Affidavits from minors

Is this allowed? My ex had an underage teen write a very long and false affidavit. He is not even 18.

I thought that affidavits had to come from those over the age of eighteen.

If that is right, how do I object to this? Is it hearsay?

An affiant must be 18 or older, you may object on that basis.

The judge did not allow the affidavit, but not because of his age, although that is how I objected. The judge said it would not be used because the child was not there for cross examination. THIS in turn was carried over as the reason that the judge would not take into account the spontaneous exclamations made by this same boy in response to his father’s physical and verbal abuse on an audio recording. From reading this board, I was under impression that children’s reactions to abuse at the time shold be admissible due to an effect on the listener.

So which is right? Excluding the affidavit (and therefore my evidence) based on child not being in court to be cross examined? Or is it because of his age?

And CAN duplicate copies of audio recordings be admitted or must it be the original. My original is damaged and it is a regular cassette. I wasted valuable time rewinding and fast forwarding because they would not allow me to use the digital copy that had been made in case something ever happened to the original.

If the judge viewed the situation as hearsay, the denial would be because of the witnesses unavailability.
Duplicate audio recordings may be admitted, unless the other side make a successful argument that only the original be used pursuant to the rules of evidence ( best evidence rule).