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Jazz Ad

[FAQ] The ultimate active / passive thread.

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What is an Active / Passive bass ?

  • A passive bass works by simply pluging it into the amp with a cable. No need for a power source other than the bass itself.

  • An active bass requires electrical power, usually provided by one or several onboard batteries. Sometimes, it has an integrated rechargeable accumulator or is powered by an external source through a dedicated cable. All active components can share the same power source.
There are 3 different electronic zones in a bass.

The bass is considered active if any of these 3 zones is electrically powered.

passactive.jpg

passactive.jpgpassactive.jpgpassactive.jpg

 

Active / Passive Pick-up ?

  • A passive pickup produces an electric signal based on the vibration of the strings. The signal is then send through the cable. Comparing the signal provided by the pickup(s) with the ground gets you an accurate model of the string vibration that can then be converted to sound by the amp.

  • An active pickup will work the same way, but usually at a lower impedance. An integrated small preamp then boosts the signal level to adjust to the next section, whatever it can be. Some active pickups don't even have magnets at all. They use electromagnets, powered by the battery.
Active / Passive Gain section ?

  • The gain section lets you adjust the general volume of the instrument. It can be placed before or after the EQ section but it will always be somewhere between the pickup(s) and the output jack.

  • On many basses, the gain section is nothing but a volume knob. That's the way a passive bass will be, with or without an active EQ section. A bass with active pickups and passive electronics will also be this way. On some basses there is no gain section, meaning that you can't control the volume of the instrument; it has to be done with an external device such as a console or a volume pedal.

  • An active gain section will be a preamp, boosting the signal to get more gain and a hotter signal.

  • For an active gain section on a passive pickup, the preamp can also be used to lower the impedance provided by the PUs.
Active / Passive EQ section ?

  • The EQ section lets you alter the signal by cuting and boosting some frequencies. Others can be VERY evoluted, with multiband EQs, parametric EQs, band, low and high pass filters,phase shifters, ...

  • Some instruments simply don't have an EQ section. On many basses, the gain section is nothing but a low-pass filter, the usual "tone" knob you will find on most classic instruments (Fender P and J basses for example).

  • You can add an active EQ section to an overwise completely passive instrument.

  • A passive EQ control is limited in its possibilities. You can't boost the signal with it, since it has no power to lift the level of the signal, even on a limited port of it. YOu can give the impression of boosting by cutting all other frequencies. That's the reason why there is a lot more mediums in your signal when you turn down a passive tone.
Pros / cons ?

  • In the beginning, 25 years ago, differences in sound were big between active and passive instruments. Nowadays it's more a matter of taste.

  • An active instrument may provide more gain. It can be nice to push a weak amp or go directly into a mixer.

  • Lower impedance on active instruments will mean less noise, longer cables without signal loss and more constant signal even when running through cascades of effects.

  • Passive pickups are simpler. Low technicity means more reliability. ie, you won't have to worry about battery change or preamp frying.

  • If you have a switchable active EQ and/or gain section, you'll be able to play even if you run out of batteries. You will also have the possibility of playing with a "pure" passive sound.

  • Passive instruments have a more "organic, natural and warm" sound, active pickups are "beefier, better balanced and cleaner". This is a completely subjective issue, prone to start fights. Technology evolved a lot on both sides and pickup manufacturers work hard at erasing differences between the 2 systems.
Nate42's additions/clarifications

  • The reason active pickups are lower impedance is simply due to having fewer coils of wire. This lowers their susceptibility to noise (those coils are essentially noise antennas), and also reduces their overall output. The reduced output is why active pickups require a preamp.

  • The preamp in active pickups is mounted within the pickup casing itself. This is done both for convenience and for noise reduction - the sooner along the signal chain that you boost the signal, the less oppurtunity there is for noise to get in.

  • It is quite possible to have a bass with active pickups that has passive volume and tone controls.

  • Another side effect of the fewer coils of wire on an active pickup is a more even frequency response - meaning the pickup has less 'character' and more accurately represents the sound of the bass.

  • Active pickups aren't particularly common. A passive instrument with an active eq is the most common active instrument. Don't assume your pickups are active just because you use a battery.

  • And on a related note, many amps have seperate active and passive inputs. The active input simply has an attenuator to reduce the signal level of very hot active instruments so it doesn't overdrive the preamp. You should always try the passive input first, even if your bass is active, cause most basses aren't hot enough to really need the active input. If you use the active input when you don't need to, you're reducing your signal (and thus your signal to noise ratio and overal volume) for no good reason.
J.'s additions/clarifications

  • It bears repeating too: even though basses with active electronics usually have more output than totally passive basses, there are some exceptions. I'm sure we've all played a bass with some jacked-up overwound passive pickup that had output up the wazoo.

  • I think the worst kind of electronics to have are the really cheap actives. In my opinion, active electronics don't get very good until you start getting into mid-grade basses. The really really cheap instruments with active electronics usually have really cheesy preamps that don't do much more than induce noise.
    ___________________________________________________

    | Instrument | Electronics |

    | |_______________________|

    | |Pickup | Gain | EQ |

    |__________________________|_______|_______|_______|

    |Fender Jazz Bass Standard |Passive|Passive|Passive|

    | | | | |

    |Fender M

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Hey that is exactly what I was looking for, thanks! :)

Very informative, it should be made a sticky somewhere. Maybe on the Bass Forum FAQ?

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Originally posted by bassaussie

On a passive instrument, how would a 2 band eq work?

I have schematics for that BA.

But just the same as a passive tone, it won't work on specific frequncy but on full bands.

It would be high pass / low pass dual filter, or sweepable band cut.

You need dioded or/and transistors to limit to a frequency and separate 2 bands, both those components being polarized.

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Originally posted by Jazz Ad

I have schematics for that BA.

But just the same as a passive tone, it won't work on specific frequncy but on full bands.

It would be high pass / low pass dual filter, or sweepable band cut.

You need dioded or/and transistors to limit to a frequency and separate 2 bands, both those components being polarized.

 

So, if I read that correctly, basically it's got a cut on both bass and treble, right?

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Originally posted by bassaussie



So, if I read that correctly, basically it's got a cut on both bass and treble, right?

Yup. That's how old Gibsons were wired.

I've also seen a Guild with a sweepable medium cut.

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Good stuff. So on my bass I have active pups, an active 2 band eq, a pup blend, and what I believe is just volume (not gain). I can switch the active eq on and off as well, I almost always leave it on but I've wondered, what is the purpose of being able to switch it on and off, what's the advantage?

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Originally posted by Jazz Ad

Yup. That's how old Gibsons were wired.

I've also seen a Guild with a sweepable medium cut.

Actually only one Gibson was wired like that - Les Paul Triumph , and it had double coil taps and other goodies too :D

ps. jazzy, why are you off aim :o

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Originally posted by Jazz Ad

Yup. That's how old Gibsons were wired.

I've also seen a Guild with a sweepable medium cut.

 

Cool, thanks. I'm not sure, but I think that may be what Ernie Ball are doing on the passive version of the SUB basses they've just released.

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No Questions, Frenchman. You've done well. You deserve this!

 

 

 

 

 

 

 

 

 

 

lugfrench.jpg

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Originally posted by Jugghaid

Good thread Jazz Ad.

Actually, I'm just bored of seeing the same question again and again :D

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Originally posted by Jazz Ad

Actually, I'm just bored of seeing the same question again and again
:D

 

True...true. But usually these turn into a "Passive is better" ...."NO ACITVE IS BETTER!!!!"......"Tastes Great!!!"..."Less Filling!!!" type of argument without the hotties tearing their clothes off. I know you are more of a fan of passive basses but this thread is very objective and avoided that whole usual nonsense. Fact is they are both great and different....that's why I have both kinds of basses. ;)

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I always thought that black knobs meant active and chrome knobs meant passive. I wasn't able to figure out what Gold knobs were for, though.

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Originally posted by Jugghaid



True...true. But usually these turn into a "Passive is better" ...."NO ACITVE IS BETTER!!!!"......
"Tastes Great!!!"
...
"Less Filling!!!"
type of argument without the hotties tearing their clothes off. I know you are more of a fan of passive basses but this thread is very objective and avoided that whole usual nonsense. Fact is they are both great and different....that's why I have both kinds of basses.
;)

 

And tubes are better than solid state. Mine was tube, with a 12ax7 sticking up out of the body from the upper horn. I kept bumping it loose and finally it broke. I could

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Originally posted by Jazz Ad

Gold knob means Jazz Ad.

If it's a shiny bald gold then it means BOALG.
:D

 

Hey, with those new digital switching amps, is there any reason you couldn't have an on-board 400 watt amp?

 

S'pose you'd want to be carfull about tripping over the ac cord though.

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Originally posted by RobRoy

Hey, with those new digital switching amps, is there any reason you couldn't have an on-board 400 watt amp?


S'pose you'd want to be carfull about tripping over the ac cord though.

And you'd want that because ?

If anything, an onboard preamp with direct out to table/poweramp would be nice.

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Originally posted by Jazz Ad

And you'd want that because ?

If anything, an onboard preamp with direct out to table/poweramp would be nice.

 

As with so much today, because you can, like led

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Originally posted by Jazz Ad


You need dioded or/and transistors to limit to a frequency and separate 2 bands, both those components being polarized.

 

Um...that's not quite true. You can use capacitors or inductors to do the same--that's how a 3-way crossover works in speaker cabinates.

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