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Old 2nd April 2007, 06:43 AM   #1
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Default 6SN7 pre-amp

I am going to build a 6SN7 pre-amp in accordance with the attached schematics in which I will use one kind of 6SN7 for the first stage (both channels) and a different type for the last stage. Can you please advise and comment on this project (any problems, changes to the schematics to be made, etc...) before I get started.

Thanks a lot.
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Old 2nd April 2007, 07:23 AM   #2
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errr... where's the schematic?
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Old 2nd April 2007, 07:36 AM   #3
Cobra2 is offline Cobra2  Norway
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@ Andersen; do a few posts in the "Introductions" - section:
http://www.diyaudio.com/forums/forum....php?forumid=7
And your limitation will be lifted sooner...

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Old 3rd April 2007, 02:15 AM   #4
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Hi,
If you don't understand what every piece is doing, or how it is interacting with the others, build it exactly as shown. Mixing two different 6SN7 won't give you any problems. Once you get a better feel for how the pre works, then you'll know better how to answer these questions( more likely, you'll just have different ones ). Questions are good, ask as many as you can, and keep asking until you understand the answer.
Cheers,
Douglas
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Old 3rd April 2007, 02:20 AM   #5
Apex Jr is offline Apex Jr  United States
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I've been wondering about the 6SN7's
And this thread brought it up again, SO,
What are the differences between them
GTA's and GTB's and others
I know the mil version 5642 is a great replacement
but why....

Steve @ Apex Jr
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Old 3rd April 2007, 02:42 AM   #6
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Quote:
Originally posted by Apex Jr
I've been wondering about the 6SN7's
This will answer even the questions you didn't know you had about various 6sn7 varieties: http://www.head-fi.org/forums/showthread.php?t=119638

However, see this thread where it is argued, inter alia, that the 6sn7 is not all that great, at least in some places (it gets going around post #10 or so): Driver valve discussion
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Old 3rd April 2007, 07:05 AM   #7
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To Cobra2: noted with thanks! I've just made my introduction and still wonder when I can post the schematics.

To Bandersnatch: Thanks for your support. There would be quite a lot of questions when I can post the schematics.

I'm going to use 5692 RCA Red base at the first stage and 6SN7A Sylvania Metal base at the second stage.
Attached Images
File Type: jpg pre 6sn7 no 1 ver1.jpg (47.0 KB, 3443 views)
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Old 3rd April 2007, 12:02 PM   #8
jeapel is offline jeapel  Canada
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hi

maybe ?

-adjust for 300v B+ for ~ 150 to 200 v across 6sn7
-adjust for 6.1v heater for long life
-transfo is always a weak part why not a cathode follower
-in my 6sn7 i use a c4s ccs with good result
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Old 3rd April 2007, 12:33 PM   #9
EC8010 is offline EC8010  United Kingdom
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Andersen: Frankly, that circuit is a very poor "design" and throwing exotic and expensive valves at it is not going to rescue it. What do you actually need to do? What is the sensitivity of your power amplifier? What output do your sources produce?
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Old 3rd April 2007, 12:53 PM   #10
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hey-Hey!!!,
I have a similar reaction to 801. I have not built like that, and prefer an all-tube active load on a single 6SN7 stage. The tube active load, made from a triode and pentode arranged as a cascode mu-follower has been very effective. It also lowers output Z to a level that lives comfortably driving 7k Ohms. It is the tube version of the MOSFET ccs as described by Gary Pimm.

IMO, fewer stages sound bettre than many. The PS also achieves its voltage output resistively. That's another thing I don't like doing. LC then a VR tube shunt regulator perhaps?

The single tube operating with a CCS load allows the sonic texture of the tube to show. I'd hate to wast such valves as you have on something that did not showcase them...
cheers,
Douglas
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