New Naksa Amplifier! Quick Initial Impression......

AKSA · « **Reply #120 on:** 16 Jul 2010, 11:00 pm »

Nice going John!

Won't be long now.....

Hugh

jkeny · « **Reply #121 on:** 16 Jul 2010, 11:17 pm »

Thanks Hugh, as long as I can stay off the drink, hic

Enjoying a nice bottle of Sauv Blanc from Marlborough Estates - a little vineyard in a little island off Oz, I believe

Anyway, layout looks OK to you?

AKSA · « **Reply #122 on:** 17 Jul 2010, 12:04 am »

John,

Looks fine!!

However, you may find that using an existing amp case for a new module takes much more time than you had planned, because all sorts of controls, wires and components are just slightly different, which can be annoying. You finish up with something pretty good, but lots of holes in the case you will never use.

However, nice layout, compact, and clean.

Hugh

jkeny · « **Reply #123 on:** 17 Jul 2010, 12:14 am »

Yea, I know that dilemma very well - trying to shoehorn something into an ill-fitting case can be a nightmare but this was just so damn close a fit that I had to do it & it appeals to my frugophile sensibilities.

(I smile a lot more when I've had a drink or two

)

jkeny · « **Reply #124 on:** 17 Jul 2010, 10:08 pm »

OK, an update - I started a thread over on DIYA to document the build & after the usual argy-bargy (I swear that place is full of sociopaths) it has now settled down http://www.diyaudio.com/forums/solid-state/170341-new-aksa-amplifier-build-pics-naksa.html

So let me bring both threads up-do-date:
I've just about finished - everything done except the leds to be connected ( these are the wires hanging over the front - there are 3 wires for two leds on each side - I'll only be connecting one led each side.)

This turned out to be a really neat fit for the Naksa board - there are no holes or awkward fits in the final build. I will make a decision about the final placement of the toroid once I have listened to the amp. If it's current placement has some sonic downside, there is room over on the right where the speaker out & PS -in connectors are located.

I will look at an LDR lightspeed vol. control (this will require a small 5 or 15V PS - I'm sure I have some of these) & also maybe re-doing the front panel into something more suited to the hopefully high quality sound of this amp - if it sounds special, I want to make it look special. Any ideas?

I will be powering it up tomorrow.

Edit: One question about lead dress - now that I look at the pic, should I re-route the three ground wires up to & along the back panel rather than crossing the PS AC leads - I know the answer is probably yes! I've run these PS AC wires along the bottom of the case taped down with white tape.

VYnuhl.Addict · « **Reply #125 on:** 18 Jul 2010, 12:17 am »

Gaetan,

Thats alot of gain!, but its another way of doing it for sure.. That should have also allowed you to decrease the compensation values leading to better Slew Rate, this would be gain compensation, increasing the gain to decrease the Feedback factor, balancing this around gain stage degeneration can often lead to some decent sound over just maximising loop gain and throwing it all into the treacle of negative feedback...

You use your ears to determine all of this, in my eyes you have a clear advantage here!...

Colin

Quote from: gaetan8888 on 12 Jul 2010, 03:30 am

Hello Colin

Wen I was sim and prototyping my last amp, and chating with Hugh about it, I was obsessed by reaching very low lf and hf distortions with a nice thd spectrum, my amp was excellent sounding.

But after few thinkering I've decided to lowered a lot my gnfb ratio for a lower feedback in my prototype, giving a close loop gain of arround 40 db, the sound became better, more alive and more define. The thd spectrum was not very different but the sound was different.

I was aware about the effects of medium to high feeback on the sound but I did not take it seriouselly enough.

Most modern amps, including very costly commercial amps, use very complex topologies with high feeback giving very nice measurement but a bit lifeless and ordinary sound.

There is some thread in the other forum where some "brains" talk about their amps going down to .0000something% thd, and all the guys giving them high praise. But none of them did listened to those amps.

Bye

gaetan

jkeny · « **Reply #126 on:** 18 Jul 2010, 09:26 pm »

Have it working now with my test rig but no time to move it to a proper configuration to evaluate its sonics.

I will be doing this tomorrow & having a good listening session!

AKSA · « **Reply #127 on:** 18 Jul 2010, 11:02 pm »

Excellent work, John!

We await your assessment of the sound!

Thanks for the piccies......

Hugh

jkeny · « **Reply #128 on:** 19 Jul 2010, 07:41 pm »

Time for a preliminary review:
I moved this to my ever-changing main system (I'll detail it below) & turned it on & nothing ........... but music came out of the speakers (I bet this gives Hugh a shock

). Like all great amplifiers this seemed to get out of the way & not draw attention to itself. So this impressed me to start with.

I had to stop enjoying the music & start critically listening to to de-construct what I was hearing. First off I noticed how quiet this amplifier is - even with volume up full, no hiss, no sound from my speakers (I don't think I've experienced this before). I played some Nat King Cole tracks that I had recently used & I was familiar with (showing my age now!) & his voice was more silky than I had heard before & the massed strings were very convincing. I then tried Gorillaz, Plastic Beach for something at the other end of the spectrum (more electronic) & I noticed how fast & dynamic the sound was - the electronic sounds on this album are fast & discordant at times & a lesser amp can muddle things up a bit.

I then used my favourite album for testing audio equipment - Herbie Hancock's; "The Joni Letters". I find a number of tests on this can easily trip up an audio device - the wire brushing on the snare drum/cymbals can sound like hiss on some systems; the sax & piano is a good test of instrument rendition & the various singers test the midrange for any over emphasis. On all counts this amp was exemplary - the first of mine that got everything right - no over-emphasis in any area; an even-handedness that explains why it gets out of the way & just lets the music come through.

So to use a local phrase from this part of the world - it's wicked good! I'm chuffed & happy as a bunny - I just need to improve the rest of my system to the standard achieved by this amp - see below for existing system.

I'm hoping to soon be able to have a shoot out between it & some other well respected amps both DIY & commercial. I will post here if & when I achieve this.

Existing system:
Source: Dell inspiron 600 laptop running Foobar V1.0.3
USB transport - my modified Hiface via SPDIF into a PurePiper DAC (will be changing this to a Sabre based AckoDac soon)
Naksa amp (still using cheap pots from Samson donor amp - will be changed to LDR vol control)
Jordan JX92S DIY speakers

I'll post some pics later

AKSA · « **Reply #129 on:** 20 Jul 2010, 06:45 am »

John,

Many thanks for a very good review. I don't think I find anything there I would disagree with. Let me address your points!

#1 This is an extremely quiet amp. During the distortion test, Dr Graham Huon believed it was better than 95dB S/N with no special attempt to reduce hum pickup at the test leads. Weighted, the noise should be well below -100dB. In subjective terms, this means that after you switch it on, you can't tell the amp is running, and it means that the resolution is stunning because almost none of the quiet sounds are obscured by noise.
#2 You mentioned forcing yourself to stop listening to the music and start analysing the sound. This is a characteristic of a very good amp, and reflects strong musicality. The other thing you notice is that your foot is tapping, and you don't tolerate people talking over the music.
#3 Wire brush in jazz is indeed an acid test. All too often it comes across as electronic noise.
#4 The speed of the amp is reflected in the phase shift; only three degrees at 100KHz, up there with the best.

I really appreciate that you have given it a good test, and your use of words and obvious musical choices indicate you are very experienced in assessing gear. My market is, in fact, people who have been around the block, tried it all, and you are clearly one of those!!

Thank you again, now I'M CHUFFED AND HAPPY AS A BUNNY!!

Hugh

jkeny · « **Reply #130 on:** 20 Jul 2010, 08:13 am »

Thanks Hugh,
I know I've been around the block a number of times but I was hoping it didn't show so obviously

I'm hoping to change out the cheap vol pots today & use a LDR based vol control. I may also get to installing a Sabre based DAC. I will report my results & further listening impressions if/when I do.

PSP · « **Reply #131 on:** 20 Jul 2010, 03:27 pm »

Hi Hugh,
Do you have any thoughts on how the NAKSA will do with low-impedance loads?

Peter

AKSA · « **Reply #132 on:** 20 Jul 2010, 11:02 pm »

Hi Peter,

Good question. I have not exhaustively tested it sub four ohm. I've reason to believe it will go to 4R, no lower, because the output stage is higher impedance and lower global feedback than the AKSA.

I believe a larger version of this amp would be fine with down to 3R. This is something I'm working on right now, in fact.

More to follow.....

Cheers,

Hugh

AKSA · « **Reply #133 on:** 21 Jul 2010, 12:38 pm »

Welcome, Mike.......

Folks, we have a speaker developer in our midst, possibly one of the best in Oz (except Laurie, of course!!)

I hope you find something here you like, Mike Lenehan......

Hugh

jkeny · « **Reply #134 on:** 21 Jul 2010, 08:06 pm »

Good God, I really wasn't fullsome enough in my praise of this amp - the more I play it & listen the more astounding it sounds. I don't know if this is a burning-in or if I'm playing for long periods & it's reaching a nice thermal equilibrium (no heat coming from the heatsink vanes) - but it's incredible.

I'm trying to put my finger on it's sonic secrets and all I can come up with is that it is so quiet & THD is so low that the instrument tails are clearly revealed giving a true foot-tapping & engaging sound to it. I'm in the process of finishing a Sabre DAC & can't wait to hear what an improvement in the front end will reveal. Problem is I just don't want to stop listening to music with this amp.

My amp shoot-out will have to go up a level I think & I'll be calling in the big guns to compare to this amp in the form of an Air Tight tube based amp - one of the best amps I ever heard but I have a feeling this Naksa will be it's match. It's a very tall order, Hugh & I wouldn't be disappointed if it doesn't match up, after all the Ait Tights are high-end sounding & price http://www.6moons.com/audioreviews/airtight/airtight.html

Hugh, my hat off to you - I knew you were a good designer but this is truly exceptional.

AKSA · « **Reply #135 on:** 21 Jul 2010, 11:58 pm »

Hi John,

This is wonderful news, now I'm waiting on some of the other guys to come to the forum with their assessments! Your articulate style is much appreciated, John, you express it well.

From my standpoint, during the design and refine process, after meeting the basic engineering requirements like low noise, low THD, efficiency, clip, and frequency response, all of which are must dos in my view, I'm really only interested in musical engagement, but you can't measure it. So the question becomes: Does it tap your foot, draw a smile and roll the occasional tear down the cheek? Years ago I noticed this was the clear feature of the single ended triode amp, and realising it could be done, from that point the quest was on to achieve it with SS.

The AKSA did get part way, and was a very successful amp, having the X factor and selling hundreds. But it lacked bass heft, at least to me, resolution could have been better, and the noise levels were a tad high. The LF improved upon this markedly, particularly with bass and resolution, but this latest, the NAKSA, is a step up again, and I'm very pleased. It is the sparest design I have ever done, with a low component count, very good reliability, and the X factor in spades.

I must read the Air Tight review, it sounds pretty good. A tube amp is tough to beat, recently in Melbourne a NAKSA went head to head with a 18W Cymer EL34 PP Class A and the owner concluded it was no longer a matter of which was better - they were different, and there was music he actually preferred played on the NAKSA.

I have found that the biggest determinants of sound quality, in order, are topology, feedback regime, and capacitor choice. These are the three big ones, at least for me.

Thank you John!

Cheers,

Hugh

yammy1688 · « **Reply #136 on:** 22 Jul 2010, 12:59 am »

Hey all,

I believe I was one of the first to get this thing shipped and up and running, but work has prevented me from getting extended listening sessions in so I'll just post my brief impressions after a few days of short sessions.

it's not cased and has some power cables dangling close by so i've got slight hum (particularly when a nearby power-hungry video card goes into 3d mode), but will sort that out in time.

as for my setup: buffalo2 ess sabre dac -> diy borbely preamps (none of these are cased either, and contribute to the hum). Gallo 3.1

OK here goes:

Very balanced tonally. Nothing stands out, yet everything is there! Know what I mean?
It gives music that that palpablity factor. Instruments sit solidly in the image and are clearly delineated.
I know it sounds a bit cliche, but it's just gives an extremely smooth presentation without any perceived detail loss.

I will post more as I get more serious listening sessions in.

Thanks again Hugh,

-Ken

AKSA · « **Reply #137 on:** 22 Jul 2010, 11:33 am »

Ken,

It's a pleasure, I'm thrilled you like the NAKSA, and most grateful you took the leap of faith. I did indeed make an amp that got well out of the way, I like your use of the word 'palpability'. I think it communicates the presentation very well!!

Cheers, and thanks for the endorsement,

Hugh

sureshm · « **Reply #138 on:** 22 Jul 2010, 01:54 pm »

Hugh,

I was wondering if your amps have balanced inputs or just single ended inputs? With balanced DACs being more common in DIY, would a balanced input be something you are interested in and what impact would it have on the distortion profile?

Thanks

Suresh

AKSA · « **Reply #139 on:** 22 Jul 2010, 10:08 pm »

Hi Suresh,

I constantly get this question. The answer is a resounding no. Let me ruffle a few feathers and tell you why I do NOT supply balanced lines.

Balanced lines are used in pro audio for extreme quiet. If the hot signal conductors carry opposite phase in a very noisy environment, common mode induction will cancel, so you have graveyard quiet signal.

However, such circuits null even order distortion, leaving very low levels of odd order. Further, they either require a trafo (expensive, a Jensen from California is around $100) or more circuitry, which adds distortion, odd order, of its own.

The argument is strong for minimum distortion in recorded music playback. But zero distortion is generally not possible. Therefore we should profile it so that even order, if possible, should be higher than odd. Balanced line mitigates against this profiling.

I do not recommend balanced lines for any of my products. If I were building pro-audio gear for use in noisy environments, the arguments would be entirely different.

DACs often use balanced signal processing - voltage output sigma beta circuitry - but this is not for reasons of noise, rather the topology and constraints dictated by high audio output with limited digital supplies (5V). Consequently for different reasons some sources use this signal mode.

I'm sorry Suresh, these are my reasons, carefully considered, but no.

Cheers,

Hugh