I thought last Thursday was going to be just one of those Covid Thursdays. That was until I opened the 2nd hand website Marktplaats here in The Netherlands. A handsome looking Marantz CD-94 was staring at me with an asking price of €50, with only one printed circuit board (PP-16) missing. The seller (Tony) bought the CD-94 at a thrift shop in Amsterdam with the idea of restoring it to its former glory. Only one thing kept him from finishing the project; leaking capacitors affected parts of the circuit board in such a way that the PP16 was beyond repair. After a phone-call, we agreed on picking up the cd-player for €75 on Friday in Amsterdam. On the first inspection, the player seemed to be in good condition, so I took the player home. On the second inspection, we (my son and I) opened the player, and it looked in good order for its age! There were some visible stains on the bottom plate, caused by the leaking capacitors. But overall, it only needed a new PP-16 and a recap.
Luckily, I had a PP16 (the printed circuit board with the two big capacitors on it) lying around somewhere. I bought that particular PCB from someone who sold it as a ‘for parts only’ deal. The only destroyed part of this CD-Player was the CDM1 drive-unit. But the buy gave me a lot of useful spare parts to use in new builds with these CD-Players, and spare-parts for these CD-Players are very hard to come by these days. But sometimes you get lucky and find the parts that you need. And remember that a spare CDM1, a set of drive-belts can come in handy! I am also the guy that never throws away any part of a Marantz CD-94. Not even a copper screw gets thrown out by me! And I also like to experiment with different CD-Player parts, like side panels. To experience how they influence the sound signature of the CD-Player. I bought four extra pairs of side panels for my CD-Players. One set of side panels came from Ukraine (Abbas Audio), and they were considerably heavier than the original ones. The other three pairs of side panels that I own came from Marantz ST50L tuners. The panels weigh about 2.5 kilos a pair and are a good upgrade for a CD-94 or a CD-94 MKII.
In this player that I bought in Amsterdam, there was also an integrated circuit that I have never seen before. There was an M4804A was sitting on the PD16 printed circuit board. It turned out to be the predecessor of the SAA7210P. Philips and Marantz used the M4804A in some of their CD Players, such as the Philips CD650 and the Philips CD304mk2. This particular I.C. was used in the Mission PCM7000 as well. Philips discontinued the M4804A because of disc start-up problems and replaced it with the more known SAA7210P. If you encounter a PD16 printed circuit board like my one, you will have to change some of the I.C.’s. So the SAA7220P/A and the M4804A have to leave the party. I am replacing them with a SAA7220P/B from a 1995 production run and a SAA7210P from a 1993 production run. A SAA7220P/B produced in 1995, you might think, but Naim Audio used these in their CD3s. In an upcoming blog, I will write about the repair, and upgrade that is done to this CD player.
Around 1987 the engineers at Marantz started fitting CD players with these heavy Zamac side panels. Zamac is a family of alloys with a base metal of zinc and alloying elements of aluminum, magnesium, and copper. The Zamac panels had excellent damping properties and added to the overall stiffness of the chassis. The first CD player that ‘received’ them was the Marantz CD-95. Among the last CD players that got them were the Marantz CD-80 and CD60. After six or seven years Philips and Marantz stopped using them on their CD players.
The die-cast chassis, used in the Marantz CD-94 was inherited from the Marantz CD-34, CD44, and CD-54. The zinc-aluminum alloy die-casting chassis is used to suppress the internal fine oscillation of in- and external vibration. According to Philips, the CDM1 was also made of the same alloy.
In 1987 Marantz started to use 3mm metal plates as a base plate under their CD players. The first CD player that received a metal plate was the Marantz CD-94 Limited. The main reason for this move from the thin metal sheets (that were used on the Marantz CD-94) to the 3mm metal plate is that the plate adds to the stiffness of the housing. The plate also improves shielding and adds additional damping of unwanted vibrations. If you ever want a cheap upgrade (instead of expensive OPA627s) you could fit a metal plate onto your CD-94 as well. Add three brass spikes from Dynavox, a full recap, and new belts, and you are upgraded to “limited standards” as well.
Philips could also study the effect of these changes on the internal layout of the CD-Player. By making 2D models in PHILPAC1 a frequency response model could be made to study the frequency of vibrations. A rigid body model could be made in Systan2 3D to look at the changes made to the CD player’s body. The engineers could also import models from Ansys3 into Systan. Philips used these models mainly to study machines that they made for internal use, but it does not seem far-fetched that these models were used to design the CDM1 or the chassis that the Marantz CD-94 used. I know this for certain because there are released papers that the CDM3 was developed using these techniques.
Computers have been used as well5 in the design process to predict circuit behavior before an actual circuit is available. This was done by means of so-called circuit simulators such as SPICE, PHILPAC, and PANACEA4. Naturally, the success of these predictions depended heavily on the accuracy of the models used to describe the (circuit) behavior of the individual components in the circuit. On the other hand, mathematical complexity yielding only minor improvement inaccuracy must be avoided. Generally, explicit analytic models were preferred.
I want to finish this blog with some pictures. As always are my blogs under construction. New insights might urge me to change my opinions on what I have written. So stay tuned… and see you at my next blog.
 PHILPAC; used for making 1D and 2D models to study concepts. PHILPAC, PHILIPS proprietary circuit simulation package. PHILPAC was also used to make MOS circuit designs (ICs). Philpac originated from Philips ISA. The designers also had Tramos at their disposal to make MOS circuit designs. Tramos originated from Nijmegen.
 Systan; For the global analysis of the mechanical system and as a tool to build models from ANSYS together and to refine Rigid Body Models.
 ANSYS; For describing and analyzing in detail the internal dynamic behavior of components.
 PANACEA, PHILIPS proprietary circuit simulation package.
 Computer-developed print layout, so that every component and every earth point got its optimal place, excluding hum from unwanted earth points (from a Dutch CD-960 advertisement).
Last updated: 07-05-2022