[AKSA]

Incidently, warming up was not a reason for any change as I had been playing the system for nearly 2 hours prior to your arrival.

Hmmm, Theo, could it be that you grew used to it, and positively enjoyed it after a few drinks???

This effect is very pronounced, happens to everyone, and very difficult to design out.  Some say the only way to do it is the double blind test, but to me, it's too difficult to set up and it does not account for individual tastes, which is a big factor in audio as it's such a personal thing.

Hugh

[gerado]

Hugh,
getting used to it? Possibly had some bearing but was far too pronounced to be the total explanation. Im certain when you go back and have another listen you  might agree and  i would be interested in your findings.
Lyn could report what happens over the next week. It is an evolution of a new life form he has there in his listening room.

[andyr]

Lyn could report what happens over the next week. It is an evolution of a new life form he has there in his listening room.

Jeez, what were you guys smokin, as you were listenin! 

Regards,

Andy

[gerado]

Andy dont get me started on your system.
Is it still sounding like you dont have any speakers in the room?

[LM]

Not smoking Andy, drinking!

Hugh, I am quite affronted with people questioning our scientific techniques.  It was planned to have been a genuine double blind session - after the second Chivas.  But Theo piked after one as he had to drive home so it was only single blind.

As to the new life form Theo - still thinking that one through

[andyr]

Andy dont get me started on your system.
Is it still sounding like you don't have any speakers in the room?

Absolutely, Theo! 

For the last 2 weeks, I haven't had any (working) speakers in the room as I have started the process of installing the Maggie drivers into the new hardwood frames - and this involves cannibalising both to make one! 

Still a bit to do on the RHS speaker and then I have to do the left ... so it will be at least 3 more weekends! 

Regards,

Andy

[LM]

Hugh,
getting used to it? Possibly had some bearing but was far too pronounced to be the total explanation. Im certain when you go back and have another listen you  might agree and  i would be interested in your findings.

Theo, your wish was my command.   Hugh popped by for an hour or so today to hear the 34hr old version rather than the 4 to 7hr old version he heard last week.  It will be interesting to hear his view but to me it hasn't changed in any way I can pick in the 3 or 4 hours of play since you left.

I don't know about a new life form but the old one has sure picked up its skirts.  I'm finding the frequencies perfectly balanced now, wads of fine detail and really solid and realistic depth.  I know it still has some settling down to go but I'm already inclined to think in terms of overall system refinement that this has been the most profound change yet.  Overall the system now seems highly detailed and very, very musical with seemingly no distortion, quite fatigue free and with great focus and a fabulous sense of 3D space.  It's a lovely feeling that words describing why can't really capture but I just keep wanting to put on another LP or CD and keep listening. aa

[AKSA]

Thanks Lyn,

Let me give my impressions.  I cycled gracefully around to Lyn's today and heard his system to my complete satisfaction.  (And gave Guy, his son, a solo ride on my Kamakazi, hell, he used more revs than I do, quite scary!!).   

A famous track oft used by audiophiles is 'Flight of the Cosmic Hippo' by Bela Fleck.  This track is meant to demonstrate huge, grand canyon bass and sharp definition, with a few afficionados saying it also shows great imaging.

I have always found this track spectacular, but focussed more on effect than the music, which is actually pretty good, a nice tune, and beautiful playing.

Today I realised after a few bars (that's music, not chocolate......) that this was the most musical rendition I'd heard, with absolutely nothing to distract from the skills of the musicians.  No longer was it a 'hifi' sound;  it was completely transparent, with all emphasis on the performance, and extraordinary details revealed at the bottom, near the noise floor, and imaging to die for.   

I guess you'd have to say mission 95% accomplished.  I have only to spend the remainder of my life teasing out the last 5%, doubt I'll get there.  Not that I can pick anything bad - it really was that good.....

Philip, Ron, my sincere, genuine thanks to you both for making me realise that there was more to come from this six year old design.   

And thank you Lyn, for being such a determined, patient audiophile!   

Cheers,

Hugh

[gerado]

Lyn, Hugh,

Im glad I heard what I heard and not what I wanted

Its a means of playing musical instruments in harmony now , not a hi fi system as you noticed Hugh
Its such a good feeling when one experiences a system that has crossed into that magical realm.


So you start with a GK1 moded, add some Soraya a sprinkling of mods, the V sonics and you are almost done.
Just be done with it Hugh and complete the chain

[PT914]

Hi,

There is still a question in my mind.  Which is better, the original design at C4 with a 24 uF cap or the "ginger mod" with a 67 uF cap at C4.  Some brave soul will have to do the comparison which will be time consuming and may be subtle.  But the single smaller cap at C4 is the easiest to do.  I have the double and larger cap.  The present sound from my system is so good, I'm not changing anything soon.

Cheers,
Philip

[LM]

I'm not changing anything soon.

Philip,

I'm completely with you.

I can't answer your 'which is the best configuration' question (unless it's a purely rhetorical question in which case you already have ) but I can thank you again for your discovery.  Incidentely, I chose 24uF rather than any other value as It was the biggest I could fit comfortably in my enclosure without excess pain. In other words, I could go bigger than 20 with 24 ideal but 33 and certainly 47 would have been quite problematic to fit in my case.  However, the results are so good that even if other brands or sizes prove better in trials, I sure the improvement could only be marginal and I'm quite content with the 95% performance I now have.

[RonR]

Hi all,

Thanks for being so patient, this "quick test" turned into a bit of a marathon. Here are the results of my testing over the last few weeks.

Firstly, a description of the test equipment and set-up:

1. The split GK-1 boards were removed from their case as there wasn't enough room in the original case for experiments.
2. 2 x 6VA 15-0-15 potted transformers were used, which gave a slightly lower quality power supply than the usual GK-1 transformers.
3. Only the Solid-State section of the GK-1 was used for the test, output was taken to LF55s via a stepped attenuator with Vishays, later upgraded to TKD Stepped attenuator (tests were re-run after installation).
4. A daughter board was added above the GK-1 boards to hold the Caps on test and 2 multi-way switches to easily select which caps were in circuit.
5. C7 options:
    a. Oscon SP 47uF + 0.22uF Evox SMR Bypass - The best I've heard until these tests
    b. Wima MKS2-XL 22uF
    c. Sonicap GenI 20uF + Sonicap GenII + 0.47uF Bypass
    d. Solen 20uF 250V
    e. Relcap AudioCap 40uF PPMF
6. C4 Options:
    a. Black Gate N 47uF - The best I've heard until these tests
    b. Wima MKS2-XL 22uF
    c. Solen 20uF 250V
    d. Sonicap GenI 20uF
    e. Relcap AudioCap 40uF PPMF
7. T4 Options:
    a. BC557 - Original
    b. BC560 - Low noise replacement
8.  T1+T2 Options:
    a. BC557 - Original
    b. BC560 - Low noise replacements
9.  The last 3 caps were chosen for their physical size, as most people won't have loads of room in their GK-1 cases for anything much bigger than these.

The results:

I've based the Cap results on a standard score of 50%, which is the benchmark using the Oscons/Black Gates.

1. Wima MKS2-XL 22uF
Moving from the Oscon / Black Gates to the Wimas gave a useful improvement in detail and high frequencies, but these caps only gave around half the improvement to the soundstage of the physically bigger caps. 60%

2. Solen Fastcap 20uF 250V
Natural sounding mid-range, nice treble, accurate bass with punch. The soundstage really opened out with these.  75%

3. Sonicap GenI 20uF
With or witout bypass, the Sonicap was not a success at C7. It lost out on the start/stop of bass notes to the Solens, but still bests the Wimas. 70%
At C4 however, the Sonicap was marginally better than the Solens. There was slightly more high-frequency detail apparent. 78%

4. AudioCap PPMF 40uF
These caps extended the bass by easily half an octave or more. Maybe it was the value of 40uF, or maybe the construction. Sounded "right" and balanced from the word go. Alot like the solens, only a little bit more of everything: Sweeter treble, slightly more open mid-range, extended bass. Soundstage was as good if not slightly better than the Solens. 85%

One caveat with these: The Aksonic speakers I'm using in my system do not have the bass response of the V-Sonics which will replace them. There is the possibility of too much of a good thing here giving a hump in the bass response, in which case I'd go for the 40uF AudioCap at C7 and the 20uF Solen at C4.

5. Changing T4 from BC557 to BC560
There was a distinct lowering of noise by around 25% at full volume with shorted inputs when this transistor was swapped out. I couldn't detect any drawbacks in the sound. Worth doing.

6. Changing T1 and T2 from BC557 to BC560 (Matched)
I couldn't detect any improvement in noise performance with this change, but there was a slight "Mechanical" tinge to the sound with these in place. I was not able to source the same make of transistor that Hugh uses for these. Perhaps this is the reason for the slight degradation in the sound. For the record I used Fairchild transistors, maybe the On-semi version would be better?

Cheers,

Ron.

[kyrill]

Prima Ron
    

Great  report
Kyrill

[AKSA]

Ron,

Simply incredible, thank you, I will contact you privately later in the day.   

Cheers,

Hugh

[gerado]

The Bob Crump mod,

now that West is about to dispatch the caps for the GK and the hood is coming off the GK I was going to try the Bob Crump mod if I could find a clear description what to do.

Does anyone have a link or a description what to do for a stepped attenuator with resistor steps?

Theo

[DSK]

Theo, the late Bob Crump asked me specifically not to publish these details anywhere on the web. Out of respect for Bob and the remaining CTC members (Thomson and Curl) I will PM you the details rather than post them here.

[gerado]

Thank you,

and I will respect those wishes.

reading about one gets the impression he was very much respected. I will look him up and learn a little more about the man and his life.

[AKSA]

DSK, Theo,

Bob Crump was much loved, from what I gather.  John Curl presently posts on DIYaudio.com, and has a whole thread devoted to the Blowtorch, details of which he has sparingly released over the last three years.

John is a very testy character, and enjoys a good fight.  He's even had a shot at me, for whatever reason I cannot imagine!

Cheers,

Hugh

[stvnharr]

This thread has been quiet for a long time, and I've just made some minor changes in my GK-1, so here goes.

T4 - BC560 in BC557 out
C19 grid coupler - .01uf Sonic Platinum out, replaced with 1000pf LCR FSCEX polystryrene
C21 output - wire link out, replaced with stock Auricap bypassed with .01uf Sonic Platinum.

The T4 is from the other thread.  I had wanted to return the Auricap as output and use a new Auri-T teflon as bypass, but pcX didn't have them in stock, so I used the Platinum.
I've come to really like the LCR caps from using them in my cd player modifications.  With a teflon cap at the C-1 input, the grid coupler doesn't really require a teflon, and the LCR caps are nice replacement if you want to change the stocker.  The LCR's are only available from Farnell, AFAIK.

The overall sound change with the about is quite small really.  Perhaps a slight noise lowering with the low noise 560.  There is quite a bit of voltage at the output, so a cap is best here rather than wirelink, and a teflon bypass of the stock Auricap is a very good way to go.

I think I can weld the lid on now, or at least until I decide to make a bigger and nicer chassis.

[whubbard]

C21 output - wire link out, replaced with stock Auricap bypassed with .01uf Sonic Platinum

Well now here is a funny thing. I just put the Auricap in at C21 as the wire link just wasn't working. Hugh and I could not figure it out for out lives, but with a wire link in at C21 the GK-1 tube section would not work. I am going to be putting in a 1uF Platinum at C21 in the near future, but I have to make sure I have room for it first.

I too will soon be putting in BC560s, however the AudioCaps will have to wait as I know I don't have room for both of them and the Platinums.

-West