Looks like JoeE SP9 and I are going to do a little arm wrestling over terminology here. I think we agree, generally, though. RCA plugs are standard connectors for most HIFI gear, and for all phonographs. This is because the RCA plug and jack combination provides shielding all the way aroind the center, signal carrying conductors without interruption.
You may have a "phono" input on your Sylvania, but it is a "ceramic phono" input. A "ceramic phono" input will be designed to take a relatively high voltage, in the .3 to .5 volt range, (300 to 500 millivolts, or 300 to 500 thousandths of a volt), and it will have a very high input impedance, or about 1 megohm (That's one million ohms). A typical line input will take the same voltage, but will have a lower imedance, or about 200K (200 thousand) ohms. A line input is not designed for a cartridge, but for an electrical signal from a CD player, a tuner or a tape deck. It will not work with a ceramic cartridge. It will reduce the bass.
Anyway, this is because the Sylvania was designed for this record player or a similar one. It will have a different input circuit.
Your new amplifier may very well work with the magnetic cartridge that you have just purchased. Inputs for a magnetic phono suitable for your cartridge will mostly be labelled "phono." Sometimes they will be labelled "magnetic phono" or "RIAA phono." Sometimes they will be labelled "moving magnet" or "moving coil."
If the new amp is from a HIFI manufacturer, say Dyna, Pioneer, Yamaha, Fisher, Leak, Quad, etc. chances are that an input labelled "phono" input is designed for a moving magnet cartridge and has the proper equalization and impedance for your ADC cart. If it is from a home phono manufacturer such as Sylvania, RCA, Magnavox, Zenith, etc, you might find that an input labelled "phono" will be set up for a ceramic phono. For that situation, you will need the preamp described.
Anyway, you can always just stick the new record player into the input labelled "phono" on the nerw amp and see if it works. You won't hurt anything. The worst that will happen is that it will be low in volume and have no bass like what you have now. If that's the case, just buy the magnetic phono preamp and you will be cured.
You should also check the needle on the ADC cartridge, and if you don't know where it came from or how old it is, you might want to replace it. Chances are that http://www.needledoctor.com
will have a stylus(needle) listed for it. You can Google the replacement number and maybe get a better price from a different vendor. Worth a try.
And here's another too long post from the old smart-a**. I think it was JoeE that said that all guys named Joe have this characteristic.
Good luck from the old guy named Joe.