> Are they universally transformer-based or are there active outputs with coupling caps?
Yes.
Also transformerless without caps.
The situation is: you can only get 10mA, and preferably 2mA, from Phantom. Mikes are sometimes able to output over 1V, and may be loaded in 200 ohms; that's over 7mA peak. A step-down transformer swaps current, though you may then run out of voltage on P-12 power.
In general, the decision to use a transformer is about price and market. The $99 mikes can rarely fit iron in the budget. $500 mikes can. $2,000 mikes may be used by people who don't want iron in the path. It isn't about rational engineering.
> how closely the currents match between pins 2 and 3? Do DC imbalances normally exist?
Shouldn't be unbalance. In many common hot-switch situations (even phase-reverse), an unbalance makes a big POP. Unbalance hinders any iron in the preamp. Both sides play a part: the preamp (or external supply) should have reasonable resistance balance, and the mike should pull both pins equally. I don't know how badly some models may ignore this detail.
Yes.
Also transformerless without caps.
The situation is: you can only get 10mA, and preferably 2mA, from Phantom. Mikes are sometimes able to output over 1V, and may be loaded in 200 ohms; that's over 7mA peak. A step-down transformer swaps current, though you may then run out of voltage on P-12 power.
In general, the decision to use a transformer is about price and market. The $99 mikes can rarely fit iron in the budget. $500 mikes can. $2,000 mikes may be used by people who don't want iron in the path. It isn't about rational engineering.
> how closely the currents match between pins 2 and 3? Do DC imbalances normally exist?
Shouldn't be unbalance. In many common hot-switch situations (even phase-reverse), an unbalance makes a big POP. Unbalance hinders any iron in the preamp. Both sides play a part: the preamp (or external supply) should have reasonable resistance balance, and the mike should pull both pins equally. I don't know how badly some models may ignore this detail.
