I discovered CDP ground plane. What should I do with it?

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I have read a thousand times about how important CD player ground plane issue is. I still haven't quite understood what I should do with it. :confused:

I coloured the ground plane of my Sony DVP NS900 analog output PCB (brown):
http://kotiweb.kotiportti.fi/audiovideo/download/manual analog_Page_1_vari1.gif

Here are the schematics of analog output PCB:
http://kotiweb.kotiportti.fi/audiovideo/download/analog_output1.png
http://kotiweb.kotiportti.fi/audiovideo/download/analog_output2.png

Should I separate the ground planes (cut some jumpers) of each OPA amps and connect them to power input on the right (CN301 connector pin 3, area B10) with separate wires (star ground).

I'm worried about is the 5 V regulator (IC351 B1-2) that is feeding the DAC chips .The ground trace is a mess and the regulator is located about 15-20 cm from the DAC chips which are on another pcb. The ground plane of the DAC pcb is connected to analog output pcb through CN101 connector (area D4).

I was thinking that it might be wise to cut the ground and voltage supply traces from analog output pcb to DAC pcb and place the regulator closer to DAC PCB and use a separate wire to connect DAC pcb ground straight to power input on analog output PCB (CN301 connector pin 3, area B10). (I will still have to have a regulator on analog output PCB for feeding the digital output circuits)

Here are some pictures of the pcb's. The small DAC chips are on the bottom side of the SMD pcb. (I've changed some components after taking a few of the photos)

http://kotiweb.kotiportti.fi/audiovideo/DIY/modailua3/image/obj54geo43pg1p5.jpg
http://kotiweb.kotiportti.fi/audiovideo/DIY/cdout/image/obj87geo53pg1p5.jpg
http://kotiweb.kotiportti.fi/audiovideo/DIY/varahtelyt/obj129pg1geo146p5.jpg
http://kotiweb.kotiportti.fi/audiovideo/DIY/varahtelyt/obj317pg1geo274p5.jpg
http://kotiweb.kotiportti.fi/audiovideo/DIY/varahtelyt/obj263pg1geo167p5.jpg

I'm sorry about the huge pictures. I just want you to see every possible detail. If you need more pictures, please ask.

Thanks for helping me out!!! :angel:
 
Correct me if I'm wrong, but your grounds (I wouldn't call them planes) already seem separated. You gave them the same colors, but upon a quick look, I couldn't see them connected at any point...

Also, where are your dac's ?
I would think that THE dac (usually a all in one giant smd thing) is on the DSD board. So from what you're telling the 'digital' supply is located on the analog board and fed through the connector to the DSD board. BTW these dacs are already (symmetrical) voltage out, the opamps are just filters/buffers and to go single ended.

Well at least you don't have a switching psu (for the analog) which is allways good !!

hth

A8
 
I will replace some of the SMD electrolytic caps with Os-Cons. Some of the SMD caps are very small and impossible to replace with my skills and equipment.

I was thinking that I might get better results if I place a second 5V regulator right next to the DAC chips. Now the distance between regulator and DAC is huge.

I could also cut the ground wiring from the original regulator so that for example digital output circuits (optical and coaxial) can't cause any interference. Now the digital output circuits and DAC are are fed by the same 5 V regulator and I would like to make the power supplies separate. This picture will probably make things more clear:
http://kotiweb.kotiportti.fi/audiovideo/download/ps.jpg

Or should I stick with the original configuration and just change or add some bypass caps?
 
"I still haven't quite understood what I should do with it."

Unless you can measure that there is a difference in potential, or that capacitor ripple current is upsetting a regulator's performance, why do you want to do anything with it?

Yes, they are frequently done wrong. The only way to know for sure is to be able to measure it, because only then will you know what to do about it.

If you can't, you are most likely stuck with it.

Jocko
 
Ok. The regulation stays as it is. :)

I changed the three SMD electrolytic caps that were marked in the picture in my previous post. I used 100 uF Os-Con caps.

I almost soiled my underwear when removing one of the caps :D
I heated it with two solderin irons. Apparently I applied too much heat and the cap exploded! There was a big blast and thick brown smoke and the metal can flew about 30 cm high. :smash:

I think I'll continue building my Tentlabs XO power supply.

Thanks for help! :)
 
Usually a good way to connect two grounds between two digital sections, DSP chip and DAC chip for example is via one (or two in parallel) ferrite beads. This technics allows for same DC and low frequency AC potential, but for high frequency AC (RF) it represent very high impedance, depending on ferrite material used preventing influence of two stages on their performance at high frequencies.
 
Extreme_Boky said:
Usually a good way to connect two grounds between two digital sections, DSP chip and DAC chip for example is via one (or two in parallel) ferrite beads. This technics allows for same DC and low frequency AC potential, but for high frequency AC (RF) it represent very high impedance, depending on ferrite material used preventing influence of two stages on their performance at high frequencies.


Hi

This will only work correctly if NO AC currents flow through that bead.

If it is the case however, induced voltage will appear in series with ALL signals crossing that barier - Conclude yourself what impact hat may have. Some may like the sound that is the result of such architecture, I do not:

http://www.tentlabs.com/Info/Articles/Supply_decoupling.pdf

Bottom line: Keep groundplane closed and make sure no or contolled currents flow through the plane

Instruments are things like series inductors / resistors combined with local (and well connected) decoupling. Other are the deliberate use of shunt regs with high input impedances

http://www.grimmaudio.com/ad1grimm.htm

cheers
 
Here's a picture of the Oscons that I used to replace the original SMD electrolytic caps. I had to remove the old caps because there wasn't any other good place for the caps. I tried to keep the cap leads as short as possible. Is the lenght of the leads critical?

http://kotiweb.kotiportti.fi/audiovideo/download/osconit.jpg

In the backgound you can see AD8065 OPA amp module (from LC Audio) and OPA627 module. The smaller output caps are Glack Gate HQ NX 47 uF in Super-E-Caps configuration.
The small PCB is an LM317 regulator module:

http://kotiweb.kotiportti.fi/audiovideo/DIY/modailua3/image/obj38geo38pg1p5.jpg
(The resistor values are smaller to maintain a sufficient load at all times)
http://kotiweb.kotiportti.fi/audiovideo/DIY/modailua3/image/obj52geo29pg1p5.jpg

Tomorrow I get MSR860 diodes for power supply.
 
DIAR said:
Here's a picture of the Oscons that I used to replace the original SMD electrolytic caps. I had to remove the old caps because there wasn't any other good place for the caps. I tried to keep the cap leads as short as possible. Is the lenght of the leads critical?

Tomorrow I get MSR860 diodes for power supply.


Hi DIAR,
I don't think the lead length is critical but I always keeps the leads as short as possible leaving room to solder.
The D1NS4 and the D1NS6 diodes f.a. used in the power supply are Schottky recitifiers. Be carefull when replacing these as the MSR860s have higher voltage drop.:att'n:
 
While I found MSR860 to work better than MUR860 in digital circuits, I never really compared them to anything else.

The results are fine in a DAC, but recently somebody suggested BYV26C diodes as better alternative. I didn't try them yet.

I once replaced original rectifiers in CD-94 player with MUR860 and quickly returned back to the original parts as they sounded much better.
 
DIAR said:
It's good that you mentioned the difference in diode voltage drops. MSR860 has 1,7 V voltage drop and D1NS6 only 0,58 V.

I'll have to find out somehow wheather I can use diodes with higher voltage drop or not... :(


Hi DIAR, Well under the load they have in the player I think the MSR860 has 0.6V voltage drop and the 1DNS6 about 0.3V. So the difference would be 0.3V. Maybe I am too cautious as that is not a big difference.
 
I changed the diodes to MSR860. They fitted nicely and there seems to be no problems with the higher voltage drop :)

I'll let the diodes burn in a while before making a judgement.


I must admit that somewhere along the way the sound has got worse in some areas. For example ambience and echoes aren't that clear as they have been. Also the sound is somewhat restless and fatiguing now. I believe one of the mods to blame might be the LM317 regulator. The first LM317 regulator module I made sounded very good but actually didn't work perfectly. Sometimes I heard pops but the ambience and feeling of precence was wery strong. I made another regulator module which was smaller and used smaller polypropylene caps but the sound wasn't as good as with the malfunctioning regulator. It amazes me that a misoperating component can actually sound good.

Does anyone have an idea what might cause restless and hard sound (as if the upper mids are a bit hard and emphasized). Of course The player might be a perfect source ( :cannotbe: ) and it is the other equipment that is causing listening fatigue (Densen Beat B300XS, DACT CT2 passive preamp and Dynaudio Audience 52).

Other mods and tweaks that I have done (random order).
- I've chaged original OPAs to OPA627 and AD8065 (stereo and 5.1 front channels outputs)
- Changed 100 uF Elna Silmic coupling caps to 2*47 uF Black Gate Hi-Q NX (Super-E-Caps) (for stereo output only)
- Changed power supply diodes to MSR860
- Changed 7805 regulator to LM317 (with the resistors, caps and protection diodes)
- removed muting transistors
- Added a few ferrites to power supply cables
- Changed the power cord to IEC plug and DIY power cord
- Made a low impedance 1. stage line filter
- I use 2*0.47 uF huge polypropylene caps between hot and neutral (so called Auricap tweak)
- Changed a few DAC power supply bypass caps to Os-Con
- Damped the enclosure with thick rubber sheets
- Damped the oscillators with rope caulk
- I use different combinations of bicycle inner tube platform and DIY rollerblocks and Cerabals etc. I change the combinationg from time to time.


It's very difficult to hear all the changes that the mods are actually causing. Some areas might get much better and some might get just a little bit worse which is unnoticeable. After piling many of these degradations the effect becomes very noticeable but it is impossible to say which mods ware responcible for the degradation of sound.

Actually one reason might be the acoustics of my listening room. I previously concidered it to be very good (it is) but now I'm starting to notice that there is much to improve. Maybe the fatiguing sound is result of unwanted reflections and echoes.
 
Perhaps too high a value of coupling capacitance in the signal path, that would roll off the lows a little.

The problem with so many mods done at once is it's hard to work out exactly what form of success you've had at each stage. One might have detrimented another.

Don't chase your tail on this as you'll never be happy, but don't doubt your other gear at the same time - chances are it's still just the way it was before you started modding, after all, you've done nothing to the other gear.

You can always undo it all, backtrack, and start again, perhaps with more testing between each modification. Or just undo one mod at a time and see what happens....

Good luck

diy-er
 
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