The planar v72 from scratch

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solkatten

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Yep Im ok with 0,05 % figure, mostly H2 just need to fix the high end ringing…
I must say Im impressed with clearity and details that the 6s17-v brings. Its very non microphonic and silence… with a -12 dB pad on the output gain controll work fine👍
 

gyraf

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Do we know anything about it's service life expectancy? That's where a good deal of the mil-spec tubes fall short, because they were made for utmost reliability but for a very short lifespan..

/Jakob E.
 

solkatten

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Do we know anything about it's service life expectancy? That's where a good deal of the mil-spec tubes fall short, because they were made for utmost reliability but for a very short lifespan..

/Jakob E.
5000 hours in the nose cone of soviet Nukes up to 500g of acceleration
 

solkatten

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Here is the input stage + LP and HP. Just a bit of fixed feedback, to kick down gain a notch, keeping THD low and input impedance high...
The pentode line stage (E81L) is a modded version of Jonte Knif Therapy pre... To build this stage was the reason I bought the LL1671 trafo in the first place...

On the input I going to try my home brewed 1:4,5 toroidal IPT...

 

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solkatten

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Its up and running...
I settle on the grid leak scheme, for optimal noise performance... 22K x2 substitutes the 6k8 x2, wich delivers the feedback and provide the grid leak bias for the 6s17k-v at 2,5ma. Cathode is now grounded. Theres DC on the vol. pot so I haft to have seperate C for feedback and coupling to the next stage... And now there is a slight roll off above 10K, I probably haft to remove the zobel network on the IPT after the transformer change...

Edit: The slight roll of above 10K is due to miller c in the line stage (E81L) in triode mode, in UL and pentode mode freq. response is flat like a panncake...

The E81L idle at 15ma at ca 180V.
 
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