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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: What PP amp to build? posted by speleo on April 2, 2007 at 06:47:34:
find an amp with the 6sj7as input :6267 values are also close.Float the 6BL7 heater if you need to: it is high 200v so ok.
6SJ7 dc into grid of 6BL7 for general values see vinnie 845 driver.
just add resistor under cathode to bring it up= (anode voltage of 6sj7+ 15volts bias of 6bl7) divided by currrent of 6bl7 (probably 22ma is good)
then put same resistor on top of cathode of 6bl7. this creates your phase inverter a la' dynaco/hafler. then cathode & anode film/foil cap coupled to grids of kt77. then you need an overall feedback path which is the real downside of the hafler path.
williamson is worse: remember this.One solution for no overall feedback path. Use phase inverter first, say 6bl7: great tube for this.
run into 6SL7 dc into KT77's grid. To do this you must float the cathodes of the KT77's up to the 6SL7 cathode ouput voltage.
Then run a single resistor unbypassed this means straight into the cathodes of the 6SL7's so that you get degenerative feedback from the anodes of the kt77's to the grids of the KT77's. you probably will get enough feedback that you will not have to use overall loop feedback, assuming you are running the kt77's UL.
So, have fun: also I assume now that you want already drawn tested schematic. I am being hard on you: I am sorry. It is just that this is a genuinely insightful answer to your question (and will probably build a better amp from your parts.)
Big Peace,
-3db
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Follow Ups
- Use 6sj7gt into 6BL7 into Kt77's all octal. - -3db 18:11:22 04/09/07 (0)
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