Beginner question about passive wiring

[tfcreative]

Any previous work that I've done has been harnessed or prepackaged  in some way, but I'm working on a passive instrument from scratch and am unfamiliar with some of the basics. As I understand it, the only thing separating a volume pot from a tone pot is a capacitor coming from the negative of the pot, and the tonal characteristics of the pot depend on the capacitor type. Am I way off?

Just to clarify my intent: two passive pickups, each going into its own tone pot, then into a 4-way rotary switch, then to master volume. Hopefully that's not a rediculous idea. Any input is appreciated.

 

[jackthehack]

It's hard to tell what you are wanting to on this one; what type of pickups? Tappable? Why 4-way rotary on this implementation, what phasing or other ??? are you wanting to do?

 

[tfcreative]

Dingwall FD-3 pickups, and a dingwall designed rotary switch in place of the blend (bridge, neck, series, parallel if I'm not mistaken). At this point, I'm just looking to make sure that the tone pots actually function as passive tone pots and not just another volume pot in the line. This is where my question of capacitors came in.

 

[-CB-]

Tone controls, for best results, should be on the "hot" side of things.  That is, on the signal as it comes to the volume control, not as it leaves the volume control.

If you want a 4 way switch and a toggle... you might want to take a look at the circuit I've designed, and used now in two (soon to be three) guitars with great results.  That setup gives you "normal" guitar tones (neck/both/bridge) via the toggle switch.  It also gives you series pickups (both, has to be), and gives you half out of phase (both pickups, has to be).  You "could" do it full out of phase, but frankly, the half out sounds better.  To that, you can add... a regular tone control, middle control and bass control if you like (but you'll have to add more passive things, an inductor).

 

[tfcreative]

Right now I do have the tone pots planned to be in front of the switch, which is in front of the volume. I wasn't sure if I would create problems putting tone pots in front of the switch, but I can't find anywhere that it would.

I guess if I boil down to the simplest question that I'm asking, it's "how do I wire a passive tone pot?" regardless of the rest of the configuration. Everything else I've had any part in has been something like an EMG system where you just get prewired pots. So is it as simple as using a 250k pot with the appropriate capacitor? Is the capacitor on the hot side coming into the tone pot or on the negative side leaving the tone pot?

 

[Alfang]

Tf    you should study a few schematics of volume and tone controlls and try and figure out whats going on. It's fairly simple electronics, if you can wrap your brain arround whats going on there, you can better figure out what it is you wanna do. Many books and websites will tell how to wire it, but not many explain well how it all works.

Your last post seems to tell me you haven't even looked a schematic?

Typical guitar wiring is  passive, as opposed to active, which requires power.
passive uses the power of the circuit to function without external power.

 

[jackthehack]

Checked the pickups, they're for a bass... Don't know shit about that other than vintage Jazz Bass circuit with 2 vols, 1 tone... Everybody else pick up on the fact it's a bass?

Regardless, tone pots don't go in front of the vol pot(s) or switches for that matter,,,

As it would seem like you're unfamiliar with schematics, go to seymourduncan.com or guitarelectronics.com and study on all the bass wiring diagrams to start...

 

[tfcreative]

Alfang,

The problem that I'm encountering is that I can't find a schematic for what I'm attempting. I've looked at some guitar schematics; the pickups came with a schematic that only references a blend and master pots; and the rotary switch only came with a guide from pickups to master and ground; any bass related diagrams that I have found online are all active and include a battery. Nothing I've looked at directly references tone pots in a passive system.

Perhaps I'm not adequately explaining the simplicity of my question as it's getting all clouded in the other components of the system; perhaps my questions is more complicated than I realize (which I am willing to accept). If those of you with more experience than I would indulge me, can I simplify the scenario? Imagine that this is a simple passive P-bass: 1 pickup, 1 tone pot, 1 volume knob and a jack. My present understanding leads me to believe that the hot from the pickup would go into the tone pot, then a capacitor would be placed in between the tone and volume pots, then out the jack (I'm not addressing negatives or grounds in that scenario). All I'm asking is this: is the capictor the difference? Are the volume and tone pots otherwise identical?

 

[tfcreative]

Oh yeah, sorry if I forgot to mention that, this is indeed a bass.

 

[tfcreative]

Regardless, tone pots don't go in front of the vol pot(s) or switches for that matter,,,

Ok, this may be what I'm getting at, which is why I can't find any drawings related to what I'm attempting. What I'm hoping is to have independent tone knobs for the pickups like a strat, but in order to do so they have to come before the switch that acts as a blend. Is that even doable, or is the concept doomed from the start? If I have to live with a master tone that comes after, I'll survive.

 

[jackthehack]

The pots themselves are identical, but may differ in impedence.

The volume pot controls the output signal level, volume, that's it...

The capacitor and tone pot are wired together to provide a variable low pass filter. This means when the filter is engaged (tone pot is turned) only the low frequencies pass to the output jack and the high frequencies are grounded out (cut) In this application, the capacitor value determines the "cutoff frequency" of the filter and the position of the tone pot determines how much the highs (everything above the cutoff frequency) will be reduced, i.e., at 0 nothing above the cutoff frequency is sent, at 10 the filter is effectively bypassed and all frequency spectrum gets sent. And the rule is: Larger capacitor values will have lower cutoff frequency and sound darker in the bass setting because a wider range of frequencies is being reduced. Smaller capacitor values will have a higher cutoff frequency and sound brighter in the bass setting because only the ultra high frequencies are cut.

Not sure you followed that...

Here's a wiring diagram for a "blend" circuit for a Jazz bass:

http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=jazz_bass_blend

 

[tfcreative]

Jack,

Thank you so much, that's exactly what I was looking for: a simple primer on passive tone pots. Everything else I've looked at seems to assume that someone already knows this stuff. This should be enough info for me to finish planning and start work. Thanks again.

 

[tfcreative]

Just want to say thanks to all that chimed in. I've done the wiring and everything is working (according to taps with the screwdriver, my neck doesn't come for a week).