Ive been looking at the service manual and noticed there are 2 Scematics for the main DAC PCB. One is calle 'revision 7' and has chokes on the output near the phonos. How can I tell which version I have? I noticed my PCB is green and the one in Brents machine is blue? Also there are a lot of parts marked 'revised' in the parts lists? Confused, can anyone clear up this mystery?!
Mike
Mike
Hi Mike,
As I'm a new member I can't e-mail you. I like to know where you find the service manual, I love to get one for 640c v1
Many thanks,
Kevin
As I'm a new member I can't e-mail you. I like to know where you find the service manual, I love to get one for 640c v1
Many thanks,
Kevin
Hi Kevin.
I suggest doing a google search. I got mine through a freind. They're out there, just keep looking and you'll find it.
Maybe Lee can help you, he has a 640C
Mike
I suggest doing a google search. I got mine through a freind. They're out there, just keep looking and you'll find it.
Maybe Lee can help you, he has a 640C
Mike
Hi Mike,
Brent has a 4/7 (revision 7). If you look at his (2).jpg photo,
between the clock and the c5 capacitor, you'll see a ferrite bead.
If you have one, then you have a revision 7. If not, you have a 6.
If you have a 6, don't sweat it, I'm sure they both sound the same.
Best Regards,
Ned
Brent has a 4/7 (revision 7). If you look at his (2).jpg photo,
between the clock and the c5 capacitor, you'll see a ferrite bead.
If you have one, then you have a revision 7. If not, you have a 6.
If you have a 6, don't sweat it, I'm sure they both sound the same.
Best Regards,
Ned
kchu1377, your email is not enabled on the forum. If you would like the v1 service manual just email me at:
lee at diyhi-fi.co.uk
Cheers, Lee.
lee at diyhi-fi.co.uk
Cheers, Lee.
Awww, I love our little emails. LOL!
Ive been talking to a guy from CA technical dept and hes confirmed my board is fine and my machine not 'graded' or anything. I was thinking of getting a 'revision 7' populated pcb to see if it sounds any different. Probably wont be cheap though.
Been listening to the CA tonight and the sound is growing on me. I still have acouple of issues with the bass lacking weight, its defo more articulate though. Dynamics are fantastic, and detail better. The seperation of instruments has improved. The treble seems to high again and 'shhh' sounds in vocals are too obvious. The overall tone could be warmer, smoother and more musical.
Next on the agenda - after carefull consideration - are:
- Kiwame resistors in the signal path from the last opamps to the phonos. (Brent, can you tell me what the resistors around the opamps are doing and if its worth changeing them also)
- Panasonic FC psu caps. (am I right that these are the best?)
- Better regs on the opamp supply.
- BG Nx DAC decoupling caps.
- Rubycon ZLH caps on DAC supply.
- Clock upgrade but not sure which. Maybe C1 with a dedicated supply?
Feel free to advise comment please.
A question:
There are 2 small orange caps in the signal path near the phonos. Also 3 around the main opamps and 1 on each of the other opamps. (Ceramics I think) I want to change these for somthing better, polyprops maybe? Any ideas, is it worth it?
Mike.
Ive been talking to a guy from CA technical dept and hes confirmed my board is fine and my machine not 'graded' or anything. I was thinking of getting a 'revision 7' populated pcb to see if it sounds any different. Probably wont be cheap though.
Been listening to the CA tonight and the sound is growing on me. I still have acouple of issues with the bass lacking weight, its defo more articulate though. Dynamics are fantastic, and detail better. The seperation of instruments has improved. The treble seems to high again and 'shhh' sounds in vocals are too obvious. The overall tone could be warmer, smoother and more musical.
Next on the agenda - after carefull consideration - are:
- Kiwame resistors in the signal path from the last opamps to the phonos. (Brent, can you tell me what the resistors around the opamps are doing and if its worth changeing them also)
- Panasonic FC psu caps. (am I right that these are the best?)
- Better regs on the opamp supply.
- BG Nx DAC decoupling caps.
- Rubycon ZLH caps on DAC supply.
- Clock upgrade but not sure which. Maybe C1 with a dedicated supply?
Feel free to advise comment please.
A question:
There are 2 small orange caps in the signal path near the phonos. Also 3 around the main opamps and 1 on each of the other opamps. (Ceramics I think) I want to change these for somthing better, polyprops maybe? Any ideas, is it worth it?
Mike.
Get the best clock and regulators you can buy.
judge which are the best by the specification measurements.
judge which are the best by the specification measurements.
I'd have to understand those measurements first, but good point.
Ive learnt loads so far though, more to come. By the end of this I'll be a 640C mod expert! Might start a company.....
Ive learnt loads so far though, more to come. By the end of this I'll be a 640C mod expert! Might start a company.....
Ned.
Thanks for the info above.
Everyone, check this out:
Below is the frequency response of the lm4562.
Huge rise in the treble band, explains why it makes a bright CDP sound worse, may add coils to keep it down or a parallel capacitor just before the phonos. Would need to be able to measure the response of the player in order to get the right values though.
Thanks for the info above.
Everyone, check this out:
Below is the frequency response of the lm4562.
Huge rise in the treble band, explains why it makes a bright CDP sound worse, may add coils to keep it down or a parallel capacitor just before the phonos. Would need to be able to measure the response of the player in order to get the right values though.
Mike 5Khz plus is right up in the high treble reason and this should not be causing you any problems.
Your problem is regulation, the rails are too noisy in the CA. A clock will also improve timing.
Brent
Your problem is regulation, the rails are too noisy in the CA. A clock will also improve timing.
Brent
They do sound a little bright. The 640 has a bright presentation already and to my ears the LM4562 have highlighted that. Dont get me wrong though there are definate positives on this opamp. Anopther factor is that my amp is also a bit on the bright side.
Im going to continue wih the mods, including what you suggest and hopefully things will get more balanced. Obvoiusly my amp will need upgrading eventually too. Also my speaker cable dosent help. I think that needs changing sooner rather than later. Moneys tight so I might go for the new Chord stuff.
Im going to continue wih the mods, including what you suggest and hopefully things will get more balanced. Obvoiusly my amp will need upgrading eventually too. Also my speaker cable dosent help. I think that needs changing sooner rather than later. Moneys tight so I might go for the new Chord stuff.
Attenuating your amp inputs or interconnect will bring a less harsh/bright sound. What often happens (and with same manufacturer stuff) the output voltage is to high (typically 2Vp-p) for the more delicate input sensitivity of the amp (typically 500mV).
This causes a slight input distortion that is heard as an over bright over aggressive sound. Attenuating the leads or input lowers the input signal and cures this, all you do is turn the volume knob more for it to be louder (after all 12oclock is usually max v on an amp).
Another benefit to the attenuation is the fact you are using the vol pot further round and at these points the channel seperation is much better + its easier to find the desired volume.
When you attenuate the leads its always done in the rca plug at the amp end. Use good quality 0.1% tol resistors).
Brent
This causes a slight input distortion that is heard as an over bright over aggressive sound. Attenuating the leads or input lowers the input signal and cures this, all you do is turn the volume knob more for it to be louder (after all 12oclock is usually max v on an amp).
Another benefit to the attenuation is the fact you are using the vol pot further round and at these points the channel seperation is much better + its easier to find the desired volume.
When you attenuate the leads its always done in the rca plug at the amp end. Use good quality 0.1% tol resistors).
Brent
Thanks Brent.
I have noticed the ouput of the CDP is higer since the the mods.
When attenuating the cables/amp is it it important to use good quality resistors and would different ones have a different sound?
Should I use the values you give ion the schematic?
I have noticed the ouput of the CDP is higer since the the mods.
When attenuating the cables/amp is it it important to use good quality resistors and would different ones have a different sound?
Should I use the values you give ion the schematic?
Using the following resistors from RS will have no impact on the sound character.
Yes -11db is a pretty decent attenuation so use the these values.
10K = 166-728
6K81 = 166-560
P.S these resistors are also brilliant around the opamps.
Brent
Yes -11db is a pretty decent attenuation so use the these values.
10K = 166-728
6K81 = 166-560
P.S these resistors are also brilliant around the opamps.
Brent
Thanks brent.
By the way, have just installed 0.39uf Crosscaps in my speakers. Treble sounds better now and the sound is a touch warmer.
RE: Attenuation.
I'm considering upgrading the volume pot in my amp, could I use a different value pot to acheive the same effect as you mention above?
Mike
By the way, have just installed 0.39uf Crosscaps in my speakers. Treble sounds better now and the sound is a touch warmer.
RE: Attenuation.
I'm considering upgrading the volume pot in my amp, could I use a different value pot to acheive the same effect as you mention above?
Mike
excellent.
I do think your amp is overbright and with other items maybe a touch on the brighter side its not adding up to the best balance.
Keep us posted on the attenuation
Brent
I do think your amp is overbright and with other items maybe a touch on the brighter side its not adding up to the best balance.
Keep us posted on the attenuation
Brent
mikesnowdon said:
Changing pot will bring audiable benefits but it won't do what the Fixed attenuation is doing or not in the same way. It's also down to where the given resistance is on the pots as to what volume each pot gives. You could still have high input sensitivity with another pot. With the fixed you know its correct.
Some people may argue the case here but I do think you would have to test quite a few pots first to find the perfect one.
A pot is also much more expensive. I have attenuation on the input and a TKD pot.
Brent
I have been messing about quite a bit with my 640v1. It is now running an entirely new, fully discrete class a output stage (cheers for the help there Brent).
Also fitted an extra tx supplying a +5v SPower on dac analog and +5v Audiocom Invisus on clock & buffer.
Sounding very, very good now.
Lee.
Also fitted an extra tx supplying a +5v SPower on dac analog and +5v Audiocom Invisus on clock & buffer.
Sounding very, very good now.
Lee.
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