Bartolini Preamp Question

[Frank Miller]

I recently was given a Tobias Killer-B4 for repair that has a broken output jack and volume control. When I opened it up, I saw that there are FOUR internal trimpots.

It looks like a Bartolini NTMB preamp, but, to the best of my knowledge, Bartolini only supplies ONE trim pot for system gain.

Could someone with experience with Bartolini's preamps please inform me of what the other three trim pots do? Until I replace the broken volume control and jack, I cannot tweak them to find out for myself.

 

[abarson]

If it's anything like my Tobias Growler, you actually have two EQ preamps, one for each pickup. Each preamp has one trimpot for mid boost and one trimpot for treble boost.
https://bartolini.net/wp-content/uploads/Docs/Electronics/Specials/Growler-Reissue-Instruction.pdf

 

[Frank Miller]

If it's anything like my Tobias Growler, you actually have two EQ preamps, one for each pickup. Each preamp has one trimpot for mid boost and one trimpot for treble boost.
https://bartolini.net/wp-content/uploads/Docs/Electronics/Specials/Growler-Reissue-Instruction.pdf

Thanks for the idea. It remains to be seen if this applies to the Killer-B as well.

The Bartolini wiring diagram for the Growler has two three-position switches for mid- and treble-boosts for each set of coils.

The Killer-B has only one three-position switch. I have heard differing claims for this switch: Selectable midrange turnover frequencies OR midrange cut/flat/boost.

This model is reputed to have a pull-switch on the volume control for slap tone. Perhaps some of the trim pots are for pre-selecting the slap tone treble and bass boosts. That would account for two of the trimmers.

So, if two trim pots are for slap tones and one is for overall system gain, that still leaves me with one MYSTERY trimmer.

Until I get a working volume pot and jack, it's all speculation.

 

[cenkbass]

Could you update us on what you found out?