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virtual earth mixer NE5534 problem
virtual earth mixer NE5534 problem
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Old 17th April 2017, 10:34 AM   #21
b0red2tears is offline b0red2tears  Australia
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Quote:
Originally Posted by AndrewT View Post
Read John Roberts:
cmos 4066 as an audioswitch?
Thanks, that reinforces my belief that it IS possible to make this work well.
John Roberts writes:

"You will need to experiment with edge rates of control switching signals to minimize audible clicks and avoid DC offsets in the opamp for obvious reasons. I think I also staggered the rise time so the gate control signal to open hit first and to close hit second. That way you didn't short active minus inputs to ground. "

That is precisely what I'm trying to do but unfortunately I don't have enough of an understanding yet to achieve it. I bought several cd4007ub inverters after they were mentioned by zero D, for learning purposes. I put together this:

https://i.imgur.com/8OeI3Sg.png

It leaves one unused inverter (in pin10,out pin 12) so was hoping to use this circuit for the control switching signals. Could anyone suggest what components to include and where, to achieve a delay? And what is meant by "edge rates"?
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Old 17th April 2017, 11:03 AM   #22
AndrewT is offline AndrewT  Scotland
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edge rates is referring to the steepness of the switching impulse, usually measured as V/us
OFF rate can be different from the ON rate.
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Old 26th April 2017, 11:04 AM   #23
audio_tony is online now audio_tony  United Kingdom
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Douglas Self's book Small Signal Audio Design has some detailed information on signal switching with FETs and CMOS - you would do well to buy a copy.
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Old 30th October 2017, 12:56 AM   #24
b0red2tears is offline b0red2tears  Australia
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Default SOLVED

Just revisiting this old thread to confirm that I did eventually succeed in using the 4066 CMOS ic with good results and post the diagram to help anyone else who might be interested. There sure was a lot more to it than an initially bargained for; it required all the suggestions from the experts on here to be implemented before I was able to achieve acceptable levels of distortion, offness and quiet switching. These included switching at virtual earth, shunting de-selected input to ground and getting the timing right.
However implementing these suggestions first required me to learn a lot before I was able to understand them.
Thanks heaps to everyone for your help, it was a good learning experience. The following books were also incredibly useful:
Small Signal Audio design by Doug Self
Handbook for Sound Engineers by Glen Ballou
<img src='https://i.imgur.com/aCQ5V59.jpg' />
Click the image to open in full size.
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Old 30th October 2017, 01:22 AM   #25
b0red2tears is offline b0red2tears  Australia
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just try that image again
Click the image to open in full size.
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Old 1st November 2017, 10:01 PM   #26
Zero D is offline Zero D  United Kingdom
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Hi there. Thanx for updating your thread with the good news It just shows that persistance & patience can do wonders !

I'm glad i was able to help in some way
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