Please see http://www.audio-gd.com/R2R/R1/R1EN.htm for full details. This comes with the TCXO upgrade and USB isolator upgrade. Originally I bought this as an R2R-1DAC and bought the upgrade board to transform it into a R1. The only difference is that you can now change the settings by using the buttons instead of having to open up the unit. Updated the firmware, the USB blaster to do this is part of the deal. Due to cosmetic impurities and the DIY I've set the sale price to a sharp €524.99 (ex. paypal fee and shipping).