Hi Mike,
Yes the middle 2 are the analog output.
How do you have them decoupled? Also what size of cap ( C38, C54 etc) do you have at the middle 2 op-amps?
I have OPA627 in those locations and 100uf Blackgate with .01 Wima film in parallel (V+ and V- to ground) as well as a .01 film between V+ and V- .
Yes the middle 2 are the analog output.
How do you have them decoupled? Also what size of cap ( C38, C54 etc) do you have at the middle 2 op-amps?
I have OPA627 in those locations and 100uf Blackgate with .01 Wima film in parallel (V+ and V- to ground) as well as a .01 film between V+ and V- .
Hi Mike,
I had 10uf blackgate but after much reading, for the opa627, the consensus seems to be 100uf is optimal. if you have any good 100uf caps (cerafine, silmic etc) give it a shot. I think the film cap might be chip op-amp dependant.
I tried the 100uf with film over 10uf with no film and i like the results better.
i upgraded all power regs to mc7805ct (15v for audio section) and the results are good so far.
I had 10uf blackgate but after much reading, for the opa627, the consensus seems to be 100uf is optimal. if you have any good 100uf caps (cerafine, silmic etc) give it a shot. I think the film cap might be chip op-amp dependant.
I tried the 100uf with film over 10uf with no film and i like the results better.
i upgraded all power regs to mc7805ct (15v for audio section) and the results are good so far.
I removed the DC blocking caps on my output too. no issues, i cant see you having any issues either.
Try the Muse first, I like Muse caps, they are cheap and seem OK in most locations.
Did you notice an improvement with the Spower regs?
The first Spower I will try will be for the clock and then maybe servo supply.
I am starting to like the 640CV2 a lot.
Do you have any other ideas for mods?
Have you replaced your rectifier diodes yet?
Try the Muse first, I like Muse caps, they are cheap and seem OK in most locations.
Did you notice an improvement with the Spower regs?
The first Spower I will try will be for the clock and then maybe servo supply.
I am starting to like the 640CV2 a lot.
Do you have any other ideas for mods?
Have you replaced your rectifier diodes yet?
I'll do that.
I have some shottkey diodes and Panasonic FC cap's to fit in the main PSU.
Probably some bitumen damping material and possibly a new thicker, heavier bottom plate with spike or cone feet would be good.
Some Carbon film resistors around the output stage would probably be good too.
Im planning a seperate PSU and Transformer for the clock also. And better regs on the DAC's. Maybe even give the digital rails of the DAC's their own trafo too. I haven't done anything to the servo yet. How does it affect the sound? What's worth changing on it?
I have some shottkey diodes and Panasonic FC cap's to fit in the main PSU.
Probably some bitumen damping material and possibly a new thicker, heavier bottom plate with spike or cone feet would be good.
Some Carbon film resistors around the output stage would probably be good too.
Im planning a seperate PSU and Transformer for the clock also. And better regs on the DAC's. Maybe even give the digital rails of the DAC's their own trafo too. I haven't done anything to the servo yet. How does it affect the sound? What's worth changing on it?
Anyone who has read this thread will probably know Ive been running stupidly overkill Kiwame resistors on the output.
Today I changed these to Caddock's as the Kiwames were just wrong, they were sitting there like antennas picking up RF and not helping to keep the signal path as short a possible.
I also changed the local decoupling cap's on all opamp to Wima 47nf polyester film. The reason for this is that I was hearing a slight grain in the treble and it was suggested to me that too much local capacitance could cause this. The wimas have improved the treble and the sound is more balanced too with a slightly warmer texture.
I removed the film bypass on the +VE opamp supply cap, and tacked a 47nF wima on each of the +/- rail caps (thanks to Kevin for the heads up). Also fitted a pair of Panny FC'c on the main board PSU.
Finally I installed a PFM Flea with dedicated PSU from Brent.
If anyone is considering adding a Flea to their CA this is the best way to implement it (as advised by Martin Clark):
Build up the Flea minus the Tent XO, Ferrite, and 47nf resistor (on the output). You add these to the CA motherboard instead. The CA already has a decent XO but you can add the Tentlabs module if you like. I might do this myself just to see.
640C V2 mother board track side:
You will need to cut the tracks on the XO +VE input and signal output. Regulated +5V and 0V from Flea connectswhere the 7805 would be.
The Flea:
Normally the output cap is on the the Flea but I installed in the C5 location on the 640 motherboard so It can be closer to the XO module. You can take you +5V output and ground wire from the vacant C9 pads on the FLea (or link them to OP2 and OV).
PSU:
The PSU is built on one of Brent's boards. It consists of shottkey diodes and a 1000uF 35v Panasonic FC cap with a 47nF wima film bypass. I trimmed a bit off mine to save space. I used a Multicomp 3.2VA 15v trafo from Farnell.
Ive only had the machine up and running for an hour but I can already hear an improvement from the above mods. Brent told me how much potential this machine had before and I really think I'm beginning to realize this now with my 640.
_______________________________________
Next up I plan to add a dedicated Trafo and a 4 separate PSU's feeding the DAC's. Initially I'll use standard 7805 regs and later add 4 PFM TeddyReg's. I'll be using Brents PSU's because I really like them for the compact size and flexibilty.'Flea' details and schematic.
Today I changed these to Caddock's as the Kiwames were just wrong, they were sitting there like antennas picking up RF and not helping to keep the signal path as short a possible.
I also changed the local decoupling cap's on all opamp to Wima 47nf polyester film. The reason for this is that I was hearing a slight grain in the treble and it was suggested to me that too much local capacitance could cause this. The wimas have improved the treble and the sound is more balanced too with a slightly warmer texture.
I removed the film bypass on the +VE opamp supply cap, and tacked a 47nF wima on each of the +/- rail caps (thanks to Kevin for the heads up). Also fitted a pair of Panny FC'c on the main board PSU.
Finally I installed a PFM Flea with dedicated PSU from Brent.
If anyone is considering adding a Flea to their CA this is the best way to implement it (as advised by Martin Clark):
Build up the Flea minus the Tent XO, Ferrite, and 47nf resistor (on the output). You add these to the CA motherboard instead. The CA already has a decent XO but you can add the Tentlabs module if you like. I might do this myself just to see.
640C V2 mother board track side:
You will need to cut the tracks on the XO +VE input and signal output. Regulated +5V and 0V from Flea connectswhere the 7805 would be.
The Flea:
Normally the output cap is on the the Flea but I installed in the C5 location on the 640 motherboard so It can be closer to the XO module. You can take you +5V output and ground wire from the vacant C9 pads on the FLea (or link them to OP2 and OV).
PSU:
The PSU is built on one of Brent's boards. It consists of shottkey diodes and a 1000uF 35v Panasonic FC cap with a 47nF wima film bypass. I trimmed a bit off mine to save space. I used a Multicomp 3.2VA 15v trafo from Farnell.
Ive only had the machine up and running for an hour but I can already hear an improvement from the above mods. Brent told me how much potential this machine had before and I really think I'm beginning to realize this now with my 640.
_______________________________________
Next up I plan to add a dedicated Trafo and a 4 separate PSU's feeding the DAC's. Initially I'll use standard 7805 regs and later add 4 PFM TeddyReg's. I'll be using Brents PSU's because I really like them for the compact size and flexibilty.'Flea' details and schematic.
Hi Guys,
I'm looking for appropriate Lundhal tranies for CA v2. I would use full potential of balaced output from Wolfson CV4024 and use transformers to convert signal to not balanced. I had idea to use tubes for that but some say that transformers are better. Unfortunately I have no idea what parametres transformer should have.
Thanks for any ideas ..
I'm looking for appropriate Lundhal tranies for CA v2. I would use full potential of balaced output from Wolfson CV4024 and use transformers to convert signal to not balanced. I had idea to use tubes for that but some say that transformers are better. Unfortunately I have no idea what parametres transformer should have.
Thanks for any ideas ..
cambridge 640
hi , Thomo could you send that 640 picture with better resolution to my email , i have a 740 i want to modd as soon as warranty is over.thanks.my email is luisduarte@netcabo.pt
hi , Thomo could you send that 640 picture with better resolution to my email , i have a 740 i want to modd as soon as warranty is over.thanks.my email is luisduarte@netcabo.pt
DIY low noise regs!
Hi.
I thought I would share with you a recent mod.
I replaced the DAC regs with a simple DIY low noise reg. Its basically just adding a VBE before the 7805. A nice cheap simple mod that works wonders as the Wolfson DAC's in this machine have poor PSSR. The VBE's also help to isolate the supplies even better
Details on the VBE are here.
Hi.
I thought I would share with you a recent mod.
I replaced the DAC regs with a simple DIY low noise reg. Its basically just adding a VBE before the 7805. A nice cheap simple mod that works wonders as the Wolfson DAC's in this machine have poor PSSR. The VBE's also help to isolate the supplies even better
Details on the VBE are here.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I installed 330uF/25v Muse KZ caps after my VBE'd 7805 regs and the effect was a subtle improvement in all aspects of the sound. I had previously installed 470uF Ruby ZLH on the DVDD rail's and 220uF Blackgate's on the AVDD rails but the KZ's are much better. I'm not sure if the improvement comes from having the same size caps on each rail or if its just that the Muse are better caps...
Another change I made was to change the post reg caps on the opamp supply. Originally the player has 1000uF caps in this position but I had changed these for smaller 470uF Blackgates. Again I chose Nichicon KZ caps and selected 1000uF as this was the specified value from the factory.
These new caps were quite big making them tricky to install. For 2 of the DAC supply caps I had to remove a small 47nf bypass cap and use its location to install the bigger 330uF Muse caps. I first checked the schematic and found that there was an additional film bypass right at the DAC chip so removing the extra film cap was no issue.
Overall with these 'boosted' regs and new caps the player is sounding much better in all areas. Timbral detail is much improved and it sounds more dynamic too. Best thing is that this didn't cost much at all, about £20 all in Such a cheap yet effective mod, I recommend it!
(I'll add some pics shortly).
Another change I made was to change the post reg caps on the opamp supply. Originally the player has 1000uF caps in this position but I had changed these for smaller 470uF Blackgates. Again I chose Nichicon KZ caps and selected 1000uF as this was the specified value from the factory.
These new caps were quite big making them tricky to install. For 2 of the DAC supply caps I had to remove a small 47nf bypass cap and use its location to install the bigger 330uF Muse caps. I first checked the schematic and found that there was an additional film bypass right at the DAC chip so removing the extra film cap was no issue.
Overall with these 'boosted' regs and new caps the player is sounding much better in all areas. Timbral detail is much improved and it sounds more dynamic too. Best thing is that this didn't cost much at all, about £20 all in Such a cheap yet effective mod, I recommend it!
(I'll add some pics shortly).
Pics as promised...
I thoroughly recommend using the Nichicon MUSE KZ in this player. I also recommend sticking to the specified values and in particular making sure that both DAC digital and analogue reg's have the same size cap on the reg output.
On the DAC I would have used 16v KZ caps but couldnt find them so went with 25v. These are quite big and you'll need to bend the leads a bit to get them in. On the 1000uF output stage caps you will need to move the R1 & R11 resistor under the motherboard. You may have to move C22,23 also. Its tricky to fit them in but well worth the effort!
The DIY regulators are a great little mod too, especially if you cant afford the Sercal, Tetlabs, New class-d reg's, etc. Adding a simple VBE to a generic 78** makes a nice improvement for pennies per reg.
My next plans for this player are to install some Polystyrenes in place of the ceramics around the opamp,s. Add a second toroid for a dedicated DAC supply using CRCRC filtering - one bank for digital supply and another for analogue. So that's 6 caps in total. The main supply to the rest of the motherboard will also be getting a CRCRC filtered PSU. To do this I need to move the trafo and make some room in the front right corner for my new PSU boards. I'll be populating these boards with Shottkey diode's and either 4700/40v BHC or 3300uF/35v Nichicon FG caps. Resistors will be normal 0.47R 1W types.
As yet I have done nothing to the servo board. To be honest Im not really sure what's going on under that copper hood. I'll probably fit some low ESR PSU caps and VBE filter on the regs at some point. These reg draw quite a lot of current so I'll need to build more beefy VBE's, Martin Clark recommends the BD139 in place of the BC547C for higher current situations.
As it is this player sounds excellent!!
Chhers!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I thoroughly recommend using the Nichicon MUSE KZ in this player. I also recommend sticking to the specified values and in particular making sure that both DAC digital and analogue reg's have the same size cap on the reg output.
On the DAC I would have used 16v KZ caps but couldnt find them so went with 25v. These are quite big and you'll need to bend the leads a bit to get them in. On the 1000uF output stage caps you will need to move the R1 & R11 resistor under the motherboard. You may have to move C22,23 also. Its tricky to fit them in but well worth the effort!
The DIY regulators are a great little mod too, especially if you cant afford the Sercal, Tetlabs, New class-d reg's, etc. Adding a simple VBE to a generic 78** makes a nice improvement for pennies per reg.
My next plans for this player are to install some Polystyrenes in place of the ceramics around the opamp,s. Add a second toroid for a dedicated DAC supply using CRCRC filtering - one bank for digital supply and another for analogue. So that's 6 caps in total. The main supply to the rest of the motherboard will also be getting a CRCRC filtered PSU. To do this I need to move the trafo and make some room in the front right corner for my new PSU boards. I'll be populating these boards with Shottkey diode's and either 4700/40v BHC or 3300uF/35v Nichicon FG caps. Resistors will be normal 0.47R 1W types.
As yet I have done nothing to the servo board. To be honest Im not really sure what's going on under that copper hood. I'll probably fit some low ESR PSU caps and VBE filter on the regs at some point. These reg draw quite a lot of current so I'll need to build more beefy VBE's, Martin Clark recommends the BD139 in place of the BC547C for higher current situations.
As it is this player sounds excellent!!
Chhers!
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I found Brent's site cd upgrades dac, regulators, clocks, power supplies, diy psus, mains filter plugs, mains purifiers, opamps (including Burson Audio discrete opamps), capacitors, diodes & transformers, but who is this Lee that sells the Black Gate caps? I had a quick look but couldn't find anything...
It's good to see this thread is still active, I haven't visited here for a long time.
Nice and neat work there Mike, bet that player's sounding very good now.
I dimly remember that under that copper can the servo is using a separate oscillator. I replaced this with a dedicated clock and I'm pretty sure I got improvements, but it was a long time ago now. I've done this on quite a few players and have got improvements, so it's definitely worth a go.
Cheers, Lee.
Just found a very interesting document from Wolfson:
Decoupling and Layout Methodology
for Wolfson DACs, ADCs and CODECs
These decoupling requirements are echoed in the WM8741 datasheet.
Decoupling and Layout Methodology
for Wolfson DACs, ADCs and CODECs
These decoupling requirements are echoed in the WM8741 datasheet.
It's good to see this thread is still active, I haven't visited here for a long time.
Nice and neat work there Mike, bet that player's sounding very good now.
I dimly remember that under that copper can the servo is using a separate oscillator. I replaced this with a dedicated clock and I'm pretty sure I got improvements, but it was a long time ago now. I've done this on quite a few players and have got improvements, so it's definitely worth a go.
Cheers, Lee.
Thanks for the compliments Lee.
My understanding is that the 74HC buffer's the master clock output to both the DAC's and the servo board. I could be wrong though as I've not looked the Servo schematic much to be honest. As it is I have replaced (through necessity) my XO with a Thrichord one and the Flea is just supplying clean low impedance power to the master clock and 74hC buffer i/c. I'll look into that servo clock tonight. Thanks for the heads up
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