[TenTec] Ear Phone Audio

[Barry N1EU]

Point of information:  when I owned an Orion 565, I also used Sennheiser
HD280 headphones.  I needed to crank AF Gain to maximum to get decent
volume.  I spoke with the factory and they told me there were series
limiting resistors at the headphone jack and I might want to lower the
resistance of said resistors.  I believe I cut the value of those resistors
in half and was very happy with the extra volume.

My guess is this is what might be happening here - nothing is actually
broken, but maybe I'm wrong.

73, Barry N1EU

On Thu, Aug 25, 2016 at 3:08 AM, Gary J FollettDukes HiFi <
dukeshifi at comcast.net> wrote:

> The Orion uses a separate LM386 for each channel of the headphone line.
> Thus it is unlikely either of these is faulty is it is unlikely they would
> both fail in the same manner. In addition, your sidetone level is strong,
> and this signal shares these amplifiers.
>
> The AK4524 SUB-CODEC develops the signals going to these output devices
> and this CODEC seems to function independently from the MAIN-CODEC that
> produces the speaker output. The speaker is driven by a separate power
> amplifier chip, a TDA1013B
>
> The analog signal inputs to the SUB-CODEC are, one from the sub receiver
> and the other from the rear panel AUX IN jack.
>
> The main receiver audio comes from the main CODEC. This audio gets to the
> stereo headphone CODEC via the SPODTBUSA lines.
>
> It is not clear where the sidetone is routed but it is generated in the
> CPU. It is not clear the routing of the sidetone.
>
> However, I did notice that there are selections for eh various levels in
> the AUDIO menu.
>
> Have you visited this menu tab? I don’t have an Orion in front of me but
> the secret may lie in selections within this menu item.
>
> Gary
>
>
>
> > On Aug 24, 2016, at 3:18 PM, Arthur Lewis <wa8vsj at gmail.com> wrote:
> >
> > *Thanks Gary..*
> >
> > *Art WA8VSJ*
> >
> > On Wed, Aug 24, 2016 at 3:39 PM, Gary Follett <dukeshifi at comcast.net>
> wrote:
> >
> >> No, it does not. The issue you now describe will require that I look at
> >> the schematic tonight and get back to you.
> >>
> >> Sent from my iPad
> >>
> >>> On Aug 24, 2016, at 1:58 PM, Arthur Lewis <wa8vsj at gmail.com> wrote:
> >>>
> >>> *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.
> >>>>>
> >>
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