Condenser Microphone - What is it?

kubeek

Joined Sep 20, 2005
5,724
Not really. Electrets capsules usually have a bulit-in jfet transistor, usually meant to operate at a few miliamps current. Condenser studio mikes have their own amplifier built in, usually meant to operate with 48V bias voltage. Condenser capsules should have none of that and be just a two plates in mid air.

It would be better if you showed what you want to replace with what and then talk about if the replacement is possible.
 

Thread Starter

vol_

Joined Dec 2, 2015
93
Not really. Electrets capsules usually have a bulit-in jfet transistor, usually meant to operate at a few miliamps current. Condenser studio mikes have their own amplifier built in, usually meant to operate with 48V bias voltage. Condenser capsules should have none of that and be just a two plates in mid air.

It would be better if you showed what you want to replace with what and then talk about if the replacement is possible.
I want to know if i can use EITHER an electret capsule or a condenser capsule for a hearing aid device that uses a transistor to preamplify or to buffer (?) a signal for a NJM2073 IC mono amplifier (mono in BTW). I want to be able to use both capsules (electret and condenser) for the same circuit.

The schematic i use is here. I will replace thought the TDA2822M with its contemporary equivalent NJM2073, which shows better proporties.

Thanks everyone!
 

kubeek

Joined Sep 20, 2005
5,724
I would guess that a condenser would need a larger supply voltage to have any a reasonable output signal, and the input impedance of the NPN transistor would load it too much.
 

Kermit2

Joined Feb 5, 2010
4,162
Electret-microphones commonly use jfet input and condenser mics use a 48 volt "phantom" supply.
Most quality audio mix boards have a setting that will supply the on board circuitry of condenser mics when they are plugged in.
 

GopherT

Joined Nov 23, 2012
8,012
I want to know if i can use EITHER an electret capsule or a condenser capsule for a hearing aid device that uses a transistor to preamplify or to buffer (?) a signal for a NJM2073 IC mono amplifier (mono in BTW). I want to be able to use both capsules (electret and condenser) for the same circuit.

The schematic i use is here. I will replace thought the TDA2822M with its contemporary equivalent NJM2073, which shows better proporties.

Thanks everyone!

An electret microphone is a type of condenser microphone. The microphone in the image is an electret microphone. A "standard" condenser microphone needs a DC bias voltage (3 wires) and the bias is normally 12, 24 or 48 volts - depending on the microphone. An electret microphone has the bias voltage built in as a permanently charged capacitor ("electret"). Check the definition of Electret on Wikipedia if you want more - no need for us to retype it here.

An electret microphone typically has a circuit board with a JFET transistor already built in so it can provide a decent output drive current.

An electret microphone costing less than one US dollar sounds surprisingly good.

Note that your circuit may not be extremely efficient with regards to battery life. Electret microphones need a milliamp or so of current so a standard hearing aid battery will not last more than a few 10s of hours with that circuit. check the current draw on your amplifier chip as well.
 
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