Active/Passive question.

[rshack]

i don't see any question marks, so i guess there are no questions.

 

robb.

I don't have any questions either.

 

I just came across this thread by accident... was looking for something else but found this instead... and, boy howdy, I just learned a bunch of relevant stuff I did not know. (I love it when that happens ;-)

 

So, thank you!

[rumpelstiltskin.]

welcome, rshack! whereabouts in AL are you? i used to live in meridian, MS, which is not far from the border, near butler. i spent a lot of time up in birmingjam and down in orange beach.

 

Anyway, it makes me want to maybe study up on some basic electronics before I start shopping to upgrade my POS amp so I can tell my knee from my elbow, ears notwithstanding.

 

i think the biggest things you absolutely must understand when buying an amplifier are the relationship between watts and ohms, and the relationship between watts, sensitivity, and SPL. if you know a few things and can work a calculator, you won't have to ask any "which will be louder?" questions. even better, armed with numbers, you'll be able to figure out who is honest with their specs and who isn't based on what you hear when you play.

 

robb.

[SteveC]

I thought it was such a simple question...

[plangentmusic]

welcome, rshack! whereabouts in AL are you? i used to live in meridian, MS, which is not far from the border, near butler. i spent a lot of time up in birmingjam and down in orange beach.

 

Anyway, it makes me want to maybe study up on some basic electronics before I start shopping to upgrade my POS amp so I can tell my knee from my elbow, ears notwithstanding.

 

i think the biggest things you absolutely must understand when buying an amplifier are the relationship between watts and ohms, and the relationship between watts, sensitivity, and SPL. if you know a few things and can work a calculator, you won't have to ask any "which will be louder?" questions. even better, armed with numbers, you'll be able to figure out who is honest with their specs and who isn't based on what you hear when you play.

 

robb.

 

That is a separate topic and one with which I agree. Again, for me, it comes down to what is the end result as opposed to the "whys and how." Nevertheless, I'll offer an olive branch of sorts and call on your expertise in this area. Two power heads that I've always found to be far less powerful than their wattage would suggest is SWR and Trace Elliot. They sound great low, but turn a 500 watt amp up halfway and it should blow down doors, yet those two barely cut through the band.

 

Now we can get into which frequencies cut more than others. All those sweet highs get lost in the mix and a lack of mids will create a sense of less volume. But I'm tellin' ya. Even with proper ohms, in every case, those heads simply don't have the output. Any thoughts? Or am I nuts?

[Russkull]

I thought it was such a simple question...

There is no simple question - only a simple answer.

 

Wait, there's not that, either!

 

ok, but you do realize that you can have active pickups with a passive tone circuit or passive pickups with an active preamp, and both can be considered "activated by a battery," right?

This was interesting. Having only owned passive basses, I was under the impression that "active" always referred to the second category - passive pickups with an active preamp.

 

Forgive my ignorance (and maybe this was covered in all the tech discussion) but could Robb or someone explain active pickups?

[rumpelstiltskin.]

why are you only turning it up half way?

 

let's ignore power rating chicanery and only discuss technical details that are not very obvious. did you know that volume controls are rarely linear? -- as in, put the knob to half way up and i should get half the power output. they are logarithmic -- the more you turn it up the more (or less, depending upon how it's wired) the output increases. here's an example:

 

http://www.ozvalveamps.org/pots/pottaper.gif

 

in the picture above, the logarithmic taper makes the volume rise slowly at the beginning and quickly approaching max. if it is reverse log the volume rises quickly at the beginning and slowly approaching max, you can have considerably more than half power at half way up. linear is the only way where half way up is half way up.

 

so that's one way that amp A could be louder than amp B at "half way up."

 

now, bass signals are very dynamic, which means there's a large difference between the peaks (e.g. a slap or a pick attack) and the average (e.g. the sustain of a note). this is relevant because the loudness is really a function of the average, and not the peaks.

 

(you know how a television show goes to commercial and the commercial is way louder than the show? that's because the FCC limits maximum *peak* signal level, rather than average level. the advertisers know this and compress the ever loving bejeebus out of their audio to boost its loudness without exceeding FCC limits.)

 

did you know that most people can't really hear 1%THD, and that they don't really identify distortion until it's approaching 10%? if you push a signal farther into clipping, the peaks are clipped, but the average can continue to increase, which makes it louder. now, part of SWR's image is very clean, very hi-fi reproduction. so maybe they set their clip indicator to light up at 1%THD rather than 5% or 10% like their competitors might. and maybe they wire their log volume pot such that you get a lot of the available power towards the end of the pot's travel. that leaves a lot of power unused at half way up.

 

right away, you're looking at the average user not being at all aware of any of this and perceiving amp A as being louder than amp B, when really they both are capable of the same output, but with drastically different looking settings.

 

and more can be said about frequency response and efficiency, but that is another topic entirely.

 

robb.

[rumpelstiltskin.]

This was interesting. Having only owned passive basses, I was under the impression that "active" always referred to the second category - passive pickups with an active preamp.

 

Forgive my ignorance (and maybe this was covered in all the tech discussion) but could Robb or someone explain active pickups?

 

lug explained it well:

 

An active pickup can use less windings and just use a preamp to boost the signal back to where it needs to be. This allows a wider frequency range since more windings usually means more inductance and more inductive reactance. Inductive reactance effects higher frequencies more than lower (opposite of capacitive reactance)so more windings, while giving a higher output, limits upper frequency.

 

basically, an active pickup is a very low inductance pickup that therefore has a very weak signal. however, the upshot is that it generally is more sensitive and has wider frequency response. in addition, if we put a little preamp inside the pickup that provides enough gain (and only gain), we can boost the signal to a usable level and gain the benefits of the low inductance pickup.

 

robb.

[lug]

lug explained it well:

 

robb.

....chest swells with pride....

 

.....head swells with conceit.....

 

......neck grows to support large head......

 

.......pullover shirt grows to tight and can't remove due to larger head.......

 

.....strangles self with pride.......

 

.....dies......

[plangentmusic]

why are you only turning it up half way?

 

.................

I SEE WE CONTINUE TO TALK PAST EACH OTHER. I AM NOT TURNING IT UP HALF WAY. I ALWAYS KEEP THE MASTER ON 10 FOR MAXIMIMUM CLEANLINESS AND THEN ADJUST THE GAIN. I WAS MAKING THE POINT THAT EVEN WHEN TURNED UP HIGH, THE OUTPUT DOESN'T SEEM TO BE AS MUCH AS OTHER HEADS.

[/color].......................................

 

let's ignore power rating chicanery and only discuss technical details that are not very obvious. did you know that volume controls are rarely linear? -- as in, put the knob to half way up and i should get half the power output. they are logarithmic -- the more you turn it up the more (or less, depending upon how it's wired) the output increases. here's an example:

 

http://t2.gstatic.com/images?q=tbn:ANd9GcRoWd7ViDqBJKZaYeF_zT8_1ERNa-XrKQnnZg_MoyFIF_C6H5FhYV2k5-xHCA

 

in the picture above, the log pot is wired so that the volume rises slowly at the beginning and quickly approaching max. now, if the log pot is wired the opposite, such that volume rises quickly at the beginning and slowly approaching max, you can have considerably more than half power at half way up.

 

so that's one way that amp A could be louder than amp B at "half way up."

 

.............

 

THAT'S NOT REALLY WHAT I'M TALKING ABOUT. LOL NEVER MIND. : )

 

......................................

 

now, bass signals are very dynamic, which means there's a large difference between the peaks (e.g. a slap or a pick attack) and the average (e.g. the sustain of a note). this is relevant because the loudness is really a function of the average, and not the peaks.

 

(you know how a television show goes to commercial and the commercial is way louder than the show? that's because the FCC limits maximum *peak* signal level, rather than average level. the advertisers know this and compress the ever loving bejeebus out of their audio to boost its loudness without exceeding FCC limits.)

 

did you know that most people can't really hear 1%THD, and that they don't really identify distortion until it's approaching 10%? if you push a signal farther into clipping, the peaks are clipped, but the average can continue to increase, which makes it louder. now, part of SWR's image is very clean, very hi-fi reproduction. so maybe they set their clip indicator to light up at 1%THD rather than 5% or 10% like their competitors might. and maybe they wire their log volume pot such that you get a lot of the available power towards the end of the pot's travel. that leaves a lot of power unused at half way up.

 

right away, you're looking at the average user not being at all aware of any of this and perceiving amp A as being louder than amp B, when really they both are capable of the same output, but with drastically different looking settings.

 

and more can be said about frequency response and efficiency, but that is another topic entirely.

...............

 

SO YOU'RE SAYING THEY MIGHT PUT A LIMITER ON THE SIGNAL. GOT IT.

 

 

robb.

 

....

[_Sweet Willie_]

plangentmusic, I think you've missed the point. Although your post with the comment about "halfway up" inspired robb.'s response, the value of what robb. had to say is less for you than for other readers who may be less experienced players (i.e., new players). Other readers might get caught up on the "halfway up" concept, and what robb. has done is help them understand how that could be misleading if they took what you wrote literally.

 

What's happened because of what robb. wrote is that less experienced players (or gearheads) won't stop at the detail of your experience that Trace and SWR (two brands among many) have sounded underpowered compared to the spec sheets, and now have additional knowledge that helps them understand why, under varying circumstances (and varying settings), different amps might sound louder or not so loud relative to one another. They can now generalize and apply new knowledge (or reinforced knowledge) to their own situations.

 

In the end, as has been stated multiple times on this thread, it's about whether what we hear satisfies our needs rather than whether what we read satisfies our needs. However, combining what we read about a product, with some additional knowledge about the science behind its intended function, and then actually trying it out gives the average player a better platform from which to evaluate.

 

Peace.

--SW

 

 

 

[rumpelstiltskin.]

why are you only turning it up half way?

 

.................

GRR. ARGH.

 

......................................

 

it was a joke. lighten up, francis.

 

...............

 

SO YOU'RE SAYING THEY MIGHT PUT A LIMITER ON THE SIGNAL. GOT IT.

 

no (although they probably do that). i'm saying they might structure the gain such that the preamp doesn't drive the power amp nearly as hard as some other manufacturer, so on the best day you're just tickling what the power amp is capable of, and the average level doesn't get as high as other amps of similar power. this can also be known as reliable design (you know, so the amp doesn't blow itself up), which may also be why trace and SWR have reputations for being bulletproof.

 

robb.

[SteveC]

I just wanted to know if I was really hearing something or if I was crazy. Didn't really think it would spur all this.

[rumpelstiltskin.]

it didn't.

 

robb.

[Big Daddy from Motown]

Nice job Robb.

 

[Tom Capasso]

Robb - I gave the TV commercial explanation to my wife. We hate that commercial volume stuff.

 

Yeah - engineers can talk about loading and the myriad of specs - and all that does affect the tone.

I guess I was right about the engineers - thanks Robb.

 

Tom

[plangentmusic]

why are you only turning it up half way?

 

.................

GRR. ARGH.

 

......................................

 

 

 

 

it was a joke. lighten up, francis.

 

...............

 

 

 

 

SO YOU'RE SAYING THEY MIGHT PUT A LIMITER ON THE SIGNAL. GOT IT.

 

no (although they probably do that). i'm saying they might structure the gain such that the preamp doesn't drive the power amp nearly as hard as some other manufacturer, so on the best day you're just tickling what the power amp is capable of, and the average level doesn't get as high as other amps of similar power. this can also be known as reliable design (you know, so the amp doesn't blow itself up), which may also be why trace and SWR have reputations for being bulletproof.

 

robb.

 

 

I didn't write GRR and I apparently missed the joke Nancy. lol

 

As for an amp being able to put out X amount of power, not conducive to what the wattage suggests, that to me is simply a sub par amp -- especially since both brands are on the pricy side.

[hippie wood]

http://www.threadbombing.com/data/media/30/Point_over_your_head.jpg

[rshack]

welcome, rshack! whereabouts in AL are you? i used to live in meridian, MS, which is not far from the border, near butler. i spent a lot of time up in birmingjam and down in orange beach.

Thanks for the welcome...

 

Am a tad west of Gulf Shores (part way to Ft. Morgan)... spent a bunch of time in B'ham (Hoover) some years ago...

[Mark Schmieder]

ALL of my current passive basses have hotter output than almost ANY of the active basses I have owned over the years.

 

The main purpose of active in today's world is detailed tone-shaping.

 

Historically, this was not the case, but electrical designs are more efficient today than 20, 30, 40, or 50 years ago. It is now possible to even make a traditional Fender style passive bass with fairly hot output. In fact, Fender does.

 

I doubt I will ever buy an active bass again. Every time I try one I am disappointed. I don't like the extra boost at that part of the signal chain. It ends up creating a somewhat compressed sound once you choke it a bit.

 

On the other hand, much of 90's music is based on that sound. If I was doing 90's covers, I would feel the need for an active bass just to match "that" sound. But I'd probably instead go for an outboard whatchamacallit by Aguilar (too lazy/tired to look it up, but it gets rave reviews and is equivalent to their on-board pre-amps in a metal shell).

 

In fact, I feel that is the better approach. If you want the timbral shift (as opposed to volume boost) of an active pickup, you'll get cleaner signal by taking the outboard approach. But of course for many this isn't practical relative to stage ergonomics, setup, etc. Still, it is a way more flexible approach.

 

Batteries die. I had one gig where all four basses went dead at the same gig. Murphy's Law. It makes you look unprofessional, no matter how prepared you are. And in that case it was more than just replacing the batteries; too much to do quickly and debug during a no-gap-between-songs four-set gig with dance energy. I ended up doing the entire gig on my upright. Everyone dug it and thought the upright brought visual energy to the mix.

 

Of course, if you go for a custom approach, you will get good passive/active hybrid circuitry with clean electronics, good wiring and shielding, and most if not all of the typical "problems" of active basses solved. But boy does that ever cost money! I'd rather keep things simple and better bang-for-buck plus less to go wrong on stage.

 

Another argument against active is that it is a particular sound. With passive, you have more choices for shaping the sound, if that's what you need to do. You aren't locked into one pre-amp but can swap several outboard boxes or even several rack-based pre-amps. You also don't have to trade the bass or do expensive custom work once you're sick of its particular on-board pre-amp.

 

I spent 20-25 years of my life playing active basses. Passive basses gave me a bad taste, from my early Fenders and G&L's and Arias to my first Warwick. It was my current guitar technician (from the late 1990's onward) who finally convinced me to switch over to passive basses. I doubt anyone else could have gotten me over my prejudice against passives.

[SteveC]

Good points. I think I even raised one myself a while back - have a passive bass and buy all the outboard pre boxes if you want a certainn sound. Sadowsky, John East, Aguilar, they all have them.

[rumpelstiltskin.]

ALL of my current passive basses have hotter output than almost ANY of the active basses I have owned over the years. ... Historically, this was not the case, but electrical designs are more efficient today than 20, 30, 40, or 50 years ago. It is now possible to even make a traditional Fender style passive bass with fairly hot output. In fact, Fender does.

 

that's a great point. advances in magnetic materials have made a huge impact in both the output and frequency response of modern pickups (e.g. q-tuners).

 

robb.

[Wally Malone]

On my gig in New Orleans this past weekend they had the SWR SM-900 for the backline. I couldn't get a signal at all plugging into the active slot. I was using my Kubicki with new batteries but also recognized that there was no sound even when using the passive positions on the Kubicki. I switched to the passive plug in and it worked fine.

 

Wally

[rshack]

I doubt I will ever buy an active bass again. [stuff deleted] But I'd probably instead go for an outboard whatchamacallit by Aguilar. [Tone Hammer?]

 

In fact, I feel that is the better approach. If you want the timbral shift (as opposed to volume boost) of an active pickup, you'll get cleaner signal by taking the outboard approach.

Is that really true? (I dunno, which is why I'm asking.) Does it really matter where the preamp is? Is there a sonic difference in outboard vs. inboard with a bypass switch?

[rumpelstiltskin.]

there is some small, but measurable, amount of capacitance in a cable that will attenuate (lower) the high frequency response of your bass. you will also have passive tone controls that are rare on active basses.

 

other than that, having an external preamp is almost exactly the same as an internal one in most cases. usually the pickups in an active bass will have a volume control of the exact same value as a passive bass, but instead of going to the output jack, it goes to the preamp, which then goes to the output jack.

 

robb.

[lug]

there is some small, but measurable, amount of capacitance in a cable that will attenuate (lower) the high frequency response of your bass. you will also have passive tone controls that are rare on active basses.

 

robb.

 

One example of this are G&L basses. They have their passive tone controls before the preamp and the preamp really just acts as a unity gain line amp.

[Tom Capasso]

One example of this are G&L basses. They have their passive tone controls before the preamp and the preamp really just acts as a unity gain line amp.

 

Look at you talking all competent and technical! Somebody steal your ID?? :grin:

[lug]

One example of this are G&L basses. They have their passive tone controls before the preamp and the preamp really just acts as a unity gain line amp.

 

Look at you talking all competent and technical! Somebody steal your ID?? :grin:

 

http://www.box.net/shared/static/aemq3d9ldv.wav

[rumpelstiltskin.]

my ears hurt just looking at that URL.

 

robb.

[lug]

my ears hurt just looking at that URL.

 

robb.

 

It's not me playing, I would never do that to y'all.

[rumpelstiltskin.]

against my better judgment, i'm bringing this back to the top because i had a thought worth sharing while running the other day.

 

anthony jackson is famous for, among other things, inventing the 6-string bass and wiring his pickup directly to the output jack. this is relevant here because of the discussion on tone controls and output impedance. with the average pickup somewhere around 7k Ohms to 8k Ohms, the impedance of a pickup is two orders of magnitude below the impedance of tone controls, and much closer to the input impedance of most mixer inputs (typically around 2k).

 

i've never done this myself, but i would expect the tone to be very dynamic without a preamp and without tone controls when plugged in directly. if anyone ever gets a wild hair to take the tone controls out of their passive instrument, i'd love to get a report back. obviously this will really only work with a single pickup instrument or without blending for two or three pickups. multiple pickup series/parallel combinations also affect impedance in the same way it does for cabinets.

 

robb.