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
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
