TheRadioBoard

That is indeed a classic, Helmut!

Good craftsmanship! Another thing, a Cannon connector and what appears to be heavy gauge speaker wire, you don't want to lose a single milli-micro watt do you? That's a good thought, all the money, time, and effort to create an efficent radio, there is no reason to give it away as heat in a thin headphone cord.

Lee Pickett

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John 3:16, Acts 2:38

Well, I have nothing nearly as fancy as those cool wood phones, but...

These are the CUI piezo elements that I used with my one tube radio for the ARF homebrew contest last summer. They were tinny, but the most sensitive things that I had available. As you can see I put them on a cheap set of Walkman style headphones.



Overall they were not very satisfactory.

Last night, after being re-inspired by this discussion, I finally got around to taking them apart and installing the elements into a set of hearing protectors.



Since these elements have pins sticking out the back, I just pushed them through the foam and then through a piece of perf board (sandwiching the foam in between). Then soldered everything together. That saved the trouble of having to glue the elements to the foam.

Then I drilled a few holes in the headband, and threaded the connecting wire through to hold it in place.

Not surprisingly, this is a vast improvement over the previous Walkman style assembly. Mounted this way, there is considerably more volume, and audio fidelity is much better. Obviously, they are nowhere near hifi quality, but I was surprised at how much the bass response has improved. This is definitely a useable set of phones now.

Here are two photos of my piezo headphones.





Corne

Cool, Corne, simple and to the point.
Lee Pickett

_________________
John 3:16, Acts 2:38

thanks for the pictures Bob and Corne!

regards,
phil

Hi,

Here are my finished headphones. They are very light and all parts can be easily replaced and all coverings come off for washing. I have not finised my mystery set so I can not report on how they work. Should be able to do that soon.

Thanks Helmut

I want to say "Thanks!" to every person who worked to get the "Harbor Freight" headphones to work.

I finished mine this afternoon and just tried them out on a "looper".

Using earphones, I previously was able to detect a maximum of six stations with the loop edge pointed toward Denver (55 miles south) from a second story bedroom. Using the headphones, I just counted 15 stations! I expected improvement in the quality of what I could hear due to reduction of background sounds, but I didn't expect that kind of increase in the quantity of stations.

I reckon the next task is to improve selectivity of the looper. The loop is a square, 28 inch per side, with ten turns in parallel with a 10-365 pf cap with phenolic spacers. The detector diode is '215.

Thanks again,

Bruce

The pictures above are cool. You can call them "Helmut's Happy Headphones".

Congrats Bruce, on your headphone upgrade. I found a vast improvement over
my regular headphones, and on average were on par with the sound powered
phones. The Harbor Freight muffs did the trick!

It appears that the blue piezo phones KBT-44SB-1A have disappeared from the
surplus market. The Mallory PT-4175W are the same element except for the color.
They are also being discontinued, but I was able to latch onto a bunch of non
surplus Mallory elements.



From what I can see, this is the crystal set project of the year, thanks to several
pioneers that brought these to our attention.

Dave

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Please visit my website at: http://www.makearadio.com

Members,

Helmut. . .Nice going on the neat headphones. I like the name Exray gave them.

Bruce. . .Glad these worked out well for you. . .They are nice headphones.

Bill. . .Those Mallory units are not going away, but the next-identical ones will have a new stock number, and ROH compliant. The ROH compliant is what is making them to be stocked under a new stock number.

ROH compliant: "lead-free".

All electronic devices that are not ROH compliant, at this time will be discontinued, but stocked under a new number, ROH compliant, thus higher prices.

Those Mallory units are readily available from Dave S. at a reasonable price. They are exact replacements to the former Kyocera units.

Mike

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I like the K-I-S-S Principle: "Keep It Sane & Simple"
http://www.peeblesoriginals.com

What is the average size of a headphone jack? I was wanting to buy a headphone adapter jack for my phone and it says it fits headphones that are 3.5mm. Since i am shopping over the internet, i don't want to buy it and then have it turn out that that is some oddball size of headphones you can't find.
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market samurai ~ marketsamurai ~ marketsamurai.com

3.5 mm. The old standard was 1/4 inch.

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

OK, I have put off making a set, so who has a pair of Kyocera part # KBT-44SB-1A Piezo Elements,??

Gus

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Old age is 'when you still have
something on the ball, but you are just too tired to bounce it.'

Helmut, love the polka-dot 'phone covers. Remind me of pajamas. Getting sleepier......

A Canadian Ebay seller often has piezo elements on sale. They appear to be smaller than the recommended ones. Item #160383500785.

Would they be of any use, the price is low.

Ed.