[snip]Today I'll be taking you through some common mods for your average CD Player. Whilst this isn't a full or final list, the things you can do are nearly limitless with the right imagination and a steady soldering iron, so add a little life back to that flagging CD Player - you may just surprise yourself...! "First look to remove any muting transistors, just snip them off the board. These things are switched on when you press the next track or skip buttons, reducing the slight popping noise created by diverting part or all of the output to ground and thus muting the player. But as the transistor never actually switches off, a small amount of output is constantly drained to ground... never a good idea. The difference after removal is considerable in the scale of tweaks."[/snip]Today I'll be taking you through some common mods for your average CD Player. Whilst this isn't a full or final list, the things you can do are nearly limitless with the right imagination and a steady soldering iron, so add a little life back to that flagging CD Player - you may just surprise yourself...! [B][SIZE=3]Methodology[/SIZE][/B] I prefer to try and get the best from the circuits as they stand rather than rip out and replace. The designer must have had some aim in mind when he produced the design…? [B][SIZE=3]Case Work[/SIZE][/B] The thin pressed steel casework will need damping... foamed butyl rubber sheet or bitumen damping panels as used in the motor trade work really well. The lid and base will need damping as well, don't forget. The transport and draw mechanism can be treated in a similar way. But don't foul the workings with too much. A blue led shone onto the disc also has an effect [don't ask why as I don't know]. A green poster paint pen like the Posca pens by Uni can be used to put a green ring round the edge of CDs [including the inner hole]. If the case work is sprayed green on the inside [big job to remove all the working and mask up] this will help cut down the stray infra red scatter from the laser. The green shade depends on the freq. of the laser so a bit of trail and error is normally involved. Try getting two identical CDs and paint the edges of one... when dry do a bit of DBT. I find that the green one often sounds more relaxing [but not always]. [B][SIZE=3]PSU[/SIZE][/B] Fit a decent mains cable from inlet to CDP board. Check the thermal compound on the regulators, and upgrade to a silver based compound. Replace diodes with Schottky types of suitable rating like 11DQ10's. As these work on a different principle to the normal diodes they have none of the draw backs like reverse current generation and RF production. In effect they are much quieter and I've found them pound for pound to be one of the single best upgrades you can make. Replace the reservoir caps with Audiophile types and then bypass them with values of 10% i.e. a 1000uf with 100uf, 10uf with 1uf, the theory being that smaller caps respond faster to transient power demands, making for a faster and more detailed sounding player. Look at the quality of the power supply wires to the various parts - use a high quality copper or silver wire with Teflon insulation; routed to cross the unit at right angles to other cabling. [B][SIZE=3]Output Stages[/SIZE][/B] First look to remove any muting transistors, just snip them off the board. These things are switched on when you press the next track or skip buttons, reducing the slight popping noise created by diverting part or all of the output to ground and thus muting the player. But as the transistor never actually switches off, a small amount of output is constantly drained to ground... never a good idea. The difference after removal is considerable in the scale of tweaks. [B][SIZE=3]Op Amps[/SIZE][/B] There are any number on the market ranging from a few pounds to tens of pounds [more expensive is not always better] its often a matter of personal taste, my low cost favourite is the Bur Brown opa2604, 604 for the mono. Remove the original op amp and solder in a high quality socket - I use ones with Beryllium Copper legs. This allows for easy swapping; even with the extra connections this set up sounds better than the original in all the players that I've made the change on. As most op amps work at such a low level, the can actually be operating in class B or C. It's worth putting a constant load on the output to raise the operation into class A. There are lots of websites that give you the instructions in how to do this, but remember that in class A 50% of the output is going to be heat! You need to address that problem and add a heat sink to the op amp. [B][SIZE=3]Signal Path[/SIZE][/B] The replacement of the resistors in and around the signal path will also remove a veil from the sound… as a minimum, use Holco's precision metal film [0.01% tolerance], but there are a lot of expensive good ones about i.e. Vishay bulk foils or Audio Note Tantalum's etc. Replace the copper tracks on the PCB with silver wire [Hard work! Not to be attempted unless really confident...] [B][SIZE=3]Clock[/SIZE][/B] Replace the following with its own power supply: Trichord Research Clock 4 or similar. Consider non oversampling [this of course is specific to the DAC in the machine]. [B][SIZE=3]RF / EMI[/SIZE][/B] Copper foil shield all IC's and bundle and wrap all cables in foil, which must then be grounded to a convenient point on the case work. Cut the foil to size and stick to the top of all the IC's - use a small wire and solder the foil to the ground leg of each IC. Look to make a copper sheet screen to shield the PSU from the drive and the drive from the output stages. [B][SIZE=3]Shorting Plugs[/SIZE][/B] Build a shorting plug for the digital output: [URL]http://diyparadise.com/75ohmtweak.htm[/URL] [B][SIZE=3]CD Output[/SIZE][/B] This can be high and might be the cause of overloading the input stages of the preamp… simply use a plug in attenuation or add the appropriate resistors to the IC plug. [B][SIZE=3]Tubes [For players like the Jolida XXXs][/SIZE][/B] I like Svetlanas for me they give a velvety inky black silence and a smooth warm effect in there presentation, but these are a very personal choice. [B][SIZE=3]Dislikes and Don'ts[/SIZE][/B] I'm not a great fan of black gates… they take years to burn in, so you will never get their full benefit - their cost is prohibitive to. I like Elna Stargets in and around the PSU and output stages… they are cheaper and give an honest performance straight from the box. Replace all the caps [not already swapped] with Oscons [sg?] you can use the copper legged ones, especially around the digital section. Don't use any ferrite beads… they will squash the dynamics of the system. [B][SIZE=3]Out of Box Things to do[/SIZE][/B] Make or buy a decent shielded mains lead... these act as filters removing grunge and cack before it gets to the player. Look to use a mains conditioner beyond the power cable, and use decent wall plugs. Don't neglect to clean all metal contacts. Metal oxides act as diodes. Feet... well a simple three point system of cones will be effective - there are many on the market to suit all pockets but if you are like me, you may prefer the DIY approach. Try some domed hard wood cupboard door knobs [approx 10mm dia]. These work as well as anything. The support should be a vibration absorbing sandwich on a sand box. I use 2 layers of 5mm MDF separated with a sheet of foamed butyl rubber - kills vibration by an average of 20%, more for high frequencies. The sand box is a box full of sand [oven dried] with a sheet of MDF sitting on the levelled sand, but clear of the sides of the box by a few mm. Build the best IC you can - for me at the moment this is a simple twisted pair of solid silver 4N wire in a Teflon sleeve with bullet plugs, fabulously revealing but not as overly bright as you might expect or have been told. In my opinion you can achieve a lot by cleaning the pins of the mains plug so they shine, use Duraglit or other metal polish, and don't forget the fuse ends and the holder. In the UK the fuse is in the wall plug. A good fuse has copper caps but they are often covered in soft solder [tin and lead] - once removed, the difference is clearly audible. Also if the CDP has valve output stage, clean the pins on the valves.
