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Forums | Rap N Tap Clubhouse - Basic Crystal Radio Fun! | Radio Shack Mini Amplifier/Speaker Post Reply Send Topic To a Friend
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golfguruPosted - 12 November 2011 16:50  Show Profile  Email Poster  Edit Message  
>>> Read the Radioboard link that you provided above. >>>>

Mmmm .... innovative.... :-)

3/4" discs

This excercise is **not for the faint hearted** and should only be attempted if you really love your earplugs.

*** Open one up first to get an idea, before purchasing any parts and attempting the mod.***

(1) The sound is somewhat harsher than with the aluminium diaphragm
(2) I used a worn out blade to minimise the slot size.
(3) Can't cut too deep or you cut through the lip on the rear half
(4) Not easy to solder to the silver piezo backing without it dissolving. Silver content solder may be easier. Piezos with leads attached are available
(5) Edge connection can't interfere with rear lip (file the lip at that point if necessary)
(6) Too much heat will melt the plastic at the through-hole connection point.
(7) I "spot" glued my insert to the front half of the case - optimum might be to use a larger diaphragmed piezo, cut to size with scissors and glue to the lip on the rear half. Others may wish to experiment.

General points re: piezos,
(a) the larger the actual disc (not diaphragm), the greater the capacitance = lower impedance.
(b) capacitance, and diaphragm diameter, influence the tonal range


Edited by - golfguru on 11/12/2011 4:55:41 PM

RobertCPosted - 13 November 2011 8:57  Show Profile  Email Poster  Edit Message
Interesting modification but probably beyond what a beginner could do. I wish Western Electric would come back! I love my 509's! My next favorite is the Radio Shack Mini Amp/Speaker.
golfguruPosted - 13 November 2011 14:5  Show Profile  Email Poster  Edit Message  
It's not for beginners.

Edited by - golfguru on 11/13/2011 2:08:38 PM

PistolPetePosted - 28 November 2011 21:27  Show Profile  Email Poster  Edit Message  
I'm just a beginner, but has anyone tried hooking your set to a guitar amp? It works great and it's a good way to save a few bucks if you have one around the house.
RobertCPosted - 30 November 2011 15:39  Show Profile  Email Poster  Edit Message
Hi Pistol, great idea! Probably most any speaker/amp will work if the input inpedance is reasonably high. If you have a multimeter, you might see what the DC resistance across your amp input is. For reference, the Radio Shack speaker/amp measures about 5000 Ohms DC and typical vintage headphones measure about 2000 Ohms DC. If it works well it probably has a high enough DC resistance and AC impedance.

Edited by - RobertC on 11/30/2011 4:09:30 PM

giftsocoolPosted - 11 October 2012 20:22  Show Profile  Email Poster  Edit Message  
I just bought a nice and cheap angry birds mini speaker sound box from ebay-----supdealer. it is a newbie but they offer good service.

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