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Topics - a.narloch

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Preamps and Effects / Ampeg SVT- FET Version, need help
« on: May 28, 2009, 06:31:50 PM »
Hi everyone, newbie here  :)

I got few questions about Ampeg SVT preamp on FETs.
I try to build cheaper version of Ampeg tube amp so I decide to use fets in preamp and mosfets in poweramp.
Poweramp is finish and it works so now i must build the preamp :)
Today I draw schematics, i based on schematics:

Ampeg PortaFlex SB-12 draw by Joe Piazza:
Ampeg SVT draw by Joe Piazza:    

and articles:

I compare schematics of Ampeg PortaFlex SB-12 and Flipster and i found analogy and I use it too draw schematic of SVT.
EQ in both models (svt & portaflex) is the same so I copy eq from Flipster and I use it in my version of SVT.
In orginal SVT they use a 12dw7 tube. I read that it is a dual triode with one half from 12ax7 and second half from 12au7.
So I use J201 and MPF102 transistors, J201 I put in place of 12ax7 becouse it has a more gain
and MPF102 a put in place of 12au7 becouse it has less gain :) In nearest future I wanna project PCB but before I do it i wanna now that schematic is correct. I be very thankful if somebody check the schematic. -> my schematic

best regards

P.S sorry if my english sucks, I hope You understand me :) and I understand You :P

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