Electret Mic -> Headphones

FenderBender11 · 18th September 2012, 04:06 AM

Hello,

I'm working on a little "hearing aid" project.

I'm trying to figure out the best way to to do this for best performance.

I was thinking

Electret -> RC filter-> Preamp (to line level) -> 3 band active equalizer -> Headphone amp -> Headphones

What are your opinions on that setup? Do I need a preamp? Are the stages in the correct order? Is there any point in having the signal at line level before putting it through the equalizer?

Preamp, equalizer, and head amp would all be pretty standard op amp circuits.

Any opinions?

ethanolson · 18th September 2012, 01:48 PM

Having the preamp makes sense from a standpoint of getting the best signal to noise ratio. The further away your components are, the more its usefulness becomes apparent.

Also take comfort in the fact that nearly every respected brand who makes a condenser or electret microphone has a preamp on it of at least 7dB. Shure does it in the range of +12dB boost for their small mics (like the MX150). It's either boosted in the bodypack or via the RK100PK preamp.

FenderBender11 · 18th September 2012, 02:37 PM

Well the entire unit is only going to be around 3" x 2". So it's not like I have huge cable runs or anything. Is it better to work with a signal in an equalizer when it's at a higher Vpp?

sreten · 03:28 PM

Hi,

FWIW you'll probably find it doesn't work well at all.
Such things used to be sold as novelty toys, because
that is all they are good for, a novelty for those with
normal hearing, and near useless for hearing problems.

The design of hearing aids is far, far more complicated
than you have assumed, and the type of hearing aid
depends on the type and severity of hearing loss.

rgds, sreten.

FenderBender11 · 18th September 2012, 03:38 PM

Quote:

Originally Posted by sreten

Hi,

FWIW you'll probably find it doesn't work well at all.
Such things used to be sold as novelty toys, because
that is all they are good for, a novelty for those with
normal hearing, and near useless for hearing problems.

The design of hearing aids is far, far more complicated
than you have assumed, and the type of hearing aid
depends on the type and severity of hearing loss.

rgds, sreten.

Hmm...I KNOW hearing aids can be more complex than just a few amplifiers. I also know hearing aids cost thousands of dollars.

But, what exactly is the difference that something like this could not work? Why won't it work? Hard to tell me it won't work without good reason.

18th September 2012, 04:06 AM	#1
FenderBender11 diyAudio Member Join Date: Jun 2011	Electret Mic -> Headphones Hello, I'm working on a little "hearing aid" project. I'm trying to figure out the best way to to do this for best performance. I was thinking Electret -> RC filter-> Preamp (to line level) -> 3 band active equalizer -> Headphone amp -> Headphones What are your opinions on that setup? Do I need a preamp? Are the stages in the correct order? Is there any point in having the signal at line level before putting it through the equalizer? Preamp, equalizer, and head amp would all be pretty standard op amp circuits. Any opinions?

18th September 2012, 03:18 PM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, FWIW you'll probably find it doesn't work well at all. Such things used to be sold as novelty toys, because that is all they are good for, a novelty for those with normal hearing, and near useless for hearing problems. The design of hearing aids is far, far more complicated than you have assumed, and the type of hearing aid depends on the type and severity of hearing loss. rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow Last edited by sreten; 18th September 2012 at 03:28 PM.

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18th September 2012, 01:48 PM	#2
ethanolson diyAudio Member Join Date: Nov 2011 Location: http://binged.it/ukmr5Y	Having the preamp makes sense from a standpoint of getting the best signal to noise ratio. The further away your components are, the more its usefulness becomes apparent. Also take comfort in the fact that nearly every respected brand who makes a condenser or electret microphone has a preamp on it of at least 7dB. Shure does it in the range of +12dB boost for their small mics (like the MX150). It's either boosted in the bodypack or via the RK100PK preamp.

18th September 2012, 02:37 PM	#3
FenderBender11 diyAudio Member Join Date: Jun 2011	Well the entire unit is only going to be around 3" x 2". So it's not like I have huge cable runs or anything. Is it better to work with a signal in an equalizer when it's at a higher Vpp?