  We show that the numerical renormalization group (NRG) is a viable multi-band
impurity solver for Dynamical Mean Field Theory (DMFT), offering unprecedent
real-frequency spectral resolution at arbitrarily low energies and
temperatures. We use it to obtain a numerically exact DMFT solution to the
Hund's metal problem for a three-orbital model with filling factor $n_d=2$. The
ground state is a Fermi liquid. The one-particle spectral function has a strong
particle-hole asymmetry, with a clear apparent power law for positive
frequencies only. With increasing temperature it shows a coherence-incoherence
crossover with spectral weight transfered from low to high energies and evolves
qualitatively differently from a doped Mott insulator. The spin and orbital
spectral functions show "spin-orbital separation": spin screening occurs at
much lower energies than orbital screening. The renormalization group flows
clearly reveal the relevant physics at all energy scales.
