"Many years ago, I carried around a set of crystal headphones in my toolkit
when I worked on troubleshooting audio systems in buildings. "
Jim, for this reason I still use a Harris telco "butt" set in bridging mode
when identifying audio routing in the shack. One of the best audio tools ever
invented!
Paul, W9AC
Sent from my iPhone6
> On Aug 25, 2016, at 7:48 AM, Robert P. Santella <bobw2pnj@optimum.net> wrote:
>
> Thanks, Jim.
>
> Sent from my iPad
>
>>> On Aug 24, 2016, at 1:32 PM, Jim Brown <k9yc@audiosystemsgroup.com> wrote:
>>>
>>> On Wed,8/24/2016 10:08 AM, Robert P. Santella wrote:
>>> Impedance needs to be 30 ohms.
>>
>> NO! Headphone impedance is NOT critical. Audio power amplifiers are VERY
>> different from RF power amplifiers. Virtually all audio amplifiers are low
>> impedance sources, and are designed to drive any impedance greater than a
>> design minimum. For example, the source impedance of a loudspeaker output
>> stage is a small fraction of an ohm, and is designed to drive any
>> loudspeaker load greater than 4 ohms. The relationship between these two
>> impedances is called the "damping factor," and 100 is a typical value. A
>> well-designed headphone amp will include a low-value resistor in series to
>> protect the amplifier from being shorted when headphones are being plugged
>> and unplugged.
>>
>> Most modern headphones are in the range of 20 - 300 ohms, and a
>> well-designed headphone amp should drive all of them just fine. What matters
>> a lot more is voltage sensitivity, and headphone mfrs generally get that
>> right too. Many years ago, I carried around a set of crystal headphones in
>> my toolkit when I worked on troubleshooting audio systems in buildings. They
>> were sensitive enough that I could hear (weakly) the signal of an
>> unamplified microphone, yet the impedance was high enough that they didn't
>> load most circuits!
>>
>> 73, Jim K9YC
>>
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|