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@gmail.com> wrote:
>
> *Thanks Gary..*
>
> *Art WA8VSJ*
>
> On Wed, Aug 24, 2016 at 3:39 PM, Gary Follett <dukeshifi@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@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@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@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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