The changes involve using enhanced parts in critical areas, and fine-tuning the power supply and audio circuits with the purpose of manufacturing a musically fulfilling audio. ・Could We've A fast review of one's development up to now? : これまでの進捗についてざっと説明していただけますか？ Why must I respond to good reviews?  Responding to optimistic reviews https://www.youtube.com/watch?v=vgo6mE8l-9A