We report on an high power ultra-short pulse regenerative Yb:KLuW amplifier based on the thin disk concept. A maximum pulse energy of 571 µJ was extracted at a repetition rate of 20 kHz. Compression of the output pulses resulted in a pulse duration of 197 fs assuming a deconvolution factor of 2.16. At a repetition rate of 125 kHz a maximum average power of 17.9 W was measured in front of the compressor.