There really should be a volume control for the text-to-speech function and audio.
In many tapes, the reader is speaking quietly. This means means that if you adjust the volume so that you can hear them properly, the text-to-speech will in turn SHOUT IN YOUR EAR and give you a headache (and in time damage your hearing). And of course, vice versa; you can’t hear the tape if you adjust the volume so that text-to-speech is pleasant. To avoid this, you have to constantly fiddle the volume controls of the PC, which is just frustrating.