SWR early amp phantom blocker mod

[chrisdski]

Older SWR amps were built before phantom power became a common feature to mixer boards, hence they lack protection against phantom power on the DI out XLR. I’ve done some research and have a few build ideas from the attached pdf , but is the bare bones basic phantom power blocker as easy as 2 capacitors on pins 2 and 3 of the xlr out, positive to the board? I have some 47uf 60v caps I can use. Thanks in advance. Phantom Blocker.pdf

[g1]

is the bare bones basic phantom power blocker as easy as 2 capacitors on pins 2 and 3 of the xlr out, positive to the board?

Resistors should also be used. As mentioned in your attachment as well as here: https://www.instructables.com/Phanto...namic-Microph/

[chrisdski]

Excellent descriptions of the components used, thanks. Does the level of capacitance matter? I see they are using 100uf.

[g1]

Too low of capacitance will start limiting the frequency response. The first circuit you posted uses 10uF. I think your 47uF will be fine.

[chrisdski]

Here is the build installed in a SWR Strawberry Blonde amp head. I mounted it via an existing PCB screw mount. Works great.