by Eric Dube, Rev. 03.13.2003
Overview
I would like to make it perfectly clear that this document is only a "guide" to supplement the installation instructions of the LC Audio ZAPfilter Mk. II in the Rotel RCD-971 CD Player. I take no responsibility for the accuracy or correctness of the information printed within. In addition, due to the complexity of the installation I suggest you don't attempt this unless you are fully confident in your abilities and skills to perform the necessary work. I would also like to make it known that I take no responsibility for any damage incurred to your unit (including harm to yourself or others) while following this guide. Finally, please use common sense and safety equipment such as eye protection when working with any drilling or cutting tools including power drills and Dremel style rotary cutting tools. Also, remember you'll be working with voltage that can harm or even kill you, so make sure the unit is unplugged while attempting this.
While I thoroughly tried to cover every conceivable way of installing this to minimize the work, the confines of the space available (non-existent) within the enclosure made it difficult not to require a substantial amount of cutting and modifying of various components in order to fit the ZAPfilter unit correctly and neatly inside the CD player.
Please read every step very carefully before continuing onto the next step. There is a lot of work involved with each step, so try not to rush through it as you'll be constantly working in close proximity to sensitive components that can be damaged very easily. If you do take the time, I think you will be very pleased with the results. Your work will look very professional, and your friends won't be able to tell the work you've done from the factory.
This guide is geared for people who have thought about attempting the modifications, but didn't know exactly what was involved to do the work. I figure it should take you at least 4-6 hrs worth of time perform the installation if you use this guide. Unfortunately I didn't have any guides to go by when I did this, so it took me considerably longer to get the placement of everything just right.
Finally, I would like to thank Kevin Haskins of DIYCable for taking the time to answer all of my questions regarding the ZAPfilter installation. If you would like to try doing this upgrade, please contact Kevin as he is the LC Audio distributor for North America.
Other Resources
I recommend you print out the following documents as you will need to refer back to them as a guide during the installation process. These documents are specific to the Burr-Brown PCM63P Digital-To-Analog converter used in the Rotel RCD-971 CD player, and contain the wiring diagram and pin-outs to the chip.
Recommend Tools
Additional Supplies
Installation
Step 1: Remove the screws from the bottom sides and back of the Rotel case and remove the top cover. The cover just slides off from the rear of the unit. Next you will need to remove all of the screws holding on the bottom plate. Once that is done, find an area that will allow you to work in comfort as you'll be doing a lot of cutting and drilling.
Step 2: The picture above shows the beginning of the "modifications" required to fit in the ZAPfilter transformer. The space near the front of the unit between the power switch and CD transport assembly are shown. You'll need to remove the unused metal mounting "tab" on the transport towards the top of the picture near the white wires. It serves no purpose, and will give up some much needed space to fit the ZAPfilter transformer. When cutting please be careful as metal "dust" goes everywhere, so try to "tape-off" and cover the other areas of the CD player to prevent the metal from getting in the mechanics of the player.
Next, you'll need to cut the power switch PCB in "half." While there is circuit printing on the side of the P/S PCB you're going to remove, it is not used for anything and was probably taken from one of Rotel's other units in order to save on retooling costs for a new PCB. You can cut off much less than what I did (see picture), but I figured instead of leaving some of the trace-work behind to completely remove all of it. You can just use the cut-off wheel (woven carbon disc) for a Dremel style rotary cutting tool as it will cut through the PCB VERY quickly (so be careful not to make any mistakes - I'll only tell you this once, measure twice and cut once!!!)
Step 3(a): Next you can start to see the opening taking shape as to what you'll be left when your all done cutting. But first, you're going to need to do some cutting to the mounting plate of the Rotel main transformer shown above in the picture. Before you do any cutting, completely REMOVE IT from the metal plate from the unit (including the transformer itself.) There is just too much cutting involved and the metal dust is the worst type you want inside your CD player.
If you notice in the picture both corners of the plate have been cut. Even though only the front corner needs to be cut, I cut the other one to allow for the wires from the ZAPfilter transformer to the ZAPfilter P/S PCB to pass through when the bottom plate is installed. This allows you to permanently keep both ZAPfilter transformer and P/S PCB bolted to the bottom plate without having to remove for servicing. (I'll talk more about this later.)
Step 3(b): Also, take note of the "rounded" corner of the Rotel PCB this will help the wires pass through without snagging on the edge of the PCB. I recommend you also do this as it makes it a lot easier to install the bottom plate if you do this. The wires tend to catch very easily due to the length of the wire you have to work with. You can do this very easily if you use a sanding drum mounted to a rotary tool.
Step 4: This step is probably the hardest thing you're going to have to do for the installation, and you will need to be very careful not to cut the trace-work on the Rotel power supply PCB. If you notice in the picture above the P/S PCB has been trimmed on BOTH sides (the other side is not shown in this picture, so take a look at the next picture to see the other side.) You need to take off approximately 1/4" on each side of the P/S PCB. What you'll end up with is a spot to mount the ZAPfilter P/S PCB between the Rotel P/S PCB and mainboard PCB. To do this you'll need to use the cut-off wheel again, but first you make sure you use a marker and right angle to mark the cut lines. Do the cutting from the BOTTOM of the board so you can see how close you are to the trace-work as you don't want to mess up and cut these.
To make it easier, I suggest you un-solder the incoming AC (mains) wire (black) towards the rear of the unit. Be sure to mark the polarity as the plug is polarized. You should have enough slack in the other wires to safely move the PCB out of the unit for cutting (remember to tape off the player again for cutting to prevent the PCB dust from going everywhere.)
Once you have made the two cuts along the sides of the P/S PCB, you'll need to re-drill the board to mount back to the chassis. You will only have to re-drill the holes for the chassis mounts, not the ones for the stand-offs so leave those alone. Make sure none of the wires are in contact with the chassis, I ended up applying insulated black electricians tape (check the rating of the tape you use to be sure) to the inside of the chassis since the white wire was extremely close to the chassis. I didn't want to take the chance of a short. Finally, you can re-solder the input AC (mains) wire if you removed it, and then see the next picture for what the modified and remounted Rotel P/S PCB should look like.
Step 5: First you probably want tidy up the wiring inside the unit with tie-wraps (see pictures.) It will make it a lot easier to get the wires out of your way as you'll be installing and removing the ZAPfilter P/S PCB and transformer several times to complete this step. Before the ZAPfilter P/S PCB and transformer can be dry mounted, you want to grab a hand file and smooth out any rough edges on the things you've cut so far as well as anything else that might be sharp or cause harm to the wiring.
Now you're ready to dry mount the ZAPfilter P/S PCB and transformer. Here's where you want to make sure all the cutting/modifying you've done worked out. If it's not perfect, then go back and rework whatever needs fixing - please don't rush through this as you don't want to damage anything. Also, check to see that the Rotel transformer's secondary wiring soldered to the mainboard PCB doesn't get in the way of the ZAPfilter P/S PCB. I found a few "exposed" wires due to some sloppy soldering at the factory, so I had to re-solder a few of them to correct the problem. Otherwise if it does work out, mark out where you need to drill for the ZAPfilter P/S PCB and transformer.
If you're not handy with a drill, I suggest you start off with a smaller sized bit as a "pilot" hole and work your way up to the right size in order to be sure you have the hole in the right spot. You don't want to drill holes all over the place trying to get it right. If you have a drill press, now is the time to use it as it will be a lot easier to start the holes in the sheet metal.
Step 6: Prepare the two wires for the ZAPfilter P/S PCB. You'll need to solder in two wires to the Rotel P/S PCB shown in several pictures above. Use blue (neutral) and orange (hot) #18 AWG or better wire if you have it to "match" the primary wires on the Rotel transformer, otherwise use any two colors which you have at your disposal (it's really not important.) Be sure to cut them to the right length and tie-wrap them for neatness. I also chose to tin the ends of the wire to prevent oxidation since the ZAPfilter P/S PCB uses only a compression fitting to tie the wire in, plus it made it much easier when I constantly removed and re-installed the wire for testing purposes (I didn't have to keep re-twisting the ends of the wire to prevent fraying.) Make sure you put the orange wire in the "fused" leg/terminal of the ZAPfilter P/S PCB, and the blue wire in the other one (two outer most terminals only as the middle two aren't used.)
(Please note, the instructions above are designed for 115 volt based CD players. The wiring may be different for 230 volt based units.)
Step 7: Here's what it should look like when it's securely mounted to the bottom plate. By doing all the of the modifications previously instructed, when you remove the bottom plate from the CD player you can take the ZAPfilter P/S PCB and transformer with it. You only have to unscrew the input terminals for the orange and blue power input wires which is a lot easier than having to unbolt all of the components. It's much nicer looking and more functional to do it this way. Now, see why all that hard work paid off.
You might also have to "grind" down a little of the ZAPfilter P/S PCB board in the front (power input) if you find it catches on the Rotel transformer mounting bracket - this is expected. Also, don't be surprised if you need to take a little off the rear of the board (near the ribbon connector) as well depending on where the board is mounted on the bottom plate. There isn't a lot of room to play with.
Step 8: You want to modify the safety shield for the incoming AC (mains) terminals. To do this you want to take a pair of scissors and cut some of the "folded" section off (~3/8".) In addition, you'll need to cut a square out to accommodate the two black capacitors and two green resistors on the ZAPfilter P/S PCB. Please make sure you do this as the two green resistors get VERY hot, so you don't want to let them cook under the shield.
Also take a look at the insulated black tape on the chassis under the safety shield near the white wire at the top of the picture. Even though the terminal is not touching the chassis, it's a good idea to put a piece there due to the close proximity with the chassis. Best to prevent any possible danger areas for shorts.
You should also note the routing of the ribbon cable to the ZAPfilter PCB. You want to make sure it stays away from the two hot green resistors. While it probably won't melt it, long term exposure to the heat is not guaranteed.
Step 9: Next you'll need to mount the ZAPfilter Mk. II PCB inside the CD player. I found this to be very tricky due to the spacing of the stand-offs on the ZAPfilter PCB not matching up correctly with the space available between the trace-work on the Rotel mainboard PCB. What I ended up doing is drilling out one of the mounts for the Rotel PCB (see picture), and using longer stand-offs to clear the tops of the capacitors.
The stand-offs I used were approximately 3/4" tall and had studs on one side (* important *) and a threaded hole on the other side. You'll want to make sure one side has a "stud" (threaded end), so once you drill out the PCB mount you can slide it in and secure it with a nut on the bottom side as there is NO access from the underside of the unit for a screw to be used (see the next picture and the step below for details.) I found these along with some computer gear I had for mounting PCBs, so I don't know of a good source to buy them. You could also screw together several shorter stand-offs to get the same height if you can't find the taller ones.
Step 10: You can see the second hole drilled out for the ZAPfilter PCB. Be careful when you drill this, so you don't get too close to the trace-work on the bottom side of the Rotel mainboard PCB. The ZAPfilter PCB should be placed perpendicular with the chassis (see next picture) for proper alignment of the hole. Use the other chassis mounted hole you drilled out in the previous step as a guide for locating where this one gets drilled. By doing this, the likelihood of getting it right is substantially increased.
Next secure the stand-offs with washers (both sides) to the mainboard PCB and lock nuts (see picture.) You may find it a little difficult to fit the nut and washer in this space available towards the edge of the chassis in order to secure the stand-off down, however it's definitely not impossible. (I recommend a pair of good tweezers to hold the nut in place and just tighten the stand-off instead while holding the nut in place.) I chose to use washers on both sizes to protect the PCB in the event of jarring or shaking during transport. Finally, secure the ZAPfilter PCB to the stand-offs using washers and screws, and make sure everything is secure and properly tightened down in place (don't over tightened them - just snug them up!)
Step 11: This is what the work up until this point should look like. You can also do a "test" fitting of the ribbon cable between the ZAPfilter P/S and PCB. If you're extremely keen, you'll notice that by mounting the ZAPfilter the way we did we've lined up the inputs/outputs with the Rotel left and right channels. If you look at the picture above, on the left side is the right channel' DAC, RCA connector, ZAPfilter input and output - likewise on the right side the same holds true for the left channel. There will be no need to cross the wires, and you have the advantage of keeping all the signal wires exactly the same length as well as extremely short in length given the distance to the input and output points.
Once you have everything sorted out, you can now remove the bottom plate along with the ZAPfilter P/S PCB and transformer. The next step is somewhat optional, but still required depending on what you decide to do.
Step 12: I recommend you purchase Cardas RCA connectors and install them now. It's a bit of a pain to get the old surface mount connectors out, but if you decide not to use upgraded Cardas RCA connectors then you'll still need to remove the resistor which is connected to the "hot" or "+" input on the surface mount RCA connectors. In addition, it will be more difficult to run the output signal wire from the ZAPfilter to the surface mount RCA connectors as you will need to fish them through to the underside of the PCB to solder them to the "inputs" of the surface mount RCA connectors.
To install the Cardas RCA connectors, you will need to unscrew the rear panel of the chassis. There are several screws attached to the mainboard PCB and the mounting plate of the CD transport, and finally two screws on each side of the chassis holding it in place. You'll also need to remove the three screws holding in the two output analog RCA's and the coax digital output RCA. You don't need to completely remove it from the unit (as the AC (mains) input cords is still soldered to the Rotel P/S PCB), only just enough to free up the surface mount RCA connectors when they have been un-soldered. Now using plenty of flux and a piece of Solderwick remove the solder from the surface mount RCA connectors. Once free, completely remove from the unit and add them to your "spare" parts collection. (Note: If you wish to install an IEC connector for a removable power cord, now is the time to do it before going on to the next part. You basically have the entire back panel off and will easily have access to make the rectangular cut need to fit the IEC connector. You should be able to cut through panel with the cut-off wheel without much difficulty.)
The next step is easier to do with the rear panel still not screwed down yet, but reposition the it back to it's original spot. Next screw in the Cardas RCA connectors in their place (be sure to make sure you have the "metal" shields back in place first.) Before you tighten the RCA connectors down, be sure to replace the screws you removed when you pulled out the surface mount RCA connectors. While they aren't needed, it keeps the "stock" appearance. You'll need two 12 mm combination wrenches (spanners) to tighten them securely in place. Make sure the center pin and ground pin is point up so you can solder the hook-up wire on it when you reassemble the rear panel. Otherwise, you won't be able to get the tip of the iron in space available to solder if it's upside down.
Step 13(a): Now close the "bridges" above the input terminals on the ZAPfilter Mk. II PCB. For the Burr-Brown PCM63P DAC chip, you will need to close the bridges marked 1,3,4,5, and 7 for both the left and right inputs (see LC Audio wiring diagram for the PCM63P for a close-up picture.) Make sure you use plenty of flux to get the solder to stick to the pads and try not to go overboard with the solder. Check out this picture for a close up of the bridges already shorted.
Step 13(b): It's also a good time to solder up the "short" required for each PCM63P DAC chip. Flip the player over, and from the underside short pins 5 and 6 (see the PCM63P technical specification sheet for the pin out of the chip, remember the chip is "keyed" for direction) on each PCM63P DAC (both the left and right channels.) All you need to do is put a little liquid flux down and add a solder bubble between the two pins. You don't need to use a wire since they're so close.
Step 13(c): Finally for this step, you're going to need to remove the Burr-Brown OPA2604 opamps or whatever you might have changed them to (see the Step 9 picture directly above LClock XO unit near the 4-pack of capacitors.) There are two of them (one on each side of the 4-pack of capacitors) which need to be remove (for both the left and right channels.) They are DIP-8 layout, so take your time and use plenty of flux and Solderwick to suck away the solder from the pins on the chip from the underside of the mainboard PCB. If you have difficulty removing the chips, try applying a little heat to the "troublesome" pins while gently pulling out the chip.
Step 14: Now we're ready to tie in the input signal wires for the ZAPfilter PCB. Take the time now to refer to the L C Audio ZAPfilter Mk. II wiring diagram. The only terminals we're concerned with are the "+" and "G" inputs for both the right and left channels. The "+" input should be hooked up to pin 6 of the PCM63P DAC, and for the "G" input pin 7. Since it's not a good idea to solder directly to the chip we're going to tie it in to the next closest spot that pins 6 and 7 go to.
While we're at it, we're also going to remove the rest of the signal path since it won't be need - the ZAPfilter will be our new output stage. When cutting the wires to length try to make sure all your input signal wires are equal in length for both channels. Since the layout allows for a very short signal path, take advantage of this and keep all your wires as short as possible. Also it's a good idea to "tin" the wire ends before soldering directly to any of the terminals.
Right Channel: For the "+" input terminal, we're going to remove the jumper at J221 (you will need to de-solder this metal "staple.") Once removed, solder in the hook-up wire to the hole that contains the trace-work connected to pin 6. For the "G" input terminal, we're going to tie it into the closest end of J342 which goes to pin 7 of the right channel DAC chip. To fit both the jumper and the wire in the hole, you might need to increase the size of the hole a little. There is nothing wrong with doing this, but take care not to make the hole too large and ruin the trace-work on the underside of the board.
Left Channel: For the "+" input terminal, we're going to remove the jumper at J211 (you will need to de-solder this metal "stape.") Once removed, solder in the hook-up wire to the hole that contains the trace-work connected to pin 6. For the "G" input terminal, we're going to tie into the closest end of J341 which goes to pin 7 of the left channel DAC chip. To fit both the jumper and the wire in the hole, you might need to increase the size of the hole a little. There is nothing wrong with doing this, but take care not to make the hole too large and ruin the trace-work on the underside of the board.
LC Audio LClock XO: I'm not going to cover it in this guide as LC Audio has an excellent instructions and pictures on their website detailing the installation on the Rotel RCD-971 CD player. However, I'd like to note the excellent mounting location shown in the picture above. You only need to drill a few holes on the side of the case, and it fits perfectly in the space available. Just follow the LC Audio instructions, and no further modifications are needed. This is an excellent addition which is highly recommended!!!
Step 15: Next we need to tie the remaining "+" and "G" output terminals on the ZAPfilter Mk. II to the RCA connectors. Once again, please refer to the L C Audio ZAPfilter Mk. II wiring diagram for details. Make sure you keep the wires as short as possible and cut them to be all the same length. Also it's a good idea to "tin" the wire ends before soldering directly to any of the terminals.
Right Channel: For the "+" output terminal, solder the hook-up wire to the center pin of the RCA connector. For the "G" output terminal, solder the hook-up wire to the outside part of the RCA connector.
Left Channel: For the "+" output terminal, solder the hook-up wire to the center pin of the RCA connector. For the "G" output terminal, solder the hook-up wire to the outside part of the RCA connector.
Step 16 (Optional): If you decided to use balanced outputs, you'll need to drill holes in the chassis to mount the XLR connectors. There's room towards the right side of the coax digital RCA output connector. Finally, you'll also need to tie in the "-" output terminal in addition to the "+" and "G" output terminals as shown in the LC Audio ZAPfilter Mk. II wiring diagram. I didn't do this in this installation as it wasn't needed, however there are some great pictures on the LC Audio website which detail the mounting of XLR connectors on the rear of a chassis for the ZAPfilter installation. Please use this as a guide.
Step 17: Make sure you test all of your connections with a good quality voltmeter with a continuity option. Also check to make sure nothing will short out and the wiring is neat and clean. Refer to the LC Audio ZAPfilter Mk. II General Setup Guide for a last minute checklist of the work completed. Perform a quick power-up test to make sure you didn't make any mistakes (just in case!) Now it's also a good idea to check all of the output voltages on the ZAPfilter P/S PCB to make sure everything is operating correctly. If everything checks out, then proceed to the next step, otherwise start from the beginning and make sure you didn't forget to do anything.
Step 18: Finally, if you have a can of compressed air, give the unit a good spray to blow out any dust that might have made its way into the CD player. Then reassemble the Rotel RCD-971 CD player and hook it back up to your system. Now sit back, relax and enjoy your hard work! (I'd also recommend that you give it at least 100 hrs of burn in time before you seriously audition it.)
Contact Information
If you would like to make any suggestions/additions to this guide or you have any questions/comments concerning the actual installation, please feel free to contact me. While I'm not looking to go into business doing these modifications on a regular basis, if you feel you just don't have the technical know how or skills needed to do the installation right I might be able to be bribed into doing them for you, just drop me an email and we can talk about it.
