Cambridge Audio 640C v1 Mods

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#330
For months I have been meaning to look inside my 640 to see what I can up-grade. A new year, a new project! I would have thought that it should be quite easy to add a Dig In to the dac to use with an external source. You seem to have delved around enough inside to see what would be involved? I assume that all you need to do is identify the Dig In on the Dac board and wire up a toggle switch to the external input.
 
#331
Your probably right Puffin. The only issue is that the Skybox only has optical out. Does that mean I would need some sort of optical converter or something?

The 640C V2 is already a very good player and can compete strongly up against some very expensive competition. Theres not a lot you can do with it other than some component swaps really. Just removing a bit of grain and cleaning up the supplies enables the player to really fulfill its potential.

The player already has a decent clock so you can simply add a good low noise supply just for the clock, or if you want go for a new super-dooper clock & supply unit. I have one of Brent's Spowers on my clock. Later I plan to knock up a PSU on veroboard incorporating the spower regulator and add a small trafo for it.

Mike.
 
#333
Tube output for your 640 or 540 anyone?

CA CD player tube mods.

IMG_5230.jpg


I dont know this guy but I found it in another thread and thought it might be interesting for you.

Mike. 🙂
 
#335
Hi Ned,

It is a common upgrade to this player to remove those caps you have listed.

Just make sure to replace one of them on each channel with a jumper wire. (or you will not get output signal).

This is a very easy upgrade to try. If you do not like the sound of it you can easily go back to stock.
 
#336
Here is a question for some of the people that have installed Sanyo Oscons into the 640V2.

The (3) locations I am considering is C88, C69 and C5.

C88 and C69 follow the (2) voltage regulators feeding the digital supply of the dacs.

C5 follows the voltage reg feeding the clock.

Is this the correct place to use the Oscons? Am i missing any additional locations.

The stock C5 is a 47uf cap, I have 47uf Oscons to install, but I also have 100uf. Should i use the 47uf or 100uf?.

For the C88 and C69, the stock caps are 330uf. I do not have 330uf Oscons. I only have 100uf and 470uf Oscons. Is it OK to use the 470UF in this location? I am assuming it would be fine but I always feel good with some reinforcement.

Also can anyone help me understand the puropse of pin#21 on the WM8740? On the 640V2 schematic it lists this as DAC analogue but on the chip data sheet it says it is a digital output.

Cheers

Kevin
 
#337
mikesnowdon said:
Hi Brent.

CAnt wait to do the mods! I was thinking of changing C4 with a 10uf OSCON cap. I should check really if its what I think it is. Is it (C4) the input decoupling cap for the clock supply? If so then Its worth changing it to the oscon right? If im wrong can you tell me where the It needs to go.

Cheers, Mike.

PS, I'll post pics and report here when done so keep an eye out.
Click to expand...


C4 is the coupling cap for the input side of the regulator feeding the clock.

Should the Oscon be used on the input side of regulator? or the output side? If used on the output side, the Oscon would be between the reg and the clock. If used on the input side of the regulator, there is still another cap on the output side.

Where should it be used? Input?, output? or both input and output of the reg?

Thanks
Kevin
 
#340
On the servo PCB:

I have upgraded all caps to Panasonic FC /Nichicon FG quality.

I also replaced the 5V reg with a LM340T5 and will upgrade the 8V reg when I get some.

I also replaced the bridge with Fairchield Stealth diodes for good measure.
 
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