What am I missing using a 20 year old CD player??

An awful lot. As good as my JVC 1010 was for many years, I couldn't believe the improvement when I got an Arcam CD 23. I then went to a Sony SACD XA 9000 ES player and there was a small but not insignificant improvement on CD there also.

you might be very suprised when you hear very little diffence compared to your Sonographe SD-1. Many of the older players were very well built compared to many modern gear. Case in point I still have an older player the JVC 1050tn player and it still sounds great.

CD players improved up to the mid 90's but D/A improvements started to hit diminishing returns after this as they were so good, IMHO. The failure of SACD shows that the ordinary CD player is darn good - so much so that most consumers see absolutely no need for an improvement from something such as SACD.

Just want to throw this out there to everyone:
How about skipping issues??
I have an older CD player too..a predecesor to the SONY ES line before they had ES, and what I love about it, and the reason I still use it, is that it does not skip AT ALL !!
It will still play virtually any disc no matter how scratched or in bad shape the disc is. In the 12 years I have had this player, I have heard it skip maybe three times! AMAZING...what frustrates me now is how new equipment..more expensive gear, skips a lot more often.

I have no idea why this is, I am not an engineer, but I still use my old CD players just for this reason!

Your great experience with Conrad Johnson gear echoed mine. I enjoyed the troublefree 'dual mono' Motif MC7 preamp and eventually had it upgaded by "Bill Thalmann" of MUSIC TECHNOLOGY.COM. Wow! He brought it to another level of musical enjoyment(cleaner more dynamic,etc) very reasonably. I'd suggest a quick call to him about your machine whether to upgrade or sell. I doubt you can upgrade the power cord(ie detachable) without a mod-and I'm not sure it's worth doing; However you haven't mentioned any power isolation or conditioning. You will be pleasantly surprised at the "new" sound after simply adding isolation. Probably "most" of the digital sound you're complaining of comes from noise contamination between digital & analog. Before doing anything else you should audition a few power conditioners, "at least" to isolate the digital, but try it different ways in your system. You could find you're still happy with the Sonographe and if not you'veat least experienced what conditioning & isolation does for your system. If you want a change I believe you'll find a used Denon 3910 a very exciting machine that could be resold w/o loss if desired. It will also allow you to try some power cords-I'd suggest a basic MIT Shotgun AC1 or preferably AC2.
Their cords enhanced my listening all round. If you contact BILL THALMANN say hi from Pete who had him do the MC7. He'll likely remember, and he's a great guy to know in this business. Happy listening.