Another cheap 300B !

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IslandPink
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#1 Another cheap 300B !

Post by IslandPink »

http://vinylsavor.blogspot.com/2019/09/ ... -6kn6.html
Fairly hefty filament voltage , but fun.
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Paul Barker
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#2 Re: Another cheap 300B !

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I looked and from Thomases answers to questions he gave the volts/current/grid numbers, so I wrote them on the curves he provided. If I had a printer I would have printed on paper then guesstimated the higher voltages not provided using 2nd harmonic pinching as voltage increases with a best guess. One of the books I have provides a distortion ruler you lay on the curves so you could apply that in revers to create the curves.

But first you’d have to build it best endeavour, measure distortion 2nd only and apply the ruler at that distortion to drawer the curves. I don’t have a working curve tracer.

So it’s 30 watts p dis. Loads of current and or voltage.

Well I have the 335v b+ earmarked for Raymond Bates, which is off board, so easy to plug into any other signal section.

So I’d start at 335v @ 0.08 quiescent to evaluate. I have compactron 12 pin bases, but will need to order 6kn6’s. Out of work through illness so no ordering; patience! Sit on buy it now finger!!!

But nice to experiment with more of these indirect valves repurposed. The screen grid as usual limits volts so it’ll go to ground with suppresser which from diagram is like true el34/84 not internally connected.

If only I knew which book the distortion ruler is in. Probably Fritz.
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ed
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#3 Re: Another cheap 300B !

Post by ed »

Paul Barker wrote: Mon Mar 07, 2022 11:35 am
If only I knew which book the distortion ruler is in. Probably Fritz.
I bit!

4th ed 13.3 part iv?
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Paul Barker
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#4 Re: Another cheap 300B !

Post by Paul Barker »

Thanks Ed
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IslandPink
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#5 Re: Another cheap 300B !

Post by IslandPink »

I can't claim it'll sound as good as a DHT, but it looks decent and I assume Thomas likes it enough to report about, so it must meet a decent standard of quality.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
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