Pioneer PD-S604


Author: Karsten Hein

Category: Gear & Review

Tag(s): CD-Players

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I came across our specimen of Pioneer’s 1995 budget CD player PD-S604 while looking for an affordable replacement for our trusted Sony CDP-502ES on which the original laser unit had begun to fail. Replacement lasers for the 30-year-old Sony had been out of production for some time, and the sources I was aware of had either sold their last stock or had since become ridiculously expensive. The Pioneer was by no means on the same technical level as the Sony, however, it did have a 10-year advantage as far as our understanding of laser technology is concerned, and, like the Sony, it was built at a time when decent HiFi still mattered. The PD-S604 ranked between the lower PD-S504 and the higher-specced PD-S904 in Pioneer’s price-conscious consumer range. As such, it was no match for the fully-specced PD-S06 that came out in 1997 and weighed around 10kg, however, at just over three kilograms, the PD-S604 already offered much of the same technology.

What attracted me to the Pioneer players of this time was their patented Stable Platter mechanism which firmly holds the CD in upside-down position on a revolving platter. In this constellation, the laser reads the disc from above, finding a nearly perfect focus plane each time. On most rival mechanisms, the CD will unavoidably wobble slightly, thereby requiring constant focus and error corrections from the mechanism itself and from the software. A further benefit of the laser positioned above the disc was the superior dust protection of the optical lens. Dust particles in the room are less likely to ‘settle’ under a suspended laser than they are on a laser that sits beneath the disk. Following the old HiFi principle of “garbage in, garbage out”, the output quality greatly depends on the integrity of the early signals in the chain. Having spent years of critical listening, I have become more aware of the audible effects on music shortly before a laser starts to skip. Thinning bass output and increased sharpness of the treble are the most obvious side effects.

There is a fine line between consciously detectable noise and the kind of subconscious noise that simply makes us think less favourably of a product without the reasons being quite clear to us. The PD-S604 promised to eliminate such noise on at least two levels: Via the Stable Platter drive mechanism described above and via an upsampling feature called Legato Link. The CD’s Red Book standard supports 2-channel stereo at 16 Bit & 44.1 kHz allowing for frequencies up to 20,000 Hz. While this is also considered to be the upper end of human hearing, the sound spectrum of natural music does not end there. Vinyl LPs allow turntables to naturally attenuate higher frequencies through the limiting physical properties of the needle, thus creating a smoother fade-out. CD players, however, cut off the upper spectrum by means of filters. This way of handling the high frequencies is said to give CDs a sharper and less tonally pleasant top-end. This circumstance is often quoted among the reasons for some audiophiles to prefer turntables.

Legato Link promised to process high frequency information in a more delicate manner by using spline interpolation to recalculate the missing original waveform. Pioneer’s Legato Link was among the first digital filters using spline interpolation to pass through superior transient information, however, this did not come without side-effects and could at times leave behind some unpleasant modulation at higher frequencies. It has sometimes been said that on well recorded CDs Legato Link did work its magic, but on some recordings, the algorithm seemed to be at a loss and added information that more resembled distortion than music material. I had to find out for myself how these claims would play out in real life and decided that the PD-S604 offered the best value for money of the range. Both the PD-S904 and the PD-S06 offered a digital cinch/RCA output which the PD-S604 did not have. However, since I wanted to listen to the player by itself without the use of an external DAC, I could live with its existing features.

The original owner of the PD-S604 reported that he had been more than happy with the player’s features and sound as well. He said that it sounded superior to all the players he had owned since and that his reason for selling had more to do with the family’s sleek new audio rack that offered room for a single combined CD/DVD unit only. Upon my arrival, I found the Pioneer perched on the dining room table with some old headphones attached for demonstration. The resulting sound was mediocre at best, and so I could only test if the player was basically functional and decided I would give it a more thorough inspection at home. When I left the house of the seller, I promised that I would make his player famous by presenting it on the eiaudio blog and invited him for a visit if he should ever be in Marne. When I arrived home that night, I gave our Sony CDP-502ES one final listen and then set up the Pioneer in its place. I would test my luck with having the Sony repaired once again, but I understood that this would take some months.

With its functional but not exactly audiophile power cord connected, the PD-S604 instantly went into standby. This was a welcome feature for me, because it meant that I could rouse it from its sleep via remote control. In fact, CD players were often the only audio devices in my setups to offer the luxury of remote operation at all. OK, to offer true luxury, the layout of the remote control (CU-PD045) might have been better arranged. The Power button, the Numeric Keys for the title selection, and the Play, Pause, and Stop buttons were all of equal size and integrated within a uniform grid of buttons. This made nighttime operation a real nightmare. And the controls on the front of the player were not without quirks, either. While Numeric Keys on the front of the player made it easy to begin playback from a given title, the placement of controls here was also quite counterintuitive. The Stop button, for instance, was placed in a different row than Play & Pause, which were positioned next to the button to Open/Close the tray. I wonder how many times this player has been opened by mistake in an effort to stop the CD from playing.

On some CD players using a single power supply for the digital and analog section (e.g. Denon DCD-1420) turning off the display will lead to a cleaner sound by removing some of the digital haze. However, turning off the LCD display on the PD-S604 simply turns on a red LCD display message saying that the CD display is currently turned off. Therefore, perhaps unsurprisingly, I was unable to detect an acoustic benefit in turning the display off. Perhaps another such quirk is that the motor-driven headphones volume attenuator also affects the variable line-out volume. In audiophile listening, we attempt to reduce the number of controls and attenuators in the signal path and mostly give preference to the fixed line output. However, users who prefer the variable option may well find it a nuisance to have the two features connected. The headphone amplifier itself is a bit weak and will only sound decent with low impedance headphones made for laptops or other portable devices. Audiophile 300 Ohms would quickly drive this headphone amplifier to its limits.

I connected the Pioneer to our upgraded Rotel preamplifier with Becker ST-200 MOSFET amplifier using HBS2 silver solid core wires. The Rotel-Becker combination is generally more musical than analytical, it sounds rather enjoyable and is tonally rich rather than bland sounding. When paired with our Epicure EPI 500 loudspeakers, the combo is ideal for relaxed nighttime cruises and a great companion for hours of effortless listening. I found the PD-S604 to blend in well here. The Becker amplifier provides a good sense of order with most music choices, and the Pioneer enhanced this impression adding even more depth to the soundstage. On many occasions, I felt that the music was positioned in a perfect round circle spanning from my ears to the speakers and beyond. I appreciated the fact that with the PD-S604 the music did not lose any of the intimacy that I was used to from this amplifier to speaker combo. 

Reading the disc with great accuracy and refining the top-end with Legato Link proved to be beneficial to most recordings of natural instruments as they are found in Jazz, Blues, Singer-Songwriter, Classical Music, and other handmade materials. One some recordings, however, it seemed that the high-frequency algorithm had some difficulty discerning music content from distortion and served to amplify this noise in a manner that I had not heard from other players. These artefacts could span from pure pink noise distortion to genuine background occurrences that remained hidden on other players. On one instance, the music material repeatedly changed from muffled to transparent as if the player could not make up its mind how to best handle the high frequency roll off. On the other hand, I must confess that I have not yet heard a CD player on which all recordings sound equally well. Suffice it to say that on some recordings the treble could be more accurate and better integrated.

There is one small upgrade I could not stop myself from adding: While taking the photos for the website, I noticed how unusually light the player felt. With its disk platter ejected, one might worry that it might fall over. I therefore added a sheet of anti-resonant coating to the inside of the cabinet (see last photo). Doing so added some 500 grams to the unit and served to reduce drive vibrations on the chassis which in turn led to an even more ordered sound. I once saw this method applied from factory on the Denon DCD 1500 II and rather liked the idea as a quick fix to mechanic issues. CD-players greatly benefit from a firm stand and lots of body weight to quiet their moving parts. A small tweak with audible effect.

Adding the anti-resonant coating, I noticed another small issue with the player. On some recordings there seemed to be a slight lack of forward drive. The player could sound a bit slow on occasion, especially when the music got faster. It is well possible that this effect was further highlighted in combination with the Becker amp that would at times display a similar tendency. The impression never stayed for long, but it was noteworthy enough for me to mention it here. Fans of faster music might want to take this into consideration or at least test the player with their material to first see if it works for them. On the music that I listen to, the occasional loss of momentum never troubled me a bit.

In its current state, I am indeed very satisfied with my purchase and enjoy the warm and pleasant sound of the PD-S604. There is sufficient bass presence to make instruments sound real and well-rounded. The Pioneer’s superior sense of order and its generous spacing of instruments are attractive features for the recreation of natural instrument recordings. In my experience, the musical benefits of Legato Link far outweigh the few instances in which it does not work so well. All in all, the PD-S604 has grown on me more than our Sony ever had. The better the music material is recorded, the better this player can show what it can do.

What experiences have you encountered with this player? At the time of writing this, there was not much information on this Pioneer player to be found on the web. Click on the header picture to activate commenting and be sure to share your personal experience with us.


  • Type:  Stable Patter mechanism CD player
  • Power requirements:  AC 220 - 240 V, 50/60 Hz
  • Digital converter:  PD2029A
  • CD Mechanism:  PEA1179
  • Frequency response:  2 Hz - 20,000 Hz
  • Signal to noise ratio:  > 108 dB
  • Dynamic range:  > 96 dB
  • Total harmonic distortion:  < 0.0028%
  • Line output voltage (max.):  2 V
  • Wow and flutter:  < 0.001% (below measurable)
  • Number of channels:  2-channel (stereo)
  • Variable line output (stereo):  1x cinch/RCA
  • Fixed line output (stereo):  1x cinch/RCA
  • Digital output (stereo): 1x optical 
  • Accessory jack: CD-Deck synchro to tape
  • Headphone jack: motor drive volume control
  • Accessories: remote control unit
  • Remote batteries: 2x AAA
  • Power consumption: 15 Watts
  • Operating temperature:  +5 to + 35 C
  • Dimensions: (W) 420mm, (D) 286mm, (H) 110mm
  • Product weight:  3.9 kg
  • Country of Manufacture: Japan
  • Year(s): 1995 - 1996
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