Adding phase, polarity reverse switches to Tascam mixer, question

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. I’m going to install these switches next to the faders, so I’ll be reversing the polarity before (or after?) the faders.
 
If this were me and I wanted to do what I think you're describing, including drilling a hole for a switch, I might be inclined to switch polarity at the input instead of later in the chain like at the fader.
But then, I'm no expert on the T320, either.

There is sometimes too many things that have occurred by the time it gets to the fader including inverting preamps and inverting summation amps. One would THINK each channel would be identical, but hey, maybe not. Stranger things have happened.
 
Thanks for the reply. That’s what Sweetbeats said too. He also said I can’t reverse polarity on an unbalanced signal. So, no DI reversing
 
Well... you sorta can. But he's basically right.
If you can signal trace, grab the signal right after the input buffer amp and you can reverse it there just fine. All the pesky concerns about grounds on an unbalanced signal would then be isolated.
You can TRY it on your DI. The worst you can do is end up with a lot of hum.
 
All faders have three wires. Bad news is that this is NOT where you can fit a polarity switch. By the fader point the internal structures of the circuit are working in unbalanced mode. The only sensible place to put the polarity switching is prior to where the three wires from the input connector go to the circuit board. From that point it is tracks only. So in many designs, it’s balanced up to the preamp gain stage, and any reversal has to be before this point. I’d do it at the input end and if you are careful it’s not hard. Faders have one terminal which is ground. The one the other end is the input normally, and the one connected to the moving contact is the output. Absolutely no chance at all of doing polarity reversal there I am afraid.
 
I have had buttons to do this on all my mixers since 1983 or so. The number of times they got pressed was minimal. To avoid wrecking your mixer's resale value, maybe buy a Neutrik barrel, a male and female connector for each end and put a little switch in the middle?
 
I’m practically phobic about polarity issues eating up bass in my recordings. I think it might raise the resale value to have these switches in there, considering this is a very low cost mixer. Even if use the 3 to 1 mic distance rule, aren’t I still going to find better sounds if I check how flipping polarity affects each mic position?
 
AnalogApples said:
I’m practically phobic about polarity issues eating up bass in my recordings. I think it might raise the resale value to have these switches in there, considering this is a very low cost mixer. Even if use the 3 to 1 mic distance rule, aren’t I still going to find better sounds if I check how flipping polarity affects each mic position?
Click to expand...
Doubtful.
 
AnalogApples said:
I’m practically phobic about polarity issues eating up bass in my recordings. I think it might raise the resale value to have these switches in there, considering this is a very low cost mixer. Even if use the 3 to 1 mic distance rule, aren’t I still going to find better sounds if I check how flipping polarity affects each mic position?
Click to expand...
The 3:1 rule of thumb yields about 9dB of isolation. At a frequency which is absolutely perfectly out of phase but 9dB different in level, you get a 3.2db reduction due to cancellation. If you're making good use of polar patterns, high pass filters, goboes etc. you'll get even more isolation. I find it to be extremely rare that I need polarity inversion in real time, and when I have, one of those inverting barrels was sufficient.
 
+1. Realistically you should only really have to invert polarity if you have two pieces of equipment which are wired differently, which you should know and fix anyway,
or if you intentionally mic something with two mics 180 to each other, like the front and back of a cab or top and bottom of a snare.

I can't really see polarity inversion being much use beyond that. Maybe I don't experiment enough!
 
The 3 to 1 rule is about isolation, not phase. If is meant to isolate different instruments in the same space, not as a 'rule' for using two mics on the same instrument.

You would get the same effect if you simply turned one of the mics down by 9db.

The phase of two different sources are rarely 180 degrees out, so the switch will not bring things in phase, it will just give you two choices of out of phase. One might sound better, but neither will be right.
 
Right, 3:1 rule of thumb doesn't apply to two mics on one source. But it does apply to two mics on two sources, to reduce bleed. One of the reasons bleed is undesirable is that if the sound of a source is getting into two mics, there can be phase interactions. But if the level of the source is substantially different in the two mics, the phase interactions are minimized.
 
I'd rather move the performers apart another foot or throw up a gobo that use a polarity invert which has no relationship whatsoever to the problem,
but strokes for folks.
 
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