Passive vs. Active Circuitry?
Q: I’m just getting back into the bass and there’s something I’ve always been curious about: the differences (as well as the different kinds) of passive vs. active circuitry. What are the main differences between them, why are there only active and passive circuits, and what does it mean to have either in a bass?
A: Although I am not the most tech-savvy of bassists (and I’m sure many of you will comment back on this to add to what I say here) I think I can answer your question.
Essentially, an ‘active’ bass just has the addition of an on-board pre-amp to give the user further tonal control. Active pre-amps require one (or two) 9-volt batteries although Alembic (who I believe came up with the concept for Phil Lesh of the Grateful Dead) has given the option of additional cables to power the on-board pre-amp.
Passive controls (by definition, a pre-amp is powered, therefore you would not speak of a passive pre-amp) are generally limited to volume control and tone shaping (“tone” knob). While you can shape the tone a bit, there is not nearly the flexibility as with an active pre-amp.
The pros and cons all boil down to personal preference. Personally, I like to have pre-amps available to me but I’ve also added active/passive switches to all of my basses so I have the option of playing the bass passive OR active (the most flexible way to go, I think). Many pre-amps color the sound naturally even before you boost or cut a frequency. For this reason, many players (especially traditionalists) feel that the passive electronics deliver a more organic sound. This is true, I’d say. Many pre-amps do give the user a more “hi-fi” sound, which is desirable by some. Personally, I prefer an organic tone, but sometimes you just need to boost one frequency or another to help compensate for a particular room or to help you cut through a larger ensemble without necessarily just getting louder.
Most active pre-amps will offer a boost/cut knob for 2-4 frequencies. Most will have a volume control and a pickup pan. In addition, to those two knobs, the most common configurations are:
2-band EQ = Bass – Treble
3-band EQ = Bass – Mid – Treble
4-band EQ = Bass – Low mid – High Mid – Treble
I personally find that I’ll use low and high mids the most for shaping my tone to fit a band or stage. Therefore, I tend to go 4-band EQ (often using a “stacked” knob for my mids (meaning there are two knobs affixed to one knob space stacked on top of each other)
I hate to have to rely upon batteries, which is another reason to have a passive switch if you go the pre-amp route. There is nothing worse than your sound crapping out on you in the middle of a gig because your 9-volt died on you (has happened to me once, and I’ve been very careful to make sure it doesn’t happen again).
Now, if my battery dies or starts to sound bad, I can just flip my switch and finish the set passively.
In short, if it sounds good to you, it’s right for you. Just make sure that you explore the tonal possibilities and explore the quality of the sound coming from the instrument with or without a pre-amp and use your own judgement as to what will work best for what you’re doing musically.
If you’re slinging a P-bass in a country or blues band, I wouldn’t bother messing with active circuitry. However, if you’re playing many different styles of music and want one or two basses that can cover it all, a nice active pre-amp can certainly help with that!
Photo credit: Brett Sherman