Here's one for you guys,
On the main PCB, we have caps after the + and - 15 volt regs. They are C21 and C91 , 1000uf 25 volt.
Now why does only C21 have a 47NF film in parallel? Usually you would have both the negative and positive supply caps bypassed with film caps.
Anyways, I removed the single 47nf film (C20) and installed 2 new film caps, 1 on C21 and 1 on C91.
On the main PCB, we have caps after the + and - 15 volt regs. They are C21 and C91 , 1000uf 25 volt.
Now why does only C21 have a 47NF film in parallel? Usually you would have both the negative and positive supply caps bypassed with film caps.
Anyways, I removed the single 47nf film (C20) and installed 2 new film caps, 1 on C21 and 1 on C91.
Hi Brent.
Good to see you back.
As your the man an all that, can you give you opinion on adding a input selector to the DAC on the 640C V2 please? I can figure out the installation - see post above - but I have no idea if this will effect sound quality or if there are any other technical considerations.
I bought a Sony sky digibox with digital optical out. The plan is to use the CA as a DAC/output stage to get better sound from TV/Radio on Sky. Obviously I still want a working CDP and I dont want the sound quality to be sacrificed. What do you reckon?
Rgds,
Mike.
Good to see you back.
As your the man an all that, can you give you opinion on adding a input selector to the DAC on the 640C V2 please? I can figure out the installation - see post above - but I have no idea if this will effect sound quality or if there are any other technical considerations.
I bought a Sony sky digibox with digital optical out. The plan is to use the CA as a DAC/output stage to get better sound from TV/Radio on Sky. Obviously I still want a working CDP and I dont want the sound quality to be sacrificed. What do you reckon?
Rgds,
Mike.
CA DACmagic.
Intreresting.
Cambridge DACmagic
I reckon I'll leave the 640C alone then. Adding a good DAC for the skybox (and playstation) is a better idea. The DACmaginc look's the buisness but I dont know if I'm prepared to spend £200 for better sound on TV. Its not a priority. One thing I would consider is a good DIY DAC. Any reccomendations that dont cost too much?
Intreresting.
Cambridge DACmagic
I reckon I'll leave the 640C alone then. Adding a good DAC for the skybox (and playstation) is a better idea. The DACmaginc look's the buisness but I dont know if I'm prepared to spend £200 for better sound on TV. Its not a priority. One thing I would consider is a good DIY DAC. Any reccomendations that dont cost too much?
mikesnowdon said:Heres mine, its the rev 6. I dont have my service manual with me now but can anyone tell if my +/- 15v opamp supply has the bypass caps or not?
I know it sounds daft to ask as the pic shows 2 grey box caps but I cant check against the scematics at the moment.
Hi Mike,
The 2 grey box caps you see between the (2) voltage regs are on the input side of the regs.
It's C20 that is on the output side and is missing its counterpart.
I have a pair of Panasonic FC 4700uf 25v caps which I was thinking of using to replace the main PSU caps. Is this ok, I know the voltage is a bit close?
Also I have a pair of 1.0uF Wima polyesters which I was thinking of using to bypass the 470uf BG STD I have after the +/- 15v Spower regs on he op-amp supply. Is it worth it with the Spowers and BG caps? If not I could use them to bypass something else but what?
Any ideas what a pair of 1.0uf Evox Rifa might be useful for in this machine?
I have all these parts ready to go....
Kevin,
Can you tell me more about you mod in post 347 please?
Mike.
Also I have a pair of 1.0uF Wima polyesters which I was thinking of using to bypass the 470uf BG STD I have after the +/- 15v Spower regs on he op-amp supply. Is it worth it with the Spowers and BG caps? If not I could use them to bypass something else but what?
Any ideas what a pair of 1.0uf Evox Rifa might be useful for in this machine?
I have all these parts ready to go....
Kevin,
Can you tell me more about you mod in post 347 please?
Mike.
mikesnowdon said:
-Your Panasonic FC 4700uf 25V will be fine for the main power supply smoothers. You have 21 volts there, so your caps rated at 25 will be work.
-The Wima 1uf caps are a bit too large to use as a bypass with the 470uf BG. I would look for something 47nf-100nf.
In my post 347, these ceramic caps are installed to shunt any noise generated by the IC to ground instead of back into the V+ supply.
Hi Brent.
As you know I am looking to add a separate PSU and trafo for the clock soon. The plan is to use one of your PSU boards, I notice it allows for small value bypass caps around the regulator so I'm a little confused on how to implement it.
- I already have a +5v spower on the clock, Is it best to keep the spower reg close to the clock or can I mount it on the psu board?
(I guess if the PSU board is close to the clock its not an issue)?
- When using an spower do I need not worry about the small bypass caps on the output? What do you recommend here?
- For the main smoother am I OK with a 1000uf Pana FC? (I have one spare).
- What size trafo do I need?
Cheers,
Mike.
As you know I am looking to add a separate PSU and trafo for the clock soon. The plan is to use one of your PSU boards, I notice it allows for small value bypass caps around the regulator so I'm a little confused on how to implement it.
- I already have a +5v spower on the clock, Is it best to keep the spower reg close to the clock or can I mount it on the psu board?
(I guess if the PSU board is close to the clock its not an issue)?
- When using an spower do I need not worry about the small bypass caps on the output? What do you recommend here?
- For the main smoother am I OK with a 1000uf Pana FC? (I have one spare).
- What size trafo do I need?
Cheers,
Mike.
Hi.
Im wondering about changing the opamps in my CDP. Not sure I like LM4562 anymore. Am I right that the middle pair of the 6 have the most influence on the sound? I'll be honest I have no idea why there is 6 opamps in there I think the outside pairs form some kind of filter?
Anyway, do I need to change all 6 or can I just play with the middle pair?
Also, I dont have DC blocking caps on the output as the DC offset is low enough with the national 4562 opamps. Would adding an appropriate cap calm things down a bit while using the 4562?
Basically I find the player to be a bit too 'toppy' now. Im hankering for something a little warmer with fuller bass while retaining the detail and air of the LM chip.
cheers,
Mike.
*Still hoping for some advice on my questions in the above post too.
Im wondering about changing the opamps in my CDP. Not sure I like LM4562 anymore. Am I right that the middle pair of the 6 have the most influence on the sound? I'll be honest I have no idea why there is 6 opamps in there I think the outside pairs form some kind of filter?
Anyway, do I need to change all 6 or can I just play with the middle pair?
Also, I dont have DC blocking caps on the output as the DC offset is low enough with the national 4562 opamps. Would adding an appropriate cap calm things down a bit while using the 4562?
Basically I find the player to be a bit too 'toppy' now. Im hankering for something a little warmer with fuller bass while retaining the detail and air of the LM chip.
cheers,
Mike.
*Still hoping for some advice on my questions in the above post too.
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