Wiring to switch active to passive

[Rumble]

I recently acquired a Pedulla thunderbolt 5 equipped with Bartolini soapbars and the TC4 preamp. From what I can gather the TC4 works like a tone control, but it seems to be suppressing the top end to the point where there almost isn't any.

It's been suggested I wire the bass to run passively but I'm not sure how to do this. Any tips would be gratefully received.

Thanks in advance.

[KiOgon]

If you can find a link to exactly what circuit you've got - I'll have a look

Cheerz, John

[Rumble]

Thanks John.

You could try this (below) and follow the link to the relevant page, alternatively I could send you a pdf I've downloaded.

http://www.bartolini.net/electronics-wiring-diagrams/

Many thanks, Andy

[KiOgon]

Hi Andy,

The by-pass switch circuit shown on the TC1-6 page on your link should do the job. file:///C:/Users/John%60s/AppData/Local/Temp/TC-Booster-Preamps.pdf

Cheeerz, John

[Rumble]

Thanks John. Sorry to be a bit dim, but should there be a physical switch somewhere on the preamp or does it require a change in the wiring?

I know some of the thunderbolt basses have a switch mounted with the controls on the front of the bass, but mine doesn't. Looking at the frequency distribution graphs my suspicion is that the bass is currently set up in the low boost mode because the low end is very good.

Thanks

[KiOgon]

Yes you need a switch, DPDT IIRC with the the 470K resistors & the circuit modified to suit, if your's hasn't got it.

Cheerz, John

[Rumble]

From what I've read on the net most users don't like the switch; I can probably understand why it mine is wired to be permanently engaged.

Which wiring diagram would I follow to get an unboosted signal?

Thanks for all your help.

[KiOgon]

Perhaps users don't like the switch because - as shown in your link - that circuit only by-passes the signal from the preamp to straight out. It doesn't cut the power from the preamp so draining battery all the time the bass is plugged in, even though the signal is not even going through the amp.