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Old 21st May 2008, 09:08 PM   #1
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Default Grounded Grid Preamp

Hi all,

I am looking to borrow a Grounded Grid Preamp. If you have the kit built, and it's just sitting in your closet, i would like to borrow it for a week or so. I am looking at tube preamps with a low output impedance under 800 Ohms. The GGP fits the bill nicely.

You can either reply here, or email me directly:

raybronk@comcast.net

Thanks ahead of time for anyone who can help.

Ray Bronk
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Old 21st May 2008, 09:30 PM   #2
KP11520 is offline KP11520  United States
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Hi ray,

I am interested in how you do with this endeavor. I am interested in a Tube Pre/linestage too but unsure of what would suit me best. Maybe the people that sell the kit at Transcendent Sound have a demo policy and will send you one to demo with a credit card number. Then return it and buy the kit if it suits you. Approach them about this!

I would like to build whatever I pick to keep it under $1K. I would like to add a remote volume attenuator and maybe an on/off switch to my choice. Not sure about an integrated Phono Stage and Headphone Amp but that would be a nice package.

I have also gotten suggestions for the Aikido that is here and a lot of support comes with that and a Bottlehead Foreplay III (with the upgrade option). Both would be reasonable but the Aikido would require sourcing the parts and chassis, etc. But the best sounding and most transparent (hopefully with a holographic soundstage), would be my choice. (Lots of inputs would be nice too.) Take a look at these and see if maybe they meet your specs too.

Good luck and I will be watching! Please let us know what happens! Thanks!

Regards//Keith
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Old 21st May 2008, 09:40 PM   #3
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Hi, Well, I don't think that Transcendentsound has that kind of policy. If I can't borrow one from someone, I'll just have to save up the pennies, nickels, and dimes, quarters too, and buy and have the kit put together for me. I am told it is one of these preamps that are extremely neutral. You either love it or hate it. There's a Minimax on the Gon for $600 and something. There are others to consider too. Anyway, that's what is up here. Thanks to all that can help.

Ray Bronk
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Old 21st May 2008, 09:55 PM   #4
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Guys,

Try this on for size.

http://www.diyparadise.com/mar06/gg.html

Larry
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Old 21st May 2008, 10:09 PM   #5
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Hi larry,

Well, that's real cool. Except the schem is for the 5842, not the 6678 or the later tube.

Another reason to look at the GGP with 12AU7, because it is already built. Being blind, can't read the schems. Can solder point to point so that would be ok. I would need that connect point A to Point B stuff.

Plus, don't know the cost of these two tubes either.

Ray Bronk
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Old 22nd May 2008, 01:55 AM   #6
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Quote:
I am looking to borrow a Grounded Grid Preamp. . .. I am looking at tube preamps with a low output impedance under 800 Ohms. The GGP fits the bill nicely.
What makes you think so? Grounded grid provides low input impedance but similar output impedance to the more conventional grounded cathode.

Quote:
As GG has low input impedance, don't be daft and build one as a preamp. Unless you are REALLY DAFT.
That's what it says in that article referenced by Larry.

You could look at an Aikido design, which I've never tried but which seems to be popular.
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Old 22nd May 2008, 02:06 AM   #7
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Hi, Well, I don't want to get in to a debate here. I was just picking the GGP, because I knew it had a 200 ohm output impedance. I did not think of other configurations.

Ray Bronk
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Old 22nd May 2008, 02:54 AM   #8
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Ray, the GGP is not actually a grounded-grid stage.  What it is, is a singly-driven diff-amp with the output taken off the noninverting (grounded-grid) side. I don't think, unless you build with a device that has insanely low rp, that you're going to get an 800Ω Zout; it is still just another plate-loaded amp.

Click the image to open in full size.

A reason (not the only one) I like the SRPP is that it has gain like a plate-loaded stage, and Zout like a cathode follower.  That said, I have searched for the optimum device and worked on operating points to get Zout as low as I can, and the circuit shown here (the 6T4 has rp about 1800Ω at this OP) has Zout just a little above 800Ω.

I think that this is maybe the lowest of any circuit not using, like, a 2A3 as the active, but I'm willing to hear arguments.

Aloha, Ray n' Ray,

Poinz
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Old 22nd May 2008, 02:57 AM   #9
Salas is offline Salas  Greece
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Did you try 12B4 Poinz?
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Old 22nd May 2008, 03:31 AM   #10
KP11520 is offline KP11520  United States
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Hi Poinz,

You were proposing plans for a Tube Pre/linestage on OZMikeH's thread a few months back. You had a lot of help with ideas and the build.

How did that turn out?

Thanks!

Regards//Keith
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