i´m getting crazy with aguilar obp3 preamp wiring

lumerino · #1 07-06-2010, 01:02 AM

hi, i´m installing an aguilar obp3 preamp in a ksd 705, with much problems, first i put shield with aluminum foil at all the cavities(just said that it doesn´t eliminate any noise jeje), then i connected all the cables following the wiring diagram on the pots, bass,treble,mid etc, i connected the blend too and the volume with a push pull active /passive pot, all the grounds connected in one point (except the pickups ground those are connected to the blend pot)

well everything went fine(or at least i thought so), but when i connected to the amp , the bass was sounding with the volume turned down, i fixed it resoldering the ground lug in the volume pot, but then i noticed that when i turned down the volume and boost the bass mid and treble with the amp at considerable volume, was a hiss sound responding to the equalizer and still at higher amp volume , sounded that i played in the bass

i soldered all the pots to the ground, checked all the connections, i´m getting crazy i don´t know how to do please help me

thank you

FunkMetalBass · #2 07-06-2010, 08:23 AM

You turned up the treble knob and got a hissing sound?

That's what treble frequencies greater than 3kHz sound like.

lumerino · #3 07-06-2010, 08:36 AM

Quote:

Originally Posted by FunkMetalBass

You turned up the treble knob and got a hissing sound?

That's what treble frequencies greater than 3kHz sound like.

yes but is it normal hear the hissing sound when the volume knob is turned down?

FunkMetalBass · #4 07-06-2010, 08:37 AM

Does the amp hiss when the bass is not even plugged in?

jpTron · #5 07-06-2010, 08:43 AM

I have an OBP-2 and yes that treble pot is hissy as hell

Dirk Diggler · #6 07-06-2010, 08:57 AM

Yes if you boost anymore than halfway up you will get huge hiss along with a very bright sound. That is indeed a common issue with the obp3 and most pre's in my experience.

Another thing, I've never heard of shielding with Aluminum foil, I have always used copper foil tape. The big thing shielding is meant to prevent is 60hz ground hum. How did you attach the foil? And did you ground to the foil at some point?

Good luck,
Dirk

lumerino · #7 07-06-2010, 09:33 AM

Quote:

Originally Posted by FunkMetalBass

Does the amp hiss when the bass is not even plugged in?

no, the amp is quiet

Bass-Adrenaline · #8 07-06-2010, 09:46 AM

Well, hissing is normal when you boost the treble high and aluminum foil really isnt the right way to shield your bass.....

lumerino · #9 07-06-2010, 10:07 AM

Quote:

Originally Posted by Dirk Diggler

Yes if you boost anymore than halfway up you will get huge hiss along with a very bright sound. That is indeed a common issue with the obp3 and most pre's in my experience.

Another thing, I've never heard of shielding with Aluminum foil, I have always used copper foil tape. The big thing shielding is meant to prevent is 60hz ground hum. How did you attach the foil? And did you ground to the foil at some point?

Good luck,
Dirk

One question the issue with the obp3 preamp when i boost any knob is even when the volume is turned down?

i attached the foil all around the cavities, it is an aluminum tape . i red that the aluminum foil is a good for make the faraday cage, the onlye problem is that you can´t solder on it( as the copper foil) i ground to the foil with a screw, i ground only the bridge

thank you

FunkMetalBass · #10 07-06-2010, 10:55 AM

When the volume is turned down, you shouldn't hear anything. Does the hissing go away when you touch any of the knobs, bridge, or strings?

lumerino · #11 07-06-2010, 12:39 PM

Quote:

Originally Posted by FunkMetalBass

When the volume is turned down, you shouldn't hear anything. Does the hissing go away when you touch any of the knobs, bridge, or strings?

no , when i touch the knobs, bridge or strings, the hissing is still there, it´s so weird

rojo412 · #12 07-08-2010, 08:56 AM

Pickups send signal to volume...
Volume goes out to Preamp...
Preamp processed signal and sends to jack.

If there is even a hint of signal, the pre will boost it.

If you wired the pickups to a blend, into the preamp, preamp out to volume, then volume out to jack, it may not happen.

lumerino · #13 07-13-2010, 11:06 AM

Quote:

Originally Posted by rojo412

Pickups send signal to volume...
Volume goes out to Preamp...
Preamp processed signal and sends to jack.

If there is even a hint of signal, the pre will boost it.

If you wired the pickups to a blend, into the preamp, preamp out to volume, then volume out to jack, it may not happen.

thank you very much, please help me with this
i´m using this configuration for the active passive bass http://aguilaramp.com/pdf/support_wiring_obp3.pdf

as you can see is like a bridge between the balance and the volume and the goes to the preamp input(the blue wire)

i´m thinking about using this other configuration

http://bartolini.net/instructions/el...s/tct/ntct.pdf

is a bartolini preamp but i think is the same principle , here the balance goes directly to the preamp input, and the preamp output goes to the volume and the to the jack, (just as you said)

what do you think could it works?

thank you

lumerino · #14 07-15-2010, 11:17 AM

Job done, the aggie in the ksd705 is working without noise, i had to shield all the cavities with cooper foil, and connect all the grounds to one point and then to the cavity floor, no noise even when i don´t touching the strings with all controls flat, i turn down the volume and i don´t hear noise from my pickups, the only thing that i can´t fix is that the preamp when the volume down still has a hiss from the equa controls, the hiss responds to the equa frequencies, but i don´t know, maybe my pickups are the problem , i checked again again and all is connected correctly,

thanks for all your help,