I'm modifying a Philips cd600.
Added another power supply and regulation and lots more.
So since grounding of these players does not include the enclosure (top and bottom) i want to include those, as well as the power inlet.
So what do I do? Connect inlet and enclosure to the PCB ground? Or does one need to connect to the PCB through a resistor/capacitor or some other circuitry? or just a wire? Or do i just connect inlet ground to the enclosure and not include the PCB.....
I did some experiments and could hear quite a difference by just connecting those step by step, but now wondering what is 'correct' or 'advised' way to do this, specially also if other components are needed.
Thanks,
Wouter
Added another power supply and regulation and lots more.
So since grounding of these players does not include the enclosure (top and bottom) i want to include those, as well as the power inlet.
So what do I do? Connect inlet and enclosure to the PCB ground? Or does one need to connect to the PCB through a resistor/capacitor or some other circuitry? or just a wire? Or do i just connect inlet ground to the enclosure and not include the PCB.....
I did some experiments and could hear quite a difference by just connecting those step by step, but now wondering what is 'correct' or 'advised' way to do this, specially also if other components are needed.
Thanks,
Wouter
Hi, first check if the electronics GND make contact at all to the metal parts of the casing. I forgot most about these as they are very old. If they are not connected you can connect the PE pin of the IEC inlet to the casing with yellow/green wire and make sure to use lug/washer combination (the washer with "teeth"). Check/measure if the connection is OK. Now the casing is connected to PE and the device will be safer.
Now there can be a potential difference bewteen audio GND and PE.... which can be annoying when plugging in and out RCA plugs. You can refer GND to PE by means of a 100 Ohm 1W resistor just for a leakage path. Never connect GND to PE directly in sources, only do so in the power amplifier if you like your stuff to be safe but also hum free 🙂
Now there can be a potential difference bewteen audio GND and PE.... which can be annoying when plugging in and out RCA plugs. You can refer GND to PE by means of a 100 Ohm 1W resistor just for a leakage path. Never connect GND to PE directly in sources, only do so in the power amplifier if you like your stuff to be safe but also hum free 🙂
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I don't recommend converting the Class II appliance to Class I. This would involve replacing the 2-pin (C7 type) mains socket to a 3-pin (C14 type) IEC socket and connecting all external metal parts to the PE. Perhaps converting is also against the electric safety rules.
What you can do is to mount a ground screw on the back of the appliance, and tie PCB ground and all metal parts there. Then you can connect a ground wire to this screw, and its other end you can connect wherever you want.
What you can do is to mount a ground screw on the back of the appliance, and tie PCB ground and all metal parts there. Then you can connect a ground wire to this screw, and its other end you can connect wherever you want.
This is not good advice as tieing audio GND to the casing does not lead to improvement. On the contrary. It is asking for stray in and hum.
Let's use the terms "GND" for audio ground and "PE" for safety earth/ground.
Let's use the terms "GND" for audio ground and "PE" for safety earth/ground.
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The discussion is going towards safety, that is not what im interested in. The question is more do I connect PCB ground to the chassis and maybe to an inlet... and how this can be achieved... it needs to be safe yes, but my first interest is sound.
It may not be your interest but it is our interest to make your device also safe. As you will be changing matters with regards to PE anyone experienced will point to safety so don't expect us to compromise on that.
Safety first and at the same time better shielding without added potential differences. Three birds with 1 stone.
Safety first and at the same time better shielding without added potential differences. Three birds with 1 stone.
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You should not do that.
The CD player main board ground plane is:
1. AC coupled to the chassis at many points.... where the board is screwed down (via, usually, a combination of 0.1 and 0.01 uF caps connected in parallel, to the chassis)
2. ... and it is most likely DC coupled at a single point (one of the screws connects the ground plane straight to the chassis)... HOWEVER, this is not always the case.
You could measure the distortions & noise while trying to connect the mains ground to the case, but I would only ever attempt to do this via a capacitor. See if there's an improvement. Even if you do see an improvement, things may go bad (THD&noise-wise) if you relocate the CD player to a different power outlet... even within the same household. I am certain you will not be able to hear any difference whatsoever... I tried this before (and I have a separate, clean, thick wires' feed straight from the main power distribution board, to where my audio gear is).
I would not DC couple the mains ground to the case (chassis)
The CD player main board ground plane is:
1. AC coupled to the chassis at many points.... where the board is screwed down (via, usually, a combination of 0.1 and 0.01 uF caps connected in parallel, to the chassis)
2. ... and it is most likely DC coupled at a single point (one of the screws connects the ground plane straight to the chassis)... HOWEVER, this is not always the case.
You could measure the distortions & noise while trying to connect the mains ground to the case, but I would only ever attempt to do this via a capacitor. See if there's an improvement. Even if you do see an improvement, things may go bad (THD&noise-wise) if you relocate the CD player to a different power outlet... even within the same household. I am certain you will not be able to hear any difference whatsoever... I tried this before (and I have a separate, clean, thick wires' feed straight from the main power distribution board, to where my audio gear is).
I would not DC couple the mains ground to the case (chassis)
Metal cases are generally connected to PE in the EU by regulations. Apparently this is a class 2 device but still then potential differences may be influential.
IF this device has a plastic casing and "floating" metal upper and lower covers these can be connected to PE without much risk. As they are floating they present a larger risk anyway. It is surprising that a class 2 device uses metal covers at all. Getting such a device through certification today would present a challenge I guess.
IF this device has a plastic casing and "floating" metal upper and lower covers these can be connected to PE without much risk. As they are floating they present a larger risk anyway. It is surprising that a class 2 device uses metal covers at all. Getting such a device through certification today would present a challenge I guess.
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You are absolutely right. Audio GND and PE should not be connected. Sorry, my mistake.
Same goes to Class II appliances, that may have a metal enclosure, but the internals are still double insulated.
My remark applies to this case: the metal enclosure serves as an EMI/RFI shield, and it can be connected to the PE or to other properly grounded appliance by an earthing screw and wire. This wire has no safety role, it is purely for shielding.
And then again it also serves safety 🙂 Anywhere that darn yellow/green wire goes it is first about safety.
I would leave it as it was delivered originally.
Whenever I make something from scratch it will have the earthed chassis, but yours has been deemed acceptable via low consumption or the whatever. You will likely only risk worsening the sound by adding the ground after the fact.
Whenever I make something from scratch it will have the earthed chassis, but yours has been deemed acceptable via low consumption or the whatever. You will likely only risk worsening the sound by adding the ground after the fact.