Re: good HU w/1 preamp vs. bad HU w/3 preamps?
allyourblood is mostly right. It will not distort at the same level, but you will still get it to distort. Remember that a preamp is still an amp. It generally uses opamps rather than larger transistors and MOSFETs but it has the same limitations. Most all HUs are set up to where the preamp outputs will clip at about 2/3 volume. This becomes sooner if the bass or treble boost is used. Past the clipping point of the volume, you are just turning up the distortion.
The only problem with using the HU with the single preamp out is you will not have fader capability at the HU. You will need crossovers from another source as well. Most newer amps have those built in nowadays. If you want sub volume control you will either need a remote gain on the amp or get an external crossover with a remote on the sub output. There are many ways to work with a single out, if there weren't you wouldn't have been able to build a system back in the day cause most units only had one output.
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