I wonder what the signal paths are like on basses with a passive/active switch. I.e., is it a "true" passive which shows effects from e.g. a long guitar cord?
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The 'magic' of passive electronics?
- Thread starter robert_stuart
- Start date
Exactly. And this kind of "automatic" rolling off of some highs, and a kind of compression I think, contribute to the sound.
I'm skeptical that an "active/passive" bass enables all these effects via a true bypass.
I'm skeptical, but open to changing my mind. Can the bassist's sound in the video I included in my first post be achieved with an active bass?
Most of the ones I've seen, especially when there's a passive tone control, are a set of passive controls, which then feed into the input of an active circuit.
Yes. One reason is how the signal gets to the amp. All instrument cables reduce the signal, affecting some frequencies and loudnesses differently than others. It's called impedance here, because it's an alternating current. (Resistance is DC.)
So: a passive bass signal, going through the tone controls and then a cable, before going through gain stages in the amp, undergoes changes.
These changes don't happen in active basses, whose signal can power through (so to speak) the tone section and guitar cable.
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There's nothing special about the tone in that video you posted. Any Sadowsky with an active preamp can do that, likewise any Alleva-Coppolo.
If you took that bass, and tossed in an active preamp that wasn't voiced (like the common Bartolini, and not the TCT) you'll get the same thing. Likewise, if you plug that bass into an active external buffer, or external active preamp, you'll get the same thing.
Thank you! That was extremely interesting. Do you know of any "passive / active" switchable basses that offer a "true bypass" for passive mode and so would get cable impedance effects, etc.? Do most manufacturers do this?
I'm wondering about the Fender American Ultra II basses.
That suggests to me it's not a "true passive" with a true bypass. (?)
Because in a true passive-only bass, e.g., the instrument cable will attenuate the sound and it'll have a slower attack.
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I think that another effect of a pure-passive bass is a different ADSR envelope, for example a slower attack. I believe the tone changes over the decay where with active basses, I don't really hear much change at all. (?) I think this is key to the sound and is audible in the YouTube video I posted.
Passive isn't merely a "tone" that can be simulated with active electronics, IMO.
Passive isn't merely a "tone" that can be simulated with active electronics, IMO.
To me, passive basses feel perfectly imperfect, while active basses feel imperfectly perfect. I play both kinds.
Hmm, but it must be truly passive in passive mode as it can operate with no battery in the bass.
Yes, most basses with an active/passive switch that I've seen are true bypass, with one of the goals of them working without a battery. It's a common fear of the battery dying and/or circuit failing mid-gig, so that offers you a plan B. Or, of course, there are other uses for it, like setting up two very different sounds available at a flick of a switch, etc...
You brought up compression a couple times, and I think that is one of the things people often mention with active electronics (not passive). I can see two things happening here (tho I may be wrong) - one is true compression, leading to a quicker attack. The other may be, and I think someone already mentioned that above, simply an artefact of our hearing - if active electronics better preserve the highs, and we hear those faster than lower frequencies (I believe this is true), this gives us the impression of a faster attack. I think the compression thing is an issue (it matches my experience with some actives), but a consequence of design. If I'm not mistaken, 18V circuits help in that regard. The treble response thing, on the other hand, can be "simulated" with active electronics, by inserting capacitors before the active electronics (to simulate cable loading) or using a filter-based preamp. How well these tricks work may be a matter of preference and perception (more on that below).
There's another limiting factor of active on-board electronics (vs. those in an outboard preamp or amp/head), which is related to their on-board installation - they have to be designed for small cavities on a bass. This can lead to suboptimal components, including 9 or 18V power. I recall that some think that's still not enough, and that only a proper preamp can cleanly EQ the sound (e.g., I believe the late great Anthony Jackson said that in an interview). While this gets a bit into the "golden ears" territory, it does remind me of tonewood debates, 60s vs 70s J spacing debates, P bass vs solo P in a PJ debate, etc... For many of these, we have theories that explain the differences, but some people hear differences, and some don't. And from those who can hear the differences, some care and some don't.
And finally, this also reminds me that sometimes we perceive things that we struggle to describe, or have no known theory to explain it. Basically the Polanyi Paradox (we know more than we can tell), but sometimes a true blindspot of our (theoretical) knowledge. I'm probably getting some of this wrong, but I recall reading that folks in/around the Grateful Dead heard some artefact in the amplified sound, but it did not corresponded to any engineering principle or theory known at the time. But over time, based on their observations, a new theory/model was developed to account for what they were hearing. We see similar things in other areas of knowledge/science too - what may be consider BS in a previous era can become science once our theories and methods catch up.
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I don't think passive/active is a helpful distinction here.
Take the setup from the video. Shorten the cable, and the sound will change, because the pickup will see less capacitance from the cable.
Keep reducing the cable length, until the bass is directly connected to whatever electronics were at the other end of it. It won't have the original sound that you liked; the "magic" will have been lost; but it will still be a "passive bass".
Now miniaturise those electronics, and put them in a cavity in the body of the bass. Suddenly you have an "active bass". But it will sound exactly the same as the previous step - all you've done is moved some electronics from one side of the pickguard to the other.
Finally, add a load capacitor after the pickup, with the same capacitance as the length of cable that you liked the sound of. The magic will re-appear; you'll have achieved the sound from the video with an "active bass". Capacitance is capacitance, whether it comes from a length of cable or a ceramic cap - the pickup doesn't know the difference. Happy to be corrected by someone with more electronics expertise, but in this case I don't believe there's much more to it?
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Both can be good, to each his own, ya like what ya like, variety is the spice, Different strokes, just the Facts of Life.. Hello Larry.. etc.
That said, best 'passive Tone' I ever had was a Corvette. Sounded AWESOME, lacked for Nothing. Just too damn heavy for my weak azz.
THAT said, I usually prefer (or just end up with) Active. Usually works best for 5 strings IMO (which is all I do). However, all my current basses are active 'passive mode', so I have it either way.
T$
That said, best 'passive Tone' I ever had was a Corvette. Sounded AWESOME, lacked for Nothing. Just too damn heavy for my weak azz.
THAT said, I usually prefer (or just end up with) Active. Usually works best for 5 strings IMO (which is all I do). However, all my current basses are active 'passive mode', so I have it either way.
T$
That control emulates the input impedances of different amplifiers. DB players using piezo pickups can get very picky about the impedance…most want at least 1 Mohm, some prefer higher impedances like 5 to 10 Mohms. They do sound different.
Some examples:
My Crate B10XL amp from the 80s has an impedance of only 220 Kohms.
My TC BH250 is 500 Kohms.
On a blackface Bassman, on both channels input 1 is 1Mohm but input 2 is only 136 Kohms.
The Sansamp BDDI (all versions) has a 1Mohm impedance, but the Para Driver and Bass Flyrig are 4.7 Mohms.
Yes, absolutely. It's not a hard tone to cop or even a very unique tone. I am a passive bass guy all the way, but that tone is absolutely attainable with active electronics.
Any bass that has an active/passive switch is going to have cable loading effects in passive mode.
It’s silly to talk about compression with passive basses.
Compression describes when an audio signal is manipulated to change the dynamic range. Since the output of a passive bass is the source of the audio signal, it is by definition uncompressed.
You might try to argue that the output sounds compressed compared to what you hear when the bass isn't plugged in, but here at TB it’s controversial to think that the unplugged tone has anything to do with what comes out of the pickups.
Compression describes when an audio signal is manipulated to change the dynamic range. Since the output of a passive bass is the source of the audio signal, it is by definition uncompressed.
You might try to argue that the output sounds compressed compared to what you hear when the bass isn't plugged in, but here at TB it’s controversial to think that the unplugged tone has anything to do with what comes out of the pickups.
