Simplistic NJFET RIAA

diyAudio Chief Moderator
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R1 values with 1 Tx & 1 reg. are:

Left 2k76
Right 3K06

The 2nd Tx has arrived, do you want the new measurements with 2 Tx & 2 regs.?

If you shut it down and turn both at 3k3, then power up and measure at BC550's collector, what are the voltages? Because you can set the voltages in other ways (by trimming R source) and not create much different custom Riaa networks between channels.
 
diyAudio Chief Moderator
Joined 2002
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Measure some more if you can. You know, if the centre has a +/- 2mA useful spread it will no be much productive for calculating or building around them a general schematic. Comes down to hand picking and adjusting values around each build then. Its they can give more gain around the head amp but I don't know yet if they will be a better thing overall, or it will be just adjusting for them, have to experiment a bit with simulation. Their Ciss could be higher though. Lower noise and THD are possible on the other hand.
 
diyAudio Chief Moderator
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I would just need to add 1-2R to the left channel. That will not give much control if putting in series, if the Shinkoh were 27R we could parallel the trimmers and have control. Or maybe you have LSK that matches better the right for bias on the circuit? That would be easier... Say if you put an LSK that brings around 9.5V to the left, we can keep 3.3k R1 steady and matched between channels so Ricardo can reference. You got them on pins, yes?