80's Tobias TCT Wiring/Specs

It was recommended that I post this to maybe help other people struggling to better their post-Gibson basses or repair/return to stock pre-Gibson basses.

*DISCLAIMER*
There was quite a bit of variance over the years of Tobias. Every bass was made to order and that could include certain wiring differences in the preamp. With the TCT being a tone shaping circuit and not a true EQ setup, all of the controls affect each other. That being said, different wirings will make the TCT sound/act differently. What I am pointing out here are two common discrepancies I have found btwn Bartolini's diagrams and what I have seen of Bob Lee's work in actual 80's Tobias basses.



1. The jumper on the bass pot. Bob Lee wired the long blue wire to the middle pin of the bass pot and left it without a jumper. This subtly opens up the sound of the lows and lessens the "pull" of the treble knob on the bass knob when boosting (which to my ears equates to less low-mid scooping as you boost the treble)

2. Take those resistors off the mid knob. Bartolini says they are there to "properly bias" the mid circuit, but Bob left those off so the boost and treble shelf of the mid knob would act the way they wanted. The sound is drastically different. With the resistors on the mid-range knob, the mid boost sounds more crowded and the treble shelf is a bit upper mid heavy. With the resistors off, the mid boost is much more open and the treble shelf is much sweeter.



*OTHER THINGS TO CONSIDER*
Volume/Blend pot values. It seems they favored 500k vol/blend pots at this point as they were not yet using a buffer and did not want the dual coil pickups to be too dark, but this will come down to personal preference. If you have a buffer it is not necessary for such high value pots. Below is my Nashville era Tobias Classic V. It has a TCT preamp setup the way I have described here with 500k Vol/MN Blend pots

 

That is correct. Mike's quads were paired as p/reverse p coils and then wired as "parallel duals" at the end.
Also, to be clear, nothing Bartolini currently makes is quite like the "T" line pickups (like what was found in the old Tobias, Pedulla, Modulus, etc basses). It's unfortunate, but the decision was made not long after Bill left to discontinue them in favor of a more streamlined, general product line and different manufacturing materials. Thankfully the TCT is still around, but if you want that older Bartolini (T) sound you'll have to look elsewhere.

 

Those are reverse p orientation. If they truly are the "old formula" (T) wind pickups like Mike used in his pre-Gibson basses then they should sound amazing with a TCT. If they originally came with a buffer, then they're most likely the Gibson formula.

 

Looks like your pickup leads run into a module before they hit the blend pot, that is a buffer. It isolates the pickups from each dragging on each other and converts their signal to low z which isolates them from the load of the pots as well.

 

They will still work without the buffer, but they will sound quite different and need different pot values as they will be high z without the buffer. The T pickups the old Tobiases had were not buffered, they were more traditional (albeit custom wound) hotter pickups. Usually pickups that are designed to "need" a buffer become quite dark/lifeless without it as the gain staging/resonant peak changes drastically with the buffer removed. Also, the buffer you have is no longer available so removing it might be a one way experiment. If you're happy enough with the sound of the pickups, I say finish the wiring on the TCT and experiment with the mid trim setting.

 

Looks like yours was already wired up properly in that regard

 

Here's another example of this "Special Spec" TCT harness in a bass other than a Tobias

https://youtube.com/shorts/LaLkHbzibI4?feature=share