Characterful Krell
Krell KPS-20i
Retail price approximately $9000
A friend of mine owned a KPS-20i, which he graceously loaned to me for a review. This is a very heavy player, with super-sturdy build. Interestingly, the KPS-20i didn’t sound as muscular as I expected, instead sounding superbly fluid and refined, and even a shade too polite, with deep yet woolly bass, but that could also have been caused by ageing caps or the ageing Philips CDM-9 pro transport inside.
The CD and transport mechanism are bathed in the light of green LEDs, which you can see when you open the motorized door which covers the disc-playing chamber. Krell claims the presence of green light helps the laser recover the data from the CD, and improves the sound quality. The disc-playing chamber is sealed from outside light by the motorized sliding door.
The transport section of the KPS-20i is based on a Philips CDM-9 Pro mechanism. Not Philips’ best swing arm transport, more like one of the least reliable ones, but still a well-performing and very good sounding unit.
The laser-pickup assembly is mounted in a cast-brass block weighing 3kgs. This block holds the laser pickup, spindle, disc, and disc clamp. The whole assembly sits on additional isolation mounts attached to the chassis bottom. The entire chassis is further isolated by the unit’s external supporting feet, which are designed to neither store nor transmit energy to the transport mechanism.
Krell don’t use the standard CDM9 spindle but replace it with a custom-machined type as they found that they can reduce the tracking servo activity by reducing the effective disc eccentricity with their custom spindle. Krell claim a twofold reduction in disc eccentricity with their spindle compared to the stock Philips unit.
A star-shaped clamp, which extends to the CD’s outer edge yet has very low mass, holds the CD to the spindle magnetically.
When I compare my findings to a review I read recenlyly in Stereophile (carried out with a new unit), it is clear that my unit wasn’t 100%, as it apparently should have had very tight and articulate and super-powerful bass.
Krell KPS-25S
Retail price approximately 28.000 euro
Completely reworked from the KPS20: different electronics and different transport. What remained was the overengineering.
The heavy prismatic acrylic cover over the transport mechanism contains an electronic LCD shutter. Transparent when the transport is stopped, it turns opaque when a CD is playing, thus protecting the disc‘s data integrity from the effects of stray light.
After the CDM9, Philips started making every cheaper transports, and Krell wisely looked elsewhere. In their literature they speak of a data-grade and professional-grade transport, exclusive to Krell in North America. And indeed when searching online there are precious few players using this particular laser assembly (JVC EXU-901A – OPTIMA-4 /40S), the only ones being by JVC, Reimyo and Phase Tech, and of course the Krell KPS25S and KPS25Sc. I have no idea of these lasers’ longevity, but given the players’ age, buyers of second hand should take note of this scarcity.
The rest of the transport mechanism is also unusual, and apparently high-spec. The data-grade transport, exclusive to Krell in North America, is anchored to a massive copper plate. The high-torque disc motor, a cog-free design, benefits from rare-earth neodymium magnets. The laser assembly itself rides on a belt-driven (actually the laser assembly is thread-driven, whereby the thread itself is driven by a belt coupled to a motor), high-mass sled and is under the constant control of precise microservos. Disc clamping is handled by a electrolyzed aluminum weight that both flattens and stabilizes the disc. It is held in place by magnetic attraction when placed on the drive spindle over a disc. An ideal amalgam of high mass for stability and high torque for quick response, and decoupled from both internal and external vibration by precisely tuned elastomer mounts, the entire assembly provides the highest level of accuracy by eliminating almost all significant causes of data error.
Krell KPS-25SC
Retail price approximately 33.000 euro
I’m not a Krell expert, but I do know that the ’25 came with new DACs when 24/96 became the hype, and perhaps there were even more than 2 versions of the Sc. However, not being a Krell expert, I’m not sure what the differences are between the KPS-25S and KPS-25Sc, apart from the obvious changes to the exterior (that bold nose in the middle and shiny aluminium knobs). It’s not CAST, as this is also present on the earlier 25 model. From what I could find, I’d say that they are likely very, very similar inside, apart from the DACs used.
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Philips DAC and Transport List
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