pickup volume

[plaaty]

Hi All,

 

I've fitted new pickups in an old p / j Yamaha and changed the blend pot to a volume, so separate volume controls for each pick up.

when I put both volumes on max, or I assume the same level the output volume lowers a bit, is this normal... or should I change it back to a blend pot, 

or is there a resistance problem with the pickups where they are effecting each other/

 

Thanks for any advice

 

 

[neepheid]

The pickups are cancelling each other out. Swap the hot/ground wires of one of the pickups.

[PaulThePlug]

?.. I thought that was normal... A slight volume / output drop when both PUs are on full vol...

I've replaced the VVT on my 2x Ibby GSR PJ for VBT and went VBT on the Jazz PJ... MN Taper over AC

Edited December 3, 2021 by PaulThePlug

[plaaty]

I'll open it up and check the wiring.

maybe when it had the blend switch the drop wasn't noticeable?

 

[hrnn1234]

the volume drop when both pu's are at maximum volume, as far as I read online, is due to how the resistance of both pu's adds up. If that's so, I'm surprised it wasn't an issue before with the blend pot, as it should be the same when it's on dead center as when both volumes are at max.

[Cosmicrain]

On 06/01/2022 at 21:47, hrnn1234 said:

the volume drop when both pu's are at maximum volume, as far as I read online, is due to how the resistance of both pu's adds up. If that's so, I'm surprised it wasn't an issue before with the blend pot, as it should be the same when it's on dead center as when both volumes are at max.

Most stacked blend pots (pro' one's that is) have a different resistance taper than standard pot's for the same resistance value.  Therefore a standard volume pot say of 250K, will have the full taper from one end of the track to the other (full rotation) off = 0K Ohms and  fully rotated = 250K.  However a pro blend stacked pot has a different internal structure with regards to the carbon track meaning the summed resistance of a stacked blend pot will be different than two independent volume pots when both are fully open.  Also the individual volume pots on the bass are probably Log' pots where as I use Linear taper stacked pots for blend controls, as this makes a difference as well.     

Edited January 9, 2022 by Cosmicrain

[itu]

9 hours ago, Cosmicrain said:

However a pro blend stacked pot has a different internal structure with regards to the carbon track meaning the summed resistance of a stacked blend pot will be different than two independent volume pots when both are fully open.

I am not sure, what does this mean?

 

A Bourns blend pot (type MN) has two tracks, which end at the centre detent. Therefore the pot acts electrically exactly like two separate vols.

[plaaty]

Thanks for the info.

I think I'll change it back to a blend pot, what would be a good make?

[Cosmicrain]

1 hour ago, plaaty said:

Thanks for the info.

I think I'll change it back to a blend pot, what would be a good make?

Alpha, CTS, MEC, Bourns plus others.  I'm not sure if your bass is active or passive?  but just make sure you get the correct Ohm rating,  220K, 250K or 500K for passive pickups or 25K - 50K for active pickups.  Here's a link for the MEC passive blend control, they also do the active version.  https://shop.warwick.de/en/parts-for-instruments/warwick-spare-parts/electronics-parts/18236/mec-balance-pot-module-for-passive-pickups?c=3600

[itu]

Alpha or Mec are not true blend pots. As the tracks continue from the start to the end, it reduces the signal, also in the centre point. Bourns MN has a track that ends at the centre detent, like I said earlier. That way the signal is going straight from the blend to the vol.

 

OOOoooC--------- (neck pu)

---------CoooOOO (bridge pu)

 

C = centre 

O = ohms

- = 0 ohm track

 

Others are like

OOOOOOCoooo.....-

-.....ooooCOOOOOO

Probably you get the point.

 

I need to remind you, that if the bass has a battery powered ("active") tone circuitry, it does not automatically mean that the pickups are battery powered. Therefore the blend may be 500k although the tone stack uses a battery.

 

signal path:

pickups - blend - vol - tone -> output

 

Any single part of this path can be battery powered ("active", or rather low impedance = lo-Z).