Hi guys and gals, I have always had a soft spot for Technics CD players, specially those from the late 80's, early 90's with their unique MASH 1 bit DAC and colorful FL displays. I recently discovered their 1989 line was actually the first to feature MASH technology but it was disguised as "18 Bit Linear" due to marketing reasons. The public had the perception that more bits were "better" in a high resolution DAC, and 1 bit technology required some reeducation. The first CD players marked as such appeared a year later in 1990. The Technics SL-P555 seems to fit the bill to be a good representative of the breed. It has enough bells and whistles to scream "I am from the 80s!", it has a very nice handsome appearance with the "jog dial" style knob and it features a MASH DAC inside: the MN6471. It was launched in japan in late 1988 but it was available worldwide in 1989. It was a mid range model sitting just below the SL-P777, which sported a larger chassis but very similar circuitry. It is interesting to note, the Technics home CD player line for this year shared the exact same transport: the SOAD70A. This is a linear tracking mechanism with a magnetic rail, which is very fast and reliable. It is therefore possible to swap transports among the line with no issues. This particular era of Technics also showcases Matsushita's expertise in mass production techniques. All players share the same transport and very similar power supplies. The integration in their PCB's is also very impressive, allowing them to offer a lot of features and performance for the money. On the larger players, though they seem to have a lot of empty space inside. This is actually a boon for modders as a tube output stage and power supply can be easily added to a player. I have been recently reading a lot about CD player modifications after purchasing a Lampizator Atlantic DAC. I have heard of the Lampizator before but never paid attention to his early CD player mod adventures until now. He makes very valid points on the value of adding a tube output stage to a classic CD player. The Technics SL-P555 with it's MASH DAC is already reputed to sound good. And the larger chassis is perfect for this type of modification. I purchased a SL-P555 off Yahoo Japan via Buyee. A 100V model. It was really cheap but shipping was steep. Still, it is cool to own a Japanese domestic model and it should be arriving today in the mail. The player will be converted to 120V using parts from another Technics player, a SL-P150, a lower end model from this era that shares the same power supply and transport. I am now studying different tube topologies and approaches. I will probably go point to point using a turret board. I will add a nice size transformer and possibly schottky diodes for the power supply. The dilemma I am facing right now is where to take or "steal" the signal going to the tube output stage input grids. Lampizator and others take the signal directly off the DAC chip, bypassing the different OP-AMP buffers and muting transistors. This seems to work fine as the sound quality obtained is described as excellent and a step above stock performance. However, I think the low pass filtering should remain to filter out- of- band noise from the D/A process. And also I would like to preserve the de-emphasis circuit which is activated by a flag in the data stream of many early CD's recorded using the emphasis process. So my approach will be different.. I am studying the Carver 490T circuit for ideas and I will look at other tube based commercial CD players to see how they deal with de emphasis. One thing I like about the Technics is that it features an "emphasis" light on the front panel display to indicate a CD recorded with it is being played. Very cool feature that seems to have disappeared shortly thereafter. Stay tuned for more pictures and details as I go along with my restoration. Any thoughts and input greatly appreciated!