[TenTec] Ear Phone Audio

[Arthur Lewis]

*Gary,*
*Thanks for your comments on my earphone problem. The part that is a bit
confusing is the fact that when I turn up the volume with the earphones in
use, the sidetone on CW is head banging loud in the phones. Does the
sidetone use a different audio source?  *

*Art WA8VSJ*

On Wed, Aug 24, 2016 at 2:32 PM, Gary Follett <dukeshifi at comcast.net> wrote:

> Yes, and the peak to peak available output from an Orion, about 13 volts
> p-p, should produce head banging volume in virtually any headphone if
> working properly, even the old "cans" from the 1930's.
>
> You need to be looking at things that can affect both channels of the
> output since, at this point in the circuit, the thing is operating in
> stereo. This precludes defective dropping (ear protection) resistors or
> wiring problems. It is looking like the headphone amp output is defective.
>
> Gary
>
> Sent from my iPad
>
> > On Aug 24, 2016, at 12:32 PM, Jim Brown <k9yc at 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 at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>