Nagra HD Preamp and Nagra IV-S Tube February 28, 2019 Matej Isak René Laflamme (Nagra/2xHD) in action! Nagra IV-S Tube, first test with direct out from the Stereo head. Check out the Nagra HD Preamp in action!www.2xhd.com www.nagraaudio-hd.com