Sir Ferrum the 2nd – The Oor fully balanced fully discrete headphone amplifier with class AB power stage [€1'995] is the second product from Ferrum Audio. They'd introduced themselves on the scene with the hybrid Hypsos universal power supply. Naturally that can now be added to maximize Oor's performance. Connectivity consists of RCA/XLR inputs, a 2.5mm DC port and a 4-pin power port when used with Hypsos. Outputs are balanced XLR4 and unbalanced 6.3mm plus RCA/XLR line level. Output power into a 300Ω headphone driven single-ended is 400mW, 1.6W balanced. Input impedance is 94kΩ, Z-out on the RCA/XLR 22/44Ω. Headphones see sub 0.3Ω. Balanced gain can be -4/+6/+16dB or -10/0/+10dB single-ended. Oor measures 21.7 x 20.6 x5cm WxDxH, weighs 1.8kg and the brightness of its back-lit 'Fe' logo can be adjusted. Naturally Oor and Hypsos stack perfectly with identical casings which are sized like a Mytek Brooklyn Bridge.