active/passive push pull pot on a Ibanex SRX || HELP NEEDED

Conkal

Conkal

Jun 23, 2017
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Athens, Greece
#1
Hello all ,
I am a bassist that tries to modify my older bass, in order to be able to bypass the tone control, making it active/passive with a push/pull pot (I mean that when the tone control is bypassed i will get only the oassive signal from the pickups and not the active preamp)

*I have an IBANEZ SRX300 bass which has an electronics diagram as it is shown in the picture

*I want to install a push-pull pot like this in the VOLUME pot to turn off the tone control .
DiMarzio - 500K Push/Pull Pot
-------------------------------------
I like the idea because my main bass has it (warwick corvette $$) and i would really-really like to have it on my backup ibanez.

I have tried whatever i could and search a lot for a how-to or a schematic but could make it. the best i could achieve was to have a active/passive on off but the passive was way low with the battery on and the volume didnt change with the pot.

Please i really need your help on this.
 

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#4
I am trying to install a push pull pot that when on(down) the circuit of the active preamp will work , as it is done now and when the pot will be off( up ) then the active preamp circuir will be by~passed.

Sorry about my english i may not be clear enough.
 
#5
It won't be possible (or rather complicated) to do with your current preamp.
You best bet is to replace the preamp with another one that will allow active/passive switching.
VBBT is a very common arrangement, most preamp makers are similar ones from which you can choose.
 
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#6
Jazz Ad said:
It won't be possible (or rather complicated) to do with your current preamp.
You best bet is to replace the preamp with another one that will allow active/passive switching.
VBBT is a very common arrangement, most preamp makers are similar ones from which you can choose.
Click to expand...

Why not? All the OP has to do is follow standard active/passive switch wiring. The preamp is single input, and the pots are not PCB mount, according to the original wiring diagram.

5434343084_dd3674c0ac_o.png
 
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#8
I think it is doable . i have seen it done in some SRX basses online. Why wouldnt it be? I have already almost done it but i dont know enough to complete it.

I remind everyone that i need to bypass the (active)preamp using the PP pot
 
#10
line6man said:
Why not? All the OP has to do is follow standard active/passive switch wiring. The preamp is single input, and the pots are not PCB mount, according to the original wiring diagram.

5434343084_dd3674c0ac_o.png
Click to expand...
I have tried this but it doesnt mention the three lower rings . And while it seems to partially work there is no volume control and if i remember correctly another thing was off.

I also tried a diagram of an onboard preamp (other than mine ) that seemed similar, it also didnt quite make it.
 
#11
This is all you have to do, really. Sometimes it works better to bypass the output rather than the input or both since push-pulls usually are DPDT. Do what works best, what doesn't make noise or pops at switching.
Then you can cut the battery off the circuit but this is a bit more problematic because it WILL make loud pops that you need to manage with résistors and/or caps.
passive_bypass.JPG
 
#16
I cant spend dollars not being in the US .:-) This is a bass i have as a guinea pig. I use it to learn how to do things. I would prefer to find out how to do it than paying 20 euros for it. and it has nothing to do with the bill. It is the fun to find out and do it yourself
 
#17
I u derstand how it works but when i did try to implement this, i ended up with the volume not working.
Any ideas?
Click to expand...

JazzAd's diagram is incorrect. You can just switch the ouput, but not the way he or she has shown. But really, a push-pull will be a double-pole switch, so you may as well use both. And true bypass will be a much better option, especially with a 500K volume pot.

This is all you have to do, really. Sometimes it works better to bypass the output rather than the input or both since push-pulls usually are DPDT. Do what works best, what doesn't make noise or pops at switching.
Then you can cut the battery off the circuit but this is a bit more problematic because it WILL make loud pops that you need to manage with résistors and/or caps.
passive_bypass-jpg.jpg
Click to expand...

With respect, your diagram incorrect. You will have the load of the preamp output across the volume control when in passive mode. This will kill the bass's ouput. Also, you'll need to work out which wire from the preamp is the output and which is the switched earth. The battery earth is labelled, so this leaves two that go to the jack, and neither are labelled. The ouput earth will be short to "B1" and the pot casings. (You should confirm this with a multimeter.) The leftover wire - the preamp output - is the one you need. I've used "C2" for my diagram (because it is white), but it may well be "C1" that you have to use. (Just because it is black, don't assume it is automatically an earth.)

Then you can cut the battery off the circuit but this is a bit more problematic because it WILL make loud pops that you need to manage with résistors and/or caps.
Click to expand...

With respect, this is also incorrect. The pop from switching the battery in and out cannot be managed with resistors or caps. It is a really bad idea to switch out the battery, unless the preamp is specifically designed (biased) for this option. And this preamp is not. (I can tell this by the way the battery is wired.)

Here's how you should wire your bypass.

bypass.jpg


The (blue) resistors are optional. Because this preamp may not have been designed for bypassing, there's a chance that there is no earth reference resistor on its input and (less likely, but possible) its ouput. If the switch pops, then add R1, a 2.2 megohm resistor where I've shown. This ties the preamp input to earth and will discharge the input coupling cap while the switch is being thrown. If it still pops with the switch, then also add R2, a 220 kiloohm resistor (which ties the ouput of the preamp to earth). Use 1/4 or 1/2 watt metal film resistors.
 
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#20
Don't you also end up with tone control (boost/cut) problems?
Passive basses use tone pots that are normally 250K to 500K.
The two boost/cut pots here are 50K. And even if you can use them, they won't do the boost function anymore.
Passive circuits can only cut, they cannot boost.

If you are having trouble doing thus, it may be that it's a bit over your head.
I'm not saying you can't do it or shouldn't try as a learning experience, just that the questions are basic enough that it seems you might not be ready for this yet. For instance, you seem to be having difficulty with how to convert a non push-pull switch diagram to a push-pull switch. The wiring is the same electrically even though the physical layout may be different.

I agree that getting an active pre that is designed to be switched to passive rather than just trying to make a passive bass also work as active is the better choice.

-edit- I agree that getting an active pre that is designed to be switched to passive rather than just trying to make an active bass also work as passive is the better choice.
 
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