will not attempt to answer any technical questions so feel free to jump in any time); thank you Jay, you are on a quest; thank you Ostripper for your words about your amp design experience, very enlightening; thank you Abraxalito - it must be our shared love of L. Cohen that attracts you to my threads or maybe our interests are similar?

I noticed the pics in the first post don't expand when clicked on even though they are links to hosted pics of 2mB size. I have attached compressed versions this time:

Picture on the left is a full & empty donor case from a Samson servo 550 amplifier. Pic on the right shows the Naksa board mounted on the heatsink/back panel with outputs (blue wires) connected to the hot speaker terminals & black wires from start earth to speaker grounds. The balanced input board on the right from the Samson will be replaced with RCA input connectors & will be connected through a lightspeed vol control to the inputs at the top of the pcb (coiled black co-ax wires already connected). The 4 coloured wires at the bottom of the pic are the xfmr secondaries which will be have spades crimped to them & attached to the 4 spade connectors on the pcb.

It's a really simple build but I'm taking it slow as I don't have that much free time at the moment.
 

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