thatsright
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- #21
That last comment, emboldened, might be wrong -- my bad. But introspect for yourselves and comment as necessary.I have the Nak OMS-4/40 SM. It uses two 74-series ICs to split the data signal for the two PCM54s.
And yes: The PCM54/55/56 do indeed require:
"A Sample/Hold Amplifier (Deglitcher) is Required at the Digital-to-Analog Output for Both Left and Right Channels."
From:
The Nak seem to do this purely discretely (see schematic, p. 36).
In the Nak OMS-4/40, there is a logic splitter after that mysterious 6352 DF. I think it splits the data line into L and R. One for each of the two PCM54s. The 6352 also has the necessary multiple data-line outputs that "Y-off" to both the two 74-based splitter and the two PCM54 dacs. [Actually, several decoders and DF chips from that era had multiple data lines, such as Sony's CX23035 https://vasiltech.narod.ru/files/CX23035.pdf ].
However, because the split was done before the PCM54's, there is no longer a need for s/h switching following the dacs.
Sony (CDP-c-505) used a dual PCM56's , but with a much simpler strategy. The '56 had the tradit three I2S pins . The CXD2551 DF splits out separate DATA L and DATA R on dedicated pins (so the DATA does not need to be split externally; however, WS, or LE, does need to be switched if two "mono" DACs follow] See attachments. Note also that the PCM56 no longer uses multiple data lines.
But '53-'56 all needed analog switching for stereo operation if only a single PCM53-56 was utilized.
BOTTOM LINE: For PCM53-56 series, if you split the DATA signal into separate L and R, using appropriate glue logic, you just need the std. I/V and LPF stages after the DACs.
Aside from the S/N advantages of using two DAC chips, I'm not sure which "sounds better"? Digital switching (splitting) of L and R before the two DACs or analog switching after the single DAC? Which is theoretically faster?
Below is a SM block diag. from a 1986 Sony CDP-65 that uses a single PCM54. Note the analog switching and S/H.
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