New GK-2 preamp - diyAudio
Go Back   Home > Forums > Commercial Sector > Manufacturers > AKSA

AKSA Builders of market proven kits and modules at sound quality to rival the best in high end

Reply
 
Thread Tools Search this Thread
Old 29th September 2011, 11:37 AM   #1
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Default New GK-2 preamp

Hi Hugh,

I have taken the liberty of creating a new thread specifically for the GK-2.

It might get a bit lost in my old thread about the GK-1 repair - and we cannot have that ;-)

May I also suggest that you provide slightly more detail about the GK-2 herein - at your own pace, off course?

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th September 2011, 03:03 AM   #2
diyAudio Member
 
Join Date: Jul 2003
Location: wyoming
Jens,
If I may, I will enlighten you a little bit about the new preamp. I assisted Hugh with various aspects of the new preamp, and am quite familiar with it. At present I am the only person to have an operating unit. Hugh has only done bench testing and I don't believe has an operating unit at this time. I did a lot of things on my own initiative, thus that is why I have the preamp at this time. I have had this for nearly a month now.

The new unit has an input/gain stage that is quite similar to what Hugh uses in the new Naksa series amplifiers. The new gain stage has about 11db of gain, nearly twice that of the GK-1. Now that Hugh uses LT Spice for designing, he can similate a harmonic distortion profile for the circuit, and the profile for this gain stage is simply about as good as can be. And I believe that this correlates very well to the wonderful sound that I hear from this unit. The buffer stage is the same as that in the GK-1, no real difference.

The layout of the two stages differs slightly from that in the GK-1. In the new unit the stages are directly coupled, and the attenuator has had to be moved to the source input into the stage. I believe that the board size is the same as the GK-1, or at least very very close in size.

Hugh has already stated that the new board connects up very similar to the old board, so anyone with a GK-1 could easily replace the board with the new board, with little if any difficulty. The attenuator connects differently, and there needs to be some changes to the transformer wiring, but these are not difficult, and Hugh would be able to easily instruct.

The sound: well, it is pretty good, and I think that's an understatement. I had been using no preamp in my American system here for the past 7 years, just attenuators on the N+/LF inputs. I have been more than pleased. I never had to attenuate very much on most recordings, and the sound was quite good. But now, well, the sound just jumps out of the speakers and is cleaner, clearer, and more natural than ever. In short, inserting this box of circuitry into the system has made things better!

What made the GK-1 rather special was that buffer stage. What makes this new unit special is the excellent input/gain stage. Having used a GK-1 in my other system, since my first Aksa long ago, as in 2003, I think this new unit is a big big upgrade. And if one has a few dollars in the audio project cookie jar, I cannot think of a better way to use them than to replace the GK-1 board with this new one.

Steve
  Reply With Quote
Old 30th September 2011, 07:48 AM   #3
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Thanks Steve,

Very good info! Sounds like it's more or less a 'plug and play music' project, if Hugh is supplying finished boards.

And if it is possible to use the same trannies, motorised pot and all - then all the better. A little rewiring is not a big deal.

Hugh already confirmed that it is possible to reuse the tubes, which means that I can reuse the Siemens gold-pin 6922s I acquired a few years back. They made quite a difference, and the GK-1 is still one of the very best preamps I have listened to.

So, to get one that is even better and then not even to have to rebuild the whole remote section etc. (mine is the GK-1R) is really almost a dream come true ;-)

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th September 2011, 11:15 AM   #4
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
Hi Jens,

Thank you for starting this thread. You are an Aspen champion, and I appreciate it!!

Steve,

Many thanks for your introduction. Now, to add the story behind the development.

After about five years of consistently selling the GK1, I decided to attempt a redesign with a view to knocking it off its perch. This would have been around 2008, a year after attending Rocky Mountain Audio Festival, where I came to see that my efforts were as good as any of the products I saw there.

As is customary with my approach, I looked around for NOS tubes that were about as unlikely for audio that I could find. I settled on the 6BL8, a pentode/triode used in black and white TV sets in the sixties. I then devised a strange way of driving the screen grid which could be loosely described as a cathode follower in ultra-linear, where I used the triode to drive the pentode screen and thus control the sonics.

It took time, but after much thought I designed the circuit, then a pcb and had a few made. In 2009 I built the first.

I worked, but there was hum. It worked extremely well, actually, aside from the hum, and I and a couple of friends tried everything to eliminate the hum, but without success.

It turned out that this tube, made for TV sets, could not deliver low noise like an audio tube, and so, ultimately, I admitted defeat and cast around for other techniques.

The front end of this circuit was unique, a two transistor gain stage in single end with an astonishing sonic performance, and I wanted to keep it.

So, I thought that since the GK1 had such a flawless output stage, with a clever antiphase drone triode to improve bass response while still offering a brilliant midrange and top end, I felt that grafting the new front end onto the GK1 output stage might again work well.

I laid out a pcb about a year ago, and had a few made. Then I became thoroughly committed to the NAKSA development, and recently I've been involved with a local manufacturer to commercialise the NAKSA for use in proaudio. This slowed me down.

That's when I confided to Steve, just before he left for his annual stint back in the States, the design and my thinking. I'd had a lot of help with the schematic drafting from a friend in Jordan, and input from Romeo in Italy. These guys all contributed in their way and I am most appreciative. Anyone involved in design will realise that the gestation, philosophy and vision behind the product is long, involved, and tortuous. I read a lot of Jean Hiraga and his thoughts on the matter. Steve encouraged me, and decided to take it on, as he'd always loved his GK1, and wanted to lay out a new pcb for the design. So, he set about it in his usual methodical, disciplined way, and soon mastered the software. His layout, unrelated to mine, is a damn fine job.

Recently Steve got it all going. There was a bad moment when he'd tried everything, but couldn't get the GK2 to sound good. We all but gave up, but at my local caffeine dealer I realised why, and made a suggestion about repositioning the level control. The idea was right, the preamp blossomed, and after what seemed like only hours, Steve came back from Rock Springs with a jubilant thumbs up!

Finally it worked. The rest is history. This preamp will be my next generation product, and while I've not yet heard the final preamp through my latest amps, particularly the Soraya, Maya and NAKSA, I have a few boards, and I have bench tested it exhaustively. I have also very carefully simulated the SS gain stage, and know now exactly why it is as good as it is. I believe I've reached the point in my design evolution where I know exactly what to aim for in terms of distortion profile to get the best possible subjective effects. Essentially, distortion is inevitable in all circuits; we must learn to manipulate it, and live with it.

I have a preamp to deliver in a week, and one is built, with three more about to start this weekend. It is designed as a modular installation into an existing GK1. Same trafos, same tube spacing, same mounting holes, etc. The board is 200 x 80, compared to the original GK1 265 x 80, so it's actually simpler, in the spirit of Einstein's policy that it should be 'as simple as possible, but no simpler'.

As I remarked, I've yet to figure out the pricing; I will offer this only as a built/tested board, ready for installation as I'm quite anxious to avoid writing 50 emails a day for the next two years!!

I will come back to this thread with pictures in a day or so.

Thanks for the interest, this is quite a moment for me, I'm very, very pleased with this preamp, it's restored my interest in the GK series, and I offer a big thanks to Steve, Omar, and Romeo for helping me unstintingly. I also thank Jens for showing such an abiding interest!

Cheers,

Hugh
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com

Last edited by AKSA; 1st October 2011 at 11:57 PM.
  Reply With Quote
Old 30th September 2011, 12:09 PM   #5
diyAudio Member
 
Join Date: Jul 2003
Location: wyoming
Well, now we are going good with this one. Let me continue on a bit......
I had heard the TV tube preamp a few times. And I remember Hugh telling me awhile back that in the end the TV tube preamp was a no go.

Then a couple years back, during my development of an output stage for my cd player, Hugh suggested a modification to the existing LTP design I had been using, and this modification worked wonders from the first get go. I then wanted to make this same modification to the LTP in the GK-1 gain stage. Hugh did the design work one afternoon and I was able to soon get a prototype onto the existing board. It was a small improvement, but still an improvement. Eventually I developed a board for this design and got it implemented last April. This one was actually quite a nice improvement over the original GK-1 design, and both Hugh and I agreed on this, as Hugh had stopped in for a listen before I left for this year's work stint in the States.

Then Hugh slipped me some details of a new design he was working on that he thought would even be better. I needed a spare time audio project for the summer so I began working on a board design for myself. Eventually this all happened, and in late August I began bench testing and all. I had a few bugs with my efforts, but in the end I was able to get a perfect bench test that matched Hugh's bench tests and simulations. But when it came to the sound test, it was an utter failure. I even got to the break point when I had no more ideas or anything. That's when Hugh came up with the VOILA moment, which I received about 11pm on a Friday night. This took about 30 minutes to implement the next morning, and we had a WOW moment. And there was a flurry of emails, with each one containing more and more superlatives about the sound qualities of this new unit. And that's the story of The Aspen Preamplifier, as I like to call it, though Hugh still prefers GK-2.

Now all that is needed is for others to hear, listen and enjoy.
  Reply With Quote
Old 30th September 2011, 01:58 PM   #6
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Hugh and Steve,

Great story! I think this sort of 'organic' development is very commendable, and it would seem that the results of it are extraordinary!

Hugh, obviously my next question is: When can I get one?

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th September 2011, 11:41 PM   #7
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
Steve,

Thanks for fleshing out the story like it is, in your direct and accurate way. There's not much hype in the Aspen workshop, as anyone who has seen it will attest!

Jens,

Very soon, maybe two or three weeks?

Cheers,

Hugh
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com
  Reply With Quote
Old 1st October 2011, 02:20 AM   #8
diyAudio Member
 
Join Date: Jul 2003
Location: wyoming
Quote:
Originally Posted by AKSA View Post
Steve,

Thanks for fleshing out the story like it is, in your direct and accurate way. There's not much hype in the Aspen workshop, as anyone who has seen it will attest!

Cheers,

Hugh
Ya, I'm not too good at sugarcoating things.
But your workshop, WOW, a true delight!
  Reply With Quote
Old 1st October 2011, 08:37 AM   #9
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Quote:
Originally Posted by AKSA View Post
Steve,

Thanks for fleshing out the story like it is, in your direct and accurate way. There's not much hype in the Aspen workshop, as anyone who has seen it will attest!

Jens,

Very soon, maybe two or three weeks?

Cheers,

Hugh
Well, I think your workshop looks quite well organised, and I'm sure there are a lot of 'goodies' if one knows what to look for!

Two or three weeks? Wow! Does this mean you already have the PCB boards in stock?

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 1st October 2011, 05:15 PM   #10
diyAudio Member
 
Join Date: Jun 2006
Default GK-2 Keep Me Posted

Hi Hugh,

I am also interested in your new GK-2 as a replacement for my Non-Remote GK-1 which I built from the kit.

Sounds like the board is a drop in replacement for the original GK-1 and the only fiddling will be with sourcing a different volume control.

Please keep me posted on availability.

Mark
Syracuse, NY USA

PS - My AKSA is still going strong. I have had many hours of enjoyment from your amp.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
GK 200RCB Schematics eyoung Instruments and Amps 10 26th October 2011 11:44 PM
GK-1: Right channel dead Jens A. AKSA 26 4th October 2011 07:29 AM
Gk-71 Vladi59 Swap Meet 0 23rd March 2009 05:02 PM
Blown up GK 800rb mpm32 Instruments and Amps 1 13th April 2007 09:20 PM
GK 150 Tripath Solve Class D 0 21st November 2006 07:40 AM


New To Site? Need Help?

All times are GMT. The time now is 06:11 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2