lack of space to store a combo amp (if they live in a small room) or due to the need for a set-up which can amplify multiple types of instruments and/or voice. Alternatives to buying a bass amp for people who have noise or space constraints include a headphone amplifier or a micro-practice amp which includes a headphone jack (on bass amps, connecting headphones to a headphone jack automatically turns off the main loudspeaker). Multi-instrumentalists and bassist-singers can consider a keyboard amplifier, a small PA system, or some models of acoustic instrument amplifiers which include bass as one of the instruments which can be used; all of these options have full-range speakers that can handle the bass range. While electric bass players have used regular guitar amplifiers in large concerts since the 1960s, this is usually just for the higher register; a bass amp is still typically used for the low register, because regular guitar amps are only designed to go down to about 80 Hz. One of the reasons bassists split their signal into a bass amp and an electric guitar amp is because this arrangement enables them to overdrive the higher-register sound from the electric guitar amp, while retaining the deep bass tone from the bass amp. Naturally-produced overdrive on bass obtained by cranking a tube amplifier or solid-state preamplifier typically results in a loss of bass tone, because when pushed into overdrive, a note goes to the upper octave second harmonic. Bass players who do not have a combo amp who are playing live shows can connect their bass to a DI unit and from there to the PA system. In a well-equipped nightclub or music bar, the audio engineer can then route the bass signal to a stage monitor suitable for bass, so the bass player and band can hear the bass tone. Some standalone bass preamplifier pedals have a DI output, so this output can similarly be connected to a PA system. Bass players who are playing in small venues (coffeehouses, small pubs, etc.) will typically need to bring their own bass combo amp (or an alternative amp, such as a keyboard amp combo), because very small venues often have a very small, low-powered PA system which is used mainly for vocals. Some small venues do not have monitor speakers, or they have only one, in front of the lead vocalist. Bass players who do