[Rhythm Willie]

I am about to start replacing all the power supply and boards of my 100n+ that I have enjoyed since completing the monos in May 2003. I am keeping the cases , transformers etc.
I will post some pics shortly of the upgrade.

The old amp and power supply boards will go in an integrated amp for HT/TV use (just have to get some transformers and a case).

As usual, Hugh was very helpful and although he was busy with many orders, he still has time to promptly reply to emails and telephone queries. The new boards are a bit bigger than the old ones, but still fit OK, cutting the power supply boards in half  and resoldering the (6.8uf?) bypass caps has been easy and I am almost finished one channel (pics to come later).

One question I - I noticed (as in the old boards) there are power supply input 120uf Electrolytic bypass caps and a smaller bypass cap on the boards. On my old amp I attached some 100uf/100v Blackgate FK's bypass caps as well, which I thought improved bass definition. Should I try just adding these, or just replace the 120uf existing caps on the boards?

I am really looking forward to trying the new amps and will do a review against amps used to demonstrate the new Vaf Research I93 MK2 flagship speaker, Micrex and Arcam Full Metal Jacket monoblocks. (I think the AKSA will win, but remain open about this - Phil Vafiadis has an amazing ear for amps and it should be an interesting comparison ).

I have heard my current Vaf I93's with some of the worlds best valve amps and the $25K Halcro monoblocks and believe it or not most people preferred (and myself) the AKSA 100n+'s.

BTW when I had completed exhaustive comparisons of my 2003 Aksa's with my previous amps - Naim 250 monos and Metaxas Solitaire, the Aksa's were a clear winner,I made quite a handy profit at the time when selling my old gear.

Thanks Hugh, you are a true gentleman and passionate pioneer.

[AKSA]

Hi Dennis,

I am very pleased you are getting it all together so quickly, up to your usual meticulous assembly standards, and thank you for a lovely post, very complimentary.

Being a genital and a scollop (Oz slang for Officer and Gentleman!!) does not guarantee anything much, but it does guarantee a love of words!

I will be very interested in Phillip's assessment of the sound, he is a legendary judge of good gear.......

Many here would be fascinated to know that Dennis' great uncle (IIRC) Alfred was the man who developed the pedal radio in the twenties which revolutionised both medical evacuation and children's education in the outback of this huge country.  Dennis continues his relative's great love of electronics with brilliant assembly techniques and impeccable layout!

Cheers,

Hugh 

[bluesky]

I am fascinated to hear of the use of electros as bypass caps, it must be valid to use those expensive FK's as a bypass caps.  Previously I had only used film caps of 1/100th of the original value, or less.

I picked up some $1 - 4.7uF400V film caps and had thought of trying these out as cheap bypass caps on the 4,700uF power supply caps.  Does anyone think this would be worth the effort?  I thought it might add a bit of sparkle and speed to the mix especially in complex musical passages.

Cheers

Ian   

[Rhythm Willie]

Bluesky,

As Hugh already has 6.8uf film bypass caps across each channel's power supplies and another two film bypass caps on each board, I would'nt think it would be necessary to add even more.

The 100uf/100v Blackgates were'nt overly expensive compared to other costs(about US10), as Hugh already has some small 120uf/63v electros as bypass caps on the board, I was thinking of just replacing them with the much larger Blackgate's (would have to mount them underneath), rather than just paralleling them as in my 100N+. I thought the Blackgates added "quickness" to the bass and helped me to hear bass lines clearer in the mix - very subjective however. As they are only bypass caps BG's are probably overkill.

I will probably have to just try them on 1 channel and do some A/B listening.

[bluesky]

Sounds like they are worth the effort, I have felt that bypass caps do add a bit of speed to the mix and will install these in my build which is going very slowly but surely nevertheless.

I think the theory is that these small caps both charge up quicker and release their charge quicker which means you have two "batteries" supplying the power and reducing the ripple effect by filtering.  I would guess that a choke enhances this process even more, which is Hugh's latest power supply enhancement.

Ian

[Rhythm Willie]

Bluesky,

Yes, I think you summarised the benefits of small bypass caps very well, but in some already good designs, often they are no advantage,but if not too expensive - worth trying.  I tried some snubbers as well on my Aussie Amp NXV300, then took them out. Some also recommend a snubber/filter (100n + 5ohms) on the secondaries of the transformer(Hugh has one on the primaries). Tried this - no advantage in my amps.

Hughes common mode's look interesting, I am trying to get my head around how they work/improve things. I have done a bit of research on those Coilcraft units. Also interested in what caps in the signal path in Hughe's Soraya Signature are changed to teflon. I should try to stop this fiddling/copying addiction.

[AKSA]

Hi Dennis,

Have you got them running?

I'm very interested in your impressions!

Hugh

[Rhythm Willie]

Hugh,

1st channel is almost finished,I ran out of speaker wire to connect the + channel out, my daughter is bringing some up from Adelaide tonight as I made a new set for her (QED Silver Anniversary) and her old cables are what I  used for most of the wiring on the original amp in 2003.

Power supply shows +-48v(long run down to the shed, will check in the house hifi outlet which is 15a and about a metre from the fuse box and unswitched,we have our own dedicated transformer as we are in a rural area), bias is 61.5mv, DC offset is correcting itself nicely so all looks well. I increased the LED resistor value to 80kohm to calm down the brightness of those trendy blue frosted LED's.I used some Cat 5 to connect up the Mundorf input cap as the shielded stuff would be difficult.

2nd channel - Board is connected to heatsink, just waiting for silicon to dry which glues the new power supplies to the bottom of the rear case panel, then wire up and test, so should be finished this week. BTW your assembly and quality of soldering is top notch.

[Rhythm Willie]

There up and running for 30 minutes. I have left out the Blackgate bypass caps  to start with.  A fair bit of hum, but I started playing music anyway. The first thing that struck me was how smoooooth they sound with my Vaf I93's, these amps are never going to get fatiguing, but detail is all there, it just does'nt sound "transistory" at all - so even without any run in I am very impressed.

My first guess of what was the cause of the hum was the Mundorf  input cap and when I touched it, hum increased.

As I had silicon glued the input caps loosely to the case partition that runs between the power supply and the amp boards, I prized one away from the partition and let it hang in mid air supported only by the input lead wires, immediately hum is way down to acceptable levels. Looks like I will have to play around with it's positioning etc. Probably too close to earth.

Full report and pics with a few hours on them and after I have tried the Blackgate bypasses.

[AKSA]

Hi Dennis,

Thanks for the headz up! 

Large input caps mounted off the board can be a huge source of hum, I too have struck this.  You have to be very careful about them, as being large and unshielded they can pick up a lot of stray magnetic fields and even RFI.

I'm pleased you like the smoothness;  refinement after these years of development is a reasonable expectation, but the difficulty is NOT to lose resolution.  These amps resolve more than the AKSA, yet they also have strong, articulate bass and exceptional sound stage.

It is not always practical to leave lots of room for the input cap on the board, either, as some of them are upwards of 45mm long!

Thanks again Dennis, look forward to the long term assessment!

Cheers,

Hugh

[Seano]

Dennis!  We know what you upgraded from but what did you actually upgrade to? Or did I miss that? Holidays will do that to you....

[Rhythm Willie]

Seano,

Yes I was going to give more detail once I had some photos. My wife(a teacher) takes our camera to school as she photographs all the kids activities, their portfolios, work etc is on her laptop, then they get a CD of it all at the end of the year, so I will get the camera and take some pics this weekend.

The amps are Lifeforce Mk11 (or Soraya Mk1) including the power supplies featuring double rectifier bridges and the .15ohm resistors between the caps. They feature automatic DC offset correction and each board has 3 Blackgate caps (including 2 NX bipolars).

Mods Update:-

I have tried and then removed my 100uf/100v Blackgate FK power supply bypass caps as they did nothing to improve the sound (unlike my previous 100+n).

The hum problem being picked up by the close proximity of the input caps to the amp boards has been eliminated by connecting the amp chassis to star earth (I noticed Hugh does this in the latest photo of the Soraya CB105 and thought I'd try it with some clip leads).

As the amps run in, my first thoughts of smoooothness have changed. I can now hear all the fine details and crispness of recordings. Female vocals are especially pleasing, one can certainly hear all the instruments in very complicated mixes.  IMO the amps seem to be a very harmonious match to my speakers which I triwire with thicker cable on the bass.

[AKSA]

Thanks Dennis,

Great description, very clear.

Seano,

The LF100 was sold for about two years and recently I've moved to the Mark II version, which was in fact used in the very first Soraya retail amp.  It's a more sophisticated version of the original Lifeforce, with many subtle modifications for better performance.

The input stage carries a current mirror, proprietary matched input pairs were adopted, more linearising degen is used on the VAS, which is now buffered, and the power supply is an upgrade too, with care taken to quarantine the high charge pulses off the rectifier bridges (four in total) into one but not both caps.  This reduces intermodulation with the final filter cap, improving resolution, a trick not possible if only one cap is used.

The Mark II is an enhanced module, sold for the same price.

The Soraya has moved on, and is now three versions removed from the Mark II, with the very latest version in 150W//8R being bedded down right now!

We never sleep at Aspen....... groan     

Cheers,

Hugh 

[Rhythm Willie]

Finally got some pics of the completed rebuild.

I have realy enjoyed listenning to the amps this weekend and revisited a lot of my older wellkown CDs - Allison Krause (I'm not ino country music much, but I love her voice and style of song), Jennifer Warnes, Loreena McKennitt, Fourplay, Acoustic Alchemy,Mark Knopfler, Audiophile Voices series of Cd's, even some Enya and Dream Theatre etc etc.





 

[AKSA]

Dennis,

As we've seen from you before, a wonderful implementation (dreadful word, but you get the idea!) of a LFII, exquisitely done, congratulations.  I'm confident that Alf would be damn proud of you!

What do you think about the resolution, dynamics and sense of 'being there'?  Do you notice that more than ever you are in the performance, and it's highly musical even though the slight warmth of the AKSA is somehow modified?

Cheers,

Hugh

[Seano]

Scarily, depressingly my suspicions have turned out to be true.....Hugh is trying his hardest to gouge more dollars from yours truly and Dennis is his latest Agent Of Menace.

But I wil....l....nnnnnn........oo......tt___ _____________succcumm.....nnn...b.

<ouch>

...never knew that my Visa card had teeth!!

[Occam]

....
The LF100 was sold for about two years and recently I've moved to the Mark II version, which was in fact used in the very first Soraya retail amp.  It's a more sophisticated version of the original Lifeforce, with many subtle modifications for better performance.

The input stage carries a current mirror, proprietary matched input pairs were adopted, more linearising degen is used on the VAS, which is now buffered, and the power supply is an upgrade too, with care taken to quarantine the high charge pulses off the rectifier bridges (four in total) into one but not both caps.  This reduces intermodulation with the final filter cap, improving resolution, a trick not possible if only one cap is used.

The Mark II is an enhanced module, sold for the same price.

The Soraya has moved on, and is now three versions removed from the Mark II, with the very latest version in 150W//8R being bedded down right now!

We never sleep at Aspen....... groan     

Cheers,

Hugh

WOW! As someone who has been listening to an orignal Soraya for over a year, all I can say is that purchaser's of new LF II modules will get a superb amplifier. Many industry professionals after hearing my original Soraya have stated the amp is 'word class". I realize that sounds like hackneyed marketing hyperbole, but the amp really is that good. Its availability at that price, prebulilt with the additional savings for the diyer makes it all that much more attractive.

FWIW,
Paul, anxiously awaiting HIS bedded down 150wpc Soraya

[Rhythm Willie]

Extreme Test - We are in the middle of a record November heatwave in South Australia (Global Warming?).

Yesterday it was high 30'sC in the lounge/music room and I decided to test the Aksa out at the extremes to try to see early on that it will be reliable. I was a bit apprehensive about this. I found a lot of music with loud extremely low bass, left the lids loose and played them hard for about an hour (had to leave the room to relieve the eardrums). Tracks included Zimmer's "Thin Red Line" soundtrack, including track six which has the loudest/lowest reverberating bass drums/timpany's I have heard, literally shook the house to it's foundations. Also a number of very deep electronic bass tracks.

The Aksa took this punishment without a whimper. I removed the lid and timidly touched the driver transistors, power transistors, power supply diodes, transformer etc anticipating high temperatures, but everything felt nothing more than like at normal room temperature after all this extreme use. I am therefore anticipating many, many years of reliable listening.

BTW in association in testing with the extreme abuse - I have added an extra Nichicon KG Goldtune 4700uf cap per rail. It made no difference to the sound or bass of my smaller Vaf DC7 2 ways, but with the big, low bass and loud 3 way I93's, I can hear a better drive and control in the low registers without any other negatives so these extra caps are in permanently.

[AKSA]

Hi Dennis,

Sorry for late reply - this is a VERY good test, and closely replicates the test I do, in fact.  The amp is designed for rock concerts in Death Valley, I guess this is simply a reflection of the extreme conditions in Australia.  I note that Adelaide was at 43C yesterday, man, that's HOT.

The more I consider THD and the traditional measures of audio amplifier quality, the more convinced I become that we are measuring the wrong thing.  I think it's important, but there is some X factor we are missing.  I suspect it is merely that the dynamic stability of an amp is not taxed with a THD test, particularly with single test tones at 1KHz.

Fascinating to hear that more power supply capacitance works so very well.  That's worth knowing......  thanks again, Dennis.

Seano:  'Do not leave the room.  Merely reach for your CC, and dial up Aspen Amplifiers.  Kafka was an optimist, Aspen remains a realist....'

Cheers

Hugh

[Rhythm Willie]

Ok - I tried the new Aksa with Vaf's new flagship speaker I93 MK11 yesterday. I have heard this speaker previously both by myself and at a Vaf GTG attended by about 25 StereoNet members a month ago. Prior to leaving for Vaf I listened to it through my system :-
1997 Sony XA7ES - Unmodified Ming Da MC3a pre (1 NOS RCA 5881, 2 JJ ECC83 goldpin tubes)- AKSA - Vaf I93Mk1's.

System at Vaf was Arcam FMJ CD37 - Micrex preamp - Aksa - Vaf I93Mk11(RRP $12 - $15k AUS).

The Arcam CDP has been well reviewed and uses the latest Wolfson Dacs.

The big listening room for audition is IMO the worst of the 4 listening rooms at Vaf, it has always in previous auditions tended to suck out the bass in music and is almost too big to really feel close to the musical experience.

The first thing that struck me at the audition was a real surprise (and almost the opposite of what I was anticipating knowing that my own lounge has always sounded much better in the bass than the big Vaf room and the fact that the new amp's improvements are to me more evident in the midrange and treble regions than in the bass) and that was that I heard the best bass  I have ever heard at Vaf,Phil commented how impressed he was also, it sounded much better than at the Vaf GTG (which resulted in a number of sales). Some people have in the past criticised the Vaf's as being "too forward" - I suspect this is because they are so accurate and precise, in this audition they just sounded so effortless and smoooooth, absolutely non fatiguing. IMO it was the best I've heard music at Vaf.

Phillip Vafiadis was really impressed with the amps, but as he was interrupted by a number of phone calls and was going to have to leave early to attend a staff function for his other company Zen Technologies(alternative energy), we did'nt have time to play his own test CD's.

What we did have time to do however was to compare the setup to a full blown surround digital system. This consisted of an Oppo BDP83 HDMI digital out to an Arcam AV888 processor (RRP $9998) using that processors latest Wolfson Dacs and anolgue stages into an Arcam P777 power amp (RRP $8998).

The processor recognised "digital 2 channel" for the test. In 2 channel this setup was very very disappointing, in fact the test did'nt need to last long at all it was so bad compared to the Arcam/Micrex/Aksa system - BTW Vaf's top of the range subwoofers were  also in play during this test. I won't go into details, but in every area including bass the Aksa combo was far far superior. The surround system was particularly bad at the treble/detail/naturalness perspective. It just was'nt as musical, too digital.

It really convinced me that even with some of the best surround sound gear available in the world (Ok maybe the player could be improved, but we did not used it's analogue stages), that to listen to music, a dedicated quality 2 channel system is better by a large margin in this comparison.