Where Tim is explaining the stereo system to Jill, Jill is reading a book with the title "Backlash". The camera goes back and forth to Jill and Tim and the third time it returns to Jill, the cover is gone.
At the beginning of the episode, when Jill is reading on the couch and Tim is playing with the stereo, Jill's hair keeps switching from down to half-up in a barrette.
Right before Tim blows the speakers out, Jill is reading on the couch. In one shot the cover is on the book but when we see Jill again the cover is off the book.
When Tim is speaking to Wilson about his stereo, he describes 20 megahertz pounding through his body. The pounding effect of a stereo comes from very low frequencies; 20 megahertz is a frequency so high that it is inaudible to human ears. A frequency of 20 hertz would have been a more appropriate choice.
When glass items begin to shatter from the opera singer, the glass coffee table directly in front of the TV and sound system should have also broken.
After Tim breaks all the windows in the house because of the loud stereo, Jill informs Tim the insurance company is raising their deductible because they believe Tim is accident-prone. Insurance companies do not raise deductibles, but rather premiums, if they believe a client is a higher risk. In fact, the reverse is true: if you raise your deductible, your premium decreases because you are sharing more risk in the event of an accident.