Passive J Wiring Question

[Brent Hahn]

Passive J Bass. Would it be possible to use a twin-gang volume pot as the front knob (for humbucking at all volumes) and a push-pull volume pot as the middle knob, using it as an alternative volume control for the bridge pickup? The push-pull switch would move Hot of the bridge pickup between the rear gang of the front pot, and the middle pot. That way, using the twin-gang pot you're quiet, using the separate pots you have individual (but noisier) pickup volume controls. AKA the J configuration everyone knows.

Your thoughts?

 

[sikamikanico]

Seems like it would work, should be interesting to try. I’m trying to imagine how this might work in practice (live)…

 

[Brent Hahn]

In practice live, the idea would be that you could ride your gain up and down using one knob, not two (a win), and stay not-noisy while doing so (another win).

 

[SharpCat]

Side note, push push a nice upgrade from push pull IMHO. Still pops up but easier to activate.

 

[sikamikanico]

In practice live, the idea would be that you could ride your gain up and down using one knob, not two (a win), and stay not-noisy while doing so (another win).

yeah, I’d want a pickup selector switch + master volume. Not sure if the extra volume control for individual pickups is worth it.

 

[micguy]

Yes, using the twin gang pot, you would be quiet, but a VVT wired jazz doesn't sound very good with both volumes dialed back. You could do swells with it, but I don't think most would find that mode useful except with the volume dimed.

I have a jazz where I have a master volume control, but it's wired with both pickups as one - they're wired together kinda like one pickup, and the volume control is wired normally - like a P bass, not reversed like a normal VVT jazz. Doing it that way, the sounds with the volume control dialed back sound good.

 

[Brent Hahn]

yeah, I’d want a pickup selector switch + master volume. Not sure if the extra volume control for individual pickups is worth it.

Different folks want different things. I'm seeing a big uptick in RF-heavy situations that make a stock passive J untenable. Especially if it's a recording/streaming kind of gig. And I just about never need Jaco Honk. But I'd also like to be able to revert to the stock wiring in an unclunky way.

 

[Brent Hahn]

... using the twin gang pot, you would be quiet, but a VVT wired jazz doesn't sound very good with both volumes dialed back.

Right now I use a volume pedal to back off the gain. Is the sound of that different from dialing back the two volume pots on the bass? Or is just that less loud = less full onstage = less good? No snark intended, just not following the logic.

 

[micguy]

Right now I use a volume pedal to back off the gain. Is the sound of that different from dialing back the two volume pots on the bass? Or is just that less loud = less full onstage = less good? No snark intended, just not following the logic.

A volume pedal is wired like a P bass - the source is wired to the top of the pot, and the source sees the full resistance of the pot as a load. That scheme works fairly well, and will sound decent when the volume control is backed off.

A VVT circuit bass (most Jazz basses) is wired with the sources wired to the wipers of the pots - as you turn down a volume control in that circuit, the load resistance on the source(s) goes down - you shunt the source. With a reactive source, you don't have a volume control - it's an odd mixture of a tone and volume control. With an inductive source (magnetic pickups are reactive in the inductive sense, which means their impedance goes up with frequency) , the thing gets dull sounding as you turn it down. You can do a volume swell, and it'll sound OK, but if you try playing with both volume controls backed off on aJazz, it's dull and not at all articulate. Ask guys who play Jazz basses what their favorite tone is, and they will either say both volumes dimed, or one dimed and the other one backed off a certain amount. I've never heard someone say their favorite tone on a Jazz is with both volumes backed off the same amount.

 

[Brent Hahn]

A VVT circuit bass (most Jazz basses) is wired with the sources wired to the wipers of the pots - as you turn down a volume control in that circuit, the load resistance on the source(s) goes down - you shunt the source. With a reactive source, you don't have a volume control - it's an odd mixture of a tone and volume control. With an inductive source (magnetic pickups are reactive in the inductive sense, which means their impedance goes up with frequency) , the thing gets dull sounding as you turn it down. You can do a volume swell, and it'll sound OK, but if you try playing with both volume controls backed off on aJazz, it's dull and not at all articulate. Ask guys who play Jazz basses what their favorite tone is, and they will either say both volumes dimed, or one dimed and the other one backed off a certain amount. I've never heard someone say their favorite tone on a Jazz is with both volumes backed off the same amount.

Well then... glad I asked before I just went and did it. Being one of those guys who play Jazz basses, I'm of the both-dimed school, but hate the volume pedal (as well as the tuner pedal I have to use outdoors). So to get that, should I combine the two pickups P-style into one volume pot that stays full up, then tone, then output volume, or...? You know what you're talking about, so school me.

 

[micguy]

If you're of the both dimed school, I'd hardwire both pickups together, then wire that combo to the exact same circuit as on a P bass - one volume control (wired the right way), and one tone control. With that circuit, you'll get more range out of the tone control on the high end (it'll go a little brighter, as you only have two pots loading the pickup combo), you'll have a volume control that works well , and your bass won't hum. Yes, you'll have a control that doesn't do anything - that's a "producer control" - if someone suggests you turn something down or up, you turn that control.

 

[Brent Hahn]

Glad I asked.

 

[Derek Kay]

If you want to innervate you night consider series/parallel option for the PUs, tone bleeds for the vols, and rescaling the tone.

You would largely retain the original sounds and gain some alternatives.

 

[fig]

...rescaling the tone.

Will you explain that for me?

It might be something I'm already aware of, but not heard of it being called 'rescaling'.

I'll take a wild guess and say rescaling refers to the taper ratio of an audio pot, like 60-40 or 65-35, etc??

If I got it right, do I win a pretty helium filled balloon?

Apologies to you, @Brent Hahn, for the thread interruption.

 

[Derek Kay]

Will you explain that for me?

It might be something I'm already aware of, but not heard of it being called 'rescaling'.

I'll take a wild guess and say rescaling refers to the taper ratio of an audio pot, like 60-40 or 65-35, etc??

If I got it right, do I win a pretty helium filled balloon?

Apologies to you, @Brent Hahn, for the thread interruption.

My passive tone control is a 250k log (audio taper) pot.
Whatever capacitor you chose will dictate the tone it removes.
Adding a resistor in series with the cap will reduce the amount of that tone the pot will remove. By experiment I found a value whereby 'tone off' was a sound with just enought tone remaining to be clear but not bright like 'tone on'. I had no use for full 'tone off' and this gave me an onboard preset, if you like, keeping the range inbetween. The tone control now operates only over my useful range eg full tone for pizz, less tone for slap, pick, or reggae

Rescaling is my term, please correct me if there is a better one.

 

[fig]

My passive tone control is a 250k log (audio taper) pot.
Whatever capacitor you chose will dictate the tone it removes.
Adding a resistor in series with the cap will reduce the amount of that tone the pot will remove. By experiment I found a value whereby 'tone off' was a sound with just enought tone remaining to be clear but not bright like 'tone on'. I had no use for full 'tone off' and this gave me an onboard preset, if you like, keeping the range inbetween. The tone control now operates only over my useful range eg full tone for pizz, less tone for slap, pick, or reggae

Rescaling is my term, please correct me if there is a better one.

Thanks for taking time to explain what you meant. I don't know if there's a proper term for doing this, but 'rescaling' seems appropriate. Hey!, I just plagar...uh...learned a new term for this application LOL.

I drew this up awhile back, having seen it in schematics from a major bass manufacturer (I forget who at the moment). I saw it as a way to remove the bassy mud that can happen at the bass-off end of Tone pot rotation, just as you explained.:

So, technically it's rescaling the tone control. For this rescaling application, I shall call it...The Mud Buster Mod!

(ok, I'm not good with names. Ask my two dogs, Lug Nuts and Spoon).

For those passin' thru still learning this stuff, sometimes turning a passive Tone Control knob all the way off (treble removed) can give you unusable bassy/muddy mush. Adding a fixed resistor will electrically limit the amount of treble removed, keeping the entire pot rotational range in the usable, pleasing, chock-full-o'-goodness, range. The above drawing tells you how to find that limiting resistance.

Thanks, again, Derek Day. Since I guessed wrong on what rescaling is, you don't owe me a pretty helium filled balloon.

 

[Derek Kay]

Thanks for taking time to explain what you meant. I don't know if there's a proper term for doing this, but 'rescaling' seems appropriate. Hey!, I just plagar...uh...learned a new term for this application LOL.

I drew this up awhile back, having seen it in schematics from a major bass manufacturer (I forget who at the moment). I saw it as a way to remove the bassy mud that can happen at the bass-off end of Tone pot rotation, just as you explained.:

View attachment 5461858

So, technically it's rescaling the tone control. For this rescaling application, I shall call it...The Mud Buster Mod!

(ok, I'm not good with names. Ask my two dogs, Lug Nuts and Spoon).

For those passin' thru still learning this stuff, sometimes turning a passive Tone Control knob all the way off (treble removed) can give you unusable bassy/muddy mush. Adding a fixed resistor will electrically limit the amount of treble removed, keeping the entire pot rotational range in the usable, pleasing, chock-full-o'-goodness, range. The above drawing tells you how to find that limiting resistance.

Thanks, again, Derek Day. Since I guessed wrong on what rescaling is, you don't owe me a pretty helium filled balloon.

Good one, I see what you did, so the same but for opposite ends of the sound. I can't rely on much electronic knowledge, but if you use intuition, move fast & break things, you get results. I'm amazed that there are so many clever permutations in passive electronics that go unused. I find tone bleeds and series/parallel very useful. My passive basses become as versatile as an active, providing I dial my preamp to accomodate the extra range required.

I once modded a Stingray 5 for a push/pull active/passive option, using the 5 position switch as a passive tone dialer. That was an experiment that never finished. Louis Johnson demoed it for me in 1989. Stolen 1994.