Aguilar OBP-1 is not transparent

[Clemouze]

Salut,

I read on several thread that the Aguilar OBP-1 is transparent, is not coulouring the tone, when set flat is sounding like if it's not here, etc..

Well I don't claim that all the Aguilar OBP-1 on earth are NOT transparent, because we don't know, BUT mine is clearly not transparent !

Used with the geddy lee mex jazz pickup, seymour duncan SMB-4D or Aguilar AG4M, it DOES change the tone when set flat. It is run in 9V if it has an influence, who knows ?
The output seems even a little lower than in passive mode, bypassing the OBP. Maybe it's this slight scoop in the mids that gives this impression ?
The tone seems less punchy, obviously with less mids, and more ringing treble.

In comparison it is not as pleasant flat than the EBMM 3 band EQ.
I don't like it flat, I prefer don't use it.


That's all

Thanks

 

[ctmullins]

You may already be aware, but the OBP-1 is boost-only, so “flat” would have the knobs at their minimum position, not in the middle.

 

[Clemouze]

You may already be aware, but the OBP-1 is boost-only, so “flat” would have the knobs at their minimum position, not in the middle.

Yes for sure
With the stacked knob version of this preamp , the bass control is soooo hard to use. It seems to be flat or max , like a linear taper type of control

 

[Clark Dark]

As mentioned the OBP-1 is a boost only preamp. What I'm curious about is when I had mine it was an 18 volt pre not a 9 volt pre. According to the Aguilar website it still demands two 9 volt batteries. That might solve your problem.
Here is a diagram to add a passive tone control to the circuit
http://www.aguilaramp.com/wp-content/uploads/wiring-diagram-obp-1.pdf

 

[Clemouze]

Thank you but I already have a passive tone control

From my understanding the 9V use was OK , on the Aguilar site it le written 18 OR 9V

Also when I used it with a MM style pickup on parallel, no issue but when this pickup was in series the preamp overdrived in a bad way when bass boost was activated ( Not enough headroom

I think the 9V vs 18V is only an headroom thing

 

[RobbieK]

I'm pretty sure the OBP1 is a basic fet pre with a fender-style tone-stack for treble and bass. So, yeah, you'll have a mid scoop with both controls at halfway. Simple fet preamps (the Sadowsky pre is similar I believe) also vary a bit in output because fets vary in spec, even within the same batch. There's also the issue of variation in the sweep of the audio taper treble and bass pots. Also FWIW, I'd be surprised if switching to 18V gave you more headroom. Simple common-source fet circuits don't bias the same way as opamp circuits.

Having said that, I really like these type of preamps, and I have designed many similar ones over the years for my different basses.

If you want a "transparent" 2-band pre, then I'd recommend the OBP2. I'm pretty sure this is an opamp design with baxandall tone controls. This should give you a flat response with the controls set in the middle. Plus an opamp circuit is easy to design with unity gain. IOW, no overall cut or boost between active and passive.

The only other factor with "transparency" is if the load on the pickups changes by much between active and passive, then the two settings will sound different.

 

[Clemouze]

Thank toi for these explanations
Well it is the load difference that I hear

I chose the OBP-1 over the OBP-2 to have a more coloured tone so it's OK

 

[rolleharris]

Why install a preamp if you dont want it to change the sound of the bass? Isnt that the whole point? To be able to change the sound? If you want transparent then why just not run the bass passive? I am not being rude i am just asking

 

[Northfear]

Why install a preamp if you dont want it to change the sound of the bass? Isnt that the whole point? To be able to change the sound? If you want transparent then why just not run the bass passive? I am not being rude i am just asking

Preamp acts as a signal buffer too.
And a lot of players prefer to use it only in certain situations (boosting mids while soloing for example) and leaving it flat for the rest of the time.

 

[Clemouze]

Why install a preamp if you dont want it to change the sound of the bass? Isnt that the whole point? To be able to change the sound? If you want transparent then why just not run the bass passive? I am not being rude i am just asking

I installed the OBP-1 to have a coloured tone with the MM style pickup and a passive switch to keep the passive tone of the jazz pickups
So yes I use the preamp as a tone coloured part of the sound

 

[ctmullins]

In my experience, the tone doesn’t change very much at all when the OBP-1 is switched in. It just sounds bigger somehow.

 

[Clemouze]

In my experience, the tone doesn’t change very much at all when the OBP-1 is switched in. It just sounds bigger somehow.

Ok strange..
With the aguilar MM pickup it sounds thinner.. with the stock jazz pickup it just sounds brighter, like a transparent buffer

 

[ctmullins]

If it sounds thinner, I’m inclined to believe that either the unit is faulty or it is miswired.

I’ve had several of these in several basses, and in every case the tone got fatter and deeper in the lows, and brighter in the highs (but without changing the basic tone). I find it addictive, honestly. I usually have passive mode available to me for emergencies, but that active tone is so intoxicating that I always have it on.

 

[Clemouze]

Update , I still confirme that when set flat, full control at 0, the tone is still affected.

I hear less low mids than in passive mode.
Also the volume is a little bit lower.
Maybe because it is only running on 9V and some distorsion is already happening in the preamp ?

I will make samples recording

 

[Clemouze]

Well to be honest who on earth wants to use a preamp set to flat ? To act like a buffer ?
Indeed the lack of transparancy is not an issue for me, just an observation !