Resulting SINAD after multiple devices

[polmuaddib]

I looked online and can’t find concrete answer to what happens to SINAD after multiple devices? Is the last device most important? OR all of them contribute?
For instance, if we have a dac of 120 SINAD, then preamp of 100 SINAD and Power AMP of 80 SINAD is the final SINAD 80? And if so, then all devices before Power AMP don’t mater as long as their SINAD is over the amp’s?
Or do they all sum somehow? And how do they sum?
It would be logical to think that the noise increases in analog systems when you add them. Like making a copy of magnetic tape. If that is true for noise then it should apply to distortion also? Then every component matters even if the last is the noisiest?
thanks

 

[andreasmaaan]

I looked online and can’t find concrete answer to what happens to SINAD after multiple devices? Is the last device most important? OR all of them contribute?
For instance, if we have a dac of 120 SINAD, then preamp of 100 SINAD and Power AMP of 80 SINAD is the final SINAD 80? And if so, then all devices before Power AMP don’t mater as long as their SINAD is over the amp’s?
Or do they all sum somehow? And how do they sum?
It would be logical to think that the noise increases in analog systems when you add them. Like making a copy of magnetic tape. If that is true for noise then it should apply to distortion also? Then every component matters even if the last is the noisiest?
thanks

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Generally speaking, because the decibel is the expression of a root-power ratio, the device with the lowest SINAD will overwhelmingly determine the SINAD of the system, e.g.: