Purple Audio Moiyn 500 Series Summing Amplifier For Purple’s Sweet Ten Rack users, check out this all-new 500-series summing amplifier solution! Differential summing amplifier Custom hexifiliar output transformer 2x KDJ3 summing amplifiers 2x KDJ4 output amplifiers Discrete signal path 15K drop on resistors Requires Purple Audio Sweet Ten Rack (sold separately)