If you are using one or more laptop bricks as suggested in the pass ACA or other projects like MOFO, then what is the best way to deal with ground so as to minimize noise.
A separate earth back to the wall socket, or just let the whole lot float and tie any circuit earths to the desired rail. OR use the more typical capacitor and resistor to float the nearest rail off the earth so as to separate signal ground form PSU ground or case ground etc...
you get the general idea.
thanks in advance
Beardy
A separate earth back to the wall socket, or just let the whole lot float and tie any circuit earths to the desired rail. OR use the more typical capacitor and resistor to float the nearest rail off the earth so as to separate signal ground form PSU ground or case ground etc...
you get the general idea.
thanks in advance
Beardy
Laptop PSUs come in two varieties, ClassI and ClassII.
ClassI has a three core mains cable where PE (Protective Earth) is used to protect the user.
ClassII has a two core mains cable where extra design/build/test on the completed assembly protect the user. This will be referred to as Double Insulated and should have the concentric squares symbol on the labelling.
Do not alter either of these. !!!!!
Your audio side does not need any connection to the ground your house is standing on.
The ONLY reason that PE is used is for the Safety of the User (you and your family/visitors).
Build you equipment with all the audio connections that it needs, no more and certainly no less.
If you have a ClassI PSU, then you must ensure that the chassis of your equipment is connected to the PE wire.
Similarly, all external conductive parts must be connected to the protected chassis.
If you have a ClassII PSU, then the Safety side is already attended to. Do not make any extra connections.
ClassI has a three core mains cable where PE (Protective Earth) is used to protect the user.
ClassII has a two core mains cable where extra design/build/test on the completed assembly protect the user. This will be referred to as Double Insulated and should have the concentric squares symbol on the labelling.
Do not alter either of these. !!!!!
Your audio side does not need any connection to the ground your house is standing on.
The ONLY reason that PE is used is for the Safety of the User (you and your family/visitors).
Build you equipment with all the audio connections that it needs, no more and certainly no less.
If you have a ClassI PSU, then you must ensure that the chassis of your equipment is connected to the PE wire.
Similarly, all external conductive parts must be connected to the protected chassis.
If you have a ClassII PSU, then the Safety side is already attended to. Do not make any extra connections.
Hi Again,
I appreciate the situation with respect to the safety aspects of the PE, but what about the implications of how the ground is used with respect to the signal path... You no longer have low noise ground to use for filtering the input power etc. So whats the best approach here? Do you put filtering across the voltage rails?
I appreciate the situation with respect to the safety aspects of the PE, but what about the implications of how the ground is used with respect to the signal path... You no longer have low noise ground to use for filtering the input power etc. So whats the best approach here? Do you put filtering across the voltage rails?
the audio does not need the chassis/enclosure. Think about all the plastic cased amplifier, pre-amps, headphone amps, cell phones, CDpayers, etc.
They all work without any connection to mains.
When you have a mains powered device, it will either be ClassI and ClassII, you are unlikely to ever see a ClassIII product except in a hospital.
If you decide to build a mains powered device then it must be ClassI, you/we/me are incapable of designing building testing and guaranteeing a ClassII product.
When you build your ClassI device you must use PE to provide a link for fault based mains current to escape back the the mains distribution board via the Third wire in the mains cable. It is this third wire connection that will save the life of a user if the equipment goes faulty. It is the very low impedance of the third wire return that blows the mains fuse during a Mains FAULT current incident and saves your life.
So allow the PE to work by enclosing your project inside a metal case and permanently connect that metal case to the PE wire.
The audio circuits inside do not need any part of the metal case to work. You could place them inside a plastic lunch box and put that inside the metal chassis, it will still work.
Now that is PE and your protected chassis/enclosure removed from the equation.
BUT!!!!
there is a supplementary rule.
All exposed conductive parts must be connected to the protected chassis.
This is the BIG problem. Every screwhead, metal terminal, metal control knobs and other metal parts that are exposed on the outer surface must not kill the user when there is a catastophic fault in the mains wiring/components.
The ONLY reason for connecting any of the Audio parts to the chassis is to comply with the second rule *exposed conductive parts".
It has absolutely nothing to do with improving the quality of the internal audio circuits.
I don't know how many times I have had to explain this.
They all work without any connection to mains.
When you have a mains powered device, it will either be ClassI and ClassII, you are unlikely to ever see a ClassIII product except in a hospital.
If you decide to build a mains powered device then it must be ClassI, you/we/me are incapable of designing building testing and guaranteeing a ClassII product.
When you build your ClassI device you must use PE to provide a link for fault based mains current to escape back the the mains distribution board via the Third wire in the mains cable. It is this third wire connection that will save the life of a user if the equipment goes faulty. It is the very low impedance of the third wire return that blows the mains fuse during a Mains FAULT current incident and saves your life.
So allow the PE to work by enclosing your project inside a metal case and permanently connect that metal case to the PE wire.
The audio circuits inside do not need any part of the metal case to work. You could place them inside a plastic lunch box and put that inside the metal chassis, it will still work.
Now that is PE and your protected chassis/enclosure removed from the equation.
BUT!!!!
there is a supplementary rule.
All exposed conductive parts must be connected to the protected chassis.
This is the BIG problem. Every screwhead, metal terminal, metal control knobs and other metal parts that are exposed on the outer surface must not kill the user when there is a catastophic fault in the mains wiring/components.
The ONLY reason for connecting any of the Audio parts to the chassis is to comply with the second rule *exposed conductive parts".
It has absolutely nothing to do with improving the quality of the internal audio circuits.
I don't know how many times I have had to explain this.
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Again, not talking about safety or PE...
Most circuits have split supplies, or in the single ended supply case, have a separate, well defined signal ground, often connected via parallel cap/resistor, or a bridge and resistor to earth.
For the case when the audio equipment is floating, where would you put the input filtering - across the rails? Or perhaps for an amplifier you would use the signal ground at the input from your CD player or DAC to define a signal ground...
Most circuits have split supplies, or in the single ended supply case, have a separate, well defined signal ground, often connected via parallel cap/resistor, or a bridge and resistor to earth.
For the case when the audio equipment is floating, where would you put the input filtering - across the rails? Or perhaps for an amplifier you would use the signal ground at the input from your CD player or DAC to define a signal ground...
worst case scenario you can use an input transformer to feed signal to your gear, keeping the grounds separate. this can help prevent noise from coupling through in some systems. I used to have a laptop that was particularly full of hash, and a pair of edcor 10k:10k transformers in a plastic box (with an added 10k alps pot for volume) worked wonders on preventing the crap from coupling through to other sources
Audio Component Grounding and Interconnection - diyAudio
Audio Component Grounding and Interconnection
Says it all.
Audio Component Grounding and Interconnection
Says it all.
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