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Re:: Casio CT-6000: has it phase distortion? (main ICs?)
2014-08-08 by cowindler01@...
The Music LSI "NEC D932G" (64 pin zigzag DIL) was only used in Casio CT-6000 and likely the direct successor of D931C. It communicates with the CPU through 8 input and 4 output pins, has 17 bit audio and additional 14 control output pins for external filters, mixing ratio, stereo chorus and the like. The velocity sensitive highend midi keyboard contains 3 of these unique sound ICs; each is wired to an own DAC with different fixed analogue filter (each 3 control lines). The outputs are mixed; in chord mode the 3rd sound IC is used for chord only, else all 3 are layered as main voice. I suspect that in classic Consonant-Vowel manner the mixing ratio between multiple differently filtered sound ICs changes with keyboard velocity. The existence of so many switchable filters seems to disprove the rumour that CT-6000 was a secret unofficial first phase distortion instrument. The high timbre quality rather results of 17 bit DAC resolution and complex analogue post-processing through filters and a costly 3 line stereo chorus. Even its unique percussion generator IC HD61701 (54 pin SMD) routes some outputs through 2 external filters to shape timbres.