Aguilar obp-1 preamp - other wiring options?

etherealme · #1 09-24-2012, 07:40 PM

So, in this whole process of modifying my P/J bass, I thought I might want to do something different than the typical Vol, Vol/blend & 2 tone controls.

Essentially, are there other options when wiring up the Aguilar OBP-1?

I am wondering if someone knew off-hand where I could procure or would mind working out a diagram for the aquilar obp-1 preamp with just an input jack and a blend control or a three-way switch. Is that do-able? I really don't need to boost or cut either tone, but would prefer it set center (no boost or cut.) The switch would be ideal. Neck pup/both pups/bridge pup = position 1/2/3

If that was the set-up, what would the tone default to with no pots? Would they boost at the full 18v at 40Hz & 4kHz? How would that work?

I guess my other option is to hook the preamp up in a stomp box. One aspect about this option I prefer is not burning up batteries. I can't find a diagram for that either. There are a couple of TB threads where someone has done this, but no diagram within.

Thanks a bunch! Did a lot of searching on the topic before posting.

joelb79 · #2 09-24-2012, 07:50 PM

The OBP 1 is boost only and has no center detent. When the knobs are all the way down it is not doing anything. When they are up at all it is boosting the sound. It doesnt have any wiring options itself, it is simply bass boost and treble boost. If you were to remove the knobs then you would be doing nothing with the preamp and there would be no point to having it in the first place. Everything you do on the other side is standard passive potentiometers, so yes you can have it be blend and volume, volume-volume, vol-vol+tone or no volume and just a blend and jack.

But the preamp can only be wired one way, with the included bass and treble pots. I was trying to find a stacked knob for that preamp at one time but it was a no-go.

So essentially you are saying you want to have center spots on your existing knobs so you know where half-boosted is and leave it that way then remove the volume knob? I don't get the advantage to doing that, why not just press the mid scope knob on your amp instead?

line6man · #3 09-24-2012, 07:54 PM

Quote:

Originally Posted by joelb79

The OBP 1 is boost only and has no center detent. When the knobs are all the way down it is not doing anything. When they are up at all it is boosting the sound. It doesnt have any wiring options itself, it is simply bass boost and treble boost. Everything you do on the other side is standard passive potentiometers, so yes you can have it be blend and volume, volume-volume, vol-vol+tone or, what have you.

But the preamp can only be wired one way, with the included bass and treble pots. I was trying to find a stacked knob for that preamp at one time but it was a no-go.

EMG sells a concentric A25k/A25k pot that works for the OBP-1. I was told by Aguilar that you do indeed use the audio taper, as opposed to the more traditional linear taper used for equalizers on boost/cut preamps.

To the OP, what would be the point of wiring an OBP-1 with a fixed flat response? Wouldn't you rather put in a simple buffer with no added circuitry for equalization? This would give you all of the advantages of a buffered system, without anything extra to degrade the signal or cost a ton of money.

etherealme · #4 09-24-2012, 08:44 PM

Ok. I'm new to this, people. Try and cut me some slack as I'm just trying to learn. Wasn't that the point of this site?

Doesn't using any piece of circuitry (even as a buffer) add color to the sound? I'm open to any viewpoint, but in my experience preamps are "doing something" even when there is no equalization being tweaked. And by "doing something" I don't just mean "degrading the sound with their circuitry." From what I can hear, with no adjustments to tone pots the Seymour-Duncan STC preamps certainly are adding a distinctive flavor to the mix. Is there something I'm missing about the Aguilar?

In addition, I am mentioning the choice to use a 3 way switch in place of a blend..and I suppose if I'm totally off-base here, throw in the treble/bass tone pot. So... no volume resistance, input jack, switch, stacked tone perhaps???

Any assistance/insight is greatly appreciated. Thanks!

joelb79 · #5 09-26-2012, 03:41 AM

Quote:

Originally Posted by etherealme

Ok. I'm new to this, people. Try and cut me some slack as I'm just trying to learn. Wasn't that the point of this site?

sure thing, just wanted to see what it was you are trying to accomplish and what your thinking was behind it.

Quote:

Originally Posted by etherealme

Doesn't using any piece of circuitry (even as a buffer) add color to the sound?

Not necessarily.

Quote:

Originally Posted by etherealme

I'm open to any viewpoint, but in my experience preamps are "doing something" even when there is no equalization being tweaked. And by "doing something" I don't just mean "degrading the sound with their circuitry." From what I can hear, with no adjustments to tone pots the Seymour-Duncan STC preamps certainly are adding a distinctive flavor to the mix. Is there something I'm missing about the Aguilar?

The complexities of all circuitry will be different. IME, JFET preamps such as the Aguilar OBP-1 and Sadowsky do a great deal less to the signal when disabled (battery off). It is almost as if there is no change to the signal. this is because with the knobs down, the preamp is turned all the way down or off essentially. Once the knob is brought up the signal is boosted by the FET in addition to the original bass signal.

The Duncan preamp most likely was Opamp based and as such added its own sound via the opamp even when flat because all signal had to pass through the opamp before the jack.

It gets even more confusing when the preamp does both like an East.

Quote:

Originally Posted by etherealme

In addition, I am mentioning the choice to use a 3 way switch in place of a blend..and I suppose if I'm totally off-base here, throw in the treble/bass tone pot. So... no volume resistance, input jack, switch, stacked tone perhaps???

Any assistance/insight is greatly appreciated. Thanks!

This is not going to change how the OBP-1 is wired up. Jack stays the same, battery stays the same, obp-1 preamp knobs stay the same, you would remove your volume knobs and replace it with a switch, most likely a 3-way switch, wired like a telecaster on the 3-way. This will take the potentiometer load off of you pickup making it full open/as bright as possible. I'd say give it a shot to see if that kind of tone is what you want. To do this, the blue wire will be connected to the switch hot, and the grounds from your pickup will need to be relocated to a ground point, like the jack (since you will be removing the pot they are grounded to).

The switch would be wired like so; the wire going to the volume pot is where you tap on your blue wire.

SGD Lutherie · #6 09-26-2012, 07:45 AM

Quote:

Originally Posted by etherealme

From what I can hear, with no adjustments to tone pots the Seymour-Duncan STC preamps certainly are adding a distinctive flavor to the mix. Is there something I'm missing about the Aguilar?

Preamps present a high impedance load to the pickups. This isolates, or buffers the pickup from the cable capacitance and the load of your control pots.

This usually yields a brighter tone with a tighter low end. This is the true tone of the pickups. People are used to the warming that the cable and stuff adds, which is why people like passive basses.

If you want just buffering with no tone controls, there are a number f buffers on the market. One benefit is you are going through less circuitry, and they are often quieter.

The Creation Labs Redeemer is a nice clean buffer:

http://www.creationaudiolabs.com/redeemer

It also passes signal if you battery goes dead.

DWBass · #7 09-26-2012, 09:14 AM

Are you just looking to boost the signal? A Bart TC3 will do that for you. The battery will last forever! I'm not sure exactly what you're seeking though!!

line6man · #8 09-26-2012, 12:05 PM

Quote:

Originally Posted by etherealme

Doesn't using any piece of circuitry (even as a buffer) add color to the sound? I'm open to any viewpoint, but in my experience preamps are "doing something" even when there is no equalization being tweaked. And by "doing something" I don't just mean "degrading the sound with their circuitry." From what I can hear, with no adjustments to tone pots the Seymour-Duncan STC preamps certainly are adding a distinctive flavor to the mix. Is there something I'm missing about the Aguilar?

Technically, anything you do has some effect, but there is no inherent difference, at least in theory.

I explained this once, here:
http://www.unofficialwarmoth.com/ind...8272#msg288272

Fabass73 · #9 10-01-2012, 02:39 AM

Here is a diagram of a different option to wire the OBP-1. In this case, my jazz bass.
This way, you keep the passive filter "into the loop" at all time, passive and active position, meaning that even when the preamp is engaged, the passive filter is still working, this way your basic sound is not affected when the preamp is engaged with the switch, you just get a boost of bass and treble for which you can control the amount with the stacked pot. in any case, you'll have to route a cavity on your bass to fit 2 x 9V batteries + the preamp, there is no way it'll fit in the original cavity under the pick guard.

etherealme · #10 01-13-2013, 01:44 PM

Everything I needed to know: Active preamp, no EQ

etherealme · #11 01-13-2013, 02:30 PM

Moving forward with somewhat more of a workable understanding of buffers, I'm back to being curious if the same instructions could be followed when using the aguilar as a basic jfet buffer by just ignoring the tone pots in the diagram? The quote below is referring to a standard V/V jazz wiring with no tone control.) My preoccupation with the aguilar comes from the fact that I already have the OBP-1 but know I'm not going to use the eq boost knobs. If the OBP-1 is not ideal for this usage I'll pursue wiring up another homemade buffer, but am inquiring since I already have the preamp. In doing so, are the violet and orange leads for bass boost just soldered together? What about the treble control leads?

Thanks!

Quote:

Originally Posted by line6man

When there is only one volume pot, the wiper terminal is wired to vary output impedance. You can't do that with two volumes, however, because then you don't get independent control, so the wipers must vary input impedance against the pickups.

All you have to do is take a standard Jazz bass wiring diagram and omit the tone pot.
http://www.seymourduncan.com/support...=std_jazz_bass