Jazz Bass "Semi-Series-Wiring"

[PantoBass]

Hello people,

I am new here but have been reading the forum for many years. I'm a bass and guitar player from Germany and I have some history as an electric guitar luthier.
As I recently "reverse engineered" my long forgotten custom wiring that I developed back in 2012, I thought maybe I should post it here. I believe it is a genuinely new approach to series-wiring for VVT basses, at least I have never seen something close to this and I developed the wiring by myself on a piece of paper years ago.

Hopefully somebody will find it useful and be inspired to make some great music with it. It really makes any Jazz Bass extremely versatile

Have fun!

 

[fig]

Welcome aboard, PantoBass!

Except for the addition of the Bleed Cap, the rest of the circuit is the exact same as a very popular Series/Parallel mod that's been around for a long time. It's popular as a DIY mod and it also comes installed on some factory basses for Series/Parallel selection. Below, I added a schematic of your wiring diagram and also numbered the contacts of the pots and switch for reference.:

Here's the same circuit, minus the Bleed Cap, of the DIY mod that's been around for years. I added a schematic to it awhile back. Note that the schematic of your Semi-Series and this DIY mod are the same (except for Bleed cap). In fact, I copied the DIY schematic and re-purposed it for the Semi-Series schematic.:

For easier viewing, here's the two schematics together.:

I really like the Bleed cap idea, so I'm putting this one in my notes. Thank you for a fine post. I think folk will find your circuit very useful. If they already have the common DIY installed, all they have to do is add a Bleed cap across the two switch terminals.

 

[PantoBass]

Thank you fig for your very detailed reply with new drawings and everything! That similarity of the two schematics is a surprise to me. Even more so as I looked at the „original“ series mod not so long ago but thought „oh wow another way of mixing in series“…I didnt connect the dots that it is nearly the same thing. In the end thats even better, as it is only a small tweak to try for those who already have the first wiring in their bass. Maybe even switchable for complete overkill

What I like about the bleed cap is that the character of the individual pickups shines through very clearly but gets a nice low end punch. The resonant frequency still drops quite a bit, making it darker. Depending on the amp setup that can yield very usable sounds. I haven’t compared it to the wiring without bleed cap, so I don‘t know if that is also the case then. Probably kind of the same but different Its also cool to mix the strangle sound with a little bit of neck PU, great with reverb for spaghetti western sounds.

Let me know if somebody did an A/B test, I dont have the time right now. Beware, you may get lost in capacitor listening - makes a huge difference in how everything behaves. It is best to use croco clamps and to try without soldering first. I tried MANY caps before i decided on one.

 

[5StringPocket]

Welcome aboard, PantoBass!

Except for the addition of the Bleed Cap, the rest of the circuit is the exact same as a very popular Series/Parallel mod that's been around for a long time. It's popular as a DIY mod and it also comes installed on some factory basses for Series/Parallel selection. Below, I added a schematic of your wiring diagram and also numbered the contacts of the pots and switch for reference.:
View attachment 7323620

Here's the same circuit, minus the Bleed Cap, of the DIY mod that's been around for years. I added a schematic to it awhile back. Note that the schematic of your Semi-Series and this DIY mod are the same (except for Bleed cap). In fact, I copied the DIY schematic and re-purposed it for the Semi-Series schematic.:
View attachment 7323626

For easier viewing, here's the two schematics together.:
View attachment 7323804

I really like the Bleed cap idea, so I'm putting this one in my notes. Thank you for a fine post. I think folk will find your circuit very useful. If they already have the common DIY installed, all they have to do is add a Bleed cap across the two switch terminals.

Clever idea. Does the PantoBass bleed cap mod that allows bridge volume to adjust high frequencies when in series serve to darken the tone when dialed back? Series alignment with no bleed cap gives a low mid bump and volume increase with a rolled off treble response. Does this bleed cap provide further treble rolloff?

 

[fig]

Does the PantoBass bleed cap mod that allows bridge volume to adjust high frequencies when in series serve to darken the tone when dialed back?

Yeppers.

As the Bridge Vol pot wiper arm is dialed back (counter-clockwise), the treble high freqs passing thru the cap are being sent to ground and removed from the Bridge output. The remaining bass and mids, being blocked by the cap, continue along the series path into, and thru, the Neck pickup. Overall effect is darker tone since Bridge treble content was removed.

Conversely, when the Bridge Vol pot wiper is full clockwise, the treble high freqs pass thru the cap and travel across the top of the pot's full resistance, ultimately meeting the Neck output. The bass and mids, being blocked by the cap, continue along the series path into, and thru, the Neck pickup. Overall effect is regular series tone, since the treble was re-routed back into the main signal path. Essentially the same signal as if the cap wasn't installed.

As for volume issues, I don't know. This is @PantoBass's custom circuit that he used. Maybe he'll chime in with actual useage info. All I did was draw a schematic from the wiring diagram he provided 'cause I thought it was a neat idea he had.

 

[5StringPocket]

I was thinking of using a 4-way rotary selector with 1)neck 2)bridge 3)parallel 4)series for a 2-pickup custom build that's in the queue but it occurred to me that I almost always run biased toward the neck or bridge pickup but rarely solo either one or play dead center. I prefer two separate volumes over volume/blend so I think this schematic would work well with two RWRP single coil pickups into the Trickfish IPA preamp I'll have with this build.

The push/pull neck volume pot would be pushed down for parallel operation and pulled up for series, where it becomes master volume for the pair.
The bridge volume would be another push/pull pot which would be pushed down for active mode to engage the preamp and pulled up to disengage the preamp for passive mode.
Series or parallel with equal settings would be humcancelling but since solo single coils are subject to hum, diming the one you want as primary and backing off the other one enough to approach the tone you want while maintaining enough humcancelling to keep the noise level acceptable in a live mix would provide a wider range of useable tones than a 4-way switch.

 

[PantoBass]

The bleed cap wiring is not essentially „darker“ when bridge vol is turned down. I hear it more as neck PU based fatter sound, still with some clarity from this pickup. Of course the resonant frequency drops a bit in any series wiring, which may be a good or bad thing depending on individual pickups and amp setups. I find that in series mode, the sound with most treble is actually somewhere in the middle until upper range of the bridge volume knob. It then mimics a normal series sound the most, maybe even a bit sharper? It is the most hollow/hifi sound if you know what I mean, like both PUs on when in parallel. Very smooth combined with tone pot down. Both volumes full on seems to put the bridge PU in preference soundwise, the neck is not very loud anymore. That can be enhanced further by turning down the neck volume, until from middle down it becomes a very thin bridge PU sound. Even thinner than bridge parallel. All bass freqs are cut out by the cap and the neck is not in the circuit anymore as it is only the treble from the cap you hear. Can be useful sometimes. Actually if I am honest, on this bass and with my amps I am using stock parallel wiring 90% of the time. But its cool to have options if I need them.

 

[mhelander]

I think that converting standard Jazz Bass with VVT so that both volumes have push-pull switches, and:

• Neck volume to switch between parallel (down) or serial like here fig shared earlier, and
• Bridge volume to switch between volume (down) or have additional bridge
  
  asdf
  
  

 

[mhelander]

This would blow new life to my 80's Ibanez Jazz... and if merging with this so that the stock VVT is retained with pair of DPDT volume pots, neck pull for serial with volume controls, and neck pull for its tone control. Interesting...

Big thanks to fig drawing these schematics from descriptions, great stuff!

 

[dunderwovvy]

I was thinking of using a 4-way rotary selector with 1)neck 2)bridge 3)parallel 4)series for a 2-pickup custom build that's in the queue but it occurred to me that I almost always run biased toward the neck or bridge pickup but rarely solo either one or play dead center. I prefer two separate volumes over volume/blend so I think this schematic would work well with two RWRP single coil pickups into the Trickfish IPA preamp I'll have with this build.

I reached out to Mo Mina at Nordstrand about building a rotary pickup selector that had trimpots so I could basically have presets like you mentioned.

1. Series
2. Neck solo
3. 100% neck + ~80% bridge (parallel)
4. ~80% neck + 100% bridge (parallel)
5. Bridge solo

He said it was entirely doable, but I got rid of the project bass before getting the switch made.