Which fader wires do I switch for phase reverse?

A

AnalogApples

Member
I have a Tascam 320b.

There are two wires entering the bottom of the fader (one solid red striped, one dotted red striped) and one white wire connected to the top.
So the fader has 3 wires connected to it from the circuit board.
Does anyone know which of these wires I would swap to get a phase/polarity reverse?

I sent two identical bass guitar signals to two channels and swapped the two bottom wires of one fader but did not hear the signal canceling or any phasing effect. So now I’m stumped.

I’d like to put some DPDT on/on mini switches in so I have polarity reversal available.
 
Phase reverse is accomplished by reversing the hot and cold conductors of a balanced signal, like at the mic input. Everything else input-wise on an M-300 console is unbalanced. It’s not possible to reverse the phase on an unbalanced signal. And you wouldn’t do it at the fader anyway...those three wires are input, output and the variable signal shunt to ground, so there’s nothing to reverse.

What is it you are trying to accomplish?
 
When micing a drum set, it is nice to be able to phase reverse some of the microphones to see if I lost some bass due to phase cancellations.
It would be ideal to have a switch that can do that to both the line in and the mic in. So I can try flipping phase on a channel either while tracking or while mixing from line in.

I just want to avoid having to use those inverting cable adapters.
 
AnalogApples said:
When micing a drum set, it is nice to be able to phase reverse some of the microphones to see if I lost some bass due to phase cancellations.
It would be ideal to have a switch that can do that to both the line in and the mic in. So I can try flipping phase on a channel either while tracking or while mixing from line in.

I just want to avoid having to use those inverting cable adapters.
Click to expand...
"Phase" only refers to balanced signals. hot (+), cold (-), and ground. Unless you're also using the mic ins as a balanced line in (which apparently you can do with the 320b with the -30dB pad). You want to be able to swap pins 2 & 3 on the XLR jack. Honestly it seems like a lot of work to drill holes and squeeze in switches to do that, but that's what you need to do. The M-520 has that switch and the schematic for that board should help you. Your line in is unbalanced phone jack on your board i.e. hot (+) and ground.
 
To be fair, this issue went away once people starting using DAWs - it's a very simple process. Flipping a line input - which most are unbalanced, rarely worrks because the flip button is in the pre-amp section and the line inputs joing after this section - so on my old soundcraft, for exampl the 'phase' reverse switch did nothing at all on line level inputs.
 
Make up a 'crossed', 300mm XLR 'slug. Or buy an adaptor.

N.B. You can reverse POLARITY (same thing here) by inserting a unity gain inverting op amp stage.

Dave.
 
AnalogApples said:
I appreciate all your comments. I also appreciate that nobody has tried to tell me to just turn the microphone upside down.
Click to expand...

That actually brings up another issue. (Although mic placement also matters with phase cancellation)

You'll need to check, but the 320 XLR inputs might be pin 3 hot. (My M-520 is). Some of your microphones are likely to be pin 2 hot, so technically they're already "reversed phase" if that's the case.
 
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