Fooling a CD-4 demodulator

[kfbkfb]

https://www.allaboutcircuits.com/textbook/direct-current/chpt-13/series-and-parallel-capacitors/^^^
With capacitors, its the reverse: parallel connections result in additive values while series connections result in diminished values.


My 1st turntable, a PE 2040 (made in 1970) didn't have low capacitance cables (I bought a Grado CD-4 cart to use with it).

IIRC, no CD-4 article mentioned trying to lower the total capacitance seen by the CD-4 demod by putting more capacitors in series with the tonearm wiring, has anyone tried this approach - use a tonearm with high capacitance wiring + some capacitors in series at the turntable output and before the CD-4 demod to bring the total capacitance down to ~100pF (the ballpark for CD-4 to work)?


Kirk Bayne

 

[par4ken]

That will do nothing but add series capacitance and thus possibly causing low frequency roll off. Adding capacitors in series with a shunting capacitance will not remove the shunt.

 

[Doug G.]

Like Mother Nature, it's not NICE to fool a CD-4 demodulator!

Doug

 

[ArmyOfQuad]

There's no fooling a demodulator. It will do what it wants to do, no matter how much money you throw at it.

 

[Soundfield]

IIRC, no CD-4 article mentioned trying to lower the total capacitance seen by the CD-4 demod by putting more capacitors in series with the tonearm wiring, has anyone tried this approach - use a tonearm with high capacitance wiring + some capacitors in series at the turntable output and before the CD-4 demod to bring the total capacitance down to ~100pF (the ballpark for CD-4 to work)?
Kirk Bayne

No, you misunderstand. The capacitance of a screened cable appears as parallel component of it's impedance. The equivalent circuit of such a cable is-

You can't negate it by adding more capacitors in series.