Please answer the following question: Given the following passage  "Due to recording mastering and manufacturing limitations, both high and low frequencies were removed from the first recorded signals by various formulae. With low frequencies, the stylus must swing a long way from side to side, requiring the groove to be wide, taking up more space and limiting the playing time of the record. At high frequencies, hiss, pops, and ticks are significant. These problems can be reduced by using equalization to an agreed standard. During recording the amplitude of low frequencies is reduced, thus reducing the groove width required, and the amplitude at high frequencies is increased. The playback equipment boosts bass and cuts treble so as to restore the tonal balance in the original signal; this also reduces the high frequency noise. Thus more music will fit on the record, and noise is reduced.",  answer the following question. Note that the answer is present within the text.  Question: What is amplified by playback equipment?
A:
bass