Simplistic NJFET RIAA

[Salas]

Also:

[Zoran]

It seems to be good?
pretty flat
I saw that You are used inverse Hagg. cir for sim.
(1.91K on gif...)
*
add Cable capacitance at the input,
and output and input resistor of the next stage on out...
cheers
*

[Zoran]

use real value of output not 1Meg but 10K
with Ccable of 100-150p
input is 47K not 560 ohms
or 100 for MC
also 100-150pF of Cable
(10uF Cout)

[Salas]

I would terminate with 560R to 1K2 if I had a 60R Zo cartridge. The Hagerman assumes 60R Zo. That is arbitrary. We are free to choose how to terminate any given cartridge. I can load it down with 100R and sim for less effective input voltage (the 0.25mV will halve with 60R Zo on 100R load) and 150pF input cable parasitic. The output I have tested low before, I have a buffer for that, no worries. The 1 Meg is there to get shunted by loads, but to keep the output cap static happy when not.
Anyway, here it is as you wanted to see it. Still solid. ...In theory.

*For anybody who might be attempting this before I get a chance, be sure to remember that the gain is based on 10-12mA Idss 2SK170BL @ 9V

[jackinnj]

Try adjusting the value of R17 -- or eliminating it -- I am getting quite different results in the Salas RIAA than you are deriving.

[Salas]

Different software, and models probably. Show your best Bode and RIAA values. In case it deviates in practice we should be having a plan B.

[Salas]

Originally posted by jackinnj
Try adjusting the value of R17 -- or eliminating it -- I am getting quite different results in the Salas RIAA than you are deriving.

R17 eliminated...

[jackinnj]

Originally posted by salas
Different software, and models probably. Show your best Bode and RIAA values. In case it deviates in practice we should be having a plan B.

I use LaPlace transform with values of 3180, 318 and 75uS -- Walt Jung shows how to do this in his text "Op Amp Handbook". What I saw with R17 was a pretty serious peaking in the ultrasonic region. If you hunt around on the ADI website you can find that chapters of the book are archived.

Dennis Colin in his article "Tweaking the Passive Inverse RIAA Network" assumes the 3.18 uS compensation (Audio Xpress August 2007, a PDF can be found on the AX website http://www.audioxpress.com/magsdirx/.../colin2808.pdf --

You might want to adjust the values of the Inverse RIAA net you are using, Denis has them acurate for a micro-deci-Bel ! But regardless, the values are going to be different than those derived using the LaPlace transform.

[Salas]

So it will be better off without R17 and it will be OK in general, according to your simulations? How high did you get the peaking? Miller does not allow very high with this open loop circuit.

[jackinnj]

LaPlace --

For the enhanced RIAA include in the numerator 3.18 uS

.PARAM T1 = {3180}
.PARAM T2 = {318}
.PARAM T3 = {75}
.PARAM T4 = {3.18} ;Reference Enhanced RIAA Constant
ERIAA 5 0 LAPLACE {ENORM*V(1)}={((1+(T2*1E-6)*S)*(1+T4*1E-6)*S)))/((1+(T1*1E-6)*S)*(1+(T3*1E-6)*S))}

Edit -- there appears to be one wrong number in Table 1 of the article.