1. Can I use a mechanical tally counter on shabbat and Yomtov for Torah purposes e.g. to count how many times I repeated a Mishna? 2. Can I leave on audio siurim on my computer speakers over Shabbat or Yomtov to listem to them on sabbat or Yomtov? if not, howcome? thank you in advance

1.It is permitted however I was told by a prominent Talmid chacham that it is better not to use it. 2. The great poskim of our generation have dealt with this issue and many of the reasons appear in the Talmudic Encyclopedia (volume 18) under the entry of "chasmal" in the supplement. Among the reasons given is because of the possibility of improving or changing the volume on Shabbat , because of the noise emanating from the speakers and also because of the disrespect to Shabbat in general.(See also Minchat Yitzchak Vol.I, 107, Tzitz Eliezer Vol. III, 16).