Hi there DIYAudioers! My first post, maybe someone can help me with my project.
I've had a Sony 5-CD Changer/Minidisc deck, model MXD-D5C, for many years. The deck was designed to record mixtape-style MDs from the built-in 5-CD changer. However, it was never equipped from the factory with any digital output, only analogue outputs and a TOSLINK digital input. A couple years back I hacked my deck for SPDIF output by opening the cover, tapping the audio board for the CD and MD SPDIF signals and installing digital outputs. The project, perhaps only one step slightly above "ghetto", worked fabulously and was documented at the SonyInsider Forums here: How-to: Sony MXD-D5C Minidisc / CD Changer deck, modified to add TOSlink optical and Coaxial S/PDIF outputs - Technical, Tips, and Tricks - Sony Insider Forums
The original project had a total of 4 SPDIF digital audio outputs when I was finished: One TOSLINK and one Coaxial connection for the CD side of the deck, and one TOSLINK and one Coaxial connection for the MD side of the deck. However, I would have preferred to have had a single set of outputs that output both the CD and MD digital audio through one connector in the same fashion that the deck's analogue outputs do. Unfortunately one cannot simply mix the two signals together down one wire. The CD and MD sides of the deck each had to have discreet, dedicated connections.
I have recently acquired a second, unmodified, MXD-D5C deck and I would like to finally accomplish this goal of having the ability to automatically switch to and send digital audio of either side of the deck out of a single SPDIF connection, in order to streamline the connection to any receiver, DAC, PC, etc. with SPDIF input by means of a single cable.
Inside the machine on the audio board where I tap into the SPDIF signals for each side of the deck, the signal is considered "TTL" or, "Transistor-Transistor Logic", nominally 5 volts, and is considered correct to send to an appropriate Integrated Circuit chip. I expect that there is an inexpensive, readily available IC logic chip that would autoswitch between the CD and MD signals? I am hoping that someone here on this forum might have the expertise to send me in the right direction, as I have zero experience with ICs and I've been trying to wrap my brain around how they work the past several days. I think what I need is a "Latch" circuit that operates on the following logic:
If we assume the following on the appropriate IC Logic Chip
MD = Input A
CD = Input B,
then the Output will normally default to and pass along the signal of Input A (MD).
Therefore, if:
MD playback = Yes, and
CD playback = No, then
IC Output = MD
and if:
MD playback = No, and
CD playback = Yes, then
IC Output = CD
and if:
MD record = Yes, and
CD playback = Yes, then
IC output = MD (effectively operating as record pass-through, and is the only situation where the deck will physically "play" both CD and MD simultaneously)
and if :
MD playback = No, and
CD playback = No, then
IC output = MD (though it doesn't really matter, since the deck is in full-stop anyway).
Am I on the right track? Are the playback (and stop-playback) signals on the TTL SPDIF circuits enough to trigger any change in output on an IC at all? Does any of this make any sense? lol
Thanks!
Camron
I've had a Sony 5-CD Changer/Minidisc deck, model MXD-D5C, for many years. The deck was designed to record mixtape-style MDs from the built-in 5-CD changer. However, it was never equipped from the factory with any digital output, only analogue outputs and a TOSLINK digital input. A couple years back I hacked my deck for SPDIF output by opening the cover, tapping the audio board for the CD and MD SPDIF signals and installing digital outputs. The project, perhaps only one step slightly above "ghetto", worked fabulously and was documented at the SonyInsider Forums here: How-to: Sony MXD-D5C Minidisc / CD Changer deck, modified to add TOSlink optical and Coaxial S/PDIF outputs - Technical, Tips, and Tricks - Sony Insider Forums
The original project had a total of 4 SPDIF digital audio outputs when I was finished: One TOSLINK and one Coaxial connection for the CD side of the deck, and one TOSLINK and one Coaxial connection for the MD side of the deck. However, I would have preferred to have had a single set of outputs that output both the CD and MD digital audio through one connector in the same fashion that the deck's analogue outputs do. Unfortunately one cannot simply mix the two signals together down one wire. The CD and MD sides of the deck each had to have discreet, dedicated connections.
I have recently acquired a second, unmodified, MXD-D5C deck and I would like to finally accomplish this goal of having the ability to automatically switch to and send digital audio of either side of the deck out of a single SPDIF connection, in order to streamline the connection to any receiver, DAC, PC, etc. with SPDIF input by means of a single cable.
Inside the machine on the audio board where I tap into the SPDIF signals for each side of the deck, the signal is considered "TTL" or, "Transistor-Transistor Logic", nominally 5 volts, and is considered correct to send to an appropriate Integrated Circuit chip. I expect that there is an inexpensive, readily available IC logic chip that would autoswitch between the CD and MD signals? I am hoping that someone here on this forum might have the expertise to send me in the right direction, as I have zero experience with ICs and I've been trying to wrap my brain around how they work the past several days. I think what I need is a "Latch" circuit that operates on the following logic:
If we assume the following on the appropriate IC Logic Chip
MD = Input A
CD = Input B,
then the Output will normally default to and pass along the signal of Input A (MD).
Therefore, if:
MD playback = Yes, and
CD playback = No, then
IC Output = MD
and if:
MD playback = No, and
CD playback = Yes, then
IC Output = CD
and if:
MD record = Yes, and
CD playback = Yes, then
IC output = MD (effectively operating as record pass-through, and is the only situation where the deck will physically "play" both CD and MD simultaneously)
and if :
MD playback = No, and
CD playback = No, then
IC output = MD (though it doesn't really matter, since the deck is in full-stop anyway).
Am I on the right track? Are the playback (and stop-playback) signals on the TTL SPDIF circuits enough to trigger any change in output on an IC at all? Does any of this make any sense? lol
Thanks!
Camron
I have been studying the plans for S/PDIF IC autoswitching kindly posted at Craig's digital audio circuits page <meta name="keywords" content="digital audio SPDIF S/PDIF TOSLINK circuits schematics">
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