I'm confuse Do i need a dac for my cd player ?

Do i need a digital analog converter to my Arcam cd73?
If i will add my Sigma (tube)digital analog converter to my sytem,is this means sound improvement or just waste?
System included are Cary slm-100 amp and Cary spl-88 pre-amp.Listen mostly soft jazz and rock.Thanks all of you in advance for any information you can give.