Complex sentence: Another factor is that many cylinders are amateur recordings, while disc recording equipment was simply too expensive for anyone but professional engineers; many extremely poor recordings were made on cylinder, the vast majority of disc recordings were competently recorded.
Split into simpler sentences: Another factor is that many cylinders are amateur recordings, while disc recording equipment was simply too expensive for anyone but professional engineers. In other words, while many extremely poor recordings were made on cylinder, the vast majority of disc recordings were competently recorded.