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Old 9th April 2013, 10:23 PM   #101
andyr is offline andyr  Australia
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Quote:
Originally Posted by stvnharr View Post
Jens,
The GK-2 preamp uses a small signal dual triode tube in a cathode follower configuration in a buffer circuit. This is not a power output circuit with a high power tube with associated damping issues in the bass. There is a big difference, and I think you are confusing the two.

Steve
Hi Steven,

There are tube fundamentalists who swear that tube power amps don't soften bass transients either ... so I await Jens' test with interest.

BTW, your statement "There is really no provision for a separate subwoofer output like one could do with the GK-1. Although that being said, it is possible to branch an output off the circuit, add a capacitor and grounding resistor and have a separate output, but that is not a feature of the design." seems to me to be splitting hairs.

Hugh provides a convenient wire "take-off point" at R13, where he has soldered the res lead across several "trace-blobs" so you can easily attach the wire that goes to the sub-out RCAs. But yes, you have to mount the series O/P cap off the PCB.


Regards,

Andy
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Old 9th April 2013, 10:32 PM   #102
Jens A. is offline Jens A.  Denmark
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Quote:
Originally Posted by stvnharr View Post
Jens,
The GK-2 preamp uses a small signal dual triode tube in a cathode follower configuration in a buffer circuit. This is not a power output circuit with a high power tube with associated damping issues in the bass. There is a big difference, and I think you are confusing the two.

Steve
No, I am not confusing anything. We are not talking about power amps here. But then, I've heard many a tube preamp with spongy bass over the years

Basically, what I am saying is that since the GK-1 and the GK-2 have the same tube output stages (according to Hugh), I find it strange that I heard a difference in the bass precision when comparing the SS (Sub out) and tube outputs in the GK-1 when your experience with the two outputs in the GK-2 is different.

I am not discounting your experience, because there could a number reasons for it, including that the circuits in the GK-2 simply "fit" so much better together that there simply is no discernible difference

As I said, I will try it out in my system as well, which will be under slightly different conditions. I may well come to the same conclusion as you did ....

Cheers,

Jens
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Old 9th April 2013, 11:38 PM   #103
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Quote:
Originally Posted by andyr View Post
Hi Steven,

There are tube fundamentalists who swear that tube power amps don't soften bass transients either ... so I await Jens' test with interest.

BTW, your statement "There is really no provision for a separate subwoofer output like one could do with the GK-1. Although that being said, it is possible to branch an output off the circuit, add a capacitor and grounding resistor and have a separate output, but that is not a feature of the design." seems to me to be splitting hairs.

Hugh provides a convenient wire "take-off point" at R13, where he has soldered the res lead across several "trace-blobs" so you can easily attach the wire that goes to the sub-out RCAs. But yes, you have to mount the series O/P cap off the PCB.


Regards,

Andy
Andy,
I know exactly what Hugh has done!
There is no provision on the circuit board for a second output. Thus he accommodated with a modification from the grid stopper resistor. When we were getting the unit operational we discussed doing this as we were still thinking with a GK-1 reference. We determined that it could be done, but was not optimal and would require a complete redo of the board. When/if a new board is done for the preamp, it will likely have a provision of some sort for a second output. User modifications tend to lead to needless difficulties for all that are involved, and are best avoided.
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Old 9th April 2013, 11:58 PM   #104
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Quote:
Originally Posted by Jens A. View Post
No, I am not confusing anything. We are not talking about power amps here. But then, I've heard many a tube preamp with spongy bass over the years

Basically, what I am saying is that since the GK-1 and the GK-2 have the same tube output stages (according to Hugh), I find it strange that I heard a difference in the bass precision when comparing the SS (Sub out) and tube outputs in the GK-1 when your experience with the two outputs in the GK-2 is different.

I am not discounting your experience, because there could a number reasons for it, including that the circuits in the GK-2 simply "fit" so much better together that there simply is no discernible difference

As I said, I will try it out in my system as well, which will be under slightly different conditions. I may well come to the same conclusion as you did ....

Cheers,

Jens
Jens,
We all hear what we hear, want to hear, etc.
Yours is a special situation where the "sub" out is not really used as a subwoofer output, but rather a bass output. That is completely different and fairly unique to you.
What you really need is a preamp with 2 buffer stages, with the second one being a simple solid state buffer for the bass.
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Old 10th April 2013, 12:51 AM   #105
andyr is offline andyr  Australia
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Quote:
Originally Posted by stvnharr View Post
Yours is a special situation where the "sub" out is not really used as a subwoofer output, but rather a bass output. That is completely different and fairly unique to you.

What you really need is a preamp with 2 buffer stages, with the second one being a simple solid state buffer for the bass.
My situation is exactly the same as Jens', Steven - it comes from using speakers with active XOs.

I - and Jens - do not need a buffer for the bass (Sub) output, because our ICs between GK-2 and active XOs are not long. In my previous house, I had 11m ICs and did have to implement a ss buffer for the "Sub out" RCAs, in my GK-1.

My new environment doesn't have such an extreme IC requirement between GK-2 and active XOs and the bass sounds sensational, coming straight off R13, so I have left out this buffer with my GK-2.


Regards,

Andy
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Old 10th April 2013, 02:05 AM   #106
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I probably should have posted this in one of my previous posts, but failing that I will do so here.
Specifically the major differences in what is being discussed here between GK-1 and GK-2 are that at the grid stopper in the GK-1 there are only a few millivolts and in the GK-2 there are 50 volts. That's why you cannot do a simple sub out in the GK-2, like as in the GK-1. The voltage needs to be accommodated for somehow, which is not difficult, but this requires an additional modification.
Also, while the buffer in the GK-2 is a small signal tube with cathode follower the full circuits are not the same.
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Old 10th April 2013, 02:32 AM   #107
andyr is offline andyr  Australia
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Quote:
Originally Posted by stvnharr View Post

Specifically the major differences in what is being discussed here between GK-1 and GK-2 are that at the grid stopper in the GK-1 there are only a few millivolts and in the GK-2 there are 50 volts. That's why you cannot do a simple sub out in the GK-2, like as in the GK-1. The voltage needs to be accommodated for somehow, which is not difficult, but this requires an additional modification.
Hi Steven,

Well, Hugh suggested I take "Sub out" from R13 - so that is what I have done.

However, what you cannot do with the GK-2 (I found out the hard way and it took me 3 weeks to resolve this problem) is run the "Sub out" wire from R13 to the "Sub out" connection on the GK-1 Relay board / Manual Switch board ... because this point on the PCBs is also connected to the "Mute" relay/switch.

What you need to do with the GK-2 is run the "Sub out" wire directly from R13 to the Sub output RCAs ... and then run a separate wire from the volume pot wiper to the "Mute" connection on the Relay board / Manual Switch board.

This works perfectly - and, as I said, there is no issue with the GK-2 "Sub out" bass that I can hear.


Regards,

Andy
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Old 10th April 2013, 06:48 AM   #108
AKSA is offline AKSA  Australia
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Let me offer my design considerations.

When I did the tube buffer on the GK1/GK2 with Darl back in 2001 we devised a way of conferring bass impact without depleting the wonderful, airy romance of the midrange and top end.

Our listening test showed that tight, slam bass tended to eviscerate the midrange and the top end, which finished up sounding like very good solid state.

Thus a frequency compensation was needed to give the best of all both worlds.

On th GK1 we added a sub-out option for that who wanted to experiment with the sound. It was easy to do with the GK1, rather differently for the GK2, so I do not recommend any change for the GK2 although it is clearly possible to implement and I privately spoke with both Steve, Jens and Andy to arrange this option for bass output with no the tube buffer.

All of these decisions are subjective, based on Darl and my thoughts, and latterly, with conversations with Jens and Andy. After all, the preamp is designed for maximum pleasure for listening, but it's important to realise that people do not indeed hear the same things....

Cheers,

Hugh
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Old 20th April 2013, 02:42 AM   #109
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Quote:
Originally Posted by andyr View Post
Having at last got my GK-2 working (in its loverley new case) and run in, I have to agree with everything you've said, Jens - and couldn't have said it any better myself.

Good as the GK-1 board was (and mine went to a new home - and the buyer is rapt with it), the GK-2 does everything better!

I've been waiting for this day for a very long time but well done, Hugh. Anyone with a GK-1 should make the effort to upgrade. You won't regret you did.


Regards,

Andy

PS: The case comes from a great Italian supplier - Hi-Fi 2000 contenitori per l'elettronica, case modding HTPC, Galaxy, rack, DIYaudio, computer cases, front panel express, knobs,milled Handles, milled fronts, hi-end,. The ebony knobs were made by Duc ('lovetube' on SNA).
Wow Andy, nice pre!!! Very nice!

The GK2 really interest me.

BTW, what model is that source selector?

Thanks
Do
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Old 20th April 2013, 04:07 AM   #110
andyr is offline andyr  Australia
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Originally Posted by pinnocchio View Post
Wow Andy, nice pre!!! Very nice!

The GK2 really interest me.

BTW, what model is that source selector?

Thanks
Do
Hi Do,

The 5-way source selector is the one that Hugh supplies with the GK-1/GK-2 kit ... I am sorry but I forget the name (a well-known brand which I believe is made in the UK).

The case comes from here:
modushop.biz



Regards,

Andy
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