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Old 3rd August 2011, 06:52 PM   #11
tinitus is offline tinitus  Europe
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I did notice the cross is missing the ground connection, by nature
and thought it might cause trouble, like you say

and, when reading about 'basics', I'm obviously 'forgetting' the ccs
which, like you say, makes a whole lot of difference getting good balance

thank you

google on LTP ccs, and a lot more to read
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Old 3rd August 2011, 10:03 PM   #12
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Quote:
Originally Posted by smoking-amp View Post
The circuit in post 8 is looking better.............................With the loop gain kept just below unity though, it may bootstrap the input impedance to eliminate loading on the 1st tube stage. Might be an interesting design concept.
oh, ok, great
well, I also thought it looked better

I take it you would suggest something like 2:1 step down
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Old 3rd August 2011, 10:58 PM   #13
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"I take it you would suggest something like 2:1 step down"

Probably more. Lets say a 1 volt change on the output stage grid causes X mA of cathode current increase. (actually 2X for both output tubes together) Working that 2X current backward thru the xfmr from the cathodes to the load resistor for the input stage plate, this needs to produce less than 1 volt change there (and so on the output tube grids too). (or it will oscillate!)
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Last edited by smoking-amp; 3rd August 2011 at 11:05 PM.
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Old 3rd August 2011, 11:18 PM   #14
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Quote:
Originally Posted by smoking-amp View Post
"I take it you would suggest something like 2:1 step down"

Probably more.
well, the good thing is that the 'step down' doesn't affect the gain, as such...right ?

and primary impedance isn't so important as usual with IT....I guess ?
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Old 3rd August 2011, 11:25 PM   #15
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"well, the good thing is that the 'step down' doesn't affect the gain, as such...right ?"

The forward gain is affected a bit by the step-down ratio since it determines how much driver voltage change goes to the cathodes. But the driver plate to output grid voltage stays unity. So driver output transfer is (unity+step-down fraction) to the output stage. Ie, No big deal.
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Old 3rd August 2011, 11:59 PM   #16
tinitus is offline tinitus  Europe
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great
but the cheap IT I was looking at is no good for this
so, I can only think of Lundahl, and is not so cheap
but theory is nice, and cheaper
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Old 4th August 2011, 07:49 PM   #17
tinitus is offline tinitus  Europe
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very good info
thank you for your support
and also a big thank you to all who just looked

cheers
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