@jacadcaps
Thanks for the reply.
unfortunately my monitor does not have internal speakers and I cannot test it in this way.
but the problem lies in the powerbook at least I think
I just need to find a "male" to "male" audio cable and everything should work if they exist built I'm not familiar with these types of cables.

The quality of the video surprised me I used a simple compression in reality the quality is the same as the original if I directly use the nvidia codec with OBS.
But I was focused on how to make it work

I just wanted to add that oddly enough for it to work I had to do it like this:
i first connected the powerbook with the dvi-hdmi cable to the main monitor
I chose Mob.1 as the video output
then i disconnected the dvi-hdmi cable from the main monitor
and I connected it to the "VIDEO IN" capture card
and I used the TV with HDMI output as a "bridge"
Then work again on the main monitor with OBS
and everything works.

If I do not carry out these steps, the acquisition card does not recognize any signal with Morphos.

But now it works
I'm glad I hope to find a simple audio cable that will allow me to acquire audio as well.
Sorry for the somewhat chaotic explanation
Maybe it's useful for improving this aspect.

the card is this:
https://www.amazon.it/PTN-Acquisizione-Dispositivo-Registrazione-Videoconference/dp/B08MJ9VDQP

it is working on my powerbook you can see where I should connect the audio of the powerbook to capture the audio

an audio cable similar to this should solve the audio problem, I hope

https://www.amazon.it/NanoCable-10-24-0101-stereo-M-JACK-maschio-maschio/dp/B00CI39F9O/ref=sr_1_7?__mk_it_IT=%C3%85M%C3%85%C5%BD%C3%95%C3%91&dchild=1&keywords=cavetto+audio&qid=1625950650&s=electronics&sr=1-7

[ Edited by white 10.07.2021 - 23:01 ]