Group Buy: GK-1 Upgrade (AudioCap 40uF & BC560)

whubbard · « **Reply #20 on:** 23 Jul 2008, 05:44 pm »

Yes,

The other alternative would be 2 bars of Gold Bullion.
It's you choice

-West

Greg Erskine · « **Reply #21 on:** 26 Jul 2008, 07:44 am »

Hi West,

Can you put me down for one set.

I'll do Paypal later tonight (alcohol permitting) or tomorrow if that's all right.

regards
Greg

whubbard · « **Reply #22 on:** 26 Jul 2008, 01:14 pm »

Greg,
Your down for a set!

Once 2 more people pay I am going to order the caps and hope that the other 2 eventually get around to it.

-West

whubbard · « **Reply #23 on:** 27 Jul 2008, 03:13 am »

Alright,
I am now going to transfer the funds from my paypal to my bank and once that goes through I will order the caps.
I trust that Foster and Andy will pay soon.

I also now have a .5% Accuracy capacitor testor so I can get the caps matched well. However, I still am confused what Beta is...any help?

-West

p.s. LAST CHANCE FOR ANYONE ELSE!

whubbard · « **Reply #24 on:** 30 Jul 2008, 06:03 am »

Caps ordered.
Should have an 'estimated' delivery by friday.

-West

whubbard · « **Reply #25 on:** 4 Aug 2008, 11:06 pm »

Hi Everyone.
Thanks for paying so quickly.
The estimated delivery is September 15-26. Once I have them I will get them out as soon as possible.

-West

AKSA · « **Reply #26 on:** 4 Aug 2008, 11:59 pm »

West,

Thank you most sincerely....

This is a wonderful service for AKSAphiles, and from what I heard with Lyn's (aka LM) GK1 it should have profound impact for all takers.

Has your latest package from me arrived yet? I would expect it to arrive in the next two days at the latest, but who knows?

Cheers, and thank you again,

Hugh

Builder Brad · « **Reply #27 on:** 5 Aug 2008, 03:47 pm »

is this group buy still open?

Brad

whubbard · « **Reply #28 on:** 7 Aug 2008, 08:34 pm »

I was able to squeeze Brad in, but this group buy is now officially:

CLOSED

-West

whubbard · « **Reply #29 on:** 29 Aug 2008, 06:29 am »

Hi all,

The caps are set to arrive mid-September. I will then match and ship them with the BC560s as fast as I can. So to speed things up I would like to ask what form of shipping you all would like. Is USPS First Class okay? I will do whatever you all would like, as I will just bill you for the charges. Please Email Me your preference. If I haven't heard in a week or so I will send you an email.

-West

Peter,
Since you have already paid for shipping, yours will go out UPS as discussed.

whubbard · « **Reply #30 on:** 18 Sep 2008, 05:38 am »

Okay. The caps are on there way, and I will be taking care of all this next weekend. (Measuring + Packing). Whats even better, is that I will be doing this all with my system playing the background. So it should be an exciting weekend. Unless something major happens, they will all ship out on the 29th.

I think I'm going to wait on putting these caps in until I have listen to the system as I want to see the difference they make.

Just wanted to give you all an update.

-West

kyrill · « **Reply #31 on:** 18 Sep 2008, 07:49 am »

thx

gerado · « **Reply #32 on:** 19 Sep 2008, 12:45 pm »

aurelius · « **Reply #33 on:** 20 Sep 2008, 08:49 am »

So you're got your Orions running? Are you enjoying them?

whubbard · « **Reply #34 on:** 29 Sep 2008, 07:17 pm »

All the caps are matched and packaged in set of four (one of two). The transistors will take a little more time as they as very labor intensive to match. Unless otherwise discussed all the packages will be going out USPS First Class as soon as I get all the transistors matched.

There is one matter that must be discussed. All of the Caps are either all of the same value, or within .1uF. However the way it worked out was that one set of 4 has the values of 40.6,39.2,39.1,38.9. These were the highest 4 caps. Unless anyone would like these 'higher' values, even thought they are not as matched as the others, please post here. First come, first serve. I have all the caps in little packs, and I will just pick one to put in each box, so unless anybody would like these values, it will just wind up in the mix.

-West

gerado · « **Reply #35 on:** 30 Sep 2008, 05:19 am »

You are a good guy West!

Thanks for all your time and effort.

whubbard · « **Reply #36 on:** 30 Sep 2008, 06:21 am »

Well I'm feeling mighty bright today.

I have a wonderful bag in front of me filled with BC-560 transistors.
All of which have betas in the range of 110-220.
Which is exactly what we don't want!

I have a new bag of BC-560C transistors on the way.
All of which have betas in the range of 420-800
Which is exactly what we want!

It's good that these transistors are cheap!

silly silly me...

-West

ginger · « **Reply #37 on:** 22 Oct 2008, 12:28 am »

Guys,
I had a PM from Andy saying that he had done the "C4 mod" when he built his GK-1 and asking would he need to back out this mod when he upgraded C4 as a result of his participation in this group buy.

To save you wading back 20 pages or so the "C4 mod" is:
1) Swap components LED L1 and capacitor C4 on the PCB
2) change R14 to 10K
3) change R13 to 470 Ohms

In the original configuration C4 filters the +ve rail noise to keep the T4 current source reference voltage at the T4 base "squeeky" clean. The Current Source reference voltage is the voltage from the positve rail to T4 base.The mod does this too but also:
1) Filters any LED noise
2) Shunts any high frequencies which might be fedback to the T4 base via the collector to base capacitance of T4 (this capacitance is collector to base voltage dependent and so varies with signal).

If you have done this mod there is absolutely no need to back it out. Just change C4.

If you have not done this mod may I RECOMMEND that you do it when upgrading C4.

This "C4 Mod" was something suggested to me by Hugh based on some feedback from one of our USA fellow AKSAphiles. Technically it made good sense and after trying it I liked it. The the value of R13 (470 Ohms) was what I ended up with after the usual trial, listen, adjust cycle.

The more "technically bent" amongst you will note that the "C4 mod" R14 value of 10K results in about 1/2 the LED current as in the unmodified arrangement. That is true, but in the modified arrangement we are not relying on as low as possible dynamic impedance of the LED on the T4 base anymore and so the lower current is fine. Lower current also means lower LED noise.

On C7, those who have built AKSA 55s or 100s and recognize the front end arrangement in the GK-1 will already know that C7 is one of the most critical caps for sonic performance.

And what did I do all those years back when I built my GK-1? I dug out my notes for the GK-1 build and I see that I made a note that I used 68uF/20V OSCONs for both C4 and C7. They would have been the best choice of what I could find in my parts bins at the time. I also had noted that I used Blackgate Standards for C10 and C14 and used a Evox Rifa SMR Polyphenylene Sulphide (PPS) for C8. I would have used Blackgates for C11 and C12 as well but recall that I could only change 2 of the 4 caps due to physical space limitations and so chose C10 and C14 as the more critical ones.

Of-course you have all done something clever with C1 - havent you? No? Then flag that for the next job.

Now the one remaining thing in there which triggers my "Are you really sure?" button is that tantalum cap for C2. For a start I would have thought it should be a non-polarised capacitor although there is no real DC voltage across it in actual operation. I've discussed this with Hugh in the past and he assures me that plenty of things were tried and rejected before settling on the tantalum. Still, if someone wants to experiment and report back to us !!!! Don't be surprised if this cap turns out to be the source of some of the sonic character that we like in the GK-1 and changing it may turn out to be a backward step.

Cheers,
Ian

andyr · « **Reply #38 on:** 22 Oct 2008, 07:35 am »

Quote from: ginger on 22 Oct 2008, 12:28 am

Now the one remaining thing in there which triggers my "Are you really sure?" button is that tantalum cap for C2. For a start I would have thought it should be a non-polarised capacitor although there is no real DC voltage across it in actual operation. I've discussed this with Hugh in the past and he assures me that plenty of things were tried and rejected before settling on the tantalum. Still, if someone wants to experiment and report back to us !!!! Don't be surprised if this cap turns out to be the source of some of the sonic character that we like in the GK-1 and changing it may turn out to be a backward step.

Cheers,
Ian

Sounds like this is another project for RonR?

Wasn't he the one whose experimentation led us to this C4 & C7 40uF group buy?

Me, I implemented a 22uF BG 'NX' straight off for C2 ... so I have no idea what "the sonic character that we like in the GK-1" is!

But I do know it sounds better than any other GK-1/Swift I've ever heard!

Thanks for your advice with the C4 replacement and the "Ginger mod".

Regards,

Andy

AKSA · « **Reply #39 on:** 22 Oct 2008, 08:03 am »

Further to Ian's comments,

Yes, Darl and I tried LOTS of caps in the feedback shunt position, and to our mutual astonishment the tantalum sounded best.

One must remember that all caps in a circuit change the sound. This particular position, C2, is on the INVERTING input, so it's quite possible that it synergises with other caps in the circuit on the NON-inverting side of the amp.

Since the sound we are after is in fact a moving target, and may not appeal to everyone, then it makes sense that experimenting may not be universal, and not all 'enhancements' will be appropriate for everyone.

Accordingly, I won't comment further, but I will thank Ian for his hospitality on Saturday last when I was in Adelaide and called round to see him. He gave me a very large old 300W DIY mosfet amp which will be very useful for some nice parts! Thanks Ian!

Cheers,

Hugh