Aguilar OBP-3 - wired as 4-band?

FunkMetalBass · #1 03-09-2010, 08:07 AM

I found some wiring diagrams online with alternative methods for wiring the mid control, and I got to thinking - could it be wired to a concentric pot using the top shaft as an 800k boost/cut and the bottom as a 400k boost/cut?

**line6man** · #2 03-09-2010, 08:12 AM

I'm 99% sure that the preamp is designed with only 3 bands.
The frequencies may be selectable, but it's the same circuit used for the mid control.

Maybe you should look into a 4 band EQ like the Audere?

FunkMetalBass · #3 03-09-2010, 09:56 AM

Quote:

Originally Posted by line6man

I'm 99% sure that the preamp is designed with only 3 bands.
The frequencies may be selectable, but it's the same circuit used for the mid control.

Maybe you should look into a 4 band EQ like the Audere?

So theoretically, I could not split the signal, then re-combine it?

I'm not too interested in a 4-band EQ, nor do I want to spend the money on one, but electronics are starting to intrigue me more and more and I was just curious about potential mods.

Carey · #4 03-09-2010, 10:17 AM

This is not possible.

There are four wires that allow you to connect external capacitors to adjust the midrange frequency, one capacitor per pair. When you connect them to a switch you are accessing two different sets of default internal capacitors and putting them in the circuit which is connected to the three wires that connect to the pot.

There are only three wires that connect to the pot. So you can't add a second pot.

You can add extra capacitors to the two pairs of wires that will give you alternative frequencies by adding or reducing the amount of capacitance from the internal caps.

Make sense?

FunkMetalBass · #5 03-09-2010, 10:31 AM

Yes, that makes total sense. Thanks, Carey - I was always a bit unclear about how preamp circuitry worked. This helped shine some light on it.

(btw, just threw one of your pickups in my Jazz along with an OBP-3 and I almost cried - it sounded so beautiful)

JackANSI · #6 03-10-2010, 02:56 PM

Quote:

Originally Posted by Carey

This is not possible.

There are four wires that allow you to connect external capacitors to adjust the midrange frequency, one capacitor per pair. When you connect them to a switch you are accessing two different sets of default internal capacitors and putting them in the circuit which is connected to the three wires that connect to the pot.

There are only three wires that connect to the pot. So you can't add a second pot.

You can add extra capacitors to the two pairs of wires that will give you alternative frequencies by adding or reducing the amount of capacitance from the internal caps.

Make sense?

Actually, look at #8 on the last page of the wiring diagram..

http://www.aguilaramp.com/pdf/support_wiring_obp3.pdf

Thats still not what the OP wants, but probably the source of confusion.

FunkMetalBass · #7 03-11-2010, 07:16 AM

Quote:

Originally Posted by JackANSI

Actually, look at #8 on the last page of the wiring diagram..

http://www.aguilaramp.com/pdf/support_wiring_obp3.pdf

Thats still not what the OP wants, but probably the source of confusion.

That's exactly what I was looking at when I had the idea.

I like the idea of a variable mid selector instead of the standard 400k/800k, so I'll be wiring it up like that from now on.

jesterbass · #8 02-20-2012, 07:31 PM

Quote:

Originally Posted by FunkMetalBass

That's exactly what I was looking at when I had the idea.

I like the idea of a variable mid selector instead of the standard 400k/800k, so I'll be wiring it up like that from now on.

Is this special double pot hard to find? Any sources?

tylerwylie · #9 02-21-2012, 05:00 AM

Quote:

Originally Posted by FunkMetalBass

That's exactly what I was looking at when I had the idea.

I like the idea of a variable mid selector instead of the standard 400k/800k, so I'll be wiring it up like that from now on.

400k? Or Hz...

FunkMetalBass · #10 02-21-2012, 07:06 AM

Quote:

Originally Posted by jesterbass

Is this special double pot hard to find? Any sources?

I've only ever found two sources. MEC used to make one, and the guys at Potentiometer.com will make one. I haven't found them for less than ~$100 USD each, though.

Quote:

Originally Posted by tylerwylie

400k? Or Hz...

Wow, yeah, it should have been 400Hz/800Hz (do I get a free pass since it took almost 2 years for somebody to notice?). All the talk about pots meant that I probably just had k's on the brain.

SGD Lutherie · #11 02-21-2012, 07:26 AM

Quote:

Originally Posted by FunkMetalBass

That's exactly what I was looking at when I had the idea.

I like the idea of a variable mid selector instead of the standard 400k/800k, so I'll be wiring it up like that from now on.

That switch is selecting different caps in the preamp. You can't just put a pot on there to sweep the mids. The 1M pull down resistors are to stop the caps from popping.

The mid circuit has to be designed for that, and they generally use a dual ganged pot.

mmbongo · #12 02-21-2012, 08:38 AM

Quote:

Originally Posted by SGD Lutherie

That switch is selecting different caps in the preamp. You can't just put a pot on there to sweep the mids. The 1M pull down resistors are to stop the caps from popping.

The mid circuit has to be designed for that, and they generally use a dual ganged pot.

The last diagram shows a variable mid pot which varies between 400 and 800hz.

SGD Lutherie · #13 02-21-2012, 08:57 AM

Quote:

Originally Posted by mmbongo

The last diagram shows a variable mid pot which varies between 400 and 800hz.

Oh that's right... it does.... I even have this diagram in my notebook... nevermind then!

ddnidd1 · #14 02-21-2012, 12:20 PM

When I set up one of my OBP-3's for sweepable mids, the pot was very difficult to locate. And when I did find a useable pot, the sweepable mids were essentially useless so I converted back to the switched option.

bpa11 · #15 02-23-2012, 02:05 PM

Quote:

Originally Posted by ddnidd1

When I set up one of my OBP-3's for sweepable mids, the pot was very difficult to locate. And when I did find a useable pot, the sweepable mids were essentially useless so I converted back to the switched option.

I'm seriously considering an OBP-3 and your feedback on the sweepable mids is very helpful. I think I prefer to go with the switched option, if for anything else to keep usability straightforward.

My question is do you (or anyone else using the OBP-3 with the switched option) find that 400Hz & 800Hz are sufficient frequencies to center the mid control on, or did you use one of the alternative wiring options to bring the 400Hz down to something else?

I'm just a little concerned about the gap between 40Hz for the bass control and 400Hz.

PilbaraBass · #16 02-23-2012, 02:22 PM

If you want to understand how different frequencies sound, play around with a graphic EQ first...

Set your bass flat (or passive tone control wide open) - connect a graphic EQ - then move the sliders around individually to hear how the different bands and peaks affect your tone.

Then you will have a much better idea of what is required on your bass.

bpa11 · #17 02-23-2012, 03:45 PM

Thanks for the graphic eq suggestion. I was simply wondering if any OBP-3 owners found the gap between 40Hz and 400Hz to be a bit much.

ddnidd1 · #18 02-28-2012, 10:18 AM

The 400 and 800 hz are very useful frequencies. However, its a matter of personal preference if they're useful for you. The graphic EQ suggestion would help you find what works best for you.

FunkMetalBass · #19 02-28-2012, 02:03 PM

Quote:

Originally Posted by bpa11

I'm seriously considering an OBP-3 and your feedback on the sweepable mids is very helpful. I think I prefer to go with the switched option, if for anything else to keep usability straightforward.

My question is do you (or anyone else using the OBP-3 with the switched option) find that 400Hz & 800Hz are sufficient frequencies to center the mid control on, or did you use one of the alternative wiring options to bring the 400Hz down to something else?

I'm just a little concerned about the gap between 40Hz for the bass control and 400Hz.

That gap in frequencies is actually quite normal (even a little small). I find that using 400 Hz means I have to dial back the 40 Hz bass control - it's a bit boomy otherwise.

I really like the 650 Hz frequency for the mids, but found that the ability to switch between 400 Hz and 800 Hz was ultimately more important to me.

I also have to agree that sweepable, mids was underwhelming. Making my own pot (that broke shortly after I finished it) was a fruitless endeavor, IMO.