I've got a mic pre (basically a straight up rod elliot P66) that I'm trying to test as "completed". problems kinda a "what to do with +48 from mixer/interface(pushing +48)-> -> using bal/unbal 1/4 inch or bal XLR. into mic pre (which uses its own +- 15v PSU,) and prevent +48 from damaging transistors and opamps inside-> allow the provision of +48 to microphone (bal XLR) at the end of signal chain
reiteration/extra detail and design goals for additional clarity:
The opamps/transistors in the pre are planned to use +-15, provided via a transformer and linear regulator. plenty of power (no loading even lame P48 systems), potentially really quiet, able to be plugged into non-pro/non 48 supplying mixers/recorders etc, BUT must be able to plug into board pushing +48, and not damage the op-amps/transistors. Then the mic pre must be able to provide phantom to the mic it's preamping.
I know I can use capacitors to block. big hurdle there is nonpolar film caps large enough not to alter rolloff being expensive and physically large.
I can use diodes between opamp output and power to protect the the negative feedback inverting input.
Is there any kind of trick to protecting devices with XLR outs from the potential phantom power coming from the other end of that jack? (most of my gear has phantom on, or phantom off. not individually, or even partially switched)
or do I just need to "invest" in some reasonable NP film caps?
reiteration/extra detail and design goals for additional clarity:
The opamps/transistors in the pre are planned to use +-15, provided via a transformer and linear regulator. plenty of power (no loading even lame P48 systems), potentially really quiet, able to be plugged into non-pro/non 48 supplying mixers/recorders etc, BUT must be able to plug into board pushing +48, and not damage the op-amps/transistors. Then the mic pre must be able to provide phantom to the mic it's preamping.
I know I can use capacitors to block. big hurdle there is nonpolar film caps large enough not to alter rolloff being expensive and physically large.
I can use diodes between opamp output and power to protect the the negative feedback inverting input.
Is there any kind of trick to protecting devices with XLR outs from the potential phantom power coming from the other end of that jack? (most of my gear has phantom on, or phantom off. not individually, or even partially switched)
or do I just need to "invest" in some reasonable NP film caps?
