The new ST-6X DSP and ST4X DSP for 2021 are now shipping. Power of these new units remains at 100 RMS/Channel @4Ω for the 6X DSP and 65W RMS/Channel @4Ω for the 4X DSP, like the earlier models. But almost everything else about them is new and improved.
First the chassis: The new ST-DSP amps are the first to get the new Studio brushed aluminum finned chassis with thermal controlled fan cooling, to play hard all day long without shutting down. Both the new units have improved high speed (96kHz) digital signal processing for 8 channels to provide processed channels for an extra bass amp with the 6X DSP and for two external amps with the 4X DSP.
Both units have analog input level controls with clip lights for the most accurate input gain setting possible.
Both units have Inputs for optical inputs Digital SPDIF signals. Both units have a Zapco Comm Port to accept the optional Zapco HD-BT module for hi-definition AptX Bluetooth music streaming.