The AM Forum

Can I invert the audio phase by reversing the leads of a condenser microphone?  Negative peaks are greater than positive on this transmitter which has a phantom powered MXL 990 condenser microphone at the front of everything.

Thanks,

Jon

I take it whatever processor youre using to power/preamp the mic has no phase invert switch?

I don't believe you can switch leads in the 990....

may be wrong    ;D

Yes.  No invert switch anywhere

Yes.  No invert switch anywhere

I dont think you can flip the input leads because of the "Phantom power" arrangement. However, you probably can flip the balanced outpoot leads from the audio processor if you need to flip the audio phasing. (where there is a will there is a way)

This is a Flex Radio SDR 1000 I'm fooling around with.  The pre-amp is a sound "card", a Presonus Firebox, no balanced output.

I think phantom power is on both leads.  I'll check that.

Yes, if wired correctly, the phantom power should be balanced (DC connected to both pins 2 and three, usually through 6-10k resisitors) , so you can change the wiring without a problem. But do check since there is no guarantee the mic or preamp/power supply are wired correctly.

I don't think I would want to,... or have any need to change anything at the condenser Head, Why,..phasing is easily done out board, I don't see any benefit to messing around, and besides there are mics with built in arrangements that can be had at the flip of a switch..buy a gooder mic..My B-1 Has three settings why would I want to tare into an already Nice Mic that handles any settings Noisy environments echo environments etc..

73
Jack.
 

I'm not going to fool around with the microphone head.  I might get brave enough flip white and blue in XLR connector of a cable.  I actually own a B1 but my sister has it.  She's using it for recording.   I suppose I could sneak it back from her.

You can also buy in-line XLR phase switches. Looks just like a barrel XLR adapter (usually male-to-male).

I have a B1 - balanced, and of course needing phantom power.  I switch the phase with no problem (at the XLR connector)!  The phantom DC power is supposed to appear on BOTH balanced inputs, equally, with respect to DC ground.  Not doing so would result in a DC voltage appearing across the microphone audio output terminals, and that would not be a good thing at all !

So, you really should be able to reverse the mic at the XLR with no problem  ;)

It would be nice to have a phase reversal switch  so you could go A - B and look at the scope. Why don't you build a little Phase Splitter so you could simply change phase by flipping a switch that connected the output to either the collector or the emitter of the stage?

The thing could go in a little project box with XLR male and Female.

To stay balanced build two of them. A couple of 2N3904's, a DPDT switch and a few parts in a box with 9V battery.

Mike Wu2D

Yes. Switch pins 2 and 3 pretty much anywhere. I usually do it right at the mic because that's generally the easiest connector to get to. I also tape mark the connector that's flipped so I don't forget in the future. (Actually, I guess I DO forget which ones are flipped and need to mark them in the first place.)

 Make sure the phantom power is off when you plug and unplug these marshal mics. Pin 1 is always shield.