Hi guys, I follow a crystal radio forum and thread about hearing aid transducers came up. One fellow found a transducer with higher impedance and is looking at making crystal radio earphones with them.
Yes, there are matching transformers involved.
But I'm lost on some specs.
Here's the datasheet,
It says 0.33ma RMS AC and 0.47ma DC.
I don't know why a hearing aid amp would put DC on the transducer.
It reads to me like the hearing aid companies don't use a capacitor on the output of their amps. I assume that is to simple, but what other explanation is there for having DC on the output of your amp?
Also why on a battery operated device with a tiny battery would you waste 0.47ma for 15hrs a day? (DC current)
What is the advantage of eliminating an output capacitor. (other than saving six cents on a $1,000 item)
Can I assume the transducer diaphragm is centered to make equal maximum excursions in both directions? And, that any DC bias will lower the maximum excursion in one direction? Thus lowering the maximum level the transducer can be driven before distortion? Here's a bulletin about testing.
What do you think? Thanks, Mikek