CD-4 setup

[atomheartquad]

I just bought a 1975 vintage JVC 4VR-5426X quad receiver.
It sports a CD-4 decoder only (not surprisingly),
My player is a Linn LP-12 with a A/T M-32 moving-coil recently re-tipped with a Garrot Bros parabolic.
It goes through a Ortofon MCA-76 into the JVC.
I've tried three different CD-4 discs so far. With each one the CD-4 "radar" lights up. However, I can not discern much, if any, difference between the front and rear channels.
How do I set it up correctly?

 

[The Quadfather]

See "Calibrating the 4DD5 CD-4 Demodulator" in the "Discrete LP Formats" CD-4 section. It is much the same, especially with JVC gear.

The Quadfather

 

[JAZZIQUAD]

Hello everybody:
Getting the radar light "ON", is enough to know that CD-4 effect is achieved?

THANKS AND GOOD QUADING

JAZZIQUAD

 

[The Quadfather]

Not necessarily. The radar light indicates a phase locked condition. After you adjust the carrier level, if you turn the separation pots down, you will hear only the separation signals in all channels. It will sound like the music, only hollow. If you don't hear it, something's wrong. You bring up the main audio signals by raising the separation pot while listening to the front and rear for the side you are adjusting. When you have matched the level of the main signal to the level of the fixed separation signal, the separation will become apparent. Adjust for the most separation. A CD-4 demodulator actually is two demodulators in one box, totally independent of each other, one for the left side and one for the right. When adjusting one, you should turn the balance controls so that the other one is not heard. The carrier level is adjusted with the separation pots all the way down, (this should be done first) and adjust for the best fidelity. It adjusts both left and right demodulators at once. It is possible to improve fidelity at the expense of separation by adjusting the separation pots above the maximum separation point, but if the demod is working well, you shouldn't have to do this. Sometimes a little bit helps the sound quality without a perceptible reduction in separation, but not too much, and be sure to adjust them both equally. Normally if all is working well, the maximum separation point for the left and the right will be about the same point on the rotation of the pots. If they are signifigantly different, then you may have a bad capacitor somewhere inside. This is rather common with equipment this old, if it has been on the shelf for many years.

The Quadfather