Jazz bass pots/wiring, what values to use for better blending of volumes?

[shoulderpet]

Hi

I have recently brough a Harley benton JB-62 jazz bass which is a great bass but like pretty much every jazz bass I have ever played it has pretty uneven adjustment of volume when adjusting the volume of both pickups. 

 

To explain more on what I mean both pickups on is the classic scooped jazz bass tone, good tone but not always the best choice for cutting through, I generally like to have as much volume as possible so I always have one of the pickups on full and when I roll back the volume on either of the pickups the volume of the pickup I have rolled back seems to have a big drop in volume so for example if I start with both pickups on full and roll the neck pickup back a notch suddenly the tone is almost entirely bridge pickup, if I start with both pickups on full and roll back the bridge pickup a notch then the tone is almost entirely neck pickup. 

 

I have noticed this with every jazz bass I have ever played so I think it is a jazz bass quirk rather than anything actually wrong with the bass but I was wondering if there was anyway to get around this quirk to get better blend of the 2 volumes? I wonder if a Volume/Blend/Tone layout might be better for this than 2 volumes?  Thanks

[Oopsdabassist]

Yup Kiogon Vol/blend/tone loom, works luvverly!

[rmorris]

From your description I think a buffered / active summing system might suit you better. Suggestion - fit 'stereo' TRS output jack Buffer / DI each pickup separately and then sum in a small analogue mixer. Eg Soundcraft Spirit Folio. Old but often at a bargain price on eBay.

[sandy_r]

On 31/08/2023 at 14:35, shoulderpet said:

Hi

I have recently brough a Harley benton JB-62 jazz bass which is a great bass but like pretty much every jazz bass I have ever played it has pretty uneven adjustment of volume when adjusting the volume of both pickups. 

...

 for example if I start with both pickups on full and roll the neck pickup back a notch suddenly the tone is almost entirely bridge pickup, if I start with both pickups on full and roll back the bridge pickup a notch then the tone is almost entirely neck pickup. 

 

I have noticed this with every jazz bass I have ever played so I think it is a jazz bass quirk rather than anything actually wrong with the bass

...

 

Hi

Passive controls for multiple pickups will always have issues due to compromises made in trying to make a mixer without powered components. The compromise is between useful mixing action and losing signal level from the guitar

 

The problem is caused by 'loading' of the signal by the pickup impedances and pot resistance sections interacting as the pot wiper position is moved from full vol position (The 'optimal' technical solution for mixing signals is to use an active circuit)

 

Adding a very high impedance input buffer (eg simple FET buffer/amp) between guitar and pedals/amp may help somewhat

 

If you want to keep your bass passive and you're ok with some DIY wiring you could re-configure the existing HB wiring (sounds nasty, but is only moving 2 wire connections and adding 2 resistors) as shown in my suggested mod below.  This mod will need a higher gain setting, in general, on the amp but should then reduce the interaction between Vol controls when adjusting one/both during a session

 

With the existing 250K ohm pots, you could try 100K ohm resistors (shown in blue on the circuit) - move each pickup signal wire (ie. not its ground wire)  to the outer connection on its pot, and connect a resistor to the wiper. The other ends of the 2 resistors are connected together and then join at the Tone pot

 

Using lower values for the resistors (eg 50K or 25K) can reduce the general loss of signal level but will start to give more loading/interaction between the 2 Vol controls again - it's worth trying this to check the result

 

(Changing the Vol pots from 250K to 100K [Audio taper] and halving the resistor values could also help with reduction of general signal loss in the mod, but this would significantly increase the complexity of making the mod!)

 

Hope this helps

 

 

Edited September 2, 2023 by sandy_r

[Hellzero]

Put a set of EMG pickups, the X series with dynamics closer to a passive pickup is really excellent.

[rmorris]

1 hour ago, sandy_r said:

 

Hi

Passive controls for multiple pickups will always have issues due to compromises made in trying to make a mixer without powered components. The compromise is between useful mixing action and losing signal level from the guitar

 

The problem is caused by 'loading' of the signal by the pickup impedances and pot resistance sections interacting as the pot wiper position is moved from full vol position (The 'optimal' technical solution for mixing signals is to use an active circuit)

 

Adding a very high impedance input buffer (eg simple FET buffer/amp) between guitar and pedals/amp may help somewhat

 

If you want to keep your bass passive and you're ok with some DIY wiring you could re-configure the existing HB wiring (sounds nasty, but is only moving 2 wire connections and adding 2 resistors) as shown in my suggested mod below.  This mod will need a higher gain setting, in general, on the amp but should then reduce the interaction between Vol controls when adjusting one/both during a session

 

With the existing 250K ohm pots, you could try 100K ohm resistors (shown in blue on the circuit) - move each pickup signal wire (ie. not its ground wire)  to the outer connection on its pot, and connect a resistor to the wiper. The other ends of the 2 resistors are connected together and then join at the Tone pot

 

Using lower values for the resistors (eg 50K or 25K) can reduce the general loss of signal level but will start to give more loading/interaction between the 2 Vol controls again - it's worth trying this to check the result

 

(Changing the Vol pots from 250K to 100K [Audio taper] and halving the resistor values could also help with reduction of general signal loss in the mod, but this would significantly increase the complexity of making the mod!)

 

Hope this helps

 

 

 

Good ideas. But be aware that the 100K resistors will increase the broadband "hiss" noise. It may not be an issue in the context of an electric bass but it might be noticed in studio etc.

[sandy_r]

5 minutes ago, rmorris said:

 

Good ideas. But be aware that the 100K resistors will increase the broadband "hiss" noise. It may not be an issue in the context of an electric bass but it might be noticed in studio etc.

 

Aye - hence the para: "Using lower values for the resistors (eg 50K or 25K) can reduce the general loss of signal level but will start to give more loading/interaction between the 2 Vol controls again - it's worth trying this to check the result"