Classe Audio CDP.3

We will be looking at the Classé Audio CDP.3. Received as the kind of audiophile gift most can only dream of. It even came with the original remote which is impressively milled from a single block of aluminum. My first fear was that it was toothless and had some variation of 90's sigma delta technology which, while fine for mere mortals, is not suitable for the higher plains we are traveling to today.

Luckily the gods of chance, engineering parts selections, and favorable BOM balance have smiled on us with dual PCM1702-J, a PMD100 filter, a collection Burr Brown OPA604 and OPA2604 op amps sitting in a very competently designed output stage. The output stage as designed by Classé (note the colorful polypropylene capacitors):

R306, R309 on the right and R314 on the output of the left DAC are a nice touch to be found only on some of the finest players. They are DC offset nulling resistors hand matched for each DAC. Classé uses them to avoid a decoupling capacitor before the output RCA jacks. A wise choice.

Also a very nice toroidal transformer:

Below an EMI/Line filter. Very useful these days given the many switching power supplies we live with. Not as critical with the use of quality line filtering but desirable nonetheless: 

An overview of the player:

But what is in the black box center right?

Bam! That would be the digital section where we will be focusing our attention today. 

What was that black box about? EMI shield? Maybe, I'm betting Classé wasn't so sure that they wanted people knowing they were using a Sanyo transport in one of their players. The scandal! In an interesting twist Krell, CEC, and Parasound use the same transport in some of their more entry level players. CEC actually built one of their dedicated transports around this humble digital section. 

The Sanyo laser. Nice and reliable. Reads everything and is fairly easy to replace if it fails. The belt for the CD mechanism did need to be replaced otherwise the CD tray would open on only the third try. 

Belt wear is pretty common on older players and our specimen today is from 1995. Replacing rubber belts is really part of my usual disassembly, cleaning, and lubrication of the transport assembly. Dow Corning Molykote was used in this case and is the preferred lubricant due to its plastic compatible nature and long lasting synthetic chemistry.

I have started with modifications to the digital board. Below are the replacement bulk filter capacitors from Nippon Chemi-Con and Nichicon. The KZN replacements have 40% more μFs then stock! The KZN from Nippon Chemi-Con are rated at 10,000 hours at 105C and have excellent long life characteristics. 

Here we are replacing more capacitors. Utilizing the aptly named shotgun recap approach the power supply rails of every digital IC on this board will be replaced with a low ESR polymer capacitor for decoupling. Here we are using some of the finest the SEPC OS-CONs on IC101 which supplies power for the laser read assembly. 

It is perhaps fitting that we are using Sanyo capacitors on a board made by Sanyo. Sanyo launched the first low ESR TCNQ based capacitors in 1983 under the OS-CON brand name. 

The image above shows a comparison between a modern SEPC organic polymer OS-CON on the left and the original solid TCNQ based OS-CON on the right (both are 100μF)

Below we can see the digital board in progress. Capacitors with a red dot are upgraded with polymer. Those with a Green dot are upgraded with quality electrolytics. The polymers with the blue stripe on top are from Nippon Chemi-Con. 

Unfortunately, Classé tried to pull a bit of a fast one by not including the schematic for the digital board in their service manual. Classé I know you are an audiophile manufacturer but a service manual is incomplete if you are missing schematics for major system boards. Fortunately, a helpful Russian posted a jpg version of the schematic for an identical CEC transport. Bolshoe spasibo! With this I was able to successfully identify all of the major decoupling capacitors without having to trace the board with a volt meter. 

The output stage with PMD100 digital filter. C201 was replaced with a SEPC OS-CON. I experimented with replacing the digital filter but I found the PMD100 to be an exceptional digital filter when properly decoupled.

Classé probably should have added some multi-layer ceramics to the stock tantalum capacitor for bypass on the PMD100. The data sheet from Pacific Microsonics is quite emphatic about the need for quality low ESR capacitors if output of the filter is not re-clocked.

The Classe Audio CDP.3 sounded quite good for a stock CD player but I was not overly impressed. The highs were a touch abrasive which surprised me since it is rare for multibit R-2R dac to sound that way. Something very odd was going on with the sound stage stock. It had a closed in and muffled quality that was alleviated by the first batch of OS-CONs on the digital ICs. 

My suspicion is that these mods may be addressing jitter by properly supporting the power supply rails for these early digital ICs. Jitter is definitely a strange beast to fight. Generally using extremely fast decoupling on all the digital ICs and/or re-clocking the signal whenever possible is recommended. 

So how does it sound now? Lovely liquid mids and highs. Overtones decay like motes of dust in the sun. It rests among the shoulders of giants. Vocals shimmer with a rare presence smooth and clear. Piano is an impact whose warm tones decay into the twilit hall. 

Next task is really to add a superclock. Then the Classé will sit happily with the finest.

~Sigmore Hoffman signing off~