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The CDX2 boasts 20 regulated power supplies for the digital & analogue circuits, high quality Burr Brown PCM DAC’s, a seven-pole analogue filter, and a beefy linear power supply. The Naim path comes in the form of the undisputed XPS power supply, this multi-regulated linear supply when connected to the CDX2 power the analogue stage, leaving the internal supply of the CDX2 to take care of digital supplies. This very worthy, if costly addition give the CDX2 even more ‘balls’, further improving dynamics, depth and weight, clarity, and adding a degree of refinement to the sound.

The sound of the CDX2 is going to divide opinions, what matters is what you value in your music. If you are looking for a refined, easy on the ear sound, than the CDX2 won’t make a lot of sense.  So when asked to upgrade the CDX2 we took a long hard look at the players circuit design to make sure we ticked all the right boxes. The modified player had to keep all the strengths of the original but provide and improved sound-stage, more tonal naturalness and refinement across all frequencies. The modifications also had to be equally effective with or without the XPS, and additionally boost performance if an XPS was in use. The chosen modifications are in-line with Naim Audio’s thinking, a lower noise floor, lower jitter, and improved signal transfer. The CDX2.2 already uses ‘extra low noise regulation’ for the master clock, but a lower phase noise clock is an altogether better thing. The OEM clock in the CDX2 is replaced with the Superclock 4. This fourth generation of “Superclock” uses a discrete, ultra-low phase noise oscillator and has on-board two dedicated very low noise regulators. The task of replacing the clock is quite gruelling due to the structure of the player but the results were worth it. The two areas of performance that let the side down with the stock CDX2 were all but forgotten about, sound-stage and refinement. The new clock opened up the sound-stage creating increased front to back depth, height and width, with improved stability and pin-point focus. The upper mid-range to high treble frequencies now had naturalness, delicacy, without harshness or bite that could creep in on the stock player. The player was still as invigorating, but less tiring to listen too, making less work of unravelling the music and allowing you to get on an enjoy it.

Next up was the analogue output stage, again the character of the player could be changed by exchanging passive parts in the analogue filter, but in-line with our brief to retain strengths we chose a different approach and installed Bybee Slipstream right at the analogue output connecting directly to the DIN/RCA plugs. This was an easy upgrade to A/B, and although accustomed to the benefits of Bybee on audio signal we took nothing for granted. It took seconds to realise the improvements the Slipstream purifiers made to the sound, the music had improved spatial qualities around voices and instruments; a significant improvement in sound-staging, tones were more natural and grain-free.

The regulated supplies in the CDX2 are the industry standard LM317/LM337 adjustable type. By using multiple regulators for individual blocks of circuitry helps reduced noise levels. The core of a linear regulator is an operational amplifier. In order to reduce cost, most monolithic linear regulators, including the LM317 use a simple operational amplifier which generates additional noise. The LM317 datasheet shows the regulator has a typical output noise of 0.003% of the output voltage. With the analogue audio supplies running at 15V DC, this 0.45mVis not negligible. Additionally, the Power Supply Rejection (PSRR) of these regulators is above average at lower frequencies (100 Hz) where they manage a respectable 60-70dB. However, with increased frequency the PSRR rapidly decreases, offering only 20 db at 100 KHz.

The solution to this a discretely designed regulator specifically designed to meet the demands of audio circuits. To meet this criteria Audiocom have developed their own bespoke discrete regulators. These regulators feature (1) very wide bandwidth (2) ultra-low noise (3) high PSRR. The new regulators design means noise is rejected at the input so the circuit being powered is "isolated" from input noise (noise contribution from the Switch Mode Power Supply /SMPS).

For the analogue stage we replace the LM317/LM337 regulators with “Super-regulators”, the Super-regulator 3 will provides a PSRR of up to 120db across a wide bandwidth. The audible benefits here are immediately apparent, lower frequencies have improved control, the midrange is more open, cleaner and the highs are more extended and sweeter.

At 3 nil we might of quite while we were ahead but there was more to come. The secondary AC analogue feeds in the CDX2 are separated between digital and analogue supplies. We installed 4x Bybee Slipstream purifiers on the analogue AC rails and accessed the sound. On listening the noise floor was certainly lower, Blacks were Blacker, a veiling was gone that had previously masked elements of the music. You could now hear the finer detailing in the mix and more of the acoustic venue. Adding a further three Slipstream purifiers to the AC digital brought further benefits, and although to a lesser degree than the analogue supplies it was still more than enough for the Bybee to stay firmly fixed.

The bridge between the price gap of the CDX2 and CDS555 is not small, and an upgrade that for many will remain an unreachable goal. Our modified CDX2 is a clever mix of all that makes the original player so enjoyable with the natural, refined sound that would only ever come with a cursed brand change.

Naim CDX2 & CDX2.2 Level-1 Upgrade

Superclock 4 master clock
3x Bybee Slipstream for analogue outputs
2x Super-regulator 3 for positive analogue DC supplies.
2x Super-regulator 3 for positive negative DC supplies.
WBT 4% Silver solder throughout.

Naim CDX2 & CDX2.2 Level-2 Upgrade

Superclock 4 master clock
3x Bybee Slipstream for analogue outputs
2x Super-regulator 3 for positive analogue DC supplies.
2x Super-regulator 3 for positive negative DC supplies.
4x Bybee Slipstream for analogue AC supply
WBT 4% Silver solder throughout.

Naim CDX2 & CDX2.2 Level-3 Upgrade

Superclock 4 master clock
3x Bybee Slipstream for analogue outputs
2x Super-regulator 3 for positive analogue DC supplies.
2x Super-regulator 3 for positive negative DC supplies.
4x Bybee Slipstream for analogue AC supply
3x Bybee Slipstream for digital AC supply
WBT 4% Silver solder throughout.