Hello,
I am currently putting a Lomo YP27 (UP27) preamp in a rack. I'd like to add 48V phantom power and -26dB pads at the inputs, but the center taps of the input transformers are grounded. So I wonder which is the best way to do these mods. CT grounded input trans are not common anymore. I read some threads, and here are some options I have :
1 - simply disconnect the CT ground and add the usual circuits (2x6.8K for 48V, and resistors network for a pad). But @CJ wrote that this could change the capacitance of the coils, and perhaps the overall response ?
2 - disconnect the CT and use it with a 3,4k resistor to feed the 48V. And add a pad somewhere else in the circuit, perhaps on R32 and R33.
3 - another guess ?
Your experience on this would be greatly appreciated, thank you.
Cyril.
I am currently putting a Lomo YP27 (UP27) preamp in a rack. I'd like to add 48V phantom power and -26dB pads at the inputs, but the center taps of the input transformers are grounded. So I wonder which is the best way to do these mods. CT grounded input trans are not common anymore. I read some threads, and here are some options I have :
1 - simply disconnect the CT ground and add the usual circuits (2x6.8K for 48V, and resistors network for a pad). But @CJ wrote that this could change the capacitance of the coils, and perhaps the overall response ?
2 - disconnect the CT and use it with a 3,4k resistor to feed the 48V. And add a pad somewhere else in the circuit, perhaps on R32 and R33.
3 - another guess ?
Your experience on this would be greatly appreciated, thank you.
Cyril.
