Passive and Active?

It's a bit of an oversimplification, but yes, you're right on all counts - more or less.

 

All electric guitars and basses have pickups. "Active" refers to instruments with an onboard preamp that either boosts or boosts/cuts at certain frequencies. Active basses require a battery. Passive basses have no preamp but a pot that cuts the treble frequencies the more you engage it. There are active pickups (EMG's) that require a battery but not necessarily a preamp. So it is possible to have a passive bass that needs a battery, but they are uncommon. Active basses can have passive pickups (Stingrays) or active pickups (Spectors).

You can add an external preamp to any instrument, but it won't make it sound active necessarily. Active onboard preamps, in addition to shaping tone, decrease the loss of volume from longer cords (sometimes). You really can't make a passive bass sound active.

 

Active simply means there is an active component somewhere in the signal path. That could mean active pickups, a preamp, or both.

Active/passive switches are quite common on basses with preamps. The more correct term would be a preamp bypass switch, however, as you could still use active pickups and bypass an onboard preamp.

Many people like external preamps, but be aware that the signal must still travel through a length of capacitive instrument cable before reaching the input of an external preamp. Since the output impedance of the bass would be higher than if the preamp were onboard, you would lose some treble.

 

Not necessarily. Active simply means there is an active component anywhere in the signal path. In the case of transparent buffers, there would be no audible change in tone, nor any adjustability. Having equalization or any fixed voicing is not a requirement to any preamp.

Also, unless you have LED fretmarkers or something, having a battery on a bass almost always means there are active components in the signal path.

Note that "active" is not a sound. A bass with a buffer can be voiced to sound exactly like a passive system, if you account for input stage loading characteristics and the transparency of the buffers, to create a nearly uncolored output.

 

Excellent response. I stand corrected. Although, could you tell me what basses typically have such a buffer? I guess I just think of "active" sound to be EBMM/Spector/Warwick/G&L, which don't sound like a passive bass at all (at least the ones I've owned, and obviously I mean when the preamps are engaged).

 

there are numerous threads here that could answer your question.
the search function is a handy feature, not meaning to sound rude.
i use it all the time.

 

Depends on the design of the preamp. Basses without preamps have a tendency to sound a little darker, because the impedance of the signal allows the parasitic capacitance of the instrument cable to form a filter that reduces high frequency content, and there are often many controls in the circuit that load the pickups. In an active circuit, output impedance is lowered, so the cable does not suck the tone, and in some cases, there is a minimum of resistive loading before the preamp input, allowing you to retain high frequency content.

Most commonly, however, people tend to think of active basses as having a certain sound because their preamps have a fixed voicing that colors the tone. This is the case with MusicMan preamps, for example. These sort of tonal changes are not inherent to active components, though. They are either deliberate design choices or due to changes in the circuit, such as the effects of cable capacitance.

 

That's ok, you can't win really. If you use the search function and find an old thread you would like to comment on or get clarification on you will be accused of reviving a zombie thread. If you don't use the search function you will be berated for that. There is really nothing wrong with rehashing old material unless you believe that nothing ever changes, that there is never anything new to add to an old discussion. The only time a repeat thread bothers me is when there is another active thread discussing the same thing.

Is there an "active sound"? For many people there is. One aspect of the active sound is capacitive cable loading on passive pickups as Line6man mentions. If you put an active buffer inside the bass you can eliminate this loading. An active bass with an EQ set "flat" will do the same thing without coloring the sound of the pickups. If you can live with a very short cable to an external preamp then an external preamp can do very nearly as well. For people who use amps on stage this is not much different from just using the preamp in their main amp of course but if you run into a main amp a considerable distance away then having an active bass or an on stage preamp can make a considerable difference. Potentially you could run a very short cable to an external preamp you wear on your belt if you would like to eliminate cable effects without tethering yourself to a fixed point on stage with an annoyingly short leash.

The other aspect of the active sound is that you don't have the interaction between the pickups and the tone capacitor that you get in a passive bass. A preamp does not load the pickups anything like a capacitor does so in very many cases an active bass does sound different from a passive bass. This is not a hard and fast rule however. In-bass preamps can be designed in many ways and if you use a high input impedance on the preamp and put a passive tone control in front of the preamp you can get the "passive sound" from an active bass. It's no different from running a passive bass into a regular amplifier after all. You can even add a small fixed capacitor to get the tone shift that cable loading gives you. Some active basses are built this way but many are not.

Ken

 

ChordMelody;

Just to back up a little bit, which might help to clarify some of what has already been posted, active electronics have been added to basses to serve three different purposes:

Impedance matching - passive basses typically have high impedances which can be 'loaded' easily by long cables, causing a drop in treble (clarity).

Gain - adding a boost in gain, either for a specific frequency band or for the entire signal.

EQ - adding the ability to not only cut certain frequencies, but boost them as well.

In most cases, active electronics are serving more than one of these functions at a time. This, I think, is what leads to some of the confusion surrounding active basses.

If you think about those three functions, and the way they would be implemented, you can easily see how they could affect your tone, either as a main goal or as a side-effect of some other job it's doing.

To answer another of your questions, you asked if an outboard preamp would sound the same as onboard, and people replied (correctly) that it would not, because your signal would first have to travel through a cord. HOWEVER, since you've stated that your bass is already active, your imedance is low and the cable will have little effect upon your signal. Because of this, you could set the controls on your bass to a neutral setting and use an outboard preamp but I don't see much advantage to it unless you are particularly fond of that outboard pre's controls or tonal coloration.

I hope this helped and didn't just make things more confusing!

 

Well, in modern production, the G&L L2000 is pretty much like that (unless you use the "active/treble boost" setting). The normal "active" setting on that bass is basically a buffer with just a wee bit of gain.

An older, more obscure example would be the Ibanez Studio ST-924 basses, which just had a toggle switch that activated a clean, variable-gain preamp.

Before active basses became as widespread as they are now, I seem to remember a few companies offering add-on onboard preamps that were just buffers with a small amount of gain. It was a popular mod for P-basses in the 70s and early 80s. I think Bartolini and Mighty-Mite both offered them, and there were others that I can't recall. Most of them were little, black, epoxy-potted cubes that could just be wedged into a control cavity.

 

Here's another bass that has just a buffer with some light voicing thrown in for good measure - Fender Elite and Elite II.

 

the biggest difference to me is that you need a 9volt battery to power active pickups vs you dont neeed anything to use passive pickups. that 9volt needs to be changed every few months vs the passive pickups never really need to be changed if they're in good shape.

from a pure convenience standpoint, i'm a fan of passive pickups

 

I've never understood the battery life argument. The typical active circuit draws between hundreds of microAmps and a couple of milliAmps. Batteries should last much longer than just a few months. Change your battery once a year or so and don't worry about it.

 

The batteries usually last longer than the strings on your bass— unless you are using flats that you never change. So when you change your strings, change the battery. Or at least check it. That's what I do.

I've never had a battery go dead on me in my bass in the last 35 years. Instruments do require maintenance. You should be cleaning them and seeing if they need adjusting on a regular basis. It's not hard.

 

Agreed. The only time I've ever had a battery die on me was in a bass that had an electrical problem. I fixed the problem - no more dead batteries! Magic!

I'm pretty lazy about changing strings and I've had 9V batteries last much longer than a year. I keep a spare in my bag anyway, but I only ever needed it that one time.