Vendetta Research SCP-2A

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You can remove both a 10 ohm resistor and a 200 ohm variable resistor. Put 1k resistor
 

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Second stage ( bass boost stage) op-amps has two 18V zeners. First stage servo op-amps are powered directly from local regulators adjusted to 19.5V.

Hi Kamis,

I have done another simulation with some groundings so that the input jfets are as close as possible to the original fets (1 x K147 / J72 = 2.5 x K170 / J74) and included the 18 volts of power for the Opamp. Everything went very well.
 

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Hi Kamis,

I have done another simulation with some groundings so that the input jfets are as close as possible to the original fets (1 x K147 / J72 = 2.5 x K170 / J74) and included the 18 volts of power for the Opamp. Everything went very well.

I wish preamp to be faithful to original, without additional parts. And why six regulator transistors in parallel? Two transistors work perfectly without too much heat.
 
I wish preamp to be faithful to original, without additional parts. And why six regulator transistors in parallel? Two transistors work perfectly without too much heat.

Yes, you're right !
The six fets regulators were simulation purpose only. I know less works.
The main modification is on the input. There, I wanna keep the same input capacitance and same noise level ( look at and compare the datasheets between both fets, original and actual ). The total transconductance has increased. I have decrease drain resistors values without problem.
Look, unfortunately the original fets is almost impossible to get. So, I did that changes trying to get the same results or almost.
The fets of simulation have 16.4mA of Idss.
Idon' t know if Linearsystems has LSK170/LSJ74 with this Idss. If yes, I think is possible someone to build that simulation version of MC pre-preamp and share results with us.
I like very much this circuit for a lot of reasons and today I have a real intention to build one but I need to prepare others things before.
Regards,
eD
 
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