80's Tobias TCT Wiring/Specs

[iplay5strings]

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

 

[will4bass]

Did as you said and removed the 2 resistors and like the result very much. The bass I have is an early Nashville Gibson (#2326) which looks as stylish as the real old ones built by Michael and his team. Didn’t like the wood combo’s and hardware Gibson chose later on. Anyway, think will also remove the jumper on the bass pot and solder the blue wire directly to the pot. Never thought this would make a difference but I will find out!

 

[winegamd]

@iplay5strings what is the pickup configuration of the Burbank Tobias? I know you have said the Original quads sound similar. The schematic shows them as a two wire pickup lead. I have an older Zon with a two wire pickup lead, but the actual coil configuration is a quad with the inline coils in series, and then originally wired in series again to make a dual coil humbucker (I have since changed the inline coils to parallel, still only a two lead pickup, though). I am just curious if the Burbank pickups are the "unicorn configuration" quad coils in the P/Reverse-P configuration.

 

[iplay5strings]

@iplay5strings what is the pickup configuration of the Burbank Tobias? I know you have said the Original quads sound similar. The schematic shows them as a two wire pickup lead. I have an older Zon with a two wire pickup lead, but the actual coil configuration is a quad with the inline coils in series, and then originally wired in series again to make a dual coil humbucker (I have since changed the inline coils to parallel, still only a two lead pickup, though). I am just curious if the Burbank pickups are the "unicorn configuration" quad coils in the P/Reverse-P configuration.

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.

 

[will4bass]

This is the pick in my #2326. Obviously different than the old ones.

 

[iplay5strings]

This is the pick in my #2326. Obviously different than the old ones.View attachment 4619229

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.

 

[will4bass]

I’m not sure how to recognize a buffer…don’t even know what it does…

 

[iplay5strings]

I’m not sure how to recognize a buffer…don’t even know what it does…

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.

 

[will4bass]

Makes that a different sound as such? Could I remove the buffer or do these pickups simply require one? I took out the teo resistors of the mid eq pot and sound drastically improved.

 

[iplay5strings]

Makes that a different sound as such? Could I remove the buffer or do these pickups simply require one? I took out the the resistors of the mid eq pot and sound drastically improved.

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.

 

[will4bass]

I see no blue but a purple wire on the bass put where you described.But I guess taking of that
‘jumper’ which looks like a metal clamp would make sense?

 

[iplay5strings]

I see no blue but a purple wire on the bass put where you described.But I guess taking of that
‘jumper’ which looks like a metal clamp would make sense?

View attachment 4619407

Looks like yours was already wired up properly in that regard

 

[iplay5strings]

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

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

 

[iplay5strings]

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.

View attachment 3864267

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.

View attachment 3864716

*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

---UPDATE---
I have discovered the purpose behind the resistors on the mid pot on later TCT pres vs no resistors on the old Tobias TCT preamps. The pot values were different! The old Tobias pres used a 25K pot so there was no need to lower the overall value with resistors. The new TCT uses a 50k and those resistor create an asymmetrical behavior btwn both sides of the pot sweep. The resistor on the cut side drops the value down to 25K which makes it exactly what the original TCT mid cut circuit is supposed to be, the boost side is brought down to around 30K which actually yields more mid boost than what the Tobias circuit would've had with the 25K. Completely removing these resistors from a 50K pot yields even more mid boost. It will come down to personal prefer what you like, but now we know exactly why those resistors were left off of the old Tobias mid pots and also why the Tobias mid boost sounds different than what we hear from the current TCT stuff, it was a bit leaner from the lower boost amount.

If you want to keep the 50K pot but change the boost side to 25K as well, you just need to change the resistor on boost side to 47K to match the cut side.

 

[evilgus]

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.

Hey, I finally found this thread! Great stuff, Adam!

For years now, I've had two sets of non-drop-shoulder pickups with the lettering "MT5T" and the 5-pointed star logo, so I guessed they were custom-wound for Mike, but didn't know anything else about them. I've always assumed they were dual-coil humbuckers, but maybe that's not the case at all! However, I do think that these particular ones have a slightly different winding (or construction?) to the drop-shoulder pups. Many years ago, when I owned that black Basic 5, I compared the drop-shoulder pups that came with it, to a set of these MT5T pups (in the same bass!) and the drops were a bit darker and warmer. Unfortunately, I don't have a recording of that comparison, just the vague memory of it...LOL

I don't suppose anyone has taken a photo of the bottom-side of some drop-shoulder pups, to see if they have the same lettering? I haven't had mine out of my Classic for years and just can't remember....DOH!

In any case, I reckon Mike and crew used these ones in their "late" Pre-Gibson basses, after the drop-shoulders ran out, then left some with Gibson. Not only did my Sig5 come with some, but the other pair came out of a Gibson-built Classic 5 that was built at least a year after the Sig5!

Here's the ones that came with the PG Sig.... interesting to note that they both measured 2.14K on the meter. (Same windings for each.)

And the ones that came with the Gibson Classic... the Neck pup measures 1.94K and the Bridge pup measures 2.14K. That kinda implies a slightly "softer" winding for the neck?

The ones in the Sig5 have had a pretty hard life, the shells are nearly worn right through, in places!!!

Cheers,

EG

 

[iplay5strings]

Hey, I finally found this thread! Great stuff, Adam!

For years now, I've had two sets of non-drop-shoulder pickups with the lettering "MT5T" and the 5-pointed star logo, so I guessed they were custom-wound for Mike, but didn't know anything else about them. I've always assumed they were dual-coil humbuckers, but maybe that's not the case at all! However, I do think that these particular ones have a slightly different winding (or construction?) to the drop-shoulder pups. Many years ago, when I owned that black Basic 5, I compared the drop-shoulder pups that came with it, to a set of these MT5T pups (in the same bass!) and the drops were a bit darker and warmer. Unfortunately, I don't have a recording of that comparison, just the vague memory of it...LOL

I don't suppose anyone has taken a photo of the bottom-side of some drop-shoulder pups, to see if they have the same lettering? I haven't had mine out of my Classic for years and just can't remember....DOH!

In any case, I reckon Mike and crew used these ones in their "late" Pre-Gibson basses, after the drop-shoulders ran out, then left some with Gibson. Not only did my Sig5 come with some, but the other pair came out of a Gibson-built Classic 5 that was built at least a year after the Sig5!

Here's the ones that came with the PG Sig.... interesting to note that they both measured 2.14K on the meter. (Same windings for each.)

View attachment 5425967

And the ones that came with the Gibson Classic... the Neck pup measures 1.94K and the Bridge pup measures 2.14K. That kinda implies a slightly "softer" winding for the neck?

View attachment 5425969

The ones in the Sig5 have had a pretty hard life, the shells are nearly worn right through, in places!!!

View attachment 5425973

Cheers,

EG

MT5T are reverse p splits, which is why they are not quite as dark/warm as the drop shoulders that were in that black Basic 5 (which are MT5C duals). Once Mike was out of the picture the part numbers on the back of the pickups stayed the same, but the sound of the pickups drastically changed under Gibson. My Classic 5 was made in 1997 and came with "MT5C" pickups in it, but they sounded nothing like the drop shoulder pickups, even after I put a TCT in the bass.

 

[iplay5strings]

Hey, I finally found this thread! Great stuff, Adam!

For years now, I've had two sets of non-drop-shoulder pickups with the lettering "MT5T" and the 5-pointed star logo, so I guessed they were custom-wound for Mike, but didn't know anything else about them. I've always assumed they were dual-coil humbuckers, but maybe that's not the case at all! However, I do think that these particular ones have a slightly different winding (or construction?) to the drop-shoulder pups. Many years ago, when I owned that black Basic 5, I compared the drop-shoulder pups that came with it, to a set of these MT5T pups (in the same bass!) and the drops were a bit darker and warmer. Unfortunately, I don't have a recording of that comparison, just the vague memory of it...LOL

I don't suppose anyone has taken a photo of the bottom-side of some drop-shoulder pups, to see if they have the same lettering? I haven't had mine out of my Classic for years and just can't remember....DOH!

In any case, I reckon Mike and crew used these ones in their "late" Pre-Gibson basses, after the drop-shoulders ran out, then left some with Gibson. Not only did my Sig5 come with some, but the other pair came out of a Gibson-built Classic 5 that was built at least a year after the Sig5!

Here's the ones that came with the PG Sig.... interesting to note that they both measured 2.14K on the meter. (Same windings for each.)

View attachment 5425967

And the ones that came with the Gibson Classic... the Neck pup measures 1.94K and the Bridge pup measures 2.14K. That kinda implies a slightly "softer" winding for the neck?

View attachment 5425969

The ones in the Sig5 have had a pretty hard life, the shells are nearly worn right through, in places!!!

View attachment 5425973

Cheers,

EG

Also, per your request...

 

[evilgus]

MT5T are reverse p splits, which is why they are not quite as dark/warm as the drop shoulders that were in that black Basic 5 (which are MT5C duals). Once Mike was out of the picture the part numbers on the back of the pickups stayed the same, but the sound of the pickups drastically changed under Gibson. My Classic 5 was made in 1997 and came with "MT5C" pickups in it, but they sounded nothing like the drop shoulder pickups, even after I put a TCT in the bass.

Thanks, that makes sense! The two sets I have sound nearly identical, aside from the lower resistance one that has slightly lower output. I've actually had the set from the Gib Classic in my Sig 5 for years, as the shells looked much better, but finally refitted the original set. Now I can decide whether to stick with the Flexcore or switch to a TCT circuit...

Cheers,

EG

 

[evilgus]

I finally bought some of that "Magnetic Paper", so that I could see exactly what is going on, for my different pickup models. Here's a photo of the MT5C (Humbucker) pickups in my Classic and the MT5T (Reverse-P) pickups in my Signature.

Cheers,

EG

 

[evilgus]

Once again, big thanks to @iplay5strings for starting this thread and supporting the rest of us through our various bass enhancements!

As a bit of an update, I finally had a (new) TCT 5.4AP pre-amp fitted in my Classic 5 (above) and am REALLY pleased with the results! That bass-heavy goodness is all back, plus the crisp/glassy top-end. The biggest surprise was how much I like the 250Hz low-mid boost on this pre-amp, it just KILLS when using the rear pickup! I mean those rear drop-shoulder pups are one of my all-time favourites, but especially with this boost going! (Yes, I'll do a good recording soon!) Plus the 500Hz and 750Hz boost settings are great to have as well, especially 750Hz boost when using both pups blended.

Compared to the WTMB+DTA 1.3 Buffer: The TCT has more overhead, so you can have your pickups closer to the strings, for more punch. And I think the top-end is just a bit sweeter and more "lively".

Compared to the Flexcore: Much more bass-heavy and more of a "Live" sound, compared to a "Studio" sound. The TCT top-end is much better, I always found the Flexcore to be a bit lame in the top-end. I miss the passive tone, but the treble-cut on the TCT is totally fine, so I'm happy!

Mmmm....now I have to decide whether to scrape up the funds to order another TCT 5.4 to go in my Sig 5 with the new Zen Blades that are about to arrive.....but I should probably try them with the Flexcore first.....

Cheers,

EG