Volume/Blend troubles P/MM

[LDonnie]

Hey everyone, I was hoping to get some help on my little problem. I have just finished building a P bass with an MM pickup, but I have the idea that something is wrong with the wiring. The volumes for both pickups work, but they blend poorly/not. Also, with both volumes full I only hear one pickup. Adjusting the pickup heights didn't help. Also, both volume bots are functional. I assume the tone is as well. What could be going on? Thanks!
Edit: this is the current wiring diagram from SD:


The pickups are an SPB-3 (QP) and a SMB-4A

[Hopkins]

Have you tried swapping the leads on the P pickup. They may be out of phase,

[BassGyver]

It's an impedance problem. These pickups are not made to work together. If i'm right, the P has a much higher impedance than the MM, resulting in a loss of signal when both pickups are connected in parallel
I got the same issue with a SPB2 and SMB4D. With both pickups on, the MM is much louder than the P.

Solutions?
- use pickups build to work together (Delano, ...)
- use the MM OR the P
- always back up a little the MM volume to get a good balance
- put a series resistor with the MM PU to permanently lower his volume (and the the well balanced sound with both volume pots full on)
- use a buffer preamp for both PU

[ZolkoW]

MM pickups often load other pickups outputs too much, but good point is to check the phase. I think, the best way would be to use an active blend for hybrid setups...

[LDonnie]

Thanks for all the responses. I was planning to get an active circuit anyway, so that should solve my problem. I suspected it could be an impedance problem. I will have to wait till I can scrape together enough cash for a preamp

[ZolkoW]

Originally Posted by LDonnie

Thanks for all the responses. I was planning to get an active circuit anyway, so that should solve my problem. I suspected it could be an impedance problem. I will have to wait till I can scrape together enough cash for a preamp

just make sure, that the preamp has two buffered inputs - not many have this feature, search for "active blend".
(this applies if the problem is the different impedance of the pickups. if it's only a phase issue, then every preamp should work fine)

[LDonnie]

Zombie thread rises from the dead! :O

I was thinking, the split coil translates into a very loud, boomy E string. It doesn't do that with any other strings. Could this be a sign that my pickup is out of phase? I haven't checked yet, because I am lazy (yes I admit!).

[SGD Lutherie]

Out of phase would make a very thin tone with almost no low end. It sounds more like you need to lower the pickup under the E string farther down, and away from the strings.

If you want a stock P and MM to work well together, consider wiring the P in parallel, and/or wire the MM in series.

[LDonnie]

Originally Posted by SGD Lutherie

Out of phase would make a very thin tone with almost no low end. It sounds more like you need to lower the pickup under the E string farther down, and away from the strings.

If you want a stock P and MM to work well together, consider wiring the P in parallel, and/or wire the MM in series.

Hey David, thanks for your response. Actually, lowering the pickup at the E side doesn't do much to help this problem. I am currently looking at options for a preamp with an active blend, so I won't be running the pickups passive for long.

[LDonnie]

Hey everyone, just wanted to let you guys know that you can solve the loud e-string problem by turning the EA-string coil 180 degrees, so the louder side is on the A-string. Because the A string is thinner the volume levels even out.

[SGD Lutherie]

Originally Posted by LDonnie

Hey everyone, just wanted to let you guys know that you can solve the loud e-string problem by turning the EA-string coil 180 degrees, so the louder side is on the A-string. Because the A string is thinner the volume levels even out.

Unless the magnets are raised higher under one string there is no louder side. It's all the same coil under the cover.

[LDonnie]

Originally Posted by SGD Lutherie

Unless the magnets are raised higher under one string there is no louder side. It's all the same coil under the cover.

It did work though. What you say makes sense, but I can definitely hear a difference.

[SGD Lutherie]

Originally Posted by LDonnie

It did work though. What you say makes sense, but I can definitely hear a difference.

That's interesting. Could be those magnets are stronger than the others.