[Elecraft] Harmonic Distortion and Audio Intermodulation in K3'sLIN OUT Port

[Jack Smith]

You'll have to address that question to the Elecraft design staff.

My guess is that it was to protect the DAC's output amplifier from short 
circuits a user might inadvertently apply across J22, the LIN OUT port, 
but that can be done with much less  resistance. In fact, the winding 
resistance of the TTC-108 is probably adequate for this purpose without 
any additional resistance.

Question: You are given a  transformer with no specifications. How do 
you determine the transformer's rated operating impedance? The answer to 
this question should suggest that there is no inherent operating impedance.

Jack


David Cutter wrote:
> Jack
>
> The obvious question is: what is the purpose of the resistor?  Perhaps 
> to create a driving source to comply with the manufacturer's data?
>
> David
> G3UNA
>
>
>> What I found is that the 604 ohm resistor between U29's output 
>> amplifier stage and the TTC-108 transformer primary winding forces 
>> the TTC-108 isolation transformer to operate in a regime where the 
>> performance improving effects of a zero ohm driving source are not 
>> available. Hence, the TTC-108's 0.5% THD performance significantly 
>> limits the LIN OUT ports performance.
>> >
>> Jack K8ZOA
>> www.cliftonlaboratories.com
>>
>>
>