The Marantz CD94 – Part1 (the drive mechanism)

A musical digital player??

If we look at the CD player situation today, there is not much to write home about…. Today we have to accept, that nearly no company is manufacturing dedicated CD transports anymore. The last decade was full of CD machines which used transports originally deigned for computers or car stereo systems – the decade of really high quality dedicated CD drive mechanisms ended around the the year 2000. Since than we got a lot less for a lot more money. Any DA converter needs a proper source, and if  we skip for a moment the whole streaming possibilities, the source for a DA converter is a sort of physical media – normally a CD or a SACD. Both optical media needs a damn good drive mechanism for reading the implemented digital data – hopefully with near to no loss, low jitter, fast and secure action, isolated from vibration implemented by the player itself or from the outer world.

Maybe you asked yourself while reading CD player offerings at the used market – why in nearly every advert you will see, there is some information written about new laser mechanisms or a brad new complete CD drive which was implied in a 4 year old machine??

Now lets jump directly to the years from 1985 – 93….the time, were you sold your record player and dived into the modern digital world. You bought your first CD player – and you had during its time in your HiFi system never any problems with the CD drive mechanism – maybe the unit needed at some stage a new driving belt for the CD drawer – but changing laser mechanisms or whole drives was not a task you had to deal with – right????

You changed in that period of time maybe the player – maybe more than once, because the big HiFi magazines told you that every new generation of CD players surpasses the actual generation – so an upgrade was mandatory….  The same story is also told to us till the CD as a mass media lost its importance agains streaming solutions. But was it really true, what was proclaimed???

Philips changed the design of their CD 0 drive to the CD 1 and later on they brought out the CD9 and all these steps were not made to design something better – it was made, because they wanted to make the things cheaper. The same can be said also about the ladder multibit DAC – in Part II of this article I will come back to that story.

Believe it or not – one of the best transports ever made was the Philips CDM 1 pro drive used in the end of the 80ties, last century – and even the first CD transport ever manufactured, the CDM 0 was a legend, regarding data integrity and fast operation. Those CDM1 pro drive mechanisms were used in the CD check machines the mastering studios used to check the digital quality of the media (digital errors). They were so good, that it was the reference, were everything else was measured against it. And of course they were expensive – made from metal cast, supplied with a sub chassis mechanism, a Rodenstock glass lens system (no plastic optics) and the speed of tracking though the index of any given CD was miles ahead of nearly anything which came later to this party. In one word – it was maybe the epitome of a CD drive mechanism – but it was too expensive to achieve a complete player, which could compete with the price of a cheap coffe – machine at the point of sale – electronic super markets…. From that time on, things got not better regarding the CD drive quality – it got worse – and today we have to accept, that in most modern CD players we will find just crap, which has to do the sensitive job of reading data from a digital media!

What really changed during all this years is maybe the quality of the DA converters – in the 80ties more that 16 bit resolution was seldom seen – and at the end of the ladder DAC period, 20bit performance was the best we could achieve with this technology. However – if we do not get the data from the media with the highest possible integrity and precision – if our source is not of the highest quality – all which comes in the signal chain after that stage is more or less questionable.

Restauration of a masterpiece:

The CDM 1 Pro drive used in one of the most well regarded CD players during those years, the Marantz CD94 (and also the MK II version of this player) will have some problems because of its long period of usage, we have to care about. Most of the units which are offered as defective, do not have any trouble with the laser diode – they all share one design problem, which we have to deal with. This design “problem” addresses the bearing of the rotary CD platter. This bearing is constructed as a plain bearing – a spindle is placed on a special plastic disc – the plastic is of such a kind, that the spindle do not need any excessive lubrication. Over the years this spindle works now its way into the plastic platter – there will be at any CDM1 pro a more or less deep groove in this plastic platter of the main drive bearing.

If the groove is cut very deeply, the distance between the CD surface and the movable laser diode is at some point too large – so the laser unit can not precisely focus anymore. The player will give us some error message – and most of the users think – the laser diode is worn out – but in most of the cases it is just a mechanical bearing problem . To solve that, we have to adjust the platter hight to a point were we compensate for the groove. This is manageable with a little bit of technical skills and a service manual developed for the specific player and its Philips drive mechanism. If we adjust the spindle height to a level, were the two axis element of our laser mechanism is positioned in its neutral level again – we are done. Of course one day the plastic disc of the bearing will be completely worn out – and there is no chance to get a replacement part as far as I know – but I can assure you – the mechanism will work for another 15 years from now on – if we do not use the player as a burn in device – playing in continuously repeat mode for weeks or months;:)) In the service manual we will find a certain voltage and the points were we can measure it to adjust the platter hight – for that procedure a perfectly flat CD has to be used with some test signals on it (CD/R made by yourself). All in all, if you know how the procedere works, it is a job done in 20minutes. If you do a good cleaning (highly recommended), the whole work will need a little bit longer.

Recap:

Another thing we have to deal with are all the electrolytics used in the player – not only in the drive compartment – I mean all the electrolytics, this is a job done with a lot of care and some patience. Today we have some great opportunities with modern designed caps. The SANYO OSCON electrolytics have a very temperature independent behaviour which is a very good thing with all the digital circuits and the drive mechanism. At other stages we can decide to use caps which we like because we think they give the unit a specific sound (Black Gates, Elna…) – and of  course we have the amazing Panasonic FC cabs, which is a strong recommendation for the power supply decoupling.

Sound experience:

After the complete recap, we will be stunned, how such an old device will sound. The Marantz CD94 has maybe one of the smoothest treble performances of all CD players I know of – it is the opposite of what we will find in most modern players – the treble has a sort of creamy gestalt! This could be a good thing – because of 100 CD´s 98 are mastered with a very hot or aggressive treble – a circumstance which seems to characterise the digital sound, but which is more or less also a problem of the software itself. To explain this more in depth, I have to dig a little bit deeper – we have to talk about production techniques in the recording stage, mixing and mastering process. If you compare a modern digital workstation as AVID Pro Tool against a 24  Track 2″ tape recorder there is a huge difference – not only in the native sound of both units – more so in the style you are able to use them. With an analog recorder we have a certain limit with the frequency extremes. We cannot put the same amount of level on the tape in the extreme bass region as also in the treble region compared to the whole midband. If we do so – the tape machine has a surprise for us – or better two of them – noise or distortion. Lets say for a moment we want to produce a Hi Hat – and we want to have a sound with the highest amount of shimmer we can afford, there is a special technique to reach that. If we would put some EQ on the Hi Hat off the tape – after we already recorded that signal, we will boost tape hiss…. – if we put all the EQ to the Hi Hat before we record it – we will be punished with less gain possible to put on the tape – otherwise the signal will be distorted – and the result will be distortion or again tape hiss. So a mixture of both techniques is the goal – a little bit emphasis befor the signal hits the tape – and a little bit in the mix, were the signal comes off the tape. The keyword here is LITTLE!. In the digital world there is not such a limit…I am technically able to put 12db boost on a Hi Hat at about 12Khz – and there is no other punishment as my bleeding ears. Which brings me to the essence of that little example….if we engineers have no technical limits, it is up to us to decide what sounds good and what sounds bad. And with too much freedom, we will face a great risk to overdue it….In other words the analogue tape recorder is one of the biggest teachers for us recording engineers in the control room. Their limits give us a sort of certainty, which we all lost with the digital age! If you are sitting 10 hours or more behind the console, you loose the ability to judge the sound – but in the analogue domain we had some security implemented into the whole system, with digital everything is possible. And this is in my opinion one of the reasons, why with the upcoming digital technologie, we miss more and more a sort of natural sound – because all is possible and often some more treble in the mix seems to be more exciting….

Now lets talk about the relationship between the producer, the artist and the recording engineer. It is a customer relationship – the producer wants a sound which competes with an international standard, the band wants a sound which is impressive and supports the idea of the song. Later on the mixing engineer will do the final work on a multi track session, often with more than 80 audio tracks implemented into the mix. Again the band and the producer wants to have the nearly finished product to be better than the reference recordings played back and forth during the mixing process. It has to be loud, powerful and impressive. So the mixing engineer will put a good amount of compression to the mix, as also a lot of EQ to make 80 tracks compatible to work with the basic idea of the song (a disaster!!!). Later on in the production process, the song hits a mastering studio – and again we have a customer relationship – the mastering engineer must bring the mix to a higher level – it is not “en vogue” to master the stuff in a natural way – it has to be louder than other comparable productions, it has to compete with the loudest tracks broadcasted at the radio. If the mastering engineer switches the mix file against the mastered version, all listeners in the mastering studio wanted to have this magic thrill – “Oh my gosh…..this sounds sooooo impressive”.

At the end of that story we will have some music mastered on the CD which has at best 8db dynamic and we will face a frequency spectrum which boosts the extremes – a lot of shimmer, plenty of bass and a down shaped mid frequency spectrum – some tricks at the Flatcher/Munson frequencies and finished is another song which works perfectly in a car stereo system while driving on a highway at high speed – but listened to a good High End stereo system, we get bleeding ears – the music is boring – because no dynamic shades are anymore detectable – and we think – “Fuck digital”….but it is not the digital technology itself – it is the way we work with all the possibilities. If you have a chance to listen to Radiohead “In Rainbows” (for example) on CD, you will hear that it is possible to achieve something great, something outstanding even pressed on a CD, there is nearly no difference between the vinyl edition and the CD – and yes this album was recorded with an analogue tape machine…

Using the CD 94 as a dedicated drive:

Coming back to the drive mechanism of the Marantz CD94 it is obvious, that this old machine will be a very good CD drive, maybe one of the best regardless of its price. If you want to skip the legendary DA converter implemented in this player – developed around one, if not the best 16bit ladder DAC the Philips TDA 1541chip set – you are in for a big surprise. But before “happy listening” we have to deal with the digital SPDIF (Sony – Philips – Digital – InterFace) interface which the engineers at Marantz implemented in this player to be able to communicate with external DA converters. You will detect a RCA jack at the back of the player – a thing, which most of the CD players have in common, regarding a SPDIF digital output. But this “standard” is wrong – completely wrong – because the SPDIF technology wants to “see” a proper 75 Ohm wave impedance. No RCA jack can deliver the proper specs implied in that technical standard – so we have to change the RCA connection to a proper BNC socket. And if we do that, we have to dig a little bit deeper. The Marantz CD 94 in it´s standard original configuration, gets its SPDIF signal from the Philips SAA 7220 digital Filter chip. The SPDIF signal is carried with the corresponding conductor path on the right hand side (mounted at the side of the chassis) daughter board and is further distributed by some connectors and cheap cabeling. So it is a good idea to grab the signal directly from the 7220 and use a dedicated 75 Ohm data-path together with a small circuit board, which brings the signal to the correct SPDIF specs – +/-0,5V and 75 Ohm wave impedance. Finally we feed the signal in our BNC connector and achieved a perfect SPDIF interface.

More modding:

If you have tasted some blood now – there is even more, you can modify to reach the best performance – even if you just use the Marantz 94 as a dedicated CD drive. The Philips SAA 7220 is the biggest problem in the whole surrounding of the TDA 1541 DA converter and its signal flow. The reason for this is the HF dirt this chip delivers into the circuits of the whole player – this is more important if you use the player as a full function CD player – but also of some interests if you use just the drive mechanism. The Marantz CD94 was built at a much bigger budget, than one might think – but at some stage Philips/Marantz hat to cut down costs, because they wanted te player to be placed at the lower end of the High End player segment. At some parts of the player Marantz decided to drop the best solutions which were technical possible. One of this cut down areas is the power supply as also the delivery of the voltages to the different sections of that player.

First of all, the Marantz has just one power supply implemented – there is no seperation between digital circuits and analogue sections, as we will find them in Accuphase CD players of the same aera  (they were of course much more expensive). Accuphase used from the beginning of their CD player development on, always two separated power supplies, which facilitates them to isolate the digital path completely from the analogue path. Marantz opted for just one power tranformer / power supply. Why do we not modify an Accuphase player than??? – Because Accuphase used a Sony drive mechanism in those years and there is no hope to get any spare part for them anymore – and if we want to buy another player as a donor – the whole story would be very expensive – and last but not least – as good as the Sony drive mechanisms were, they found their master in the Philips CDM1 pro.

So we have to deal with the power distribution inside the Marantz CD 94. Our goal is to isolate as much as possible the SAA7220 from the rest of the player – to achieve that, we have to construct a dedicated rail only used by this chip. And if you are dealing with such an idea – built more than that single voltage regulator – because I know, that after reading Part II of this article, were I will dig deeper into the DA converter of this machine, you will use the Marantz not only as a very, very good CD drive…..;-)))

The original voltage regulators are placed at the heatsink, you will find on any TDA 1541 player, be it a Marantz, a Philips, Rotel, Naim and so on…. Now you know, why these players all share the same strange heat sink at the rear side of their chassis. The original player uses 3 regulators with this heat sink together – and we put another three into this machine. This gives us enough flexibility to modify also the analogue section of this player – but more important to give the SAA7229 beast its own rail with discrete voltage regulation.

The marriage with a high performance DA converter:

If you use the Marantz CD 94 drive with an outboard DA converter using our modified SPDIF interface, you also have to get a proper SPDIF cable. It is not recommended to use a normal NF cable, which you normally use between your preamplifier and power amplifier – because a dedicated SPDIF cable has to be made with the 75 Ohm standard in mind. A very, very good choice is one of Chris Somovigos digital cables, he developed exactly for that purpose. In other words – this is one of the best options I know of. Be it a Stereovox, Stereolab or Black Cat 75 Ohm SPDIF cable – all are super performers – and you do not have to spent more money to achieve a better quality – these cables are of the highest class!

Now you have the choice to choose a DA converter you may have on top of your wish list. You can buy the newest and hottest stuff available to get the best of two worlds – the best drive mechanism ever made AND a ultra modern High End DA converter. One of the most exciting combinations will be a DCS Paganini if your speakers and the whole system is very neutral and not overly analytic. This combination is soooo good, that you will forget to play vinyl records for a long period of time. The combination is much better, than the integrated DCS Puccini CD/SACD player. The Marantz – do not ask me why, has a certain smooth sound, even if you use just the drive mechanism of the complete player. The sound of the drive is so grain free and elaborated at the treble spectrum – it is amazing – together with a very, very high resolution converter as the DCS Paganini is, you will get something which is hard to describe. If I have to characterise this specific digital sound to a moving coil cartridge, I would choose the Lyra Etna SL as an analogue opponent. A frightening resolution paired with a smoothness (used in a proper tonearm with a high quality SUT) and velvety gesture is apparent, a pinpoint accuracy which let you breathe the atmosphere of the recording event – fantastic!

If you use a pair of the legendary BBC LS3/5a monitors, the combination of the Marantz CD 94 drive with a DCS Paganini is not the best option. The LS3/5a has a slight treble rise – it is in that discipline the opposite to a well placed and integrated Quad ESL 57, which acts a little bit defensive at the highest frequency spectrum.  With the use of the BBC monitors a non oversampling tube DAC would be my first choice. And one of the finest options with a lot less money to spent as with the super expensive DCS stuff, will be the German manufacturer Acousticplan. The Digi Master  Tube DA – converter is a hell of a machine!!! If i should compare this combination with the analogue world of cartridges and turntables – I would go for the gestalt of a very nice Koetsu Rosewood Signature cart. A slightly recessed treble paired with a good punchy bass and the ability to layer the recorded space in a more integrated style. This combination is not analytic, it is about the tone, the beauty of the midband and the wholeness of the musical performance.

Stay tuned – part II of the Marantz CD 94 will come soon.

E. Strauss