optocoupling power stage - hiss with 6N137 - Page 6 - diyAudio
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Old 29th February 2008, 11:06 AM   #51
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any news about the hiss?
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Old 6th November 2012, 02:19 AM   #52
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Your groundplane is getting contaminated...................thats the reason for hiss.
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Old 6th November 2012, 10:02 AM   #53
Pafi is offline Pafi  Hungary
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I experienced noise too. Optocouplers are basically very noisy, in amplitude domain. If driving pulse transition is not fast enough, then amplitude is converted to time. Waveforming (+1 CMOS inverter before LED) solved the problem in my case.
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Old 6th November 2012, 10:25 AM   #54
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Driving the led in shunt mode solves the problem.
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Old 7th November 2012, 07:55 PM   #55
Pafi is offline Pafi  Hungary
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Quote:
Originally Posted by Workhorse View Post
Driving the led in shunt mode solves the problem.
What do you mean?
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Old 8th November 2012, 09:12 AM   #56
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Quote:
Originally Posted by Pafi View Post
What do you mean?
Have a look
Attached Images
File Type: jpg shunt drive.jpg (6.5 KB, 43 views)
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Old 8th November 2012, 09:36 AM   #57
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the problem (which is known), is the inductance of the LED, this only creates problems when used with pwm (if pwm contains audio information).
for linearity (in this case becomes noise, as says Pafi), is sufficient to saturate the LED, (as Triger input is good).
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