And what design generates what type of signal property?

For example there are dynamic mics with or without output transformers. Do they differ in the type of signal outputted?

Do most dynamics generate a balanced differential signal where pin 3 is polarity reversed?

Also where and how is the pin 3 signal polarity inverted? At the voice coil? At the output transformer?

Thanks for any help!


The output transformer just changes the source impedance (And provides some voltage (but never power!) gain).

Most preamps load the mic with a couple of k ohms, so raising the impedance to a few hundred ohms or so if it is not there to start with helps system noise performance. This is particularly important in ribbon mics which have a notoriously low output impedance (a few tens of ohms or less) and low output voltage. A transformer that steps the impedance up by a factor of somewhere between 10 and 100 and the voltage by a factor of somewhere between say 3 and 10 (Impedance transformation is always the square of the voltage transformation in a transformer) is almost mandatory with these and often built in.

As to general types, there are really the usual pressure and velocity transducers the same as any other mic, plus the slightly odd ones like ribbons (Generally figure of eight), Variable D like the RE20 designed to cancel proximity effect, oddities like the Coles Lip Mics, and such. All of these could be made using condenser capsules, but the dynamic elements have the virtue of not needing tiny spacing and gigaohm impedance levels which matters where large level excursions and water vapour may be present.

Most mics (never mind dynamic or condenser) output a more or less balanced line, on some form of 3 pin connector, usually these days XLR, but Tuchel was once popular with older German mics and weirder things have been used.

Generally expect a few mV or so at a few hundred ohms source impedance, except for transformerless ribbons where you can drop those vales by a factor of 10 - 100 or so, a kick drum mic might be quite a bit hotter, but still generally peaking at less then 1V.

  • \$\begingroup\$ Ok so the transformer only changes the impedance and the gain. But i still don't understand if the mic outputs a differential signal. \$\endgroup\$ – JAudio Apr 28 '18 at 9:39
  • \$\begingroup\$ Transformers can also convert single ended to balanced differential signals. \$\endgroup\$ – Brian Drummond Apr 28 '18 at 10:44
  • \$\begingroup\$ Most mics output a differential signal that is typically floating with respect to pin 1 which is just a connection for screening. This is different from most condensers where the phantom power requires that there be some connectivity between pin 1 and the signal lines (Generally a few k Ohms to each line), hey are typically still differential but have a lower common mode impedance in a condenser design. \$\endgroup\$ – Dan Mills Apr 28 '18 at 12:17
  • \$\begingroup\$ Could you say that if a signal is floating it is automatically differential? \$\endgroup\$ – JAudio Apr 28 '18 at 16:38
  • \$\begingroup\$ A floating signal pair is inherently differential (Actually ALL signals are differential in so far as voltages are measured as voltage differences) but possibly not balanced (which implies an equal impedance to some reference from both legs). \$\endgroup\$ – Dan Mills Apr 28 '18 at 17:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.