What size & type resistor to reduce series output?

[fig]

It's my first. ... But not bad for 1x12 maple board lumber from Home Depot, and no special skill, if I say so myself.

Hells yeah, that's excellent for your first. I'd be proud if I could build like that. Needs a name. "The Home Depot Special". Ok...maybe not that...

So I gather you have one humbucking pickup and are switching its two coils between series and parallel?

And you just want to reduce only the series output a bit with a fixed resistor (or trim pot, which is my preference)?

The two knobs are a Tone and a Volume control?

I have an idea, just wanted to be sure what everything is first. Thanks.

 

[wiscoaster]

...I have an idea, just wanted to be sure what everything is first. Thanks.

You're on target ... what's your idea?

 

[fig]

You're on target ... what's your idea?

This would use a fixed resistor or trim pot inline in the series path. Only used when in series. Removed from the circuit in parallel. If your switch is already 2 pole/2 throw (DPDT), you're golden.

Personally I like using trim pots. If you change brand of strings, or pickup, maybe a different amp, later down the road, it might unbalance things. Just give it a tweak to sort it out again.

I figure it's a starting point, 'cause there are other fine solutions posted in here. You got options, man LOL

 

[wiscoaster]

@fig - yup, that's it. Thanks for the schematics & wiring diagrams.

Where do you like to get your parts? I've got no good options local and will have to buy online. Shopping on Amazon is a zoo. If you've got a recomendation, I'd rather skip the zoo.

 

[iiipopes]

This would use a fixed resistor or trim pot inline in the series path. Only used when in series. Removed from the circuit in parallel. If your switch is already 2 pole/2 throw (DPDT), you're golden.

Um, er, won't putting the resistor, whether fixed or trim pot, between the two coils have the effect of unbalancing the coils in series and impair the humbucking attributes of the pickup?

 

[fig]

Where do you like to get your parts?

I'm gonna have to give you a homework assignment, but it's not graded and no time limit LOL. I don't do much tinkering anymore, so I don't have any preferences these days. I pick a couple from my bookmarks, compare prices and shipping, and go from there.

So here's a screengrab of my bookmarks you could look thru. Maybe someone else can make better recommendations.

 

[fig]

Um, er, won't putting the resistor, whether fixed or trim pot, between the two coils have the effect of unbalancing the coils in series and impair the humbucking attributes of the pickup?

Mostly sure it'll work as advertised, just not 100% sure. In parallel, if that resistance were inline with just one coil, yeah, I think it'd be a problem (I wouldn't even suggest it). But in series, that resistance will affect the entire signal run from ground to jack.

It's such a simple mod by adding one resistance to the existing dpdt switch, it's worth trying. If there's no audible artifacts and the series signal is tamed, mission accomplished. If it doesn't work, then he's got spare parts to try some other configs.

Since you've done something similar before, maybe you could draw up a schematic and post it. He'd probably appreciate an alternative and I can learn something new.

 

[wiscoaster]

I'm gonna have to give you a homework assignment, but it's not graded and no time limit LOL. I don't do much tinkering anymore, so I don't have any preferences these days. I pick a couple from my bookmarks, compare prices and shipping, and go from there.

So here's a screengrab of my bookmarks you could look thru. ....

Thanks!! Assignment accepted. Only two names on there that I recognized. I think the last time I bought anything remotely classified as an "electronic part" it was probably bought at Radio Shack.

 

[iiipopes]

Mostly sure it'll work as advertised, just not 100% sure. In parallel, if that resistance were inline with just one coil, yeah, I think it'd be a problem (I wouldn't even suggest it). But in series, that resistance will affect the entire signal run from ground to jack.

It's such a simple mod by adding one resistance to the existing dpdt switch, it's worth trying. If there's no audible artifacts and the series signal is tamed, mission accomplished. If it doesn't work, then he's got spare parts to try some other configs.

Since you've done something similar before, maybe you could draw up a schematic and post it. He'd probably appreciate an alternative and I can learn something new.

Thanks. Yes, it is worth a try to keep the wiring simple. I didn't do any series/parallel wiring on the guitar, it is straightforward: neck pickup hot lead => resistor => lug on the volume pot.

 

[fig]

"electronic part" it was probably bought at Radio Shack.

The good ol' days, man. LOL

Yes, it is worth a try to keep the wiring simple.

I like simple, 'cause I'm a simple kind o' guy LOL. Yeah, like I said, not entirely sure, just mostly. But if it goes horribly wrong and it opens an inter-dimensional portal, well...I hope he likes his new dimension and we will have learned what not to do LOL

 

[mrperkolator]

@wiscoaster have you tried @fig's wiring yet? I'm curious for a mod of my own

 

[wiscoaster]

@wiscoaster have you tried @fig's wiring yet? I'm curious for a mod of my own

No, I've got something even more radical in the works as mods for my Squier Bronco. (But will be using one or more trim pots per his suggestions.) Stay tuned.

 

[44me]

Fig’s circuit functions by padding the volume pot, so if it’s 250k, you would need a 250k resistor to cut the volume in half. Notice that this also puts resistance in series with the tone circuit, opening it up and making this control ineffective.

 

[Discount Bassy]

Oh, I suppose somebody's going to want a pic of the bass:

View attachment 4565498
Please be gentle. It's my first. I know there are members here who are really, really good at this. But not bad for 1x12 maple board lumber from Home Depot, and no special skill, if I say so myself.

This reminds me a bit of a stingray egg case for some reason.

 

[wiscoaster]

This reminds me a bit of a stingray egg case for some reason.

Hah!! Considering the stingray is an incredibly beautiful and graceful animal, I'll take that as a compliment.

 

[Discount Bassy]

Hah!! Considering the stingray is an incredibly beautiful and graceful animal, I'll take that as a compliment.

It was not intended as any sort of insult. Good work on your project!

 

[wiscoaster]

Thanks!!

 

[fig]

Notice that this also puts resistance in series with the tone circuit, opening it up and making this control ineffective.

Here's the series circuit, simplified. The resistance of the coils and attenuating resistor is parallel with the tone control, not series.

Maybe I misunderstood the statement?

 

[5StringPocket]

The pickup coils, when put in series, add their inductance. In parallel, their inductance is halved by the combination. A pickup by itself does have a resonant frequency (because the coils do have some interwinding capacitance), but that's very much a "tree falling the forest, nobody there to hear it" thing - when loaded by a cable, the resonant frequency is lowered much more than in the theoretical case where....you can't hear it, because you haven't hooked it up to anything.

Rolling back a tone control a "smidge" damps the resonant peak - it lowers its amplitude a bit - you lose some upper mids - say at 2 kHz or so. Above and below that, it does essentially nothing to the response - if the pickup has too much 10kHz, and you roll off the tone a bit, it still does the SAME thing at 10 kHz, even with the tone rolled back a bit. Loading the pickup capacitively MOVES the resonant peak (downwards) in frequency, not in amplitude. In doing that, you increase the lower mids below resonance some, and you lower the high frequencies above the peak - it can be a considerable amount, depending on the values of the pickup and load capacitor. Quadrupling the load capacitor will lower the treble stuff above resonance by 6dB, and move the peak down about an octave (the aforementioned interwinding capacitance makes the math not exact).

A lot of people don't really understand what a tone control on a passive bass does. It's a very common misconception that "it just turns down the treble". That's kinda true, but there is a lot of nuance that that statement misses.

This is an interesting approach and I see how it would work but don’t understand why the physical connection is made as described. The tone control provides a variable treble bleed to ground through a small cap before the output jack. It’s a parallel branch. Wouldn’t a switchable loading cap from the volume pot to ground just provide more of the same? I’d like to understand how one cap would just attenuate the resonant peak while the other cap (with what appears to be a similar signal path) would shift the peak.

 

[44me]

Here's the series circuit, simplified. The resistance of the coils and attenuating resistor is parallel with the tone control, not series.

Maybe I misunderstood the statement?

View attachment 4606721

Sorry - quick comment while eating breakfast.

People think of the tone circuit as being a simple RC low pass filter, but there's more to it. It's really an RLC resonant filter, with the L being the coil inductance. When you add resistance in the loop, you increase LC damping that decreases the peaking that occurs just before high frequencies start to roll off. The audible effect of this peaking is significant, so while you will get amplitude attenuation, you will also greatly impact tone circuit behavior.

While not as easy to switch, moving the resistor between the tone circuit and volume pot provides the desired volume cut with minimal tone circuit impact (parallel damping is reduced when the resistor is in, but the audible effect is small).