Cambridge Audio 640C v1 Mods

[Thomo]

Hi everyone. Just thought I'd start a thread showing the progress I've made modding my Cambridge 640C player.

Just started with it really - changed opamps to lm4562's and beefed up the analog supply caps so far. Will be doing plenty more soon.

Does anyone know of some specific mods to this player? Particularly the Servo board?

I'll post some pics soon.

Regards, Lee.

[sq225917]

Lee, there's nothing thats worth doing to the servo board, unless you wanted to fully regulate it and give it its own transformer.

Bits are bits, the servo board does not 'limit' the ability of the optics to extract the correct data, the only interplay possible could be via the transformer.

If you wnat to mod the unit, damp the base of the chasis under the cd mech with dynamat, this will tighten up the bas significantly.

You can also replace the monolithic regulators that feed the XO and the dac chips with discreet units, Tentlabs shunts etc.

You could replace all the stock caps on the DAC/output board with Pana Fc's and Oscons, they have little effect.

I have an 840 with Tentlabs clock, Tentlabs regs for dac chips and the XO, i swapped the stock opamps for AD chips and LM4562's, all of which benefitted the sound removing digital hash and clearing up the treble.

But the biggest improvement came from damping the case work and particularly the alloy webbing structure that supports the cd mech with dynamat, this made a huge chnage to the bass presentation, really tight, no overhang.

the dynamat was £20, the electronic upgrades cost £300, and the dynamat was by far the largest change, a real difference in clarity, the electronic work just polished the sound and removed some slight remaining glare in the treble.

[Thomo]

Hi, thanks for your reply. I have extensively modded my Marantz CD67, and was just wondering if this cambridge could get anywhere near it.

I have removed the dc blocking caps as there's no dc to block!
I also removed some of the crappy mylar caps right on the dac and replaced with Black Gate Nx hi q's.

Also replaced the four mylar's at the opamps, C8 C11 C38 C40 with 220uF Black Gate STD's.

The sound is now much clearer and more detailed, with far better bass.

More coming soon lol...

edit: also removed those poor quality Bi-polars from the reg outputs

Lee.

[Thomo]

[Fidelity Audio]

I've just bought a new V2 to upgrade, the servo pcb is identical but the main pcb is much bigger (due to twin dac and associated circuits). I've looked at the servo pcb and there are things you can do like regs and better caps but there is a lot more to do around the psu and dac. The Psu is pretty poor, every reg runs off one volt rail so adding extra txs would benefit.

Brent

[Thomo]

Hello, thanks for chiming in

Is this player compatible with this:http://www.audioupgrades.co.uk/discrete.shtml

I thought about adding extra tx's etc, plenty of room. I should be getting some in stock to play with fairly soon.

Lee.

[sq225917]

is that fish i can smell.?

[Thomo]

ha ha

[Fidelity Audio]

LOL @ Lee

I will be adapting the discrete to work with it yes lol

Brent

[SimontY]

Originally posted by sq225917
is that fish i can smell.?

Someone get the cap polarity wrong?