Fw: [TenTec] Clear Speech Unit

[WA3FIY]

One other matter to carefully........and I do mean 
carefully.........consider is the maximum volume level available at 
the headphones.   It should be standard practice to limit the 
maximum volume at the headphones to a level that is loud enough 
to be heard but no more, regardless of how high the volume is 
turned up on the radio or other device.   This can usually be done 
by wiring a resistor in series with the 'phones.   The value 
depends on a number of things including the impedance and 
efficiency of the 'phones, the power available and it's 
impedance.   Values in the low to mid 100's of ohms is a good 
starting point and one can proceed from there.   

Please take it from one who knows from first hand experience, 
protect your hearing!!!!!!!!!!!!!!

-73-

-Lee-

On 1 Nov 2002 at 9:14, Allan H. Kaplan wrote:

> Installation of the Radio Shack output transformer, #273-1380, as
> W2GCX describes, is a good fix for any application driving a load with
> over a few hundred ohms impedance.  I am quite surprised that  
> "Earphones or a small speaker work exceptionally well (much more
> audio)"   through the transformer.   I would expect these low
> impedance loads to be transformed to VERY low impedance at the audio
> amplifier IC.  Pushing the AF Gain to high output might then overload
> the IC and damage or distortion might result at high output with a low
> impedance load on the transformer.   Within those limits it is a good
> fix. Allan, W1AEL One of the hams at Ten-Tec.
> 
> 
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