Cambridge Audio AZUR 640C V2 CD Player Level-1 Upgrade

The auction is for the modification only and does not include the Cambridge Audio Azur 640C CD player which must be purchased separately.

This is a service for modifying Cambridge Audio CD players (please ask for other manufacturers & models)

If you own a Cambridge Audio 640C and want to upgrade then you are going to need to spend in the region of £800 - £1000 on a new CD player to hear any marked improvement. Audiocom have developed two levels of upgrades which drastically improve upon the 640C and surpassing stock players to at least £1K (level-2). Here is how. The 640C is considered budget or ‘entry level’ in the Hi-Fi market but in fact uses one of the very best DAC’s available, the Wolfson WM8740. The WM8740 is the choice by Arcam in their top of the range FMJ CD36 player. Cambridge Audio have scaled down the performance of the 640C to meet the ‘budget’ market, and used cheap, lower grade parts for the  WM8740 ‘s associated audio circuits to place it below their costlier 840C. With the stock 640C the WM8740’s performance is understated, performance held back and you do not hear anywhere near the potential of these 24-bit player.

The Audiocom level-1 upgrades install an active analogue stage using superior op-amps to those in the stock 840C, add an ultra-low jitter reference master clock, improve component level quality for the power supplies, decoupling and signal coupling. Level-2 advances performance by upgrading the audio board DC regulated power supplies and upgrading the power supplies and regulation of the Precision Servo 2.0.

24-Bit DAC Magic

Like other Cambridge Audio products gone before it, the 640C’s excellent circuit topology means serious improvements can be unlocked. With a justifiable and practical expenditure the 640C V2 loses its foibles and becomes a thoroughly capable and refined CD player.

The 640C is divided in to two main PCB’s, the servo PCB (digital) and main PCB (digital & analogue), it is the main PCB which is the focus of the Level-1 upgrades. Containing main power supplies, regulation, master clock, DAC & analogue output stage this PCB is certainly where most of the action happens.

First off we replace the ‘cooking grade’ capacitors used for power supply reservoir (smoothing AC) for Panasonic FC type. The FC series although not selected as “audio grade” outperform several types of electrolytic pitched at the audio market. The main PCB contains several fixed voltage regulators for the +/- 15V analogue supply, +5V DAC supplies. High grade bypassing is essential to reduce noise and impedance on the power supply lines; here more general purpose capacitors are upgraded to Panasonic FC & Rubycon ZA type.

The master clock in the 640C hides underneath a screening can and is labelled ‘low jitter’. Beneath the can we find a TCXO which is powered by a 7805 regulator. The output of the TCXO is buffered by a 14-pin CMOS inverter and the outputs from this sent directly to the Wolfson WM8740 DAC’s. This arrangement has several drawbacks, the limited power supply rejection of the 7805, output noise of the 7805, CMOS gate oscillator in the TCXO has poor signal to noise ratio; the selected crystals inside the TCXO have low Q and a used in parallel mode, a method which is highly susceptible to digital noise injection. To attain the highest level of sound quality from these circuits the OEM clock is removed and replaced with the Superclock 4-S ultra-low jitter master clock.

The post DAC filter in the 640C is a little unusual, it uses what is called a ‘double balanced’ filter rather than the normal low-pass filter. A total of 6x NE5532 operational amplifiers follow the Wolfson WM8740 for filtering and buffering. The 5532 is an ordinary consumer grade op-amp, a great workhorse in its day but it can be significantly better by modern op-amps. Here we use a mix a top spec op-amps costing 20x the price of the 5532 to wring the most out of the WM8740 DAC’s. The superb LME49720 are enrolled for the filter stage, then AD825 on Brown Dog adapters for output signal buffering. The AD825’s we found to be superior to the LM4562 or LME49720 for signal buffering. To finish we replace the cheap non-polar electrolytic & HF bypass capacitor for output signal coupling with a Black Gate N capacitors, the N series are the connoisseur’s choice for signal coupling sounding better than most audio grade film capacitors.

Cambridge Audio 640C Level-1 Upgrade @ £235.76

1x Superclock 4-S ultra-low jitter master clock.

2x Panasonic FC analogue power supply capacitors.

2x Panasonic FC analogue regulator bypass capacitors.

4x Rubycon ZA capacitors for WM8740 DAC decoupling.

4x LME49720 op-amps for differential filter stage.

2x AD825 modules for output signal buffer stage.

2x Black Gate N output signal coupling capacitors.

Sontech SFRT-AL resonance control.

WBT 4% Silver solder used throughout.

Showdown

The 640C V2 already ranks as the best player under £500.00 so what does spending an extra £240.00 bring in real terms? We left the Level-1 modded 640C on repeat 24/7 for 100 hours before making our assessment. The 640C has a characteristic of sound which is easy to latch on to, perhaps it’s the signature of the WM8740 DAC’s that shine through. Having another unmodified 640C to hand we sat down and made the comparisons. Listening in to the unmodified 640C we started out with a man who knows how to play piano; Ludovico Einaudi and his recent album Divenire was set to play. On the title track ‘Divenire’, this excellent piece can be beguiling and the stock 640C managed the intro well but as soon as the track became more complex the highest treble notes started to harden and the recordings leaner balance did not bode well with the 640C.  Moving to the modified 640C the same track ‘Divenire’ showed an enormous shift in music making ability, the modified 640C was streets ahead. The piano sounded that much more real and 'live', the timbre and tones of instruments were more believable. The music flowed effortlessly with superb coherence keeping control and poise during the intricate shifts in tempo. 

Sting’s Sacred Love album puts any CD player through its dynamic paces and the unmodified 640C fared much better with this album. The sound was lively and intelligible throughout and ‘Forget About The Future’ conveyed and excellent sense of feeling. However, the powerful notes on this track were understated, thinner, blander the sound compressed with less space. Switching to the modded 640C and with the first track ‘Inside’ Sting had yet to sing and the realisation of extra power, depth and spatial qualities felt. Stings voice was strikingly real, full of meaningfulness; raspy and rich in character. Behind the voice the instruments surged with energy, control; details and nuances uncovered; the sound shimmering with passion and life.The modded 640C’s finest achievement is that it maintains an open and uncluttered perspective on all recordings, even those CD’s in the ‘don’t play’ box get a look in!

How to Order

The Cambridge Audio Azur 640C V1 or V2 Level-1 modification is supplied & installed by Audiocom for £235.76 inclusive (excludes carriage).

Once you have purchased the Level-1 modification please contact us to schedule and book your 640C for the installation. We can offer reasonable rates for insured courier collection & return to mainland UK from your home or workplace (excludes weekends).

The modification work is completed with 2-3 working days from receipt of the CD player. The Level-1 modification is covered by a 2 year parts & labour guarantee, this guarantee excludes any OEM parts such as laser & LCD display.