This part of the blog is to describe the process of the CDP01 which is essentially a kit-type CD player for audiophiles. I don't generally have the flexibility to add rich content on diyaudio.com as I do here. Its also easier for me to update everything in one place, even while on the road. Therefore this category in the blog is where all the info is posted. This blog here will therefore be perma-linked to the revelant post on diyaudio.com
What is this about?
As most designers know, CD player designs are shrouded in secrecy, partly due to Sony and Philips and their alleigance to the music business. The patents have expired now, and still its kept secret. I am tired of seeing Chinese crap players being sold with zero chance of customization or even further development, so I decided to design something proper, and in addition to this, this has been a personal goal for a long time.
Ah but how come there are difficulties- surely hacking can sort this out?
The CD player is a pretty complex piece of kit. It has multiple PID based servos to control the disc spindle motor, the lens focus, the lens tracking, and the SLED. These are not simple things, as anyone who has done work on PID servos in software will attest. Furthermore, getting concise and complete technical info on the DSP chip has always been a real challenge. Until around 1999 it has been virtually impossible for me to get any information on anything CD player related. Even getting the parts themselves has been a difficult thing to do.
In terms of parts I noticed there was suddenly a glut of Sony pick-ups and CD deck mechanisms going for insane cheap prices all over the show at regular shops in and amongst the Arduino stuff. Even since then I have been trying to make a design to use these cheap parts.
I have attempted to listen in on the bus comms between the CD player DSP and MICOM, but without knowing what registers are present in the DSP, its like taking a stab in the dark. Even with a logic analyzer, if you don't know what you are listening to, how can one know what to do with it? Also adding to this frustration is that some values are specific to the hardware- Sony designs are often "adjustment free" but in reality the MICOM has a table of tuning values stored in EEPROM that are programmed during factory testing. Without having a clue about the registers, and the firmware, its kind of impossible to know what value does what.
Also, if the chip features anything to do with WMA/MP3 playback, the datasheet will not exist on the internet, probably due to all the licensing and royalties demanded by Fraunhofer IIS and Microsoft and all those watertight NDAs
What process have you followed?
I have approached everyone, including Sony, NXP(Philips) and even some Chinese manufacturers such as ALi Corporation. None of those companies would listen to me. In fact, the latter Chinese company played the race card with me, and in the end Panasonic of Japan, told me, there's "no market" for this anymore. In general, as the owner of a small company, it becomes kind of hard to be taken seriously by these large corporations, until 2017 when my fortunes changed.
Fortunes changed? What happened?
So I am a regular reader of elektrotanya.com and I look what is available in the shops, or what I get in for repair or even what I find in the trash. In January 2017 I noticed there was a new car CD player from Sony out on the market.. so I got the service manual and saw they used a new chip from ON Semiconductor. I got the datasheet and noticed that it has everything including an embedded sequencer- its preferred method of control is macro commands via a plain vanilla serial interface.
So without getting my hopes up, I approached ON Semiconductor via the local agent in SA (EBV) and I wrote them a letter explaining my intentions and desire to build high-end audio equipment. Imagine my shock and surprise, when they sent me the complete and full documentation of that chip, including a reference design, with extremely important info about the laser pick-up block the chip is optimized for. After many years of persistence, my tenacity has paid off.
So what chip are you using?
I am using the LC78615E from ON Semiconductor.