the lower diagram is correct, but the NFB lower leg also returns to the signal ground.davemar73 said:
I now prefer to see the signal ground taken from the RCA barrel/ground tag to the main Audio Ground (Star Ground). This seems to be more resistant to inducing hum/buzz than all the other ways I have tried.
Designing and building double-insulated equipment is actually easier than earthed equipment. In some German forum it is highly advocated, because of that.AndrewT said:
The handicap lies in testing. Mains voltage inside the amplifier (or any other equipment) must remain isolated from all metal parts that can be touched without the use of a tool. And it has to remain that way even during and after a defined mechanical impact, which is what DIYers usally cannot guarantee.
On the other hand, which DIYer can do the obligatory earth resistance and insulation tests to guarantee the safety of his earthed, self-made equipment? Must work carefully and hope for the best outcome.
I have been following this thread as this is a concern of mine as it should be for all. But I have never hooked my neutral to my chassis. For the very reason quoted above. I have had no issues with hum ever. Mind you I am no expert. I feel as though I build very solid equipment and "I" feel safe in "my" designs. There are extreme "very good to very bad" levels of design, engineering, and execution with DIY. I have personally seen some very scary wiring and chassis layouts. Lets just keep it safe and keep this thread going to educate more people.
many of the ideas in this thread appear lethal!
I went to a very good seminar by Bill whitlock od Jenson transformers at the AES in London, follow this link for the papers:
http://www.jensen-transformers.com/apps_wp.html
the second paper for students is good safe information.
regards
I went to a very good seminar by Bill whitlock od Jenson transformers at the AES in London, follow this link for the papers:
http://www.jensen-transformers.com/apps_wp.html
the second paper for students is good safe information.
regards
avyrez said:hello
which one is the best variant in interconection
connect the cable shield at one end or both ends
The best (and correct) variant is to connect the shield on both ends. Leaving the shield disconnected at one end is a means to interrupt hum loops. If you prepare cables like that
a) mark them, so you do not use them for anything else.
b) be aware that you are curing the symptoms instead of the disease.
Anthony C Smith said:
A 2 hour audio version of the Bill Whitlock London seminar is available at:
http://www.aes.org/sections/uk/meetings/a0705.html
You will need to have a printed copy of the "2005 Generic Seminar Template" paper in front of you, just to follow along.
AndrewT said:
Hi, Andrew,
My post answered post #105 and its attached schematic, not #108.
Post #108 is one example, where the poster must find the best compromise whether the advantages of shielding the signal wires are bigger than the disadvantages of increasing the capacity between signal wires and ground. Or maybe the increased capacity is also an advantage, because it could accidentally create a convenient RF-filter. There is too little and too imprecise data to decide that from a distance.
Although there is a small possibility that this schematic could lead to hum. If there is a star-point for signal return on the PCB (signal ground, IN- or whatever it is called there), the potentiometer's gound wire and the RCA's ground wire should go there individually and both be connected to that point.
From the feedback circuit's point of view it is also better to connect the speaker return to the PCB's ground. That entails however sufficiently big traces one the PCB for the current involved.
Regards
David
hi,
what type of capacitor should i use for 100 nf in Rod Elliot's article?
http://sound.westhost.com/earthing.htm
ordinary film or polyester caps are sufficient or should i use class X2 type?
and also what is the voltage rating for this cap?
thanks..
what type of capacitor should i use for 100 nf in Rod Elliot's article?
http://sound.westhost.com/earthing.htm
ordinary film or polyester caps are sufficient or should i use class X2 type?
and also what is the voltage rating for this cap?
thanks..
A ceramic or normal film capacitor will be sufficient as long as the bridge rectifier is either working normally or internally shorted. If the unlikely event of a phase to amplifier ground short ocurrs at the same time as the even more unlikely event of an internally open-circuited bridge rectifier, the 10 Ohm resistor will go up in flames anyhow and it doesn't matter, if the capacitor does the same or not.
I bit the bullet and tested a similar arrangement to the ESP Disconnecting Network.pacificblue said:
Wired the mains Live from the fused IEC socket to the network with the other side of the Network to Safety Earth.
I blew the fuse holder apart when I switched on. The majority of the glass and copper fuse disappeared with a big bang.
The Network components measured as unaffected by the Fault current and looked unaffected.
Yes, I didn't want to give another impression. It is so unlikely that four high current diodes go open circuit at the same time, even Murphy's Law may not apply anymore.
If the rectifier is internally shorted, there is virtually no voltage across the resistor and capacitor, so any resistor and capacitor would probably live forever on that condition.
And if the rectifier is in working condition you will get 1 or 2 V across them until the fuse reacts. You could probably even get away with a 1 W resistor and a 6 V capacitor there.
A 35 A bridge rectifier usually survives several 100 A of short circuit current per diode, before it fails. This circuit is as safe as you can reasonably design one.
If the rectifier is internally shorted, there is virtually no voltage across the resistor and capacitor, so any resistor and capacitor would probably live forever on that condition.
And if the rectifier is in working condition you will get 1 or 2 V across them until the fuse reacts. You could probably even get away with a 1 W resistor and a 6 V capacitor there.
A 35 A bridge rectifier usually survives several 100 A of short circuit current per diode, before it fails. This circuit is as safe as you can reasonably design one.
hi,
i'm getting a little obssesive about safety earthing nowadays.
and a bit confused between these two schemas..
in digi's schema safety earth is bonded to chassis..
http://www.diyaudio.com/forums/attachment.php?s=&postid=1539987&stamp=1213600606
but in original network schema, safety earth is going to rectifier's shorted ac legs..
http://sound.westhost.com/earthing.htm
are these two wiring same? or am i missing something?
thanks a lot..
i'm getting a little obssesive about safety earthing nowadays.
and a bit confused between these two schemas..
in digi's schema safety earth is bonded to chassis..
http://www.diyaudio.com/forums/attachment.php?s=&postid=1539987&stamp=1213600606
but in original network schema, safety earth is going to rectifier's shorted ac legs..
http://sound.westhost.com/earthing.htm
are these two wiring same? or am i missing something?
thanks a lot..
the first is wrong it shows the Safety Earth going to a terminal block and from the Terminal block to chassis.
The second is correct but misleading.
It shows the Safety Earth going straight to chassis but the diagram implies it could come off the terminal of the rectifier.
All exposed conductive materials must be permanently connected to Safety Earth.
Take the Safety Earth wire direct to chassis with a short robust mechanical fixture, or even welded but not soldered.
From above the permanent fixture take a connection from the Safety Earth to the Audio Ground. This can be a direct wire connection or as shown in fig2 of ESP through a Disconnecting Network.
BUT,
that connecting wire and/or Disconnecting Network must survive longer than it takes the mains fuse to rupture and for the arc to extinguish. This fault current can run to kA.
The bigger the mains fuse the longer it takes to disconnect the fault.
The second is correct but misleading.
It shows the Safety Earth going straight to chassis but the diagram implies it could come off the terminal of the rectifier.
All exposed conductive materials must be permanently connected to Safety Earth.
Take the Safety Earth wire direct to chassis with a short robust mechanical fixture, or even welded but not soldered.
From above the permanent fixture take a connection from the Safety Earth to the Audio Ground. This can be a direct wire connection or as shown in fig2 of ESP through a Disconnecting Network.
BUT,
that connecting wire and/or Disconnecting Network must survive longer than it takes the mains fuse to rupture and for the arc to extinguish. This fault current can run to kA.
The bigger the mains fuse the longer it takes to disconnect the fault.
