Part of the very first Kyocera audio components made under Kyocera's own name and not under the recently acquired Cybernet, the latter having been and still being today a major OEM provider. The C-901's back T-Tag confirms the Cybernet origins.
Although originally presented at the Japan Audio Fair of october 1981, the 901 separates were to remain (shortlived) export items as Japan only saw the later 910s : DA-910, C-910, B-910.
Yet, Kyocera's main export target, the US of A, also saw two "10s" : the A-910 (a very beefed up japanese A-710) and the second version of the DA-910. These were however export-only.
Also, later on but in microscopically infinitesimal amounts, the PL-910, the B-910 and C-910.
The C-901 is an all Class A and all DC preamplifier with complementary push-pull Darlington output stages.
Its six inputs are mainly geared up for LPs (two inputs) and sound fiddling wih three-way parametric (?) tone controls (bass,mid and treble) with selectable turnover frequencies for the bass and treble.
The one and only (undated) mini-catalog the C-901 and B-901 were shown in before being replaced by the 910s doesn't say more than this !