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Old 7th September 2006, 03:39 AM   #1
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Default Questions about this line stage

So I am ready to try my first tube project. I found this schematic on the web. I have a few questions. Keep in mind that I have very limited knowledge of tubes, I have been reading some but it is not sinking in very fast. The 6h30 is a dual triode? Here each half is forming a differential pair? Or am I way off? Suggestion for a ps for the B+? I am going to change the front end a little but I don't think that will matter much here. Thanks for any and all help
schematic

One other question, I have not been able to find out what this is. I got it from a site in China.
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Old 7th September 2006, 04:04 AM   #2
lndm is offline lndm  Australia
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The 6H30 is a dual triode. This appears to be a balanced stage. The 6H30's appear to be connected as buffers (with no gain), separately buffering each phase of the balanced signal.

Guessing based on the fets, it may be a mic pre. Are you still looking at designs?
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Old 7th September 2006, 04:10 AM   #3
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Well I could build something else. I chose this based on the fact that I have most of the parts and because it is balanced. Balanced tube preamps seem to be in short supply and I don't know enough to desing one myself. I also have been building some simple preamps with jfets. So this seemed to fit in with what I have been working around.
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Old 7th September 2006, 06:50 AM   #4
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The J-Fets are running as a diff pair with a J-Fet Current Source in the tail for good balance . The 6H30 are running as cathode follower buffers to give low output impedance. I doubt that it will impart much "tube-e-ness" to the sound but why not give it a go and see for yourself.
If you are doing this as an "experiment" and a "learning experience" rather than as a final "work of art product" then allow plenty of chassis space and a big enough power supply that you can expand your experiment to something like this if you want.
http://www.vacuumstate.com/schematics/rtp3c_s.gif
The link is to a full balanced phono stage plus line stage
Cheers,
Ian

P.S.
For learning:
Morgan Jones "Valve Amplifiers"
Allan Wright "Tube Preamp Cookbook" (the link shows one of the designs from that cookbook)
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Old 7th September 2006, 12:35 PM   #5
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It is much more a experiment than a end all be all amp. It has tubes and it is simple. Plus the only thing I should need is a transformer. I am sure I will have more questions.

Thanks.
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