Hey Allaround surround:
Distortion toward the end of the record? What kind of cartridge and stylus are you using on your CD-4 setup? Some are not that good, even if they are rated for CD-4. That was a problem I once had. Now, I can't tell the difference between the inside or the outside of the record. They both sound good. I use an Audio Technica Trackmaster 8. That would be the same as the AT331LP. Your Pioneer demodulator is probably OK, but you might need to finely adjust the carrier level. This should be done s-l-o-w-l-y while listening with the separation pots turned down. That gives you only the subcarriers. Listen to only one channel, left or right, at a time. I find this works best with headphones. Adjust for the least distortion. The right point might not be apparent if you are close, but of course, if you hear the distortion all the time, it is probably your stylus. Some turntables don't work good with CD-4. I use a Marantz 6300. It works great. I have found that demodulators vary too. I have two JVC 4DD5 demods. One works great, the other, not as good. But it is probably just a matter of alignment in this case. Getting a CD-4 system to work right can be frustrating at times. If you get the stylus/ cartridge/turntable combo right, you're almost there. Incidently here's my setup, which I know works well.
Marantz 6300 turntable
Audio Technica Trackmaster 8 cartridge with linear contact stylus (this cartridge has been renamed as the AT331LP)
JVC 4DD5 demodulator, well tuned.
Incidently anyone else that has a CD-4 setup that works well, let's get a list going for those who haven't acheived CD-4 subliminance yet. Those would be mostly newbies.
The Quadfather
