Hi DIY fellows,
usually, I use a 220 ohm resistor parallel with a 220 nF capacitor to connect the case with the ground of my opamp circuits. I wonder if any theory exists why these (or similar) values should be used !?
The result on two variables can be considered:
- The amount of noise that is added to the ground
- The shielding properties of the case (Faraday cage)
Any information would be appreciated!
Fedde
usually, I use a 220 ohm resistor parallel with a 220 nF capacitor to connect the case with the ground of my opamp circuits. I wonder if any theory exists why these (or similar) values should be used !?
The result on two variables can be considered:
- The amount of noise that is added to the ground
- The shielding properties of the case (Faraday cage)
Any information would be appreciated!
Fedde
fedde said:(just solved one of the biggest problems I still had)
Fedde [/B]
DIYaudio does it again.... if everything would be this easy .....
J-P
ik hou van Holland, landje aan de Zui......
breguetphile said:A step further than just a low resistance would be what alephs use. If you use a thermistor which will only be resistive when current is flowing, otherwise its close to 0 ohms. This is described in one (if not more) of the aleph service manuals.
Yup, I always do it like this. EXCEPT that you must use a NTC, not a PTC. This means that it should be about 5-10ohms when little or no current is flowing throug your ground, but it drops to a very low value when conducting any significant current. Another elegant solution would be to use a std rectifier bridge as in ZV4.
----------------------------------------------------------------Peter Daniel said:It seems like 220ohm is a bit high. Usually 10ohm is being used.
Theses things sre done in 110V areas. Be careful in 220V region. I don't believe one should connect reoung to chasis via any resistor!
Even the Japanese have abandoned this practice, but still seems to take place in Taiwan.
unsafe ?
Are you talking about putting a resistor in between the mains earth and the case
OR
connecting the case directly to mains earth and linking the circuit earth (e.g. transformer centre tap) to mains earth via a resistor
If you mean the second case (no pun intended), please explain why you think this is unsafe
Are you talking about putting a resistor in between the mains earth and the case
OR
connecting the case directly to mains earth and linking the circuit earth (e.g. transformer centre tap) to mains earth via a resistor
If you mean the second case (no pun intended), please explain why you think this is unsafe
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