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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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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: 211 Amplifier Upgrade – Help with suggestions posted by GORDONny on June 14, 2012 at 15:41:55:
Hey all, I am still in corsica but going home tomorrow... Thanks for the interest in my gadgets.
The first stage is an ordinary "grounded cathode" stage with a negative supply. Ground is a relative thing, that's all... The big advantage of doing it this way is that the ccs position allows the use of a resistor to do the level shifting. I use IXCP depletion mosfets in cascode, but you can use whatever ccs you like. That is an enormous simplification from doing it the other way round. The ccs impedance will be much much higher than any dropping resistor so you lose very little gain. It is safe too, because anything that happens to the 2nd stage will still have the output tube grid just the plate chokes dcr away from ground. The downside is the chronic downside of all dc coupled circuits: complex power supplies.
The power supply circuit is sneaky too. It is a bridge circuit. And, choke input! Chokes work perfectly well with ac on them too... and the ac allows for smaller less gapped chokes. This circuit has negative regulation.
jc
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Follow Ups
- RE: 211 Amplifier Upgrade – Help with suggestions - nanana 09:10:59 06/16/12 (1)
- RE: 211 Amplifier Upgrade – Help with suggestions - GORDONny 10:18:07 06/16/12 (0)
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