• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Red imP(asse)

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Pasting together 2 of SY's designs -- since I have the imPASSe pcbs. The compensation is only approximate -- will have to put it on the "bodeelizer" when I get it soldered up:

An externally hosted image should be here but it was not working when we last tested it.


For clarity, some of the resistors are not shown. The LED in the cathode of the first stage is replaced with a 1K resistor for connection to the feedback network.
 
While we're at it, here's a better SPICE model for the 6SL7 -- can be improved but it more closely represents the data sheet:

.subckt 6SL7GT_J__TUBES__1 1 2 3
+Params: MU=77 KP=550 KVB=300 EX=1.18 KG1=1220
E1 7 0 Value = {(V(1,3)/KP)*LN((1+ EXP((KP/MU) + ((KP*(V(2,3)+.5))/(SQRT(KVB+V(1,3)*V(1,3)))))))}
RE1 7 0 1e12
G1 1 3 VALUE = {(((V(7))^EX)/KG1)*(1+SGN(V(7)))}
RCP 1 3 1e12
C1 2 3 2.3e-12
C2 1 2 2.1e-12
C3 1 3 0.7e-12
R1 2 5 2000
D3 5 3 dx
.model dx d(is=1e-09 rs=1 cjo=10e-12)
.ends
 
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