Yes diff preamps have their own voice. Its same thing with high end audio speakers. B&W, Theil, Monitor Audio, etc with the same cd played thru them will sound a little diff thru each. However there is specific frequency ranges which have diff effect on a sounds qaulity. For example theres a specific area of the midrange which when accented causes what ussually referred to s nassally sound. Just as theres a part of the bass spectrum that most gives that thumpy boomy muddy qaulity to bass. Accent or diminish an area of upper treble and human voices thru a speaker system will sound more lifelike in person there. Or less so because of overtones seldom heard thru low end budget speakers. Theres also a part of the treble range humans are specifically very sensitive to which when boosted creates annoyance and irritating treblyness. Take a 20 band eq and play full spectrum orchestra music that includes a prog rock band. With care you can make the mid budget speaker system sound more like high end audio one. And you can also learn what the various areas of bass, midrange, and treble effect. On indiviudal instruments and common traits held by various instruments found within a given range of frequencies. The ideal is to use a bass whose woods and pups create a great voice for you passive. The active eq just is added for two things.
1. That change to the sound created by conversion to HiZ is a desired one. Tone controls left at flat, no boost, no cut.
2. Your bass control either helps you dial out room booomyness, or something else boosted or cut useful to you because of how that freq, say 40hz is nicer center for you rather then 120 hz. Even when your playing the D or G string. Your mid control might be to add in some nassallyness if your into that, or to cut thru the mix better cause well after all that is the common midrange freq specified for that. Or you prefer a part of the midrange to boost now and then that more relates to growl. Treble cause you either want to use it for benefit to sound in overly hard venues that accent that treble range (2k-4k that humans are extra sensitive to) which annoys easilly when dominate. Or to accent or cut that higher area of treble for reason. This reason might relate to a part of the human voice overtone range that ussually helps you tell wether your listening to a person in person, or simply over a common speaker system. Which also has an interesting effect on bass guitar voice btw. Or perhaps your going for something else related to overtone content. With the glocks really high treble center your more doing the former. With my own preferred lower setting of 6khz I'm useing the same part of the sound spectrum Id use with synthesizer piano to give it more acoustic piano type overtone accent.
Heres a useful freq chart. It can help one learn what areas of sound spectrum for example cause various things. Link Removed