Hi all
I am new to DIY so please forgive some stupidquestions or comments I might make . Over the last few weeks I have learned a lot from the questions and answers many of you have posted here. As a consequence, the bug has bitten and I am well on the modification madness. My humble 1991 Philips CD624 is the first victim and will be undergoing some, hopefully beneficial, changes.
Below is a List of Proposed Modifications:
Replace master clock: (TENTLabs XO2)
Master Clock power supply (TENTLabs XO Supply)
Replace op-amps in output stage: (AD8065, AD8066, OPA627, OPA637, OPA2134, LM6172)
Add extra transformer(s)/psu(s)
Replace power cable with EIC type (filtered & screened)
Replace all 1N4002 and 1N4148 diodes on with Schottky type: SB150/MBR150, should I use bigger ones ie MBR3100?)
Replace 78XX voltage regulators with LM317, LM337
Replace capacitors on power supply with better ones
Replace some resistors (Not sure if they make any difference)
Replace output capacitors
Remove muting transistors (Maybe replace with relays)
Replace metal jumpers with higher quality copper wire (Maybe)
Add a switch to turn off display (Maybe)
Disconnect headphone circuit (Maybe)
Add 75ohm resistor to digital output RCA (I can switch it off or should I disconnect it while CDP is open)
Replace op-amp NMJ4560 on turntable motor control (Not sure what to use)
Add heatsinks to all IC's to reduce vibration??
Shield some components with copper sheets
Add copper sheet to inside cover of player
Add dampening material to top and bottom of case
Add dampening material to transport mechanism
Replace feet (Isopods/Vibropods)
I have read that adding additional transformers and power supplies make a real difference. However, this is where things get a little tricky for me with my lack of electronics experience.
From the schematics, it looks like there is one transformer with two seperate secondary windings. One of these seems to power the display only with about 4V. Could it be AC as there doesn't seem to be a rectifier on this line? The other secondary winding is 60V with a centre tap giving 30 - 0 - 30. There are additional taps for +/-21.2V and +/-10V.
The +/- 21.2V pass through a rectifier and voltage regs giving +/-15V DC. This seems to supply the analogue output stage (one dual opamp) and the headphone section. There is also a connection to the Kill circuit, which I think is the muting system. There is also a tap off this line, before the reg, going to the Kill circuit. So my understanding is that this power supply only runs the analogue stage, except for a few connections which are not active while music is playing.
Q1: Would there be a benefit to adding a seperate transformer for this section? If so, should I just add a small toroidal 18 - 0 - 18 unit to the rectifier after disconnecting the original transformer from this section or is there a better way? What should I do about the centre tap from the new transformer? Does it just connect to the existing ground or does the ground for the entire analogue section now need to be seperated from everything else?
The +/-10V taps from the existing transformer feed to another rectifier and then unregulated to the rest of the main board. Another feed is taken from this rectifier and through some regs to provide +/-5V to the main board.
Q2: Would it be a good idea to add another transformer here, maybe two, one for each voltage? Again, I would like to ask the same questions as above. Also, would it be a good idea to regulate the +/-10V lines?
This would leave the original transformer to power the display and mechanism only.
Q3: Is it generally better to add multiple small transformers for each section or one larger and better quality transformer with multiple seperate output windings?
I know I have asked a lot of questions here and I would really appreciate any assistance some of you experts might be able to give me.
Thanks
Fin
I am new to DIY so please forgive some stupidquestions or comments I might make . Over the last few weeks I have learned a lot from the questions and answers many of you have posted here. As a consequence, the bug has bitten and I am well on the modification madness. My humble 1991 Philips CD624 is the first victim and will be undergoing some, hopefully beneficial, changes.
Below is a List of Proposed Modifications:
Replace master clock: (TENTLabs XO2)
Master Clock power supply (TENTLabs XO Supply)
Replace op-amps in output stage: (AD8065, AD8066, OPA627, OPA637, OPA2134, LM6172)
Add extra transformer(s)/psu(s)
Replace power cable with EIC type (filtered & screened)
Replace all 1N4002 and 1N4148 diodes on with Schottky type: SB150/MBR150, should I use bigger ones ie MBR3100?)
Replace 78XX voltage regulators with LM317, LM337
Replace capacitors on power supply with better ones
Replace some resistors (Not sure if they make any difference)
Replace output capacitors
Remove muting transistors (Maybe replace with relays)
Replace metal jumpers with higher quality copper wire (Maybe)
Add a switch to turn off display (Maybe)
Disconnect headphone circuit (Maybe)
Add 75ohm resistor to digital output RCA (I can switch it off or should I disconnect it while CDP is open)
Replace op-amp NMJ4560 on turntable motor control (Not sure what to use)
Add heatsinks to all IC's to reduce vibration??
Shield some components with copper sheets
Add copper sheet to inside cover of player
Add dampening material to top and bottom of case
Add dampening material to transport mechanism
Replace feet (Isopods/Vibropods)
I have read that adding additional transformers and power supplies make a real difference. However, this is where things get a little tricky for me with my lack of electronics experience.
From the schematics, it looks like there is one transformer with two seperate secondary windings. One of these seems to power the display only with about 4V. Could it be AC as there doesn't seem to be a rectifier on this line? The other secondary winding is 60V with a centre tap giving 30 - 0 - 30. There are additional taps for +/-21.2V and +/-10V.
The +/- 21.2V pass through a rectifier and voltage regs giving +/-15V DC. This seems to supply the analogue output stage (one dual opamp) and the headphone section. There is also a connection to the Kill circuit, which I think is the muting system. There is also a tap off this line, before the reg, going to the Kill circuit. So my understanding is that this power supply only runs the analogue stage, except for a few connections which are not active while music is playing.
Q1: Would there be a benefit to adding a seperate transformer for this section? If so, should I just add a small toroidal 18 - 0 - 18 unit to the rectifier after disconnecting the original transformer from this section or is there a better way? What should I do about the centre tap from the new transformer? Does it just connect to the existing ground or does the ground for the entire analogue section now need to be seperated from everything else?
The +/-10V taps from the existing transformer feed to another rectifier and then unregulated to the rest of the main board. Another feed is taken from this rectifier and through some regs to provide +/-5V to the main board.
Q2: Would it be a good idea to add another transformer here, maybe two, one for each voltage? Again, I would like to ask the same questions as above. Also, would it be a good idea to regulate the +/-10V lines?
This would leave the original transformer to power the display and mechanism only.
Q3: Is it generally better to add multiple small transformers for each section or one larger and better quality transformer with multiple seperate output windings?
I know I have asked a lot of questions here and I would really appreciate any assistance some of you experts might be able to give me.
Thanks
Fin
Anything else that you want to know.....?
Best suggestion:
Only change one thing at a time. Trying to do what you have up your sleeve is something that I would not recommend that someone try all at once. Especially first time out.
Places to start:
Better clock. Has to have a clean supply. A good distribution scheme, too. Maybe Guido will supply some answers.
But power supply......
You can make another transformer/regulator section for the analog: I do it all the time. But if it has all the same mistakes as the stock one, then why bother? Cleaning up all the ground loops can make a big difference just by itself.
You would need good test equipment to do that. Another option would be to make a battery powered amp to drive headphones that you can listen to the rails. Something like a AD797 or so would work.
My bet is that if you hooked that up to all of your supply rails, listen, and get the noise out, you will have lots of stuff to do. And learn.
Jocko
Best suggestion:
Only change one thing at a time. Trying to do what you have up your sleeve is something that I would not recommend that someone try all at once. Especially first time out.
Places to start:
Better clock. Has to have a clean supply. A good distribution scheme, too. Maybe Guido will supply some answers.
But power supply......
You can make another transformer/regulator section for the analog: I do it all the time. But if it has all the same mistakes as the stock one, then why bother? Cleaning up all the ground loops can make a big difference just by itself.
You would need good test equipment to do that. Another option would be to make a battery powered amp to drive headphones that you can listen to the rails. Something like a AD797 or so would work.
My bet is that if you hooked that up to all of your supply rails, listen, and get the noise out, you will have lots of stuff to do. And learn.
Jocko
Hi, read your post in the other thread i posted a while back. I was going to say keep it simple - but others have already done that, listen to them, they know a lot lot more than me! Dont try and do too much at once, its a recipe for problems. If it were me i would try some/all of the following, but not necessarily all at once.
1st find schematic for the player. 2nd carefully dismantle the player and become familiar with where everything goes and how it dismantles and how to put it back together. Simple thingss that are good are replacing the mains cable - supra lo-rad is good basic cable for this. I have made little boxes from thin copper sheet to cover ICs in the past. I made these by cutting out a box plan and folding it into a box to put over the IC, the copper edges on the base covered with insulating tape and a strip of blu-tak. This is then soldered by small length wire to the gnd plane. I have had good results with this and it only requires removal of the lid. Covering the digital ICs is good - big microprocessor somewhere near the transport (probably) for example. Damping the case can be beneficial and also perhaps a blob of blu-tak on a few caps.
A new clock is a good thing to do (pref with good supply). New caps are a good thing - uprated parts and maybe slightly larger in the analogue supply. can be good too. Start small and see where you are. Can I make a bold suggestion, leave the op-amps in. Although sometimes good things can be had, i often find that the character i like is changed too much. (unless u dont like it!) Does your player have op-amps external to the ones in the saa7323 itself? Supplying the DAC with a cleaner/seperate 5v is a good thing. Plus better decoupling aronud the DAC and perhaps the decoder too.
1st find schematic for the player. 2nd carefully dismantle the player and become familiar with where everything goes and how it dismantles and how to put it back together. Simple thingss that are good are replacing the mains cable - supra lo-rad is good basic cable for this. I have made little boxes from thin copper sheet to cover ICs in the past. I made these by cutting out a box plan and folding it into a box to put over the IC, the copper edges on the base covered with insulating tape and a strip of blu-tak. This is then soldered by small length wire to the gnd plane. I have had good results with this and it only requires removal of the lid. Covering the digital ICs is good - big microprocessor somewhere near the transport (probably) for example. Damping the case can be beneficial and also perhaps a blob of blu-tak on a few caps.
A new clock is a good thing to do (pref with good supply). New caps are a good thing - uprated parts and maybe slightly larger in the analogue supply. can be good too. Start small and see where you are. Can I make a bold suggestion, leave the op-amps in. Although sometimes good things can be had, i often find that the character i like is changed too much. (unless u dont like it!) Does your player have op-amps external to the ones in the saa7323 itself? Supplying the DAC with a cleaner/seperate 5v is a good thing. Plus better decoupling aronud the DAC and perhaps the decoder too.
Fin,
if I remember correctly , your cdp has a groundplane divided in sections.Check this.If true,Jocko's remark about grounding will turn out to be the cheapest and most basic modification to perform.Search the web for some articles.(and read them...)
Guido Tent has a usefull article posted somewhere.Ask him.
Martijn
if I remember correctly , your cdp has a groundplane divided in sections.Check this.If true,Jocko's remark about grounding will turn out to be the cheapest and most basic modification to perform.Search the web for some articles.(and read them...)
Guido Tent has a usefull article posted somewhere.Ask him.
Martijn
Rotellian,
I have never seen the PCB in your Rotel.(My experience with bitstreamers is somewhat limited)In 1990 some of my friends bought the early ones.(Philips).Whe supplied every chip with it's own regulated powersupply,shortened local groundwiring and restored the groundplane.It worked, and without measuring equipment,we didn't come up with any new ideas at that time.
Restoring the grounplane meant:
-soldering all gaps
-connecting every chip to it
-disposing of some groundtracks
(Nowadays I would add some resistors and coils in signal and supplylines(thanks to Guido's article) and use an oscilloscoop.)
martijn
I have never seen the PCB in your Rotel.(My experience with bitstreamers is somewhat limited)In 1990 some of my friends bought the early ones.(Philips).Whe supplied every chip with it's own regulated powersupply,shortened local groundwiring and restored the groundplane.It worked, and without measuring equipment,we didn't come up with any new ideas at that time.
Restoring the grounplane meant:
-soldering all gaps
-connecting every chip to it
-disposing of some groundtracks
(Nowadays I would add some resistors and coils in signal and supplylines(thanks to Guido's article) and use an oscilloscoop.)
martijn
Bricolo said:
I wrote a concise article that can be found here
http://members.chello.nl/~m.heijligers/DAChtml/Supply_decoupling.pdf
I wrote this based upon 6 years experience with Philips (being active on the field of EMC and signal integrity on both PCB and silicon level)
There is a lot of nonsense about grounding and decoupling on the web, so be careful out there
enjoy
G'Day
Thank you to all who replied to my post. Your help, advice and comments are really appreciated. Some of it has been over my head but I am frantically trying to catch up and understand.
Some of you have suggested that I ask Guido Tent for some answers!!! Guido will probably say that it is all I have done for the past six weeks. He has been extremely helpfull. Thanks Guido.
I know the list of mods I have is extensive and I don't plan to do them all at once. I am trying to develope a "master plan" based on advice from those more knowedgable them me. Once I determine an overall direction (ie. what should be replaced, removed, added etc.), I will then start to implement each step, one at a time, from most important to least. This will hopefully avoid duplication of work, ie. moddifying the analogue section only to replace it later. (You can tell I used to be a scientist).
Joko
I plan to use Guido's clock and PSU. What's the distribution scheme?
When you add the new transformer/regulator, what do you do with it's ground or 0V?
If I build a new and completely seperate analogue stage on a seperate board, provide it with it's own transformer/PS and ground, will this help avoid this mistakes in the original?
How do you go about cleaning up the ground loops? Is it the same way as Rotellian, Martijn and Guido do?
Peter Daniel
I plan to do this in the fullness of time but need to work out which ones are most important or is it a matter of replacing them all?
Guido
What other issues should be solved first?
KevinLee
I have had a look at this site and it is really good.
Rotellian
Thanks for all the info. I really like the small copper boxes idea. I have the service manual and schematics for the CDP and have learned a lot from just studying the diagrams.
The CD624 has one dual NJM5532 opamp after the SAA7323. Most people seem to say that this opamp has good specs but doesn't sound very musical. I have no idea as I have not compared any others yet but will probably do this towards the end of the process after more fundamental issues have been addressed (ie. clock, power supplies and decoupling). Does that make sense?
As you know, I am interested in redirecting the analogue signal around the onboard opamps in the SAA7323. These apparently are part of the low-pass filter and are of similar or lower quality to the NJM5532, according to Thorsten Loesch's article supplied to me by Guido.
[http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html[/URL]
I was thinking of taking the signal before the onboard opamps to a seperate board comprising a new filter and final analogue stage. Deciding which design or components to use is the problem. However, this is probobly a long way off still and I hope to have a lot more experience and knowledge by then. If anyone has suggestions, I would be most interested as at this stage, plagerism is the order of the day!
Martijn
Did you have a 624 or have you worked on one previously?
The ground is taken from the centre tap on the transformer and then linked around the board using metal jumpers and copper traces on the board. Is this what you mean? Should each section of the groundplane be connected directly back to the transformer or power supply instead of passing through a mass of links and traces? I think this is what Rotellian is suggesting and sounds like a good idea.
Can you provide some more detail for thos of us who have never tried something like this?
Guido
You have lost me again! Please explain.
Thank you to all who replied to my post. Your help, advice and comments are really appreciated. Some of it has been over my head but I am frantically trying to catch up and understand.
Some of you have suggested that I ask Guido Tent for some answers!!! Guido will probably say that it is all I have done for the past six weeks. He has been extremely helpfull. Thanks Guido.
I know the list of mods I have is extensive and I don't plan to do them all at once. I am trying to develope a "master plan" based on advice from those more knowedgable them me. Once I determine an overall direction (ie. what should be replaced, removed, added etc.), I will then start to implement each step, one at a time, from most important to least. This will hopefully avoid duplication of work, ie. moddifying the analogue section only to replace it later. (You can tell I used to be a scientist).
Joko
I plan to use Guido's clock and PSU. What's the distribution scheme?
When you add the new transformer/regulator, what do you do with it's ground or 0V?
If I build a new and completely seperate analogue stage on a seperate board, provide it with it's own transformer/PS and ground, will this help avoid this mistakes in the original?
How do you go about cleaning up the ground loops? Is it the same way as Rotellian, Martijn and Guido do?
Peter Daniel
I plan to do this in the fullness of time but need to work out which ones are most important or is it a matter of replacing them all?
Guido
What other issues should be solved first?
KevinLee
I have had a look at this site and it is really good.
Rotellian
Thanks for all the info. I really like the small copper boxes idea. I have the service manual and schematics for the CDP and have learned a lot from just studying the diagrams.
The CD624 has one dual NJM5532 opamp after the SAA7323. Most people seem to say that this opamp has good specs but doesn't sound very musical. I have no idea as I have not compared any others yet but will probably do this towards the end of the process after more fundamental issues have been addressed (ie. clock, power supplies and decoupling). Does that make sense?
As you know, I am interested in redirecting the analogue signal around the onboard opamps in the SAA7323. These apparently are part of the low-pass filter and are of similar or lower quality to the NJM5532, according to Thorsten Loesch's article supplied to me by Guido.
[http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html[/URL]
I was thinking of taking the signal before the onboard opamps to a seperate board comprising a new filter and final analogue stage. Deciding which design or components to use is the problem. However, this is probobly a long way off still and I hope to have a lot more experience and knowledge by then. If anyone has suggestions, I would be most interested as at this stage, plagerism is the order of the day!
Martijn
Did you have a 624 or have you worked on one previously?
The ground is taken from the centre tap on the transformer and then linked around the board using metal jumpers and copper traces on the board. Is this what you mean? Should each section of the groundplane be connected directly back to the transformer or power supply instead of passing through a mass of links and traces? I think this is what Rotellian is suggesting and sounds like a good idea.
Can you provide some more detail for thos of us who have never tried something like this?
Guido
You have lost me again! Please explain.
The schematic for 624
Fin: do you have the service manual of schematic for the CD624? I have a 615 and suspect there are similarities...
Btw, I have shorted out the output caps of the 615 (great improvement, but check the DC voltage on the output) and use OPA2134 instead of the original opamp...
Good luck and Sunny Christmas downunder!
Tom
Fin: do you have the service manual of schematic for the CD624? I have a 615 and suspect there are similarities...
Btw, I have shorted out the output caps of the 615 (great improvement, but check the DC voltage on the output) and use OPA2134 instead of the original opamp...
Good luck and Sunny Christmas downunder!
Tom
Guido
What other issues should be solved first?
basically all majotr design issues like supplies, clocks etc. Otherwise it makes no sense in upgrading components
You have lost me again! Please explain. [/B][/QUOTE]
One groundplane. All grounds of components, and decoupling capacitorsto the plane like in my article. External supplies, especially the ground, should be connected to the point at the PCB where the circuit is that will be fed by that new supply
thats' all.....
Ciao
What other issues should be solved first?
basically all majotr design issues like supplies, clocks etc. Otherwise it makes no sense in upgrading components
You have lost me again! Please explain. [/B][/QUOTE]
One groundplane. All grounds of components, and decoupling capacitorsto the plane like in my article. External supplies, especially the ground, should be connected to the point at the PCB where the circuit is that will be fed by that new supply
thats' all.....
Ciao
Zombie
I will email it to you later today. The Philips CD615, 618, 624, 634, 824, 834 and Marantz CD41, 42 & 43 were all very similar, I think. The main reason Hi-Fi choice didn't really like them was because they all sounded quite similar and they thought that was boring!! I wonder when we are finished our mods, will our CDP's still sound similar to each other or quite different.
Anyway, I hope the manual is of use and thanks for the tips.
I will email it to you later today. The Philips CD615, 618, 624, 634, 824, 834 and Marantz CD41, 42 & 43 were all very similar, I think. The main reason Hi-Fi choice didn't really like them was because they all sounded quite similar and they thought that was boring!! I wonder when we are finished our mods, will our CDP's still sound similar to each other or quite different.
Anyway, I hope the manual is of use and thanks for the tips.
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