807 Tube Triode Connected

Posted on Feb 7, 2014

This is a very nice amplifier design and it is very difficult to improve it. I am glad about the results because that's a very good way to verify my 6DJ8 and 6L6GC Spice models, like I tell you before, the 6L6GC and 807 have very close caracteristics and I get very close results to what you schematic said It is a really good idea to use the 1N5312 and 1N5313 diodes current limiter for the phase splitter current mirror but I don't have their Spice model so I just use the incorporated SIMetrix current source, it does exactly the same thing .

807 Tube Triode Connected
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This is something you should take care of as soon as possible because I know the 6DJ8 are very expensives ... The phase splitter tubes operation point look very good to me so I draw a corrected version with a close operation point for the driver too and a safe Va under 130V. Like you can see, you just have to change the 33K cathode resistors for 18K (R12 and R13) and add two 4,7K 2W (or more) resistor (R23 and R24) and a 47uF filter capacitor (C3) to get a 268,8V supply for the driver tubes. There is just a little bit more distortion this way but nobody will notice any differences for sure. Of course, the distortion is a little bit higher but it is so simple ... However, there is a simple way to improve it, since you already use a current mirror for the splitter cathodes, why not use adjustable ones for their plates, using a good "TO220 high voltage DN2540 power depletion MOSFET" as current limiter ... It improve the distortion and the gain ... It is still very simple and cheap, a DN2540 cost about 2,50$ and last for life but each time you replace your four 6DJ8 drivers, it cost you over 100$, think about it ... A phase splitter like that just need a 200V supply or a little more if necessary so you can get a better filtered supply for this stage. I left a 48V "headroom" for a signal up to 34V RMS plus 15,8V for the DN2540 Vds, it is plenty enough, just provide a very small heatsink for each of them will help if they get...

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it is intresting schematic,i desided build it   Sep 30, 2017

can you help me with parametres of output transformer?

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