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Old 28th May 2015, 08:30 PM   #1
max1979 is offline max1979  Italy
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Join Date: Apr 2015
Default Hypex unbalanced input and app notes


I'm building a dual mono class D amp based on UcD400 (and SMPS400A400).
I'd like to add balanced and unbalanced input with the ability to switch from one to the other and that seems pretty easy looking at chapter 4.5 of the application note provided by Hypex (Dealing with legacy pin 1 problems).

Considering this app note in case of unbalanced input (RCA), it seems that the "GND" is connected to the chassis via a resistor and a cap but in another app note (Amplifier signal input wiring) it is directly connected to the chassis.

Am I missing something? What am I supposed to do?
In case, what's the proper value of resistance and what the value for the cap?
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Old 27th December 2015, 05:16 AM   #2
Ronj is offline Ronj  Singapore
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Location: Singapore
The Application notes already gives the values.. 100Ohms(R) and 100nF(C) respectively. However, it also says, as consumer equipments are usually "ground lifted" you can let go of this RC network and directly short the ground(Pin1) to Chassis.
That is why in, in the apps note you see them tied together and connected to RCA chasis PIN.
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Old 27th December 2015, 05:52 AM   #3
max1979 is offline max1979  Italy
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Join Date: Apr 2015
Thanks Ronj, I'm currently using the RC network with the suggested values and everything works great.
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