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Post by Johnkenn on Jun 21, 2017 9:33:15 GMT -6
I've got the dbox and Svartbox da's. I am trying to send digital signal out from my Apollo so I can hear both the different da's. The SB only has a spdif connection. Same with the dbox (spdif to aes cable). If I were to connect one via the spdif connection on the Apollo and then get an adat to spdif converter for the other, will my Apollo send signal out of both digital outs or is it an either or?
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Post by kcatthedog on Jun 21, 2017 10:00:53 GMT -6
Check you Apollo settings but I think its either or not a combined digital out ?
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Post by jeromemason on Jun 21, 2017 12:56:04 GMT -6
Could the RCA connection not just be split?
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Post by Johnkenn on Jun 21, 2017 12:59:40 GMT -6
Could the RCA connection not just be split? IDK, could it? |
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Post by LesC on Jun 21, 2017 15:35:10 GMT -6
Yes, the SPDIF connection can be split, it should be no problem.
If you use the SPDIF and and ADAT outputs, then I believe you can actually send two different signals to each converter. For example, use one for an analog chain and the other for monitoring. The problem is that ADAT to SPDIF converters are very expensive, at least the ones that I've found. This is what's prevented me from getting a second SvartBox.
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Post by svart on Jun 22, 2017 6:36:34 GMT -6
Split SPDIF..
Most modern SPDIF I/O chips are nothing more than AESiD (single ended 75 ohm AES3) so the outputs are usually a little higher in voltage than SPDIF specification.. However, most receiver ICs are only looking for *edges* to trigger on. They don't really care about the voltage level of the incoming signal as long as it's enough to trigger a 1 or a 0.
That being said, the SPDIF/AESiD spec is defined as 75r, so most systems will have a 75r source impedance (usually set with resistors) and a 75r load (also usually set with a 75r resistor)..
Some folks will know that in transmission line theory, this type of termination scheme forms a resistive/impedance divider, so that the load only sees half the signal amplitude/voltage.
If you split the signal and add another parallel 75r load, then the source now sees 37.5 ohms instead of 75r.. You'd just double terminated your signal.. And the signal will be divided once again, to about 33% of what it originally was.
Some transmitter ICs might be able to handle the extra load, but some will not.
In either case, your signal level reaching the receiver chips might be too low for the receivers to properly decode.
I wouldn't split the SPDIF or AES signal as you might get strange anomalies in the audio and/or bit-level errors in the datastreams that might not be heard right away..
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Post by stratboy on Jun 22, 2017 19:47:51 GMT -6
Yes, the SPDIF connection can be split, it should be no problem. If you use the SPDIF and and ADAT outputs, then I believe you can actually send two different signals to each converter. For example, use one for an analog chain and the other for monitoring. The problem is that ADAT to SPDIF converters are very expensive, at least the ones that I've found. This is what's prevented me from getting a second SvartBox. My Motu 16a can configure its opto I/O as adat or toslink. If the apollo can do the same you can buy toslink opto to coax adapters cheap. That's how I interfaced my Svartbox. |
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Post by jeromemason on Jun 22, 2017 21:10:51 GMT -6
Split SPDIF.. Most modern SPDIF I/O chips are nothing more than AESiD (single ended 75 ohm AES3) so the outputs are usually a little higher in voltage than SPDIF specification.. However, most receiver ICs are only looking for *edges* to trigger on. They don't really care about the voltage level of the incoming signal as long as it's enough to trigger a 1 or a 0. That being said, the SPDIF/AESiD spec is defined as 75r, so most systems will have a 75r source impedance (usually set with resistors) and a 75r load (also usually set with a 75r resistor).. Some folks will know that in transmission line theory, this type of termination scheme forms a resistive/impedance divider, so that the load only sees half the signal amplitude/voltage. If you split the signal and add another parallel 75r load, then the source now sees 37.5 ohms instead of 75r.. You'd just double terminated your signal.. And the signal will be divided once again, to about 33% of what it originally was. Some transmitter ICs might be able to handle the extra load, but some will not. In either case, your signal level reaching the receiver chips might be too low for the receivers to properly decode. I wouldn't split the SPDIF or AES signal as you might get strange anomalies in the audio and/or bit-level errors in the datastreams that might not be heard right away.. If you were to make a buffer, what slew rate would be the minimum? I'm not up to snuff on the digital side. |
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Post by Johnkenn on Jun 22, 2017 21:24:55 GMT -6
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Post by LesC on Jun 23, 2017 0:09:10 GMT -6
Yes, the SPDIF connection can be split, it should be no problem. If you use the SPDIF and and ADAT outputs, then I believe you can actually send two different signals to each converter. For example, use one for an analog chain and the other for monitoring. The problem is that ADAT to SPDIF converters are very expensive, at least the ones that I've found. This is what's prevented me from getting a second SvartBox. My Motu 16a can configure its opto I/O as adat or toslink. If the apollo can do the same you can buy toslink opto to coax adapters cheap. That's how I interfaced my Svartbox. I believe the Apollo is the same as my RME UFX in this regard. Yes, you can use the opto I/O as adat or SPDIF, but you can only have one active SPDIF. So you can use either the RCA SPDIF or the Toslink SPDIF, but not both at the same time for two different signals. I didn't know this for the UFX when I bought it, the fact that it has only one digital receiver is buried deep in the manual and I was very disappointed. When I checked the Apollo manual, it was the same, unless the newer Apollo's have been upgraded with two digital receivers. |
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Post by svart on Jun 23, 2017 11:41:58 GMT -6
Split SPDIF.. Most modern SPDIF I/O chips are nothing more than AESiD (single ended 75 ohm AES3) so the outputs are usually a little higher in voltage than SPDIF specification.. However, most receiver ICs are only looking for *edges* to trigger on. They don't really care about the voltage level of the incoming signal as long as it's enough to trigger a 1 or a 0. That being said, the SPDIF/AESiD spec is defined as 75r, so most systems will have a 75r source impedance (usually set with resistors) and a 75r load (also usually set with a 75r resistor).. Some folks will know that in transmission line theory, this type of termination scheme forms a resistive/impedance divider, so that the load only sees half the signal amplitude/voltage. If you split the signal and add another parallel 75r load, then the source now sees 37.5 ohms instead of 75r.. You'd just double terminated your signal.. And the signal will be divided once again, to about 33% of what it originally was. Some transmitter ICs might be able to handle the extra load, but some will not. In either case, your signal level reaching the receiver chips might be too low for the receivers to properly decode. I wouldn't split the SPDIF or AES signal as you might get strange anomalies in the audio and/or bit-level errors in the datastreams that might not be heard right away.. If you were to make a buffer, what slew rate would be the minimum? I'm not up to snuff on the digital side. Total bitrate for 192K would be around 13MHz. I would select an opamp/buffer that's unity stable and flat to at the very least 25MHz(preferably 50MHz or more) for ample headroom to preserve signal "squareness". Absolute care should be taken for layout and decoupling for least amount of noise. |
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Post by stratboy on Jun 23, 2017 15:22:14 GMT -6
A quick search says you can buy SPDIF splitters inexpensively that operate up to 96 kHz.
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ericn
Temp
Balance Engineer
Posts: 14,934 
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Post by ericn on Jun 23, 2017 16:13:00 GMT -6
A quick search says you can buy SPDIF splitters inexpensively that operate up to 96 kHz. Yes but you have no idea what your getting! |
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Post by Ward on Jun 24, 2017 7:10:36 GMT -6
svart, Just a little side note for info purposes... the ohm symbol can be used in standard typing. ΩIt is achieved by holding down the option key and pressing the 'z' key on any mac.
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Post by svart on Jun 24, 2017 7:13:23 GMT -6
svart, Just a little side note for info purposes... the ohm symbol can be used in standard typing. ΩIt is achieved by holding down the option key and pressing the 'z' key on any mac. I'm not on a Mac.. Also, the electronics industry uses the ohm symbol and "r" interchangeably! |
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Post by Ward on Jun 24, 2017 7:18:56 GMT -6
svart, Just a little side note for info purposes... the ohm symbol can be used in standard typing. ΩIt is achieved by holding down the option key and pressing the 'z' key on any mac. I'm not on a Mac.. Also, the electronics industry uses the ohm symbol and "r" interchangeably! Fair enough. We could start gofundme for you, so you can own a mac.  |
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