can any active bass be set up for a passive option

liquid sunshine · #1 03-15-2011, 11:04 AM

i have been told that the only way to do it is if the pickups are passive. but from things i have read on here that seems to be untrue.
what i am looking to do specifically is to add an opb-3 to my 2004 precision deluxe and i would like to make the volume push pull active/passive. right now the pickups are stock.
i might switch them but i would like to hear what a new pre will do for me first.

if you feel like explianing it to me cool if not a yes or no would be enough to make me happy i plan to order the preamp asap and find someone i trust to install it

PSPookie · #2 03-15-2011, 11:15 AM

Yes, you can do this. Most active basses have passive pickups and a preamp (like yours). There are some active pickups but they are the exception rather than the rule.

Muzoid · #3 03-15-2011, 11:17 AM

Yup...doable....seymourduncan.com will have a wiring diagram for you I believe.

**line6man** · #4 03-15-2011, 11:29 AM

Active/passive switches simply bypass the preamp on basses with preamps.
You can bypass the preamp if you have active pickups, but the pickups will still always be active.

With active pickups, you can add a preamp bypass switch to any bass. (So long as the preamp is not PCB mounted, those are hard to modify.)
With passive pickups, you can add a preamp bypass switch to any bass, but you need to make sure you have a 250K/500K volume pot before the input of the preamp, not a 25K/50K after the preamp. If the volume pot is controlling the low impedance output of the preamp, the low resistance of the pot will kill most of the output of your passive signal.

**line6man** · #5 03-15-2011, 11:30 AM

Quote:

Originally Posted by liquid sunshine

what i am looking to do specifically is to add an opb-3 to my 2004 precision deluxe and i would like to make the volume push pull active/passive. right now the pickups are stock.

Those are passive pickups.

liquid sunshine · #6 03-15-2011, 01:55 PM

thanks for the help guys.

puddin tame · #7 03-15-2011, 04:32 PM

active warwicks (not rock basses) come with push/pull active/passive so its definitely a thing

Kael · #8 03-15-2011, 04:50 PM

Quote:

Originally Posted by puddin tame

active warwicks (not rock basses) come with push/pull active/passive so its definitely a thing

Not always so. My main fretted bass is an active Streamer LX6. There is a push/pull pot on the volume knob that bypasses the preamp, but the pickups themselves are active. If you take the battery out of the bass, it makes no sound.

Most pickups are not active though. Even in the warwick line, most of the pickups are passive.

britainblues · #9 03-15-2011, 04:58 PM

http://www.bestbassgear.com/wiring-d...-volume-pp.pdf

mmbongo · #10 03-15-2011, 05:32 PM

It's true that the pickups have to be passive in order to do this. You can't do it if the pickups are active.

**line6man** · #11 03-15-2011, 05:33 PM

Quote:

Originally Posted by mmbongo

It's true that the pickups have to be passive in order to do this. You can't do it if the pickups are active.

Not at all.
You can still bypass your preamp, regardless of what you have feeding into it.

drpepper · #12 03-16-2011, 08:17 AM

Quote:

Originally Posted by line6man

Not at all.
You can still bypass your preamp, regardless of what you have feeding into it.

Help me out with this...

An active pickup, by definition, requires power to operate because the pickup design itself includes preamplification, correct?

If you provide power, you are powering the preamp. So, how can you "bypass the preamp" and still have an active pickup operate?

If you're saying the battery isn't powering the preamp in an active pickup, what is it that is being powered?

You can "bypass the eq," not boosting or cutting anything, but that's not bypassing the preamp (i.e., passive operation), it's just forgoing additional tone shaping--aka, setting it flat with a switch.

Chasarms · #13 03-16-2011, 10:00 AM

You are correct. Active PUs like many EMGs have powered buffers within the PU. But, you can still wire those into another preamp, which could be bypassed. It completely depends on the overall design of the circuit.

Quote:

Originally Posted by drpepper

Help me out with this...

An active pickup, by definition, requires power to operate because the pickup design itself includes preamplification, correct?

If you provide power, you are powering the preamp. So, how can you "bypass the preamp" and still have an active pickup operate?

If you're saying the battery isn't powering the preamp in an active pickup, what is it that is being powered?

You can "bypass the eq," not boosting or cutting anything, but that's not bypassing the preamp (i.e., passive operation), it's just forgoing additional tone shaping--aka, setting it flat with a switch.

**line6man** · #14 03-16-2011, 10:28 AM

Quote:

Originally Posted by drpepper

Help me out with this...

An active pickup, by definition, requires power to operate because the pickup design itself includes preamplification, correct?

If you provide power, you are powering the preamp. So, how can you "bypass the preamp" and still have an active pickup operate?

If you're saying the battery isn't powering the preamp in an active pickup, what is it that is being powered?

You can "bypass the eq," not boosting or cutting anything, but that's not bypassing the preamp (i.e., passive operation), it's just forgoing additional tone shaping--aka, setting it flat with a switch.

The active/passive switch simply removes the preamp from the signal path. The pickups will always be active, and the preamp will still be drawing current from the battery(s) regardless of whether or not it's in the signal path.
Active/passive switches are not power switches for the active semiconductors in the bass. They are simply true-bypass switches.

And FWIW, A preamp is more than just an EQ, it is also a buffer, sometimes a gain boosting buffer. Setting the EQ flat is not the same as bypassing the preamp. This is especially true when preamps are voiced to color the signal, even when set flat.

drpepper · #15 03-16-2011, 11:41 AM

Quote:

Originally Posted by line6man

The active/passive switch simply removes the preamp from the signal path. The pickups will always be active, and the preamp will still be drawing current from the battery(s) regardless of whether or not it's in the signal path.
Active/passive switches are not power switches for the active semiconductors in the bass. They are simply true-bypass switches.

And FWIW, A preamp is more than just an EQ, it is also a buffer, sometimes a gain boosting buffer. Setting the EQ flat is not the same as bypassing the preamp. This is especially true when preamps are voiced to color the signal, even when set flat.

Okay, let's back up here...

The OP was interested in adding an opb-3 to have push/pull - active/passive volume knob capability on his bass.

It was noted that this would be possible so long as his bass has passive pickups.

You disagreed, saying "Not at all. You can still bypass your preamp, regardless of what you have feeding into it."

Again, to clarify, what you're saying, in this context, is that a bass with active pickups can be set up with a (additional) preamp with push/pull - active/passive volume knob...

That seems rather nonsensical. To what end would this be done, if the the pickups are active?

You seem to be blending two circumstances together and speaking of one preamp. Unless I'm missing something, active pickups are "active" specifically because they have integrated, powered circuitry, including a preamp. That preamp cannot be bypassed and have the pickup remain operational. If it could, it would be a passive pickup. And adding an active/passive switch...err...I can't even follow the logic of what an active/passive switch to a second preamp is supposed to be doing...

And the active/passive switch on my Brute is effectively a "power switch" for the active electronics (the preamp). This is functionally demonstrated by the fact that I can take the battery out of my NTMB and it doesn't affect its passive operation.

EDIT - Ah ha...okay I see - You ARE saying you can add and bypass a second preamp - gotcha

**line6man** · #16 03-16-2011, 11:54 AM

Quote:

Originally Posted by drpepper

Okay, let's back up here...

The OP was interested in adding an opb-3 to have push/pull - active/passive volume knob capability on his bass.

It was noted that this would be possible so long as his bass has passive pickups.

You disagreed, saying "Not at all. You can still bypass your preamp, regardless of what you have feeding into it."

Again, to clarify, what you're saying, in this context, is that a bass with active pickups can be set up with a (additional) preamp with push/pull - active/passive volume knob...

That seems rather nonsensical. To what end would this be done, if the the pickups are active?

Active pickups with a preamp are not as common as active pickups through passive controls, but people do it all the time.
For example, EMG has a line of preamps and things that pair well with their active pickups.

Quote:

Originally Posted by drpepper

Unless I'm missing something, active pickups are "active" specifically because they have integrated, powered circuitry, including a preamp. That preamp cannot be bypassed and have the pickup remain operational. If it could, it would be a passive pickup. And adding an active/passive switch...err...I can't even follow the logic of what an active/passive switch to a second preamp is supposed to be doing...

We're talking about the preamp with the EQ, not the one built into the pickup.
The pickups are always going to be active, the active/passive switch simply removes the "EQ preamp" from the circuit.

Quote:

Originally Posted by drpepper

And the active/passive switch on my Brute is effectively a "power switch" for the active electronics (the preamp). This is functionally demonstrated by the fact that I can take the battery out of my NTMB and it doesn't affect its passive operation.

Um, no it is not. As long as you have a cable plugged into your output jack, the preamp is drawing current from the battery.
In active mode, the signal goes through the preamp, and in passive mode, the signal goes straight to the jack without passing through the preamp, but the preamp is still being powered by the battery.

The fact that you can play in passive mode without a battery is because the preamp is not in the signal path in passive mode.

Here is standard active/passive switching.
As you can see, passive mode simply reroutes the signal from the volume pot(s) to the output jack instead of going through the preamp. The power from the battery is not switched.

mmbongo · #17 03-17-2011, 12:01 PM

Quote:

Originally Posted by line6man

Not at all.
You can still bypass your preamp, regardless of what you have feeding into it.

How do you plan to run an active pickup passively? You have to have a battery just to turn them on.

drpepper · #18 03-17-2011, 12:43 PM

Quote:

Originally Posted by mmbongo

How do you plan to run an active pickup passively? You have to have a battery just to turn them on.

That wasn't making any sense to me either, but he's saying that it is technically possible to add active electronics (such as the opb unit the OP was asking about) to certain active pickups and the active/passive switch would function to bypass the preamp in the opb. The pickups would still be active...

Why someone would want to do this, and the practicality of it are different questions.

I think it's a matter of commonly misunderstood/misused terminology (i.e., "active bass") and technical correctness versus practical correctness and relevance.

Raymeous · #19 03-17-2011, 12:59 PM

Bypassing a preamp with active pickups is very doable, however the OP was asking about passive/active not active with pre/active witout pre.

The results are still very similar, the uncolored sound of the pickups. However with some systems using passive pickups with an active preamp, you can run the bass in strictly passive mode if the battery dies. Pretty handy trick if your battery (batteries) fail during a show.

**line6man** · #20 03-17-2011, 01:19 PM

Quote:

Originally Posted by mmbongo

How do you plan to run an active pickup passively? You have to have a battery just to turn them on.

Reread what I say.
You can still bypass your preamp, regardless of what you have feeding into it.

I never said anything about running active pickups passively.

Seriously, why is this such a difficult concept for everyone?
Active pickups are always active, preamps can be put in, or taken out of the circuit.