Still having this issue:
My version numbers are the same as https://www.whonix.org/wiki/KVM#Debian_stable (click expand and scroll down to check version numbers).
Changing
<pre>
<sound model='ich6'>
</pre>to
<pre>
<sound model='ac97'>
</pre>solves it.
But there are 2 more debian stable related issues, that I will post in separate threads. So maybe we don’t have to make this change, but can fix the root of this issue.