[painkiller]

I've just put together my LF55 monoblocks, and would like to post some initial impressions, even though they have been playing for less than 10 hours. I'll also be posting some pictures tomorrow.

My previous amp was a SKA GB300D (about 200W into 8R), and there will be comparisons.

Speakers are Triangle Antal Esw, and the source is a heavily modified pioneer dvd-player. I initially used an SKpre with 12dB gain, but this was too much, so now I run the amp through a 10K attenuator directly from the source. The LF55 is set up with 24V/150VA trafos giving a supply voltage of +-34.4VDC. Internal wiring is Mundorf Silver/Gold.

First of all, there is little doubt that the Lifeforce is in a different league than the SKA. It it better in every way, even though my SKA was tweaked to the teeth.

Wiring and setup was really easy, and the manual wasn't really necessary, as the PCBs are thoughtfully labeled. Bias and offset were just slightly off. The amp doesn't seem to get warm at all, as it's coupled to an extra 3 mm aluminum board. Build quality is top notch. It is very stable, and my girlfriend is not scared to turn on my system any more. She never dared to touch my SKA, as it had a loud pop when powering on, hissing noises coming and going, and it seemed to be more unstable. 

First of all, the LF55 is dead quiet, no hum or hiss. There's just a slight pop when switching on and off. Initial impression is that the harshness that I've experienced previously in my setup is gone. Female voices which have had this unpleasant tone are now more relaxed and have that spinechilling effect. My girlfried commented that the sound "seems more detailed in time", i.e. better transient response/more silence in between tones. Timbre of small details is also very natural, and makes instruments stand out even more. Sometimes it sounds like the music is being played slower, because each beat is that much clearer. Echo on recordings is presented very good, and makes the overall soundstage much more lifelike. All in all it's less clinical than the SKA. Bass response in noticeably extended, and deep bass is clearer and tighter. My speakers tend to have that in-your-face sound, but with the LF55 the sound is more laid back. Very pleasant.

I haven't had the opportunity to play at louder levels, so I cannot comment about the dynamics yet, but nothing indicates that the amp sounds less powerful than the 200W SKA.

Now I'm eager to get to the serious listening and get to know the amp better. I do have a feeling that this is an amp I can live with for quite some time.

[kyrill]

hi painkiller

with the 10K attenuator in series with the Aksa what will de CDP see as the input impedance of the amp?
Hugh can tell you.

What is the output impedance of the CDP?
I would not be surprised if a Burson audio buffer will bring your setup to a higher plane
it did with mine as with many others

[rabbitz]

Hi painkiller

You can reduce the gain on the SKpre from 12dB to 6dB by changing R2, R18 to 2K.

As suggested, you can also add a Burson Buffer in between the source and pot as it does help the sound big time. I took mine out of the case supplied and installed it in my pre case so each source can use it's capabilities. I gave the discrete power supply the flick and use a IC based supply to give me ±21V rails.

Interesting observation on the GB300. I had a GB150 for a short period.

[AKSA]

PK,

Many thanks for your review, despite the 10 hours since first hearing it I found your approach truly long term rather than short term - very well done!

The LF55 is a terrific little amp, and goes very loud.  There is no schematic published, but it has more tricks than a monkey on a mile of vine, and I'm very proud of it.  It was a fun pcb to design, too, with the increased flexibility of double side.

The standouts over the AKSA are probably the resolution and the spatial details.  There are moments with that amp when the sense of intimacy is profound, any closer and you'd have to ask the songstress to stop kissing you!!  (Nice feeling for an old codger like me!)  But with each new release of amp, I have to say all these qualities just get better and better, and I've just received word from Jeff Dorgay of Tone Publications who has just tested the Soraya that he thinks it is a marvellous amp, and very, very good value for money compared to the big guys.  That was nice!!

A Burson Buffer is a good addition to your lineup if you are using a 10K pot, which will load down your digital source appreciably.  Peter (Rabbitz) advises this and he is 110% right.  I've heard the combination, examined the Buffer closely, and I endorse them strongly.  In fact, I wish I'd designed it!!

Thank you again for your review.

Cheers,

Hugh

[painkiller]

I've made a separate analog stage for my cd-player consisting of AD843 at 2.5x gain. This op amp can swing 25V p-p and has an output impedance of less than 0,02R across the audio band. There was little difference with or without the pre, but because of the gain it was more practical without. I guess there could be some advantages with a discrete buffer, but I think I'll try a tube buffer instead.

Yesterday I got the chance to play at louder levels. It seems that there are no restrictions to volume, and the sound really opens up. No sign of dynamic compression. A drumkit at realistic sound levels is no problem for this amp. It's heavy hifi without being physically heavy.  aa Very nice.

There is one thing about the sound though. To me it sounds like a too low input filter cut-off. I don't know any other way to describe it. It would be interresting to try a smaller filter cap.

[AKSA]

Jurgen,

Interesting observation!  The input filter is set at 6dB down at 133KHz.  You could try reducing the series resistor to say 680R;  this would about double the cutoff to 250KHz.

However, the amp is extremely fast, and a LP filter is necessary to stop cell phones and stray RF from affecting it, so be circumspect about the adjustments!!

Cheers,

Hugh

[painkiller]

http://www.diyhifi.org/forums/viewtopic.php?f=21&t=435&st=0&sk=t&sd=a&start=645

This thread (page 44) over at diyhifi.org has some interresting remarks about the Fc. Look at the graph with Fc=100kHz. Carlos even suggests not going below 500kHz. There should be clear audible differences when comparing 125kHz with 2-300 kHz.

Cap values nearing 1nF to tend to restrict sound. I'll try 250kHz and come back with results.

[painkiller]

I decided to reduce the value of the filter cap instead. Result is that the amp lets through more of the noise from that hopeless delta-sigma dac. Other than that there is no apparent problem. The sound is immediately a lot more airy, and sort of "less compact". It may come across as being a bit thinner, but I guess that depends on the rest of the system. I definitely like it better this way, and it should make an easier load for the source.

The impression I have is that this amp is extremely detailed and extremely fast, without losing the tight bass or timbre. Very impressive. It's absolutely wonderful to listen to. I'm usually a bit impatient, and tend to skip between songs often, but now I find myself listening through whole songs before even noticing it. That has to be a good sign. Now I just need better speakers! 

[AKSA]

PK,

This is an extremely positive review;  thank you for taking obvious time and trouble to put it carefully through its paces. The development of the Lifeforce was long and arduous, and there was a lot of empirical testing to be absolutely sure it delivered as I had intended.  It looks simple because it is compact and light, but it is quite a complex piece of circuitry since this level of performance can't be had with the sort of rudimentary circuits available in the sixties and seventies.

Thank you for trying the change to the LP filter.  I presume you used 470pF in place of the 820pF silver mica?  Interesting that you could pick the crud coming off the digital source;  this is in fact something I'd found too and caused me select the values I did.  You've chosen a particularly compromise which differs from mine, but as you said, there is an upside as well as a downside.

Thanks again Jurgen, appreciate the careful thought in your review,

Cheers,

Hugh

[painkiller]

I actually ended up with 320pF. I believe this value would work for most people. I have very little filtering in my cd player, and the noise is barely noticable.

I changed coupling caps (128 SAL-RPM) and input resistor (PRP) also. Now it's really amazing. I can't imagine any amp being better than this. It would be interresting to try the Soraya, but I'm satisfied for now. Just enjoying music again! 

My next priority is new speakers. aa Maybe some Bastanis kit. Looks interresting.

[RonR]

Tried this last night using 1K RN55D and 470pF Polystyrene. A definite improvement, with no discernible hash coming through from my DAC. (http://members.chello.nl/~m.heijligers/DAChtml/dactop.htm)

Recommended, if you can get away with it.

Cheers,

Ron.

[AKSA]

Thanks Ron!

You might also consider keeping the 820pF/1nF cap, and replacing R1 with say 470R.  That would have, I expect, the same effect precisely as it would about halve the time constant, doubling the corner frequency.

Much appreciated,

Cheers,

Hugh

[AKSA]

Jurgen,

I have heard the Bastanis, made in Germany, at RMAF in Denver.  They are very good and I commend your choice.

However, I also urge you to consider the VSonics, which are almost there.  They are MUCH cheaper, and just as good.  I will have them on sale in the next week.

Cheers,

Hugh

[andyr]

Having just upgraded my AKSA 100, 55 & 25 (all N+s) to Lifeforces, two things bring a smile to my face when listening now:
* more transparency (delicacy, resolution ...), and
* lower bass.

An un-missable upgrade IMO! 

See here for pics of the amp upgrade project:
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=487&pos=10

This is the first pic - go through to #9 (but, sorry, I can't seem to work out how to get them in order!  ).

Regards,

Andy

[LinegrohalomanUpjoy]

Folks,
A clean slate for Lifeforce listening impressions!!
Please reserve for ACTUAL REVIEWS, people who have HEARD IT,
and wish to comment on the sound, good or bad.

Discussions about other aspects, such as
- value for money,
- relevance to DIY, etc etc,
should be put into a fresh thread.

Sorry for the bother!
Cheers, Hugh

Hello
> Hugh 'aspenamplifiers' Dean 
> my audio friends of all parts of world
> and the others 

Some background history goes:
---------------------------------------
On january 8th 2006 me, under the alias 'lineup',
started this topic in another board:
AKSA 55, 100 - Listening impressions

Because I honestly thought AKSA Amplifiers deserved it
( seeing all those other (no names mentioned) amps having such attention ).
Since March 2007 this topic is dead, which only menas nobody posted.
There was a clash between me, some moderator and a few others
and this took a lot of the spirit away from AKSA Amplifier listeners.

The latest post was made by a faithful AKSA Owner: Destroyer X.
I am bound to add: Who Else would do it!

Anyway, in 13 months my AKSA Topic generated 317 Posted Reply.

AKSA 55, 100 - Listening impressions  (   1 2 3 4 5 ... 13 = Last page )     
Topic Starter: lineup
Repliies: 317
Viewed: 24,705

Now to my real message.
To anyone happen to read this and being interested in LifeForce

From my post #278, written 12th January 2007:

ASPEN AMPLIFIERS
- and Hugh Dean has mentioned some new release: AKSA Lifeforce
- AKSA Lifeforce 100
- AKSA Lifeforce 55
- AKSA SWIFT PREAMPLIFIER

Link reference:
http://www.diyaudio.com/forums/showthread.php?postid=1104650#post1104650

This is the first time Lifeforce is mentioned in this topic
and later I also introduced LifeForce with an Image, into same thread.

  Onwards there are some Sound Reviews of Lifeforce, as well as other opinions.
So if you are interested, have a read and compare your own impressions.

Then come back here and post!
Because this is a friendlier and more open place, in my opinion.
At least for the older audio guys, like me and Mr Dean of Australia.

-------------
lineup date of birth 1951 May
posted in Sweden at 2008-04-18 at 03:30 GMT

[AKSA]

Welcome, Lineup!!

You were born the same year as me, you poor bugger......  old age is not for sissys!!

Thank you for your comments, I will go have a good look, and Carlos and I are still good friends!

Cheers,

Hugh

[painkiller]

Now I've been living with my LF55's for a while, and I think I owe both Hugh and future owners a little followup.

Usually, when it comes to long term listening, I tend to find downsides no matter how good a product is supposed to be. There's always some tiny flaw that keeps getting in the way of experiencing the music. This is not the case with the LifeForce amps. It strikes me over and over again how good my system sounds, even with a cheap(ish) source and seriously compromised speakers. I also enjoy music much more after I bought the amps, and it's easier to get involved in the music.

It seems quite irrelevant to speak about bass punch, midband clarity details and so on, because it all sounds right. Bottom line is that these amps are exceptional at reproducing sound the way it was meant to be. End of story. It's the last amp you'll ever need to buy.

[AKSA]

Thanks Jurgen,

That's a resounding, ringing endorsement, and I'm really pleased.  You've lifted my spirits this cold, wet wintry day!!

It may seem hard to believe, but there are even better amps than the Lifeforce - the Soraya, and soon, a 200W version called the Aztec.

Cheers,

Hugh

[Felipe]

Hi all,

I know i haven't been here for a while, but professional issues sure mixed up my life quite a bit.
I have been away from my Aksa gear for 8 months now....too much i telll you.

Now...lets talk more about that Aztec of yours... aa ... when can we see it and how can i get my hands on it ?

[AKSA]

Hi Felipe,

Now, are you settled in Sao Paulo?  Or Rio?  What is the job like?  Do you get to go home every couple of months?  As a newly wed, they owe you that, the buggers......

The Aztec is coming along.  It is the 200W Soraya, essentially.  Entire front end and VAS is built into a 20mm x 28mm module with 12 pins, which plugs into the main board, which is 280mm x 80mm, with four pairs of output devices.  The module and main board are designed and manufactured, and the prototype is presently under construction, but a smaller version has been made and auditioned by Colin in Canada.

Needless to say, it's pretty good!!   

The power supply will be +/-62V, and will incorporate DC speaker protection.  Power will be 195W into 8R, and 312W into 4R, conservatively, yet to be formally measured.  Case design is under way;  it will use 100mm tall heatsinks, compared to the Soraya's 75mm.  Power is from two 500VA toroids.  This amp will have more grunt than a pig farm, and more volume than Van Morrison.  However, it will be subtle, and detailed, beyond anything out there in the commercial world, I'm sure of this.

I really have to stop developing amplifiers.  It costs too much and it's taken over my life......

Ciao,

Hugh