I've found the vias that I need to get DSD output from my Philips 963sa. I have the Digital ground, DSDright and DSDLeft all pretty close to each other at the top of the board. The DSDCLK that is up by the top of the board where the other pads has 75ohms of resistance between it and the DSDCLK input of the AD1955. Would it be OK to work from this close by DSDCLK pad for my DSD output into the Buffalo II, or should I go with the much farther away pad that is close to the AD1955? The pin for DSDRight (pin 8) doesn't have a pad close to the chip, or I could pull everything from right by the AD1955.
Basically I'm wondering if a 75ohm resistance between the two clock inputs is a good or a bad thing. If it is good to have that between the two inputs, then I'm in luck and have all the pads I need fairly close together.
Thank you for taking the time to read this. Once I get the DSD output up and running, I will post pics so others can see how it can be done. I bet a lot of people have this player sitting around.
Thank you for reading my post.
Aaron.
Basically I'm wondering if a 75ohm resistance between the two clock inputs is a good or a bad thing. If it is good to have that between the two inputs, then I'm in luck and have all the pads I need fairly close together.
Thank you for taking the time to read this. Once I get the DSD output up and running, I will post pics so others can see how it can be done. I bet a lot of people have this player sitting around.
Thank you for reading my post.
Aaron.
High speed digital signals, especially clocks, are often series terminated. This usually means a low value resistor, of maybe 22 to 100 ohms, depending on the characteristic impedance of the PCB traces and the nature of the load, is placed in series with the signal at the transmitting end. I would recommand finding the source of the clock, solder a resistor to the source as close as possible (< 1 cm) and take the signal from the resistor. If you need to carry the signal a few centimeters, try using a twisted pair scavenged from a CAT6 or CAT5e cable. If you have a high speed scope (>= 100 MHz) you can probably play with the resistor value to get as clean of a signal as possible at the terminating end (look for clean, fast edges and as little ringing as possible; you really don't want garbage during the transition between levels). It doesn't matter much what it looks like at the transmitter. Make sure that you also 'scope the clock at the AD1955 input too... make sure you haven't messed it up by adding another load to the clock source.
Take a look at http://www.pericom.com/pdf/applications/AB023.pdf too. Or google "series parallel thevenin termination".
Take a look at http://www.pericom.com/pdf/applications/AB023.pdf too. Or google "series parallel thevenin termination".
Got it working, sounds good so far, but don't know how it would measure.
Thank you so much for taking the time to reply. I will read the article you linked soon. I am at the point where I am getting a bit over my head, but I enjoy the process of discovery, and accept that I might break something in that process.
I don't have a 'scope, but I think I am beginning to need one for the kind of work I am doing. I pulled the AD1955 DAC with ChipQuik, great stuff if anyone needs to pull a SMD mounted chip. I thought I could solder wires to the traces for the DAC, but that was way too difficult. I found tiny little vias that were hooked up to the DSD Clock (75ohms to the input at AD1955), DSDRight, and DSDLeft. With a good bit of flux I was able to solder some wires to the pads. I also found a larger pad that had the Digital Ground, and used that.
I wound up using some MIL spec silver coated teflon wire that is very thin (24awg, I think), because the CAT5e I had stripped was more difficult to work with, and having cables connected to each other tightly like that would make the strain relief difficult at first. I hot glued it like crazy after soldering the wires down (flux was a big help). I braided the three Clock, Right and Left wires together since they were fairly close to give it a bit of strain relief (waited until the mountain of hot glue dried).
Now I have the 4 wires hooked up to a RJ45 chassis mount connector that mounts from the rear. I hooked it up so that all the striped wires plus brown go to the ground, orange is DSDclock, blue is DSDleft, and green is DSDright.
I set up a short CAT5E cable so I could hook it into my Buffalo, set the Buffalo for DSD input, and plugged it into the RJ45 and.....it works! Of course, I have it going through an RJ45 connector and about 2 feet of CAT5E, plus the wires I soldered to the board and the RJ45, which I cut all the same length to try to avoid problems, so it might not be the best possible connection, but it does play music, and so far it sounds good (but I haven't gotten too far into examining the sound yet).
I am going to keep an eye out for an oscilloscope so I can have better measurements of my equipment. I have been sifting through the service manual (I should print it out to get a better handle on it), and I haven't been able to determine exactly the path of the DSD data input to the AD1955. If I did, I might be able to pick it up at an earlier point on the board.
I wish I had taken pictures before I glued it so that people could see how I did it in case they want to try. I'll try to check this thread every once in a while in case anyone else has a 963SA that they want to get DSD output from and they need help and are willing to risk losing the player to experimentation.
Here's a quick and dirty run down of how to find the DSD pads on a Phillips 963SA with a DMM.
Turn the player so that the outputs are facing you. Find the AD1955 DAC. Google and download the manual for the DAC. It has the pin diagram for the chip. Pin 1 is marked with a little dot on the chip, in the lower left hand corner. Pin 6 is the Clock, Pin 7 is DSDLeftData, Pin 8 is DSDRightData. Use your meter and check the tiny little metal points that are on the board above the chip, close to the edge of the AV board, to the right of the second ribbon cable. You will find a connection for all three up there. Then search for a connection to digital ground, which is the pin directly above Pin 1, Pin 28. There is a good one that is in a series of 4 solder pads next to the ribbon cable. These are the places I used. There could be better ones, but I haven't found them yet.
Best,
Aaron.
Thank you so much for taking the time to reply. I will read the article you linked soon. I am at the point where I am getting a bit over my head, but I enjoy the process of discovery, and accept that I might break something in that process.
I don't have a 'scope, but I think I am beginning to need one for the kind of work I am doing. I pulled the AD1955 DAC with ChipQuik, great stuff if anyone needs to pull a SMD mounted chip. I thought I could solder wires to the traces for the DAC, but that was way too difficult. I found tiny little vias that were hooked up to the DSD Clock (75ohms to the input at AD1955), DSDRight, and DSDLeft. With a good bit of flux I was able to solder some wires to the pads. I also found a larger pad that had the Digital Ground, and used that.
I wound up using some MIL spec silver coated teflon wire that is very thin (24awg, I think), because the CAT5e I had stripped was more difficult to work with, and having cables connected to each other tightly like that would make the strain relief difficult at first. I hot glued it like crazy after soldering the wires down (flux was a big help). I braided the three Clock, Right and Left wires together since they were fairly close to give it a bit of strain relief (waited until the mountain of hot glue dried).
Now I have the 4 wires hooked up to a RJ45 chassis mount connector that mounts from the rear. I hooked it up so that all the striped wires plus brown go to the ground, orange is DSDclock, blue is DSDleft, and green is DSDright.
I set up a short CAT5E cable so I could hook it into my Buffalo, set the Buffalo for DSD input, and plugged it into the RJ45 and.....it works! Of course, I have it going through an RJ45 connector and about 2 feet of CAT5E, plus the wires I soldered to the board and the RJ45, which I cut all the same length to try to avoid problems, so it might not be the best possible connection, but it does play music, and so far it sounds good (but I haven't gotten too far into examining the sound yet).
I am going to keep an eye out for an oscilloscope so I can have better measurements of my equipment. I have been sifting through the service manual (I should print it out to get a better handle on it), and I haven't been able to determine exactly the path of the DSD data input to the AD1955. If I did, I might be able to pick it up at an earlier point on the board.
I wish I had taken pictures before I glued it so that people could see how I did it in case they want to try. I'll try to check this thread every once in a while in case anyone else has a 963SA that they want to get DSD output from and they need help and are willing to risk losing the player to experimentation.
Here's a quick and dirty run down of how to find the DSD pads on a Phillips 963SA with a DMM.
Turn the player so that the outputs are facing you. Find the AD1955 DAC. Google and download the manual for the DAC. It has the pin diagram for the chip. Pin 1 is marked with a little dot on the chip, in the lower left hand corner. Pin 6 is the Clock, Pin 7 is DSDLeftData, Pin 8 is DSDRightData. Use your meter and check the tiny little metal points that are on the board above the chip, close to the edge of the AV board, to the right of the second ribbon cable. You will find a connection for all three up there. Then search for a connection to digital ground, which is the pin directly above Pin 1, Pin 28. There is a good one that is in a series of 4 solder pads next to the ribbon cable. These are the places I used. There could be better ones, but I haven't found them yet.
Best,
Aaron.
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