Im replaced the pre-amp in an ibanez BTB with an Aguilar obp-3. Everything sounds great until i roll the mids out of middle position. If i boost the mids i get a loud hiss (not a hum). If i cut the mids i get a hiss but not quit as loud. Ive gone over the wiring and soldering at least 5 times. I even ordered new tone pots from ibanez just to make sure i didnt fry them but im still getting the hiss. Any thoughts on what could be causing this? I contacted Aguilar but they were not much help.
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ObP-3 hiss
- Thread starter Shapoota
- Start date
What about the pots that came with the OBP-3? Why didn't you use those? The Ibanez pots are likely your problem.
Well the Aguilar pots have a bigger threaded post wich is 3/8, i think, and the holes are 5/16. Regardless I thought the same thing so I tried the Aguilar pots and still got the same hiss. 
thank you though.
thank you though.
i've got a Modulus Q5 bass and I replaced the preamp with an OBP-3. I have the same hiss problem. It's very apparent thru my GK heads when I dial up the Boost. It's also very prominent when I play thru a Baer ML112 cab which really pushes the high mids.
Another Modulus owner has reported the same results which went away when he replaced the preamp.
I came here hoping for a solution other than replacing the preamp!
Another Modulus owner has reported the same results which went away when he replaced the preamp.
I came here hoping for a solution other than replacing the preamp!
I have an OBP-3 in one of my basses and have the exact same problem. When I boost or cut mids I get a lot of hiss.
I've read some more posts about the OBP-3 preamp since posting this. It seems that a bad pot can cause something like this too. And that the stock pots that come with the older OBP-3 are not high quality.
Aguilar sells replacement pots on their site.
I've had problems with scratchy pots anyway so I'm going to go ahead and replace the volume/blend/EQ pots to see if this doesn't correct the problem.
Seems like something to try before replacing the entire preamp.
Aguilar sells replacement pots on their site.
I've had problems with scratchy pots anyway so I'm going to go ahead and replace the volume/blend/EQ pots to see if this doesn't correct the problem.
Seems like something to try before replacing the entire preamp.
Gotcha, thanks for the info. I've been thinking about trying the Nordstrand pre in this bass anyways but I may reinstall the OBP-3 into another bass with different pots.
I spoke to Marco from Aguilar support about the OBP-3. He emailed me this information
==
Most OBP problems are caused by wiring problems. Here are some common problems that may apply in your situation:
1. Little bitty wire strands touching the wrong thing. These can be as thin as human hair, so you have to look really close.
2. Wires that have broken, but the insulation makes it look like they are still connected. A gentle tug usually makes them come loose.
3. Broken pots. Very common. There must be 50 ways to break your potentiometer.
4. Preamp wiring errors: The pickups or the output jack are likely causes. Try soldering the black wire from the battery directly to ground instead of to the jack. This will leave the OBP-3 powered on all the time, so it's not good for a final installation, but this eliminates the output jack as a power problem.
5. Pickup problems. Are the pickups making sound? You can bypass the preamp by removing the blue and green wire, then soldering or clipping a wire from the spot where the blue wire was soldered to the spot where the green wire was soldered.
You can remove the OBP from the circuit by removing the blue and green wires, then wiring the center terminal of the volume pot directly to the jack. This bypasses the OBP, and will allow you to troubleshoot a simpler system (pickups, blend, and volume only).
One last thing: if the blue and green wires are close together, sometimes this causes "funny" things to happen. This is because the blue wire is the input and the green wire is the output, and under the right conditions this can cause coupling from output to input, yielding strange behavior. So I recommend moving the blue and green wires as far apart as is convenient (you don't have to go nuts here - but make sure you don't twist the two wires together!)
These preamps are pretty hard to break, but it can be done.
Radio problems can be tricky. Here's a list of things to check/try:
1. If the input jack is dirty or not making good contact when connecting the batteries.
2. Are the pot bodies grounded? If no, then ground them, if yes, then un-ground them.
3. Are you using extreme knob setting? Does changing the knob settings change the problem?
4. Is the cavity shielded? Is the shield grounded?
5. Do you have a solid connection to the strings of the bass?
6. Dirty or contaminated connections can sometimes cause a connection to behave like a diode. And in the radio world a diode is called an "AM detector"!
One last thing: if the blue and green wires are close together, sometimes this causes "funny" things to happen. This is because the blue wire is the input and the green wire is the output, and under the right conditions this can cause coupling from output to input, yielding strange behavior. So I recommend moving the blue and green wires as far apart as is convenient (you don't have to go nuts here - but make sure you don't twist the two wires together!)
You can isolate the OBP-3 from the pickups by turning the volume control of the bass off. The volume control is in front of the OBP-3, so when you turn the volume off, the pickups are not inputting any signal into the OBP-3, but the OBP-3 is still connected to the output jack. If the buzz goes away, then what is happening is the OBP-3 is boosting a signal that is coming from the pickups.
==
I'm going to run thru this stuff and see if anything in there helps.
==
Most OBP problems are caused by wiring problems. Here are some common problems that may apply in your situation:
1. Little bitty wire strands touching the wrong thing. These can be as thin as human hair, so you have to look really close.
2. Wires that have broken, but the insulation makes it look like they are still connected. A gentle tug usually makes them come loose.
3. Broken pots. Very common. There must be 50 ways to break your potentiometer.
4. Preamp wiring errors: The pickups or the output jack are likely causes. Try soldering the black wire from the battery directly to ground instead of to the jack. This will leave the OBP-3 powered on all the time, so it's not good for a final installation, but this eliminates the output jack as a power problem.
5. Pickup problems. Are the pickups making sound? You can bypass the preamp by removing the blue and green wire, then soldering or clipping a wire from the spot where the blue wire was soldered to the spot where the green wire was soldered.
You can remove the OBP from the circuit by removing the blue and green wires, then wiring the center terminal of the volume pot directly to the jack. This bypasses the OBP, and will allow you to troubleshoot a simpler system (pickups, blend, and volume only).
One last thing: if the blue and green wires are close together, sometimes this causes "funny" things to happen. This is because the blue wire is the input and the green wire is the output, and under the right conditions this can cause coupling from output to input, yielding strange behavior. So I recommend moving the blue and green wires as far apart as is convenient (you don't have to go nuts here - but make sure you don't twist the two wires together!)
These preamps are pretty hard to break, but it can be done.
Radio problems can be tricky. Here's a list of things to check/try:
1. If the input jack is dirty or not making good contact when connecting the batteries.
2. Are the pot bodies grounded? If no, then ground them, if yes, then un-ground them.
3. Are you using extreme knob setting? Does changing the knob settings change the problem?
4. Is the cavity shielded? Is the shield grounded?
5. Do you have a solid connection to the strings of the bass?
6. Dirty or contaminated connections can sometimes cause a connection to behave like a diode. And in the radio world a diode is called an "AM detector"!
One last thing: if the blue and green wires are close together, sometimes this causes "funny" things to happen. This is because the blue wire is the input and the green wire is the output, and under the right conditions this can cause coupling from output to input, yielding strange behavior. So I recommend moving the blue and green wires as far apart as is convenient (you don't have to go nuts here - but make sure you don't twist the two wires together!)
You can isolate the OBP-3 from the pickups by turning the volume control of the bass off. The volume control is in front of the OBP-3, so when you turn the volume off, the pickups are not inputting any signal into the OBP-3, but the OBP-3 is still connected to the output jack. If the buzz goes away, then what is happening is the OBP-3 is boosting a signal that is coming from the pickups.
==
I'm going to run thru this stuff and see if anything in there helps.
This one troubleshooting suggestion alone was very helpful. It helped me determine if the hiss was coming from my pickups or the preamp.
So has anyone come to an end? I've tried to change every pot but no improvements at all. Only when i plug alkaline batteries by the way, with electro-harmonix zync/carbon 9v heavy duty my preamp sounds just fine but i don't want to use a specific (rare) kind of battery.
