Tone stacks? are they passive?

[southtown]

I.e could i put a passive two band baxandall tone stack into my bass?

[R.G.]

There is a passive form of the Baxandall. Like most passive tone controls, it can cut only, it cannot boost. So you'll get a loss of about 20db in signal level with the controls flat.

The Fender style tone stack is an even older form of tone control. It has about the same losses as the passive Baxandall, but has no really flat frequency response. Instead, it always has some amount of mid scoop.

The passive Baxandall was conceived to give a flat response with the controls set to middle.

[Ge_Whiz]

In a sense, all tone controls are 'passive' - you can only reduce the intensity of a signal or band, never increase it. Active tone controls basically just boost the signal before or after the tone filters to compensate for the losses.

You could fit your bass with Baxendall tone controls, but you are likely to lose a lot of volume in doing so.

[Ah. Beaten to the punch by R.G. - and he quoted decibels in his answer... 

[southtown]

If i was to put it after a diy piezo pickup would i need some sort of buffer? before? after? the stack?

[newfish]

I'd say definitely after your piezo.

I put a piezo unit in my bass a few months ago - and (when I get round to it) will be putting a MOSFET booster in there (and switching jack) to bring the volume up to the magnetic pickup's volume.

Cheers!

[southtown]

plans have changed, this will be going in a ukulele now was hoping to get away from needing a battery

[George Giblet]

An example of a Baxandall tone control with preamp without the loss,

http://cscott.net/Projects/Ashbory/

Baxandall is passive, but the preamp is active.

Look up the G&L bass schematics for a passive tone control - you are limited in what you can do with totally passive.

[earthtonesaudio]

If you don't want to put a battery in your instrument, you could look into phantom power.   I seem to recall a phantom-powered JFET booster schematic out on the net somewhere.  They actually fit the whole circuit into the end of a guitar cord.

[Mark Hammer]

Our thinking tends to be too constrained by the physical dimensions of 9v batteries and the perceived need to stick a 9v battery and snap somewhere in a physical space we'd rather not modify.  If the current requirements of the circuit are modest, there is no reason NOT to consider other power sources like lithium "coin" batteries, or those sub-AA-sized 12v batteries that can often be gotten cheap.

Finally, there are plenty of ways of producing desirable tonal adjustments without necessarily suffering the passive loss of a Baxandall or Fender tonestack.  For instance, you may wish to simply limit how much bottom end the pre-amp produces, and that can be done simply by select between input caps.  Choice of emitter cap can alter top end in a single-transistor pre-amp stage, and so on.

[southtown]

so maybe i could use something like a fender p bass tone knob? except i want to be able to roll off low frequencys....