EARPHONES

[Donald S. Lambert]

I have recently gotten involved in experimenting in electronics and I have discovered that there are three varieties of earphones. You know those gadgets that plug into one ear. Way back when I was young everybody was using headphones with an impedience (right word?) of about 10,000 ohms. Of course back then all was vacuum tubes. I now have heard of and may have some of each variety of earphones. That is a dynamic (electromagnetic coil and diaphragm), crystal and ceramic. Is there a way to test to see which you have? And what about sensitivity? Which is the most sensitive or can produce sound from the weakest signal.

[russlk]

If you have an ohmmeter, you can determine if the dynamic headphone is high or low impedance. A crystal or ceramic headphone will measure open circuit. In most cases, the high impedance headphone will be more sensitive than low impedance, but quality of design and manufacture enters into that also.

[bwts]

10,000 ohm impedance are you sure?

[russlk]

I have a 10,000 ohm headset, very popular in the crystal set days.

[Dean Huster]

The crystal earphones, or more accurately earplugs, were very popular in the 1960's. I had one that came with a Heathkit 21-in-1 experimenter's kit in the mid-60s. They have a very high impedance and were useful as a hi-Z microphone as well for experimenting. Back then, your only other choice for headphones seemed to be the 2000 ohm magnetic phones. You can't find the darned things these days. Most earplugs and headphones these days seem to be 8 or 32 ohm dynamic types (electromagnetic).<p>If anyone knows of a source for the crystal earplugs, they should post that information here.<p>Dean

[Donald S. Lambert]

I got involved with this study of electronics more seriously when I bought a Radio Shack 30 in 1 (manual dated 1972) at a garage sale for the big sum of 50 cents. It was till in the original box but missing the hook up wires and the earphone or earplug. The wires I improvised and I had earplugs from an EKI kit.<p>I do have more questions about the earplugs. The dynamic ones I know about. But just what is a ceramic earplug? Is there a ceramic material that will vibrate when subjected to a sine wave? I understand that the crystal earplugs have a piece of crystal in them that vibrates in an alternating voltage somewhat on the principle of the crystal that sets the frequency of a transmiter. Greybie

[Ron H]

You can get crystal earplugs for $2.50 each from http://www.midnightscience.com/<p>The above URL is the home page for The Xtal Set Society. I purposely left off the address for the catalog, but you can easily find it from the home page.<p>I cut my teeth on crystal radios many years ago, and I still think they are fascinating.<p>BTW, as most of you probably know, the "crystal" in "crystal set" or "crystal radio" or "xtal set" is a different animal from the "crystal" in "crystal earplug".<p>Here is a great source of info on the sensitivity of various headsets. http://www.headwize.com/tech/klase_tech.htm<p>The sensitivity goes up as the number gets more negative.<p>I discovered here that you can also get crystal earplugs from http://www.mouser.com/ (p.575 in their Acrobat catalog) for about 2 bucks.<p>If you want to see a technical discourse on the fabrication of piezoelectric ceramics, see http://www.icase.edu/Dienst/Repository/ ... 001-28/pdf<p>I found all this stuff with some simple Google searches for "crystal earplugs" and "piezoelectric ceramics".<p>Ron

[Donald S. Lambert]

Hi Ron,
I just came from google and a search under crystal earphones. And I was gong to post google as a source of information if one looked under crystal earphones. This is getting to be a topic of Earphones 101. Like in a college course. The more I look the more I find. And oh yes plenty of material and a real explaination of why the crystal (ceramic) earphones don't work like dynamic ones. You need a resistor in parallel to the earphones since the earphones do not conduct. And the theory dates back to 1883 and Pierre Curie and the pizoelectric effect. Never too old to learn. Also plenty of sites to buy the little things (earphones, earplugs, earduds). I guess I forgot about looking in google. Back in 1947-48 when I went to junior college there was no such thing. Greybie.

[Donald S. Lambert]

Forgot! Thanks Ron for posting the sites for more information. Greybie.

[Dean Huster]

Ron:
<snip>
BTW, as most of you probably know, the "crystal" in "crystal set" or "crystal radio" or "xtal set" is a different animal from the "crystal" in "crystal earplug".
<unsnip><p>And, the "crystal" is a different animal from the "crystal" in "crystal oscillator". There may another Crystal that's different. Ever date her in your youth, Ron?<p>Dean

[Ron H]

<snip>And, the "crystal" is a different animal from the "crystal" in "crystal oscillator". There may another Crystal that's different. Ever date her in your youth, Ron?<unsnip><p>I think she spelled it "Kristal". Or was it "Chrystal"?<p>Earphone crystals and (oscillator) quartz crystals are, of course, both piezoelectric, which I don't believe is the case for galena or germanium (used as detectors in crystal radios). I've never heard of quartz or lead zirconate being used as rectifiers. Nor have I heard of galena or germanium being used as motional transducers. Of course, I could be wrong - I was wrong once before. <p>So - earphone and oscillator crystals - sorta like same species, different genus.<p>Ron

[Chris Smith]

But they all oscillate, rotate, or gyrate, even Crystal, Kristal and Chrystal?

[Ron H]

"But they all oscillate, rotate, or gyrate, even Crystal, Kristal and Chrystal? "<p>As I recall, one of them did osculate. Sorta like oscillate, only different. <p>Ron

[Donald S. Lambert]

This is getting a lot of information. And I do thank all of you for the effort.<p>I am now thinking of a crystal radio set. All from a posting of the XTAL society web site. And searching google I found a formual for figuring or estimating how to wind a coil for a specified mh. But I have a couple of variable capacitors that I have no idea of the pf off. So I will have to wind a coils and experiment to see what frequencies it pulls in. Of course I do have a 260pf capacitor so that is another route to go.<p>Right now I am nursing a right thumb with 5 stitches results of starting to make a box to wind a coil on. I have never used a real push stick with the table saw but I have plans for a couple so that is the next wood working project. I will use a saber saw for that. The table saw will not be used till I have push sticks.<p>By the way you can find both the crystal earphones and 365 pf variable capacitors at www.midnightscience.com the tuning capacitors come in single gang and double gang. Greybie

[Donald S. Lambert]

OOPS I mentioned mh when I meant uh which is a lot of difference. Greybie