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Old 3rd December 2006, 05:12 PM   #1
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Question About INPUT RESISTER separated from ground

Hi
I have studied various ways in this forum , and I tried a input circuit about seperating guround,but,there is humm .
May teach some knowhow to use this tech ?

I attach the test circuit .
For I tried the resistor in stock,so it is 22 ohm.

sincerely
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Old 4th December 2006, 12:04 PM   #2
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Because I was not used to English. Sorry
I do not intend to do rudeness .
Please teach me the point to be careful to
not to occur hamm.
Sincerely.
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Old 4th December 2006, 01:22 PM   #3
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Maybe ?
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Old 4th December 2006, 04:53 PM   #4
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ThanK you very much.
I have tried the suggestion at once.
And the result:Though some noises stay yet,the hamm is lower than the first try. So I will study more.
Very Thanks!
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Old 23rd February 2010, 09:25 PM   #5
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this is an interesting question.
If I know, how the "0-volt" rail is connected to the rail with GND (earth) symbol by the power supply PCB, I can give more accurate advices.
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Old 24th February 2010, 02:02 AM   #6
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Quote:
Originally Posted by turnA_zpoint View Post
Because I was not used to English. Sorry
I do not intend to do rudeness .
Please teach me the point to be careful to
not to occur hamm.
Sincerely.
Don't sweat it. I'm sure I'm not the only one, but I find it easier to read from someone who does not speak much English than it is to read from someone who's first language is English but uses poor spelling and terrible grammar.

I think its function is related to separating the source gnd from the PS gnd. Does this circuit utilize a 'star' gnd scheme?
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Old 24th February 2010, 02:24 PM   #7
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Hi tiefbassuebertr
Hi CBS240

The feedback circuit is that T-type feedback register circuit.
It's for inverted amp to degree the Number of feedback register.
I tried separating T-type feedback register circuit of source ground
from PS ground.

Though later study, I understand that is need not to separate.
And I do not use the T-type feedback circuit,too.


Thank you your gentle Reply!

Regards
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Old 23rd June 2010, 12:28 PM   #8
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Quote:
Originally Posted by turnA_zpoint View Post
Hi
I have studied various ways in this forum , and I tried a input circuit about seperating guround,but,there is humm .
May teach some knowhow to use this tech ?

I attach the test circuit .
For I tried the resistor in stock,so it is 22 ohm.

sincerely
I've made a few thoughts concerning the royal way for GND management. The idea from post #3 is near by the optimum. In opposite to that I would change follow:
1) the sketched red wire about post #3 I would connect direct to the central earth connection near by the main supply capacitors and the other site of this wire must go direct to the chynch input connector. If you have dual mono power supply (royal way), you must connect the chynch connectors not isolated to the enclosure (case, cabinet). At this aera there is the only connection between the left and right channel. For the 220 ohm resistor I would introduce a separate wire to the central earth connection.
If you have only one power supply for both channels, there are several but not perfect solutions for GND management.
2) Additional you must introduce a separate transformer and voltage regulation for the operational amplifier ICs AD8620 - each for both channels (important to avoid additional parasitic GND currents along the audio input GND signal and thus optimal audio results).
3) the 22 Ohm resistor between the clean earth and dirty earth now no longer necessary.

Last edited by tiefbassuebertr; 23rd June 2010 at 12:45 PM.
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Old 24th June 2010, 01:36 PM   #9
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Hi tiefbassuebertr.

Dual monaural is a royal road.
It is thought that I am glad if the transformer can be composed of one. However, I see the problem was not able to be solved.
Thank you.
Indeed, if the transformer is used also for the operational amplifier, it solves it. It was a blind spot.

It became reference very much.

Regards!
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