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Project Bass Electronics Confusion

Mar 9, 2015
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Hello! First and foremost, this is my first post here :) I've lurked these forums for a long time but finally decided to make a profile and join the community! I recently busted out an old Mexican Fender J bass that I had to initially see if I could sell it. However, the feels set in and I realized that besides the neck being totally trashed - which I am replacing at a later date - it does have a really nice alder body on it and the natural finish is still gorgeous.

So, I decided to make it my project to turn this thing into a metal/heavy music stud. I have a limited run FGN I use for basically anything standard tuning, so I wanted something for destruction \m/

Anyhow I'll get to the point: I want to route a MM pickup in the bridge position with the 3-band EQ (from what I've collected from previous posts, The EQ is a really big part of the sound, so I don't want to pass on it like some other builds I've seen.) I also have a Dimarzio Model J neck pickup that I was stoked to see being highly praised on here by a few different users, hopefully the combination is as gnarly as I feel it will be!

I would like the model J to have its own volume/tone pots. Then, the EQ for the MM has the knobs for hi, mid, and bass along with its volume knob. So, thats a lot of knobs with not much space. I'm also toying with the idea of a three way switch for pickup selection (I usually pre set both pickups then switch between them throughout a set depending on the part, just a personal preference) That takes up even more space though. Essentially, I've already coped with the fact that I'm probably going to have to reroute my input jack to the bottom of the bass and obviously create a cavity for a 9v to fit in. I am looking for some advice on organizing all these electronics in the most tidy way possible - if its even possible.

Here is my idea:

Use a couple concentric knobs in the build. 1 of which would control the volume and tone of the dimarzio, the other which would most likely take on the hi/low of the EQ. Then have the mid, and volume knob in normal pots. If I decide on going with a 3way pickup selector, I'll most likely have to carve up the body even more, but that is still yet to be determined because If there is a clever way to do this leaving that out, I'd take that over swiss cheesing my body.

Also, I'm curious about the pot ratings and transistors I'll have to grab for this build. I keep seeing 250k for tone and 500k for volume, and the EQ has its own set of pots unless I go for the concentric idea - then I would just look for a match there.

please let me know if they are totally bogus and opinions/helpful suggestions are always welcome!

Thanks guys!
 
Are you trying to run a passive J pickup setup with a MM pickup that has its own independent preamp? If so, you are going to need to buffer the passive pickup so that the preamp's output impedance will not short it out when the pickups are used together. You will need to either build or buy some sort of buffer circuit to lower the output impedance. The good news, however, is that buffering will take care of the issue of tone control interaction, so you won't have to worry about getting the passive tone control isolated from the other pickup's signal path.
 
So, basically everything would run off the preamp? and there would be no controlling the pickups independently? (sorry if these are noobish questions, though I've done a lot of reading on this I have never actually done any of this work in particular >_<)
 
So, basically everything would run off the preamp? and there would be no controlling the pickups independently? (sorry if these are noobish questions, though I've done a lot of reading on this I have never actually done any of this work in particular >_<)
The conventional approach is to either have a volume control for each pickup, which are summed together before it goes into the preamp, or a master volume and a blend control.
 
The conventional approach is to either have a volume control for each pickup, which are summed together before it goes into the preamp, or a master volume and a blend control.

So, in my case - if I decided on adding that three way switch, the best bet would be to have a volume for each pickup instead of a master/blend? Thanks a ton for the suggestions guys. Also, if anyone has links to helpful wiring diagrams that would be great too!
 
So, in my case - if I decided on adding that three way switch, the best bet would be to have a volume for each pickup instead of a master/blend? Thanks a ton for the suggestions guys. Also, if anyone has links to helpful wiring diagrams that would be great too!
Yes, with the pickups, volume controls, and selector switch upstream of the preamp, which would be for tone shaping.
 
So, basically everything would run off the preamp? and there would be no controlling the pickups independently? (sorry if these are noobish questions, though I've done a lot of reading on this I have never actually done any of this work in particular >_<)

No, you have a buffer on the J pickup, and the buffer sums with the preamp output. That allows the preamp to only apply to the MM pickup, and the passive tone to only apply to the J pickup.
 
THe MM is passive, as well as the J, so you can have a vol (w/tone [stacked]) for the J and a vol pot for the MM, then use the selector switch to send the signal from the MM or J or both to the preamp. Also, you can use a push/pull coil split vol pot for the MM to use one coil to match (or be separate from) the J. Bass/treble stacked, and a mid pot combines with the rest for 4 holes.
 
THe MM is passive, as well as the J, so you can have a vol (w/tone [stacked]) for the J and a vol pot for the MM, then use the selector switch to send the signal from the MM or J or both to the preamp. Also, you can use a push/pull coil split vol pot for the MM to use one coil to match (or be separate from) the J. Bass/treble stacked, and a mid pot combines with the rest for 4 holes.

This definitely could be a viable option. I think the point of the 3 way switch is to switch between the levels of the pickups though, I don't know if I necessarily care if the J pickup goes through the eq as long as I have a tone knob on it. I wish there was just one way to do everything :P oh electronics haha
 

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