Aguilar OBP-3 Scheme Question

lmbalcao · #1 09-23-2009, 07:04 AM

Hi!

I'm planning on making a custom 6 string bass and i'm facing some problems regarding the preamp scheme. I dont know if it's an important issue, but the OBP will be used with 2 Nordstrand pickups (Fat Stacks or Big Singles).

I saw this one in another bass player blog (http://mpu6stingfoderaimp.blogspot.com/) and had some really good changes, but i want (if possible) something a bit different..

Would be possible to add a switch to use the preamp in 9V or 18v mode?

It's possible to stack the added passive tone pot with the blend pot?

The mid switch can be stacked with the mid pot using a push/pull pot?

I would like to make these changes to avoid having more pots and switches..

Any help will be appreciated!

Thanks in advance!

Regards,
Luis

DriesG · #2 09-23-2009, 07:12 AM

The mid switch can be push-pull (I've got it on my Cort A4). Probably, you could place a simple switch between the two 9V batterys. About the stacked passive tone knob: don't really know, but it should be possible.
Sounds like a nice bass you're building!

**line6man** · #3 09-23-2009, 07:20 AM

Why do you want a 9V/18V switch? That sounds utterly pointless to want to run it at 9V when 18V is available, unless maybe you were trying to save battery life or something.

In either case, you can use a series/parallel switch for the batteries. Series is 18V, parallel is 9V at twice the battery life.

Stacking the blend and passive tone would require a triple ganged dual concentric pot.
MEC may sell one, but that's a tough pot to find.

Yes, you use a push/pull pot on the Mid control to select the frequency.

Bardley · #4 09-23-2009, 07:29 AM

Quote:

Originally Posted by line6man

Why do you want a 9V/18V switch? That sounds utterly pointless to want to run it at 9V when 18V is available, unless maybe you were trying to save battery life or something.

In either case, you can use a series/parallel switch for the batteries. Series is 18V, parallel is 9V at twice the battery life.

Stacking the blend and passive tone would require a triple ganged dual concentric pot.
MEC may sell one, but that's a tough pot to find.

Yes, you use a push/pull pot on the Mid control to select the frequency.

^^ +1 to all of this

I don't see the point in the 9v / 18v switch. I would be near impossible to get the tone stacked with a blend. You may have better luck stacking it with the volume pot.

lmbalcao · #5 09-23-2009, 07:51 AM

I saw in some other forums that the preamp in 18v sometimes sends a very hot signal, the ideia was to use it in 18v when possible and reduce it to 9v when the signal is too strong.

Regards,
Luís

**line6man** · #6 09-23-2009, 07:58 AM

Quote:

Originally Posted by lmbalcao

I saw in some other forums that the preamp in 18v sometimes sends a very hot signal, the ideia was to use it in 18v when possible and reduce it to 9v when the signal is too strong.

Regards,
Luís

The difference between 9V and 18V *should* have no affect on the output level or tone. It's simply a matter of headroom.
I could be wrong though.

If the signal is too hot, just turn down the gain on whatever you have the bass plugged into.

lmbalcao · #7 09-23-2009, 08:08 AM

Oh, in that case the 18v switch is useless.

Thanks for the correction.

Regards,
Luís

lmbalcao · #8 10-22-2009, 03:21 PM

Thanks for all the help!

I have some more questions.

Are the connections between the OBP and the Nordstrand correct?

Regarding the previous answers i'm going with Treble, Push-Pull Mid, Bass, Blend, stacked Volume and Tone pots.

I've been googling and found some information regarding the pots to use, but since i'm no expert in electronics, could you guys tell me if these pots are the right ones?

Trebble and Bass: 50k, Linear Taper, Center Detent
Mid: 50k, Linear Taper, Center Detent, DPDT
Blend: 250k, Dual Ganged, Linear Taper, Center Detent

Regarding Volume + Tone what stacked pot should i use? It's possible to have a center detent on the tone pot? Should it be Linear or Audio Taper?

Is it something like this? http://www.allparts.uk.com/online-sh...c-p-4072.html#

Many thanks!

Regards,
Luis

Skywalker83 · #9 10-22-2009, 03:26 PM

The blog from the original post is mine....i should really update it...*sigh*

**line6man** · #10 10-22-2009, 04:39 PM

Quote:

Originally Posted by Skywalker83

The blog from the original post is mine....i should really update it...*sigh*

...And I'm the one who modded that picture.

**line6man** · #11 10-22-2009, 04:42 PM

Quote:

Originally Posted by lmbalcao

Thanks for all the help!

I have some more questions.

Are the connections between the OBP and the Nordstrand correct?

Regarding the previous answers i'm going with Treble, Push-Pull Mid, Bass, Blend, stacked Volume and Tone pots.

I've been googling and found some information regarding the pots to use, but since i'm no expert in electronics, could you guys tell me if these pots are the right ones?

Trebble and Bass: 50k, Linear Taper, Center Detent
Mid: 50k, Linear Taper, Center Detent, DPDT
Blend: 250k, Dual Ganged, Linear Taper, Center Detent

Regarding Volume + Tone what stacked pot should i use? It's possible to have a center detent on the tone pot? Should it be Linear or Audio Taper?

Is it something like this? http://www.allparts.uk.com/online-sh...c-p-4072.html#

Many thanks!

Regards,
Luis

That pot looks to be correct.

Why would you want a center detent on a passive tone?
A passive tone control only cuts, so there is no "flat" setting in the middle.

I feel that linear tapers are better for volume, but stick with audio for the tone.
You probably aren't going to find a linear/audio stack, so just stick with the audio/audio.

lmbalcao · #12 10-23-2009, 02:28 AM

Hope you don't mind using your scheme ideia

Well, thanks once again for the help.

Luis

lmbalcao · #13 01-08-2010, 04:02 AM

Hi once again..

The bass is finished (i'll post some photos of the final job asap), but i have some problems regarding the electronics.

It was all connected using the altered scheme made by line6man posted above and the only change made was in the tone pot that was affecting the active mode aswell, so the luthier changed some wires and now it only has any effect in passive mode.

The Bass has a good tone but a very low output. My musicman has x2 or x3 more output. This one doesn't even clip my amp. To get any high volume i need to have the gain at 7 and volume above 5 (both values go from 1 to 10 and both basses with maxed volume and all eq's flat).. With my musicman the values just need to be below 5 on both amp settings.

Other situation is that the passive volume e much lower than the active volume.

Are these 2 situations normal? What can i do to repair them?

I can post photos of the wiring if needed.

Thanks in advance.
Luís