Electronic spectra of C6H are measured in the 18 950-21 100 cm(-1) domain using cavity ring-down spectroscopy of a supersonically expanding hydrocarbon" plasma. In total, 19 (sub)bands of C6H are presented, all probing the vibrational manifold of the B-2 Pi electronically excited state. The assignments are guided by electronic spectra available from matrix isolation work, isotopic substitution experiments (yielding also spectra for (C6H)-C-13 and C6D), predictions from ab initio calculations, and rotational fitting and vibrational contour simulations using the available ground state parameters as obtained from microwave experiments. Besides the O-0(0) origin band, three nondegenerate stretching vibrations along the linear backbone of the C6H molecule are assigned: the v(6) mode associated with the C-C bond vibration and the v(4) and v(3) modes associated with C C triple bonds. For the two lowest v(11) and v(10) bending modes, a Renner-Teller analysis is performed identifying the mu(2)Sigma(v(11)) and both mu(2)Sigma(v(10)) and kappa(2)Sigma(v(10)) components. In addition, two higher lying bending modes are observed, which are tentatively assigned as mu(2)Sigma(v(9)) and mu(2)Sigma(v(8)) levels. In the excitation region below the first nondegenerate vibration (v(6)), some (2)Pi-(2)Pi transitions are observed that are assigned as even combination modes of low-lying bending vibrations. The same holds for a (2)Pi-(2)Pi transition found above the v(6) level. From these spectroscopic data and the vibronic analysis a comprehensive energy level diagram for the B-2 Pi state of C6H is derived and presented.