[Radio Wrangler]

Transformer cores can be de-magnetised. Hit them with a big AC signal and then smoothly and slowly reduce it to zero. There is no need to dump the transformer or to dismantle it and anneal the lams.

If you use an audio sig gen to test one, don't just break the connection or switch off abruptly, diminish the signal gently to zero. Abrupt starts and stops of AC actually contain DC transient components.

Condenser microphones are very good indeed. There are some superb condenser mikes and recordings made with them. Some even include valves, if that is of any importance. And plenty of polarising voltage is helpful. Electrets are less high-faluting but are permanently polarised, and the only power needed is for a high impedance buffer after the capacitor. They can live with lower phantom voltages.

With care, condenser and electret mikes, transformer cores other than mumetal, transistor and digital circuitry can all be made to work very well indeed. Don't judge the whole just because there have been some grotty examples. There are some people around who can design things properly.

David