Passive Tone Control bypass for Ibanez SRFF805

[Big Benner]

Hi all,

Does anyone know how to bypass the Passive Tone Control on the Ibanez SRFF805?

"Bartolini BH1 Pickups with custom Ibanez preamp" = the preamp is an Ibanez, not Bartolini.

On other basses I use the Passive sound and set up an Active solo tone (mids 3/4 of the way up with a 1/4 bass boost for example) but the way the Ibanez Passive Tone Control works, I have to turn down the Active Treble control every time I go into Active Mode.

In other words, I want to take this Passive Tone Control out of the circuit. Any help please?

Benner

 

[line6man]

All you have to do is put a switch between the tone control and wherever it is connected in the circuit.

 

[Aidil]

All you have to do is put a switch between the tone control and wherever it is connected in the circuit.

The tone control knob is the same as treble knob... So it is connected straight to the preamp board.

 

[RobbieK]

So you're saying, the same pot is active treble and passive tone? So if the treble is set flat in active, when you switch to passive, the tone control is halfway rolled off?

hmm... Without seeing the schematic, it's hard to advise. Maybe if you could post a few good close ups of the preamp, there might be a simple way of doing this...

 

[Aidil]

So you're saying, the same pot is active treble and passive tone? So if the treble is set flat in active, when you switch to passive, the tone control is halfway rolled off?

hmm... Without seeing the schematic, it's hard to advise. Maybe if you could post a few good close ups of the preamp, there might be a simple way of doing this...

yep, and that is the problem that OP is facing.

me, I have 2 Ibby basses with the same kind of preamp, but I don't mind getting halfway tone or where ever the knob is positioned when I flick to passive mode, cause basically I don't like too bright sounding bass and when in active mode, my treble knob is mostly in the center or sometime is cutting. Getting halfway or even less passive tone might just still be the kind of tone I prefer.

 

[Big Benner]

Hi All,

So sorry for not getting to this sooner but I've finally managed to open the control cover & snap some pics.

You can see that the Treble pot is very different from the Mid & Bass. There's also a few more wires coming out from it,......... hopefully I can just disconnect the wires to bypass the Passive Tone function.

Question is - which wires do that?

Benner

 

[RobbieK]

That's a dual gang pot. An educated guess says that this is a custom pot with a B10k wafer on the bottom (pictured) for the active cut/boost and a regular tone pot on the other lower side for the passive tone cut. To check, you need to remove the pot and look and see if the lower wafer is says A250K on it. If this is the case it should be simple to disable.

Remember that a passive tone control is simply a pot in series with a cap that goes to earth. The cap and the pot may be the other way around, but all you have to do is break the chain. In your case, the tone cap may be on the little board with the treble pot. If this is the case, just remove it. If this isn't the case, or its a tiny surface mount cap, then it's probably easier to find which wire (or wires) goes to the 250K wafer and cut either one.

 

[Big Benner]

Thanks RobbieK, great advise / help so I'll look into it next week.

 

[Kenjohnson81]

How did this go? I have the same bass and was poking around inside. Did you notice that there are two spots that the input can go in the circuit board? One is 0db the other +6db. I was thinking of eliminating the passive circuit and toggling between the boosted and regular active. By default the bass is setup through the 0db, which is closer to unity with the passive circuit.

 

[Big Benner]

I haven't been able to look into it yet.

Benner

 

[touiou]

I had the same issue with the tone pot messing the sound making it sound muffled in flat and super bright when trying to add treble. The passive pot is a 500k pot connected to the main preamp board with a two cables (black red) plug.
I tried to remove the plug connected to the pot but instead of just plugged it was actually soldered as well. Stupid built in my opinion. So I ended breakin the pins connected to the pot circuit. So now it is either swim or sink.
I tried the bass in both active and passive modes and it seems that the instrument is now working properly and the muffle of the passive filter is now gone.
Unfortunately I have no tine control in passive mode (obviously) but I am overall happier with the bass coming back to life.
The fault in the design of the circuit is that instead of what is described that the passive tone is working only in the half route of the pot (I ve read that it is supposed to be full on, on centered position and close all the way down), it is working on all the range of the pot. Thus when it is centered the passive tone is actually half way down. Probably it has to do with the value of the pot being 500k instead of 250 or something else.
Anyway now it is gone and I am happy. But a little disappointed on Ibanez.