Active v passive pick ups

[Frankieabbott]

What are the pros and cons for both?

[itu]

Bass signal path looks like this:

pickup(s) - blend (or vol2) - vol - tone circuitry - output

 

If there is even one battery powered part in the signal chain, the whole system has low impedance (lo-Z) output. Understood?

 

If the pickups are true lo-Z (buffered output, battery operated), the following adjustments (pots) have less effect to the pickups. Here this can be compared to a hi-Z system...

 

"Passive" system usually consists of pickup(s) and vol(s) and tone. No batteries. Here pots - even vol - affect the sound by cutting some of the highs and output slightly.

 

Usually an "active" bass has a battery operated preamp for tone tweaking. Now get to the beginning of my post and repeat the first chapter: there are (passive) pickups affected by blend and vol, which load pickups and reduce highs and signal level (although slightly). So actually many of these so called "active" basses are passive with an added battery powered tone circuitry.

 

There are few battery powered pickups available like MEC and EMG. They have built-in buffers and thus a lo-Z output.

 

There are also few mixers like John East, and certain Audere, EMG and Noll preamps. These mixers do not load pickups.

 

I am not sure, what do you actually meant with "active" pickups, so hopefully you can refine your question after my answer.

 

One thing you should be aware of, is that the output type has effect on the following units, too: A hi-Z output drives a fuzz/OD/dist effect in a different way than its lo-Z counterpart - even when the output levels are exactly the same. 

 

I also want to point out that some hi-Z outputs are actually "hotter" than lo-Z ones. "Active" does not equal higher output level.

[Woodinblack]

Depending on if you are really  asking whether there is an advantage to active pickups or active basses (which as mentioned are generally passive pickups and a buffer or preamp), the initial (and still the best) purpose is to reduce signal loss going to your amp.

If you have an active bass, the signal created by your pickups is sent to your amp. If you have a passive bass, the signal your amp gets is the signal of your pickups and all the wiring that goes between you and your amp (or effects), so you tend to loose the high frequencies quite a bit with such a circuit.

 

Also because the output is a low impedance, you have less noise injected in your cables on a long signal run.

[Lozz196]

I’ve found that with active basses I don’t have to dig in as much to get the attack that I like. The downside is that I’m not that keen on the sound in comparison to passives so passive basses it is.

[rmorris]

On 02/10/2021 at 21:33, itu said:

Bass signal path looks like this:

pickup(s) - blend (or vol2) - vol - tone circuitry - output

 

If there is even one battery powered part in the signal chain, the whole system has low impedance (lo-Z) output. Understood?

 

If the pickups are true lo-Z (buffered output, battery operated), the following adjustments (pots) have less effect to the pickups. Here this can be compared to a hi-Z system...

 

"Passive" system usually consists of pickup(s) and vol(s) and tone. No batteries. Here pots - even vol - affect the sound by cutting some of the highs and output slightly.

 

Usually an "active" bass has a battery operated preamp for tone tweaking. Now get to the beginning of my post and repeat the first chapter: there are (passive) pickups affected by blend and vol, which load pickups and reduce highs and signal level (although slightly). So actually many of these so called "active" basses are passive with an added battery powered tone circuitry.

 

There are few battery powered pickups available like MEC and EMG. They have built-in buffers and thus a lo-Z output.

 

There are also few mixers like John East, and certain Audere, EMG and Noll preamps. These mixers do not load pickups.

 

I am not sure, what do you actually meant with "active" pickups, so hopefully you can refine your question after my answer.

 

One thing you should be aware of, is that the output type has effect on the following units, too: A hi-Z output drives a fuzz/OD/dist effect in a different way than its lo-Z counterpart - even when the output levels are exactly the same. 

 

I also want to point out that some hi-Z outputs are actually "hotter" than lo-Z ones. "Active" does not equal higher output level.

 

Nice explanations there.

If people ask me I usually go along the lines of:

 

If an 'Active Bass' has Hi-Z Pickups then it has a powered buffer or a more featured preamp with active tone controls and whatever.

It's basically putting some or all of the functionality of your preamp section into your bass.

Advantages:

Your pickups are not directly loaded by the capacitance of the cable to the amplifier.

The output signal has a lower impedance. This good because lower impedance signals are less susceptible to interference.

Additionally low-Z signals are not as troubled by cable 'handling noise' as Hi-Z signals. You may not need 'Low Noise' instrument cable that has the semiconducting layer in it to reduce this noise.

* See note on impedance below

If you prefer to have EQ etc controls on your bass then there you go.

 

Disadvantages:

The circuitry is generally battery powered - one or two PP3 batteries. So if your batteries run out of steam then you have a problem (although there's sometimes an option to switch to passive operation to get out of trouble). And in most cases accidentally leaving the bass plugged in will run down the battery.

Players love to have a long battery life for obvious reasons. But this doesn't always go hand in hand with the highest audio performance so there can be a trade off compared to your mains powered preamp.

Also if you then plug your active bass into your preamp then you are sort of duplicating functionality and increasing noise by going through more amplifier stages.

 

*Impedance - worth noting that 'Active' basses  might have a lower output impedance than passive basses. But often it is not really 'Low Impedance' in pro-audio terms as it's just the unbuffered output directly from a potentiometer wiper. The output impedance will vary with the wiper position. (This is similar to the case with many fx pedals).

Don't be fooled by the use of an XLR socket - they are often (though not always) used for security of connection but the signal is not necessarily a proper 'DI' signal in terms of level / balance / impedance.

 

re: A hi-Z output drives a fuzz/OD/dist effect in a different way than its lo-Z counterpart.

I'll just note that applies to "Fuzz Face" type circuits which basically depend on the signal source having a highish impedance for their operation.

Other OD/Dist/Clipping fx work fine with lo-Z signals - they often have a buffer so that the pickup doesn't see the bits that produce the effect directly.

Edited October 5, 2021 by rmorris

[Woodinblack]

7 hours ago, rmorris said:

*Impedance - worth noting that 'Active' basses  might have a lower output impedance than passive basses. But often it is not really 'Low Impedance' in pro-audio terms as it's just the unbuffered output directly from a potentiometer wiper. The output impedance will vary with the wiper position. (This is similar to the case with many fx pedals).

 

I would say in the vast majority the volume (and any balance) of most active basses are before the preamp, so the output is the same impedance at all volume settings. I can't think of any off hand that aren't that way, certainly that way on all of mine, but I am sure there are some that could be the other way. 

 

[Boodang]

Also to consider; the more windings on a pickup the narrower it's frequency response. Hence the idea behind active pickups is to have fewer windings but this makes for a very low voltage output. To make up for this a preamp is built in to add gain (hence the need for batteries). This has three effects, the output will be buffered (so you can't for instance put 2 active p/u's in series), it will have a low impedance output (normally 600 ohms) courtesy of the opamp used and because they need magnets that are not as strong as passive p/u's they have less pull on the strings.

Passive pickups normally have an impedence of 10k ohms, will have a narrower frequency response (but this will normally be a tailored response so not necessarily a bad thing) and because it's basically just wire wrapped around magnets is not buffered.

A lot of people do not like the bright, clinical response of active p/u's but in my experience they just need a lot of eq'ing, whereas passive p/u's have a more 'organic' tone mostly because of their tailored response. 

[rmorris]

On 08/10/2021 at 23:39, Boodang said:

 it will have a low impedance output (normally 600 ohms) courtesy of the opamp used and because they need magnets that are not as strong as passive p/u's they have less pull on the strings.

Passive pickups normally have an impedence of 10k ohms, will have a narrower frequency r...

 

Just a note to say that 600 Ohm is on the high side for a 'Low Impedance' Output although still an order of magnitude below that of a standard Hi-Z pickup. A 'real' low impedance output has an impedance below, say, 100 Ohm. Typically 68 Ohm. In the simplest case simply set by a resistor in series with the OpAmp output. It primarily serves to keep the output stable with a capacitive load - basically cables.

It also limits the current if the output is shorted. So in some battery powered pedals etc it can be 1 kOhm or so to protect the battery. But higher resistor value does increase noise.

The '600' Ohm standard is something of a legacy thing from old electronic gear where power transfer and hence impedance matching was important. With modern solid state kit it's voltage transfer that is the issue.

[itu]

On 05/10/2021 at 17:16, rmorris said:

re: A hi-Z output drives a fuzz/OD/dist effect in a different way than its lo-Z counterpart.

I'll just note that applies to "Fuzz Face" type circuits which basically depend on the signal source having a highish impedance for their operation.

Other OD/Dist/Clipping fx work fine with lo-Z signals - they often have a buffer so that the pickup doesn't see the bits that produce the effect directly.

I did not mean that they would not work, but they do behave in a different way. I have tested several compressors and fuzz/OD/dist boxes. Their behaviour as well as sound has been different with my lo-Z and hi-Z basses. No, I did not believe there would be any difference, but after quite a lot of testing I found substantial change in sound dependent on the bass' output impedance. I talked about this with a seasoned pedal maker who confirmed my findings.

I have compressors that work better in the beginning of the signal chain: I do understand that the placement in the pedal board affects effect's behaviour. When there are buffers in between, the results are naturally different.

FX loops is another story with their varying levels etc.

Edited October 10, 2021 by itu

[rmorris]

7 hours ago, itu said:

I did not mean that they would not work, but they do behave in a different way. I have tested several compressors and fuzz/OD/dist boxes. Their behaviour as well as sound has been different with my lo-Z and hi-Z basses. No, I did not believe there would be any difference, but after quite a lot of testing I found substantial change in sound dependent on the bass' output impedance. I talked about this with a seasoned pedal maker who confirmed my findings.

I have compressors that work better in the beginning of the signal chain: I do understand that the placement in the pedal board affects effect's behaviour. When there are buffers in between, the results are naturally different.

FX loops is another story with their varying levels etc.

 

Understood. But the 'driving a 'Fuzz-Face' type circuit with a lowish source impedance is the big thing that arises.

Beyond that - yeah - it's all in the circuit details. Amongst other issues a 'box' may be designed with an input impedance more suited to 'line level' sources that is generally regarded as too low for passive Hi-Z pickups - although, of course, sometimes that will be a sound that people like and want as it will, for example, go towards less sustain. At the other extreme a very high input impedance can result in resonances that over emphasise particular frequencies.

Would be interesting to hear what differences you found with Ho/Lo Z on specific pedals/boxes.

Cheers.

[itu]

22 hours ago, rmorris said:

Would be interesting to hear what differences you found with Ho/Lo Z on specific pedals/boxes.

I did this trial a few years ago. The units I tested were Jan Rey Vemuram (for guitar, not bass), an old russian Muff (that big box weighs a ton), RAT (fun 'n' thin), Darkglass B3k (good, but not for me), Darkglass Duality (yes!), Way Huge Pork Loin (a good unit), EBS multidrive (lousy), MÖG (slightly complicated and for heavy), Overlord (tube wonder with a good eq), Spruce Effects OGF (modified for bass by the maker), RaingerFX AirField (now that's what I call strange!), Rochambeau Musical Apparatus Crustacean (just like previous), Amptweaker Bass TightFuzz (tough guy), and Voodoo Labs Sparkle Drive (this has good basic sound). On top of this I have had both IE FrantaBit and Oxide in different occasion. Franta is not actually a distortion, although there were sound possibilities that sometimes amazed me.

 

What was left after the trials? Amptweaker, because it works with various signals and has really good sound - for me. Spruce Effects is clearly a hi-Z unit, but a really good sounding one - again, our tastes vary... Crustacean is still somewhere in my house, just because it is totally different. I also loved Sparkle Drive and Duality for their basic sounds.

 

I tested a few compressors, and there are few left in my three boards: tce HyperGravity and mini, they both work well at the end of the signal chain. They do have to be adjusted quite a lot before the actual use, but the work pays off. Very good sound, and price.

 

Daring Audio Phat Beam is not at its best with lo-Z signals, but it loves hi-Z signals AND fretless basses. I have not met anything similar so far. A real keeper.

[rmorris]

On 11/10/2021 at 21:59, itu said:

I did this trial a few years ago. The units I tested were Jan Rey Vemuram (for guitar, not bass), an old russian Muff (that big box weighs a ton), RAT (fun 'n' thin), Darkglass B3k (good, but not for me), Darkglass Duality (yes!), Way Huge Pork Loin (a good unit), EBS multidrive (lousy), MÖG (slightly complicated and for heavy), Overlord (tube wonder with a good eq), Spruce Effects OGF (modified for bass by the maker), RaingerFX AirField (now that's what I call strange!), Rochambeau Musical Apparatus Crustacean (just like previous), Amptweaker Bass TightFuzz (tough guy), and Voodoo Labs Sparkle Drive (this has good basic sound). On top of this I have had both IE FrantaBit and Oxide in different occasion. Franta is not actually a distortion, although there were sound possibilities that sometimes amazed me.

 

What was left after the trials? Amptweaker, because it works with various signals and has really good sound - for me. Spruce Effects is clearly a hi-Z unit, but a really good sounding one - again, our tastes vary... Crustacean is still somewhere in my house, just because it is totally different. I also loved Sparkle Drive and Duality for their basic sounds.

 

I tested a few compressors, and there are few left in my three boards: tce HyperGravity and mini, they both work well at the end of the signal chain. They do have to be adjusted quite a lot before the actual use, but the work pays off. Very good sound, and price.

 

Daring Audio Phat Beam is not at its best with lo-Z signals, but it loves hi-Z signals AND fretless basses. I have not met anything similar so far. A real keeper.

 

Impressive !