Where to "fix" reversed polarity

[SubSpec]

So, I've got a recent acquisition Blue Blueberry that was (apparently) factory modified with a bayonet mount. I suspected when initially testing it that polarity was reversed but as I also got a bayonet fitted Mouse and a bunch of capsules so I had other toys to attend to at the time. Am finally circling back to the Blueberry and did confirm it is reversed.

Simply flipping phase on my pre gets me results that are audibly comparable to what I would expect, which is to say, I *think* swapping at the XLR output pins is likely sufficient.

My question is: Is the assumption swapping at the XLR output okay or would it be a better practice to test further up the circuit for reversal, such as the bayonet connection? Might I expect any different sonic results if that were the case or is the circuit likely to be indifferent to polarity?

 

[micolas]

Hi SubSpec!
Happy New Year!

You can reverse the connections to pins 2 and 3 on the xlr output or reverse the output transformer wires.
Test the Blue mic next to another mic with the correct phase (doesn't matter if it's condenser or dynamic).

 

[abbey road d enfer]

I don't think reversing the connection at the bayonet would result in the desired polarity reversal. Best case it would do nothing, worst case the mic would simply not work.
Ther is no risk in doing it, though, except butchering connections.

 

[drtechno]

My question is: Is the assumption swapping at the XLR output okay or would it be a better practice to test further up the circuit for reversal, such as the bayonet connection? Might I expect any different sonic results if that were the case or is the circuit likely to be indifferent to polarity?

It doesn't matter where you do it, so I would swap it wherever its convenient. But probably at where they modded the mic (bayonet)

 

[abbey road d enfer]

It doesn't matter where you do it, so I would swap it wherever its convenient. But probably at where they modded the mic (bayonet)

In the absence of more detailed info, I assume the bayonet is the capsule connection.
Even though some believe it would, reversing the connections of an externally polarized condenser doesn't change polarity.

 

[drtechno]

In the absence of more detailed info, I assume the bayonet is the capsule connection.
Even though some believe it would, reversing the connections of an externally polarized condenser doesn't change polarity.

I'm thinking more of internally at the transformer, but where ever its convenient. at the xlr is what I would probably do anyways.

 

[SubSpec]

Thanks and Happy New Year to all! The replies helped me think through it more and that makes sense that the capsule connections wouldn't be responsible for the reversed polarity. I'll swap at the XLR and call it a day! Thanks

 

[Voyager10]

Possible explanation which connects the two - entirely guesswork:

With the capsule directly wired to the preamp, one side (e.g. the backplate) was being held at the polarisation voltage and the other (e.g. the diaphragm) was pulled to ground (via a 1G resistor, etc.) and used as the preamp input.

But, if it was modded to make the capsule detachable, one connection had to be ground (i.e. the mic chassis) and only one other connection was available. So maybe they rewired it so the backplate was grounded and the diaphragm was pulled up to the polarisation voltage, and also used as the preamp input (via an input capacitor and high-value FET bias resistor).

The difference between these two arrangements is that, in the first, an increase in voltage across the capsule drives the FET gate more negative while in the second the gate is driven more positive. Hence, the output phase will need to be inverted to compensate. Swapping the transformer connection (either primary or secondary/at the XLR) is entirely the right thing, if so.

 

[Voyager10]

Much cleaner if I draw it...

 

[RuudNL]

The left circuit can only be used with completely isolated capsules (LDC), while the right circuit is usually the only option when using SDC capsules, that have one capsule connection grounded.