I strongly suggest that you use RCA connectors with shoulder washers. These work nearly 100% of the time and are quite cheap if you know where to look (e.g. apexjr).
EDIT: No affiliation, but have done business with him. Great guy.
Self says in his book that the best method is to isolate the input rca jack from the chassis, and to connect its ground directly to the safety chassis ground.
The rest of the amplifier circuit connects to the safety chassis ground only through the ground wire or shield connecting the input rca to the amplifier input circuit.
The ground for an RCA plug is the signal return, this needs to go to the same point as the positive part of the signal not to chassis ground. For screening where coax is used the RCA shield/return should be connected to the chassis with a low value 1nF) cap to provide a low impedance path for RF noise picked up by the cable.
Page 23 in this article illustrates the point:
http://www.hottconsultants.com/pdf_files/aes-2007.pdf
This is also interesting.
http://www.hottconsultants.com/pdf_files/Audio Interconnections.pdf
Page 23 in this article illustrates the point:
http://www.hottconsultants.com/pdf_files/aes-2007.pdf
This is also interesting.
http://www.hottconsultants.com/pdf_files/Audio Interconnections.pdf
That's the approach I follow.
Signal ground has no connection to chassis (safety) earth.Although I was told to use a 100nF ceramic cap ... not 1nF?
Regards,
Andy
Does this mean that the point of the star ground is insulated from the chasis?
Two problems I can see:
1) If the signal cable falls off, the case is no longer protected by grounding.
2) In the case of a high-impedance short to chassis, the leakage current may not blow the fuse, and so over time the signal cable may melt or burn depending on the particular circumstances. Only if the unit is not powered from a residual-current device (AKA GFCI), however.
Nice work. Some questions for you, though:
1) You have DSP take-off as number 3 on your grounding tee. Why in this order?
2) What is a "band limiting filter"?
3) ESP shows the loop breaking resistor in parallel with the cap and bridge rectifier in the loop breaker, whereas you have these resistors right inside the amps. What are the pros and cons of each approach? Also, why not use a resistor of an arbitrarily high value?
4) Can it ever hurt to put the optional 10 nF cap across the loop breaking bridge rectifier? Also, you call it a "ground lifer (sic) bridge rectifier" though I don't believe this little doodad actually lifts the ground in the technical sense.
The real question for any design is will it pass the John Windt 'Hummer" tests?
"Overview of Audio System Grounding & Interfacing"
Bill Whitlock, 9/4/2012
page 122 & 123
Using the John Windt “Hummer”
• Monitor one output and disconnect all other I/O cables
• For reference, listen to output without the hummer connected
• Connect clip to metal chassis and touch the probe to shield contact of
each I/O connector
• If no metal chassis, connect clip to shield of another I/O connector
• A “clean” design will have no output buzz or change in noise floor
• Other test paths include safety ground to I/O shields and input
shields to output shields
• Safety ground is accessible at the AC outlet and testing the path from there to
chassis could reveal a problem due to a poorly chosen internal connection
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf
"Overview of Audio System Grounding & Interfacing"
Bill Whitlock, 9/4/2012
page 122 & 123
Using the John Windt “Hummer”
• Monitor one output and disconnect all other I/O cables
• For reference, listen to output without the hummer connected
• Connect clip to metal chassis and touch the probe to shield contact of
each I/O connector
• If no metal chassis, connect clip to shield of another I/O connector
• A “clean” design will have no output buzz or change in noise floor
• Other test paths include safety ground to I/O shields and input
shields to output shields
• Safety ground is accessible at the AC outlet and testing the path from there to
chassis could reveal a problem due to a poorly chosen internal connection
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf
Speedskater, thanks for a more up to date source of Bill Whitlock's work.
There is a fundamental difference in the approach promoted by Bill Whitlock compared to most amp builders/designers in the layout of Ground.
Whitlock's method is to connect the ground of AC Power, inputs and outputs to chassis. There is very little advice given on the ground layout within the equipment itself. There is a general ban on any form of ground loop breaker. When all the inputs and outputs are connected to chassis, there is no point using a star ground. A star ground would look more like a wagon wheel. Maybe one option would be to also connect all internal grounds/returns to the chassis. A kind of mega ground plane.
Any problems caused by connecting equipment to mains and/or other equipment are solved by modifying the connections. Isolation transformers are a preferred method.
The audio builders/designers have a different set of design goals. One of them must be: "Design equipment that can easily be connected to any other piece of equipment." Designing equipment that can only be used with modified cables or adding devices will not be very popular.
One method used is isolating as many of the grounds and chassis as legally possible. Their solutions are placed within the equipment.
Between the boxes or Inside the boxes.
The choice is yours.
There is a fundamental difference in the approach promoted by Bill Whitlock compared to most amp builders/designers in the layout of Ground.
Whitlock's method is to connect the ground of AC Power, inputs and outputs to chassis. There is very little advice given on the ground layout within the equipment itself. There is a general ban on any form of ground loop breaker. When all the inputs and outputs are connected to chassis, there is no point using a star ground. A star ground would look more like a wagon wheel. Maybe one option would be to also connect all internal grounds/returns to the chassis. A kind of mega ground plane.
Any problems caused by connecting equipment to mains and/or other equipment are solved by modifying the connections. Isolation transformers are a preferred method.
The audio builders/designers have a different set of design goals. One of them must be: "Design equipment that can easily be connected to any other piece of equipment." Designing equipment that can only be used with modified cables or adding devices will not be very popular.
One method used is isolating as many of the grounds and chassis as legally possible. Their solutions are placed within the equipment.
Between the boxes or Inside the boxes.
The choice is yours.
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That sentence worries me....Big time
As well as Bill Whitlock some other sources of EMC info are (and it is EMC engineering):
home page
Tony Waldron's EMC ranting and ravings
EMC Information Centre - The EMC Journal (Free in the UK)
floating/isolated is a legal option, many universal players are just 2-wire mains plug, isolated/floating "double insulated" construction
there are additional construction requirements for double insulated equipment in addition to the right certifications for the transformer that make it much simpler to recommend Protective Earthed 3-wire construction to diyers when the project gets beyond the wall wart PS stage
there are additional construction requirements for double insulated equipment in addition to the right certifications for the transformer that make it much simpler to recommend Protective Earthed 3-wire construction to diyers when the project gets beyond the wall wart PS stage
Read: Not one more than legally required and also not one less than legally required.