Adding additional transformers to CD player

damiangt3

Member
2014-02-14 12:07 pm
Adding additional transformers to CD player - noise

I've started playing with one of my old Marantz CD players have have decided to add an additional transformer with regulation. However one question keeps leaving me scratching my head, how do I maintain a common ground with two separate regulated power sources?

I've created a separate +/- 10v LM317/337 source for the op-amps etc which provides its own ground.

How do I 'combine' these grounds, or do I have to?
 
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damiangt3

Member
2014-02-14 12:07 pm
I spoke too soon.

I've added a second transformer with dual secondary (0-12v) put through a LM317/337 AudioWind circuit regulated to +/- 10v, this is then 'fed' back into my Marantz CD5000 to power the analogue circuitry (Cerafines and LM4562 op-amp) which it does and there's a big improvement in SQ. I used the op-amp pin 4 and 8 at the 220uf (2521/2522 capacitor point). I removed one of the original supply capacitors 3300uf (for the -10v feed) as it's not needed and used the ground here to solder a wire back to the new regulator.

However you can hear a hum when then CD is powered on (not playing) at high amplifier volumes. I'm concerned that this might be a grounding issue......thoughts?
 
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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Just took the ground from the second regulated supply and added to the other grounds. All sorted, although I was concerned that they might not be same.

CD players have often have several so called 'grounds' such as analogue ground, digital ground, servo drive ground etc. All physically connected, but that doesn't mean you can rearrange them... as you have found out.

However you can hear a hum when then CD is powered on (not playing) at high amplifier volumes. I'm concerned that this might be a grounding issue......thoughts?

Sounds like you have introduced or compromised the original grounding scheme.

Thoughts... honestly ;) put it back to original spec.
 

damiangt3

Member
2014-02-14 12:07 pm
CD players have often have several so called 'grounds' such as analogue ground, digital ground, servo drive ground etc. All physically connected, but that doesn't mean you can rearrange them... as you have found out.



Sounds like you have introduced or compromised the original grounding scheme.

Thoughts... honestly ;) put it back to original spec.

Thanks Mooly, I respect your opinion but I won't be defeated! :)

I think I'll have a prod around and find another grounding point. If that fails I might have to do as you suggested.
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Thanks Mooly, I respect your opinion......

Well I'm very pleased to hear it :p

I'm afraid I can't really give you any advice on what to try... its complex and you would have to really study the grounding arrangement so as to not introduce a problem. The reason why these issues appear is because of the small but finite resistance of the conductors/wire/print that allows voltage to be developed along their length as current flows. So you need to aim to not introduce anything like reservoir cap charging currents into a critical audio or analogue ground.

Good luck though :)
 

damiangt3

Member
2014-02-14 12:07 pm
Well I'm very pleased to hear it :p

I'm afraid I can't really give you any advice on what to try... its complex and you would have to really study the grounding arrangement so as to not introduce a problem. The reason why these issues appear is because of the small but finite resistance of the conductors/wire/print that allows voltage to be developed along their length as current flows. So you need to aim to not introduce anything like reservoir cap charging currents into a critical audio or analogue ground.

Good luck though :)

Thanks again.

I was hoping to learn from this, having read many threads on modding CD players and such like I thought that a simple CD5000 would be a good place to start.
 

Extreme_Boky

Member
2003-12-07 11:57 am
Find the point on the PCB that joins the existing filtering capacitors for analog supply. This is where you should connect your "new ground" to.

How you choose the "new ground" point is also important. To start, try to feed the center tap point from new power supply, straight to the point I described in the first paragraph.

Nick
 
Many of the threads on modding CD players (and other items) are written by people who don't actually know what they are doing. They know just enough electronics to change something and get the item to work again, but not enough to actually improve it - to do that you have to be smarter than the original designer. Naturally, any perceived change in sound is interpreted as an improvement (apart, perhaps, from increased hum!).

I would not mod a CD player, but I only have about 50 years experience in playing with (mainly analogue) electronics (audio and RF). My PhD in electronics was in a different area: RF PA. I would need to do a lot of reading and thinking about mixed-signal design before I was even tempted to mod a CD player. Others are not so constrained.
 

Extreme_Boky

Member
2003-12-07 11:57 am
The creator of the thread has shown enthusiasm and willingness to learn DIY by attempting a basic mod on a cheap player. He also said: "...but I won't be defeated", which clearly shows his determination.

Can’t we just forgo the educational and life-long experience barriers imposed by egos, and provide an encouragement and suggestion to a fellow DIY-er, that should get him quickly out of trouble.

He is just trying to learn the basics and experience the thrills of a first successful mod.

Why bring the PhD into this story? Is that supposed to help him carry out his first mod? Or maybe make him feel better by telling him that even if he manages to fix the 100Hz buzz, his mod will still be a sub-par, compared to fast speed decoupling technics and buried capacitance designs that you worked on?

Nick
 

Extreme_Boky

Member
2003-12-07 11:57 am
I spoke too soon.

I've added a second transformer with dual secondary (0-12v) put through a LM317/337 AudioWind circuit regulated to +/- 10v, this is then 'fed' back into my Marantz CD5000 to power the analogue circuitry (Cerafines and LM4562 op-amp) which it does and there's a big improvement in SQ. I used the op-amp pin 4 and 8 at the 220uf (2521/2522 capacitor point). I removed one of the original supply capacitors 3300uf (for the -10v feed) as it's not needed and used the ground here to solder a wire back to the new regulator.

However you can hear a hum when then CD is powered on (not playing) at high amplifier volumes. I'm concerned that this might be a grounding issue......thoughts?

See the photo I attached. It shows a big red cross where you should tie the grounds.

The little red lines show where to connect the -10 and +10V DC from your external power supply. NOTE: remove the links 9011 and 9012, and the links 9142 and 9137 first. I trust you are able to figure out where to connect -10, and where to connect +10V...

The schematic is for CD6000 - couldn't find the 5000 one, but they should be similar. If not, you will still get very good picture of what needs to be done

Good luck,
Nick
 

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Extreme_Boky said:
Can’t we just forgo the educational and life-long experience barriers imposed by egos
The barrier which prevents me from modding CD players is not "ego" but humility. I know I don't know enough to make a genuine improvement.

provide an encouragement and suggestion to a fellow DIY-er, that should get him quickly out of trouble.
Don't do it, is my suggestion. That is the quickest way to get out of trouble,

Why bring the PhD into this story? Is that supposed to help him carry out his first mod?
No, it was to put him off carrying out an unsuccessful mod.

Or maybe make him feel better by telling him that even if he manages to fix the 100Hz buzz, his mod will still be a sub-par, compared to fast speed decoupling technics and buried capacitance designs that you worked on?
Not at all. My point (which you seem to have failed to grasp) is that if someone with 50 years experience knows enough not to attempt it, then someone with significantly less experience is very likely to fail but may not know enough not to attempt it.

It is easy to gain experience of doing misguided mods; just do lots of misguided mods. This will not help someone gain useful knowledge and experience of doing audio DIY; it is more likely to put them off through frustration.

I note that Mooly, who perhaps has more experience of these things than me, also recommends not doing it.
 

02GF74

Member
2010-07-13 1:38 pm
I note that Mooly, who perhaps has more experience of these things than me, also recommends not doing it.

... but where's the fun in that?

One of three things can happen
1. it sounds better - great,:D pat yourself on the back and post mods so others can try it
2. it makes no noticeable difference, oh well, ..:mad:
3. it makes it worse or blows up. :eek:First case you can revert the mod, second case, cry for a bit, learn from the experience and then pick up another CD player off ebay to start again.
 

damiangt3

Member
2014-02-14 12:07 pm
Thanks guys.

It is fun and a good break from my day job as an IT Consultant! I love music, I worked for Hi-Fi company during my first year at university and the ability to influence one with the other is one of life's pleasures.

I've recapped amplifiers in the past, replaced op-amps in many devices and I'm very handy with a soldering iron. I hopefully have an appreciation of the basics of electronics although it's been years since I studied this.

Thanks Nick for the direction, really appreciate it. Luckily the CD5000 has a far simpler PCB with a star ground. I haven't done centre-tap point to the ground, I certainly have a feeling this might be the issue.

I certainly don't fancy doing any mods like this on my Marantz CD11LE!