Marantz CD-94 CD player part 2

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Upgraded CD-94 Source: compi1011. Marantz CD-94 Zamac base/chassis with ‘extra decoupling’

At the time you could buy the Marantz CD-94 in the shops, people and shops started “upgrading” these players. This so-called “modding” or “tweaking” was of course done with only one thing in mind: making the CD player better. Having owned one already years ago, I decided to buy myself a “new” one. And of course, it was already “tinkered” with. It was upgraded by a company called Siltech. They changed the op-amps to AD711JN, added capacitors/capacitance, and did something that everybody should consider who owns a Marantz CD-94: change the TDA1541 to an S1 version (or one of the last production runs of the TDA1541a). But they also forgot one thing: change the SAA7220P/A to a SAA7220P/B version. Everybody should know that the TDA1541a should be implemented with a SAA7220P/B. Why even bother putting a TDA1541a S1, S2, or a Q selection and don’t change the SAA7220 to a P/B version. Heck, some people even downgraded other players who were fitted with a P/B version to a P/A version. I do not have to mention that you should always check before you buy a second-hand Marantz CD94! Even on eBay, you can buy examples with better TDA’s, but these still come with the SAA 7220p/a. The original op-amps that the CD-94 came with are the NJM5534, not a bad op-amp at all! Marantz also fitted them in the more expensive DA-12. If you are on a (tight) budget you should always consider the TDA1541a / SAA7220p/b swap/upgrade before even thinking about changing the op-amps, and if you do: implement them the right way, and do not just change them. As one member of a Dutch forum said when looking at CD player modifications: a lot of tweaking has been done, but they forgot the “essential” mods.

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From Dutch Audio Classics: The SAA7220P/B is an improved version of the ‘A’ device giving 1dB better performance in the passband of the FIR filter, achieved by using different ROM coefficients. The other difference between the two types is that the offset in the accumulator is greatly reduced (+0.05% in the ‘B’ compared to +5% in the ‘A’). The SAA7220P/A required a +5% offset to give optimum performance when used with the TDA1541 dual DAC. However, with the ‘B’ version this offset is no longer necessary for optimum performance.

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Marantz CD-94 with the TDA1541a S1 / SAA7220P/A and AD711JN a.k.a the Siltech modification.

Essential mods/upgrades for the Marantz CD-94 are not the obvious ones like changing the clock, swapping op-amps for exotic Burson Audio ones and I could go on and on. But remember that my upgrade path does not have to be yours, and there are many ‘audio truths’! These are my essential ‘mods’:

  • Change the TDA1541 to a higher grade, like a late production model or a special selection (Beware of fakes!)
  • Upgrade the SAA7220P/A to a P/B version.
  • Put your TDA1541 and op-amps on sockets, so you can try different IC’s.
  • Implement the ‘Grundig Dem Modification’.
  • Change the values of the decoupling capacitors around the TDA1541 (This was done by more manufacturers but mainly by Grundig and Arcam (MKT for MSB pins 13 & 18 and values changed to 1uF or even 2uF).
  • Disable/take out PR16 (Headphone Jack P.W.B.).
  • Disable/take out PF16 (Optical Out P.W.B.).
  • Disable/ take out the remote control board (requires some modification of the PY16 (Display P.W.B.)).
  • Change PP26 (REG P.W.B.) to a ‘voltage regulator upgrade module from Redhill Audio (they also got a version for the Marantz CD-95, the Philips CD-960, and the Marantz CD10). Sparkos Labs Inc. also has discrete voltage regulators that you could use!
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Voltage regulator upgrade module by Redhill Audio.

Mechanical upgrades are very important and underrated i.m.h.o. Why you would ask? The answer is simple: see how the Micro Seiki CD-M2 is built and compare that to the Marantz CD-94! But still Marantz did their research and they were very well aware of the fact that other CD players were built like the CD-M2. As Tetsuya Onagi (Main Marantz CD engineer during the development of the CD-94) tells us in one of the scarce interviews that he gave on the matter (Source: All about Marantz).

Interviewer: CD started as a medium without noise, unlike vinyl. Then eventually, manufacturers started to incorporate designs to minimize digital noise and improve sound quality. When did Marantz start working on improving sound quality and noise?
Onagi: I think we started working on those issues earlier than other manufacturers. We had sound quality improvement circuitry incorporated in the Marantz CD-54 and Marantz CD-84, which were released in 1984. Back then, we used to separate the analog and digital circuit boards, and although we only used one power transformer, there were dedicated windings for the audio and servo circuits.

Interviewer: Did those improvements show up on data?
Onagi: No, not on data. We started to find these things out by trial and error, whilst we were making prototypes and holding listening tests. Eventually, we found out that we had to incorporate various sound quality improvements; otherwise, we really couldn’t gain any proper separation and ended up with a smeared sound field. Our largest discovery back then was with the full-size die-cast chassis¹ first used in the Marantz CD-94 in 1986, and we ended up using that chassis principle for the next ten years.

Interviewer: From your perspective, when did the sound quality of CD players change radically?
Onagi: Well, the best improvement we achieved was definitely with the Marantz CD-94, so that would be 1986. Due to the solid and rigid chassis design, we were able to gain a good signal-to-noise ratio with a clear and detailed sound.

Interviewer: Having worked primarily on CD players for all these years, what do you think is the secret in making a good sounding CD player?
Onagi: Well, I’d say back to basics and keep it simple. You cannot improve something inferior to start with, well you could, but there is always a limit. Say you have noise issues, you can add a shielding plate or change the grounding scheme, but they won’t be fundamental improvements. So, you have to make sure that there is minimal noise to start with. Adding a shielding plate will add to the manufacturing and parts costs and add more wiring. So the secret is in keeping the design simple and using quality parts. I think you’ll understand what I mean when you look inside a Marantz CD player.

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Tetsuya Onagi at work (taken from: All about Marantz.

But Micro Seiki had a slightly different approach, with all the knowledge that they gathered building very good turntables. The CD-M2 rosewood case/sidepanels came right of one of their turntables ( Micro Seiki AP-M1). They sort of produced the first ‘tweaked’ Marantz CD-94.

From The Vintage Knob: An oil-suspension insulating system contains a precision floating spring mounted on a damping disc and floating in vibration-damping oil, all contained in an insulator housing. This, therefore, isolates effectively the entire pivot/shaft/rotor from external vibrations.

The vibration-damping construction based on COS-MAL-ZM11 zinc alloy for high rigidity, high internal vibration damping, and a very high signal-to-noise ratio. The base is supported by tripe-construction insulators using ferrite, felt, and alloy. The side panels are of Brazilian rosewood to diffuse any kind of vibration modes — and to contribute to the classic look of the AP-M1.

This inspired me to start using one of their ideas, and that was making a new base for my Marantz CD-94.

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Micro Seiki CD-M2 base with feet.

The base that Micro Seiki constructed consisted of three sheets. One made of steel (3mm), one made of copper and one made of lead. For the first sheet, I used a 4-millimeter steel plate. The next sheet will be a copper one of 0.8-millimeter and the last, a lead one, 1.3-millimeters thick. When I finish this base it will be one of the heaviest CD-94’s on the planet, weighing approximately 17 kilograms. This construction will absorb even the smallest vibrations. Other users report using granite/wood with no feet or thick aluminum plates. Marantz eventually started using 3mm steel plates on the CD-95 and the later versions of the series (CD95-CD99SE).

If you look at the feet that came with the CD-94, cheap plastic hollow feet with some felt, you can imagine that every substitute will outperform them. The engineers filled the feet of the Marantz CD-94 Limited with portland cement. Marantz later on developed special feet (for better vibration damping), holding a ceramic-resin compound but they were only available with the Marantz CD-95 and the other models that followed. You could also find these feet on the Marantz PM-94 Limited. Since Micro Seiki used metal (brass), I opted for the Soundcare Super Spike. It uses a zinc casing and disc, with metal inserts to reduce vibrations. A better soundstage will be your reward! On my first Marantz CD-94, I used aluminum Nordost Pulsar Points. Micro Seiki even used hydraulic suspension feet under their CD-M100! As Reiner Finck2 pointed out to me lately that it is essential that you only use three feet under the CD player. This approach was also used with the Philips LHH500R CD player.

If you think I left out crucial information on the Marantz CD-94, especially the Marantz-Micro Seiki link or the Wadia link, let me know. Every piece of information is important! Till the next blog!

[1] The full-size die-cast chassis was already used by Marantz in 1984. The Marantz CD-54 used it in cooperation with the CDM1.

[2] One of the Marantz engineers who worked on the Marantz SA-10, Marantz Musical Mastering “MMM-Stream” upsampling.

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