Passive high-pass filter of balanced input breakout board (6 duals inputs)

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electrogeek
Posts: 2
Joined: Sun May 27, 2018 3:07 pm

Passive high-pass filter of balanced input breakout board (6 duals inputs)

Post by electrogeek » Sun May 27, 2018 3:28 pm

Hi,

There is a problem with the input passive high pass filter (C=1uF and R= 47K // 47K)
With the values of components from kicad SCH file (https://github.com/flatmax2/AudioInject ... ed.sch.pdf) , Fc = 1/(2 x PI x R x C) = +-7Hz

Image

When I connect a sinus generator and scope, to have output signal equal to input source, the frequency of the input signal must be more than 7 KHz .

On our input balanced breakout board, all the 12 blue capacitors (C49, 50, 53, 54, 57, 58, 61, 62, 65, 66, 69 and 70) value = 1nF -> Fc = +-7KHz. The resistors (R51, 52, 53, 54, 61, 62, 63, 64, 71, 72, 73, 74, 81, 82, 83, 84, 91, 92, 93, 94, 101, 102, 103, 104) are correctly sized.

Best regards.

richardash1981
Posts: 3
Joined: Sun Apr 28, 2019 2:36 am

Re: Passive high-pass filter of balanced input breakout board (6 duals inputs)

Post by richardash1981 » Sun Apr 28, 2019 2:55 am

Not much consolation, but my set of balanced boards have the same problem - and both the 6-way input and the 8-way output are affected, they all have the same 1nF capacitors on them!
These should be easy enough to re-solder with the correct parts, except that they are soldered under the 1/4" jack sockets, meaning you can't get to the pads to remove the existing capacitors! The best bet I can think of is to parallel 1u parts, one end can easily go onto the jack connector pin, the other end will have to go onto an 0603 resistor however which isn't very easy to do.

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