I just bougth a marantz cdr 300 cd recorder,everything seems to be working fine, but I'm not able to listen what I just recordered on any other cd player.Marantz cd 72 mr 2020.Thanks

Hi,
It sounds like you haven't followed the last step to the burning procedure. All you need to do once you've completed burning your disc is to Finalize the disc. Read below why you need to finalize as well as the steps to follow in order to finalize the disc.
Hope this helps ;)
How to Finalize Finalizing is writing the TOC (table of contents) on a disc so a CD player can recognize the number of tracks, the total time for each track, and their location on the disc. A recorded disc must be finalized to playback on a standard CD player. Once finalized a CD-R disc can be played on CD players that support CD-R playback. CD-RW discs can only be played on CD players that support CD-RW playback. Consult your CD player owner's manual to confirm supported formats. Finalizing is necessary to: • be able to play a recorded CD-R or CD-RW disc on a CD player • prevent further recording on a disc • avoid erasing tracks on a CD-RW disc • record text information onto a disc you record Notes: • A finalized CD-R disc can never be recorded onto again. • A finalized CD-RW disc can be unfinalized for more recording. • The CDR300 can play back unfinalized CD-R or CD-RW discs. • SYNC REC+FINAL mode automatically finalizes.
Here are the steps in order to Finalize your disk
1 Push Stop. The display shows the number of tracks and their total playing time. 2 Push FINALIZE. FINALIZE is displayed for about 3 seconds.