Signal levels don't affect digital tv picture quality, but if your
signal levels are out of spec, you can have picture and sound freezing,
black screens, etc.
When you call Videotron, they are able to see the live signal levels
of your set-up box and a log with the signal levels for a long period
of time. I suggest you to connect your terminal to the cable entrance
without any slitters or amplifier and syntonise the channels with
the worst signal levels. If you are not interrested by these channels,
just let the terminal turn-on on these channels when you are not home or
don't watch tv. By doing so, when you will call Videotron, they will
see the problem with your signal levels in the log.
They are able to see if you have audio/video discountinuity
(picture freezing), so if you don't have this issue and your signal is
not too bad (-12 is the lower edge), it's possible they don't do a
service call, cause after all, if there is no audio/video
discountinuity, there is no problem...
In fact, there is probably a signal problem. If a technician come
to your house to install Internet/phone service or a second cable jack,
he is suppose to have enough signal to split the cable with a 2-way
splitter (4 dBmV lost) whitout using an amplifier. In your case, that
means your set-up box will drop out of spec to -16 dBmV.
Don't wast your time and money by trying to fix it yourself,
the problem is probably with the cable line from the pole to the house
or with the equipment on the distribution line, installing an amplifier
won't fix that problem. Your amplifier is a "old fashion amplifier",
causing more bad than good, even for analog tv. It's very important
that your teminal is bidirectional, cause Videotron is using in
Pointe-Claire, a technology called Switching Digital Broadcast,
that need terminal to be 2-way to broadcast some speciality channels,
if not, you can have troubles to watch some channels sometimes.
Don't be intimidated by Videotron, you pay for the service and if
there is really a problem, they will fix it with pleasure. They want
to offer quality and trouble free telecommunication services. Be
advise that if you have some cable jacks that was not installed by
Videotron, they can't guaranty the quality, so you can have a charge
for the service call, it's why i suggested you to connect your
terminal to the cable entrance.