As hypothesized by the unified competition model (MacWhinney, 2007, 2017, 2021), optimizing training schemes can enhance second language (L2) learning by fostering various protective factors. Under such a framework, the current study focuses on how the familiarity of stimuli will affect learning Chinese phonetic skills in a computer-assisted language learning (CALL) environment. Two training conditions, i.e., training with familiar stimuli from the textbook and unfamiliar stimuli from novelty design, were administered for two groups of learners at American universities, where the classroom instructions were integrated with the Pinyin Tutor--an online spoken Chinese learning platform hosted under TalkBank. The results show that training with novelty stimuli leads to a greater pretest-posttest improvement for intermediate learners, whereas more significant improvement has been observed in training with familiar stimuli among beginning learners. The learning-enhancing power of the Pinyin Tutor is evidenced by the overall significance of the pretest-posttest improvement when consolidating the results of the two conditions. Furthermore, high retention has been demonstrated in all six aspects of the Pinyin knowledge as tested by a three-month-after delayed posttest. These findings tend to endorse a differentiated design of instructional materials with increasing novelty components as the level of L2 learning advances. The overall significant learning-boosting results accredit the design of the Pinyin Tutor, where the technological architecture and algorithms were integrated with psycholinguistic and pedagogical theories. Suggestions and implications for smart learning in general are presented.