Blog: Hot Rodding Bass Tone Circuits

[Evan Skopp]

Click here.

[Johnny the Kid]

Re: Blog: Hot Rodding Bass Tone Circuits

So does this basically switch between the active circuit and a passive circuit? I would be kind of interested in something like that.

[One Bad Monkey]

Re: Blog: Hot Rodding Bass Tone Circuits

So does this basically switch between the active circuit and a passive circuit? I would be kind of interested in something like that.

It all depends. The switch, which is called an active/passive switch, is really nothing more than a preamp bypass. It's only an active/passive switch if you have passive pickups and an active preamp, because at that point you're bypassing the active circuitry and going straight passive. And, unless you wire in a passive tone control, it's just the pickups signal going to the amp at that point (granted, I can do a whole lot with just the blend knob, so a passive tone knob for me isn't necessary).

So if you read the second part of the article where you can wire in a passive tone knob, that's where you would have a truly active/passive system because then when the active circuit is bypassed, the passive pickups and tone knob would still be active.

But as mentioned, if you have active pickups and an STC preamp, wiring the switch in really just is a preamp bypass; the signal is still active.

[Johnny the Kid]

Re: Blog: Hot Rodding Bass Tone Circuits

It all depends. The switch, which is called an active/passive switch, is really nothing more than a preamp bypass. It's only an active/passive switch if you have passive pickups and an active preamp, because at that point you're bypassing the active circuitry and going straight passive. And, unless you wire in a passive tone control, it's just the pickups signal going to the amp at that point (granted, I can do a whole lot with just the blend knob, so a passive tone knob for me isn't necessary).

So if you read the second part of the article where you can wire in a passive tone knob, that's where you would have a truly active/passive system because then when the active circuit is bypassed, the passive pickups and tone knob would still be active.

But as mentioned, if you have active pickups and an STC preamp, wiring the switch in really just is a preamp bypass; the signal is still active.

Well I read the article and didn't understand much. i'm not great with electronics and how they work. I know active pickups have a pre amp built in, and that's why they're active. So say I put into a j-bass two QP's. I use the STC-3 pre amp EQ. I want to have a standard j-bass passive tone with 2 volume knobs in addition to the STC-3 then I could install that switch which allows me to switch between the active EQ and the passive circuit, correct? I would actually be interested in doing something like that. I'm working on rebuilding a Fender Jazz Bass, and that seems like a system I would love to have. Or I might just stick to my original plan of having a set of EMG's in there (love the solderless installation).

[dystrust]

Re: Blog: Hot Rodding Bass Tone Circuits

Well I read the article and didn't understand much. i'm not great with electronics and how they work. I know active pickups have a pre amp built in, and that's why they're active. So say I put into a j-bass two QP's. I use the STC-3 pre amp EQ. I want to have a standard j-bass passive tone with 2 volume knobs in addition to the STC-3 then I could install that switch which allows me to switch between the active EQ and the passive circuit, correct? I would actually be interested in doing something like that. I'm working on rebuilding a Fender Jazz Bass, and that seems like a system I would love to have. Or I might just stick to my original plan of having a set of EMG's in there (love the solderless installation).

That's essentially correct, but I'd take a master vol / blend over vol / vol any day.

[Johnny the Kid]

Re: Blog: Hot Rodding Bass Tone Circuits

That's essentially correct, but I'd take a master vol / blend over vol / vol any day.

I was just using that as an example. I'd probably take a blend knob over a second volume knob too.

[One Bad Monkey]

Re: Blog: Hot Rodding Bass Tone Circuits

Well I read the article and didn't understand much. i'm not great with electronics and how they work. I know active pickups have a pre amp built in, and that's why they're active. So say I put into a j-bass two QP's. I use the STC-3 pre amp EQ. I want to have a standard j-bass passive tone with 2 volume knobs in addition to the STC-3 then I could install that switch which allows me to switch between the active EQ and the passive circuit, correct? I would actually be interested in doing something like that. I'm working on rebuilding a Fender Jazz Bass, and that seems like a system I would love to have. Or I might just stick to my original plan of having a set of EMG's in there (love the solderless installation).

The STC preamps come (nearly) completely assembled. You just solder in the pickups, the 9v battery cord and everything to the output jack, so you'd want to use the first layout with the passive tone knob so that when you switch it over, it's running through the passive tone knob. Otherwise the active/passive switch runs the passive pickups straight to the output jack when it's engaged, so there's no preamp at all.

[Evan Skopp]

Re: Blog: Hot Rodding Bass Tone Circuits

When you have all the EQ bands in the center detent positions, the sound is the same as if the preamp was bypassed.

[Johnny the Kid]

Re: Blog: Hot Rodding Bass Tone Circuits

When you have all the EQ bands in the center detent positions, the sound is the same as if the preamp was bypassed.

Thanks Evan.

[BlueTalon]

Re: Blog: Hot Rodding Bass Tone Circuits

I use 500K pots on my passive basses (when I build or modify). The author recommends 100-250K pots. How would the preamp respond to 500K pots?

[One Bad Monkey]

Re: Blog: Hot Rodding Bass Tone Circuits

I use 500K pots on my passive basses (when I build or modify). The author recommends 100-250K pots. How would the preamp respond to 500K pots?

The schematic I referenced from the SD site recommends 100-250K pots. The STC preamps themselves use 100K pots, with a 10K push/pull volume, and are pre-wired. If it was like Aguilar's setup where you get the parts and wire it yourself, I could see switching out pot values to see/hear the difference, but when it's all there and I only have to wire up the jack, battery and pickups, I don't bother.