Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Earphones/headphones from the junkbox

Status
Not open for further replies.

atferrari

Well-Known Member
Most Helpful Member
Earphones and headphones.

Audio was / is one of my stumbling blocks. I am at lost here.

I need to test a small directional microphone whose sensitive element is an electret mike.

I collected earphones / headphones for years, some probably from OLD hearing aids or portable radios, walkmans, cellular phones, CDs reproducers, even those given away by airlines and much more unknowns. The awful diversity of their jacks (or are they plugs?) I find it overwhelming.

Any simple way or rule of thumb, to get a rough idea of their impedance, if that matters at all, and to select one or two I could use, no risking to damage the audio amp? Sole thing I know for sure I can forget stereo.

BTW, I am going to build a (tested-working) preamp for my electret mike. What should follow? Maybe my LM386 based amp that works OK with an 8 Ohms speaker?

The unavoidable suggestion to Google, is surely to be followed later by an equivalent amount of critics on the circuits I could propose.

For the moment I would prefer a one / two chips solution.

Gracias for any help.
 
Last edited:
A multimeter will give you the resistance. Many headphones are ~32 Ohms.
 
I'm a bit vague about what you're actually asking?.

Are you wanting to build a preamp for the electret mike, followed by your LM386 amp, and feeding a pair of head/ear phones?.

If so impedance doesn't matter, the LM386 will happily feed any head/ear phones you have.
 
I'm a bit vague about what you're actually asking?.

Are you wanting to build a preamp for the electret mike, followed by your LM386 amp, and feeding a pair of head/ear phones?.

If so impedance doesn't matter, the LM386 will happily feed any head/ear phones you have.

Good :)

The preamp will be no more nor less the circuit (by Audioguru) that you made sticky some years ago. And now that you confirm this, it will be followed by my currently working LM386-based amp. Good to hear that!. :)

Gracias Nigel!
 
Last edited:
Why do you want an electret mic amplified to drive headphones? As a hearing aid?
If your hearing is normal then the LM386 with a capacitor that boosts its gain to 200 has plenty of gain so the preamp is not needed except it will produce less hiss.
 
Thanks for replying AG.

Sure you know the circuit. :) Would you say then, that I could safely take the signal from C1 to a 10K pot at the input of an LM386 leaving all the rest out?

BTW, how relevant could be the resulting hiss?
 

Attachments

  • Reduced to minimum.bmp
    1.4 MB · Views: 159
Yes, your red box can be an LM386 amplifier with a 10uF capacitor between pin 1 and pin 8 to boost the gain 10 times.

Change C1 to a 220nF or 330nF film capacitor and use a 50k audio taper volume control.
Each LM386 has a different amount of hiss that might be blocked by the sounds..
 
Gracias for the reply AG.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top