What causes volume loss when blending pickups?

[Ian the bassist]

I own a Warwick 2001 streamer Jazzman. Now I love it. Best bass ever, have it about 9 months and didn't care that much that I couldn't use both pickups together without getting a substantial loss of tone and volume. Until now.

I'm really digging the Jazz pickup and Humbucker mixed. But it just drops too much. I know this isn't the case with other Warwick Jazzman basses, as I have seen videos of them being used and being switched between settings and the volume and definition stays there.

What could be causing it? The Jazz and humbucker sound great at full volume by themselves, when panned to the middle, it's just so low and muddy. Is there a way of fixing this problem without changing the pickups or the pre-amp?

[Got2SadowskyNYC]

This could be something as simple as a cold solder somewhere.

[InternetAlias]

Physics, ruining bass guitar tones since 60s. For more information search on 'phase cancellation'.

[Codger]

+1
It could be pickups wired out of phase. It happened to me in a custom bass. Not muddy though, just weak and thin.

[dave2]

I loved the tone of mine when I had it. I love all my Warwicks.

It has the stock MEC electronics in it?
Take it to a tech and have it checked out.

[Ian the bassist]

Thanks for the suggestions guys. I think I'll take it to a tech and tell him what you guys have told me. Cheers. Yes it is the stock Mec pickups. Not sure if at some point, the preamp has been changed or messed with, as the push pull switch never seemed to do anything either.

[two fingers]

Well, to keep it simple, I'm sure you have read posts where people are measuring a pickup in ohms. Well, ohms is impedance. Impedance (roughly) is resistance. Depending on how your pickups are wired, and what they measure, each pickup could be adding resistance to the circuit.

Here's a wiring diagram that may be of some use to someone who outranks me in knowledge (as I am a 1st year electronics student). I couldn't follow along the diagram to figure out how the pickups are wired.
http://www.warwick.de/media/manuals/...055%20rev2.pdf

Either way, I have noticed it on Fender J basses for years. Particularly the neck pickup soloed is way huge compared to both together.

[line6man]

It's called insertion loss. When two pickups are parallel, the input impedance on each is lowest, and thus, the load is greatest. This is especially true of pickups of differing output impedances, as the higher impedance pickup will be more sensitive to more direct loads.

Have you ruled out the possibility of phase issues, however?

[frits51]

What type of blend pot are you using?

The Bourns type M/N blend pot gives you 100% of both pickups at the center detent. As you roll off one pickup, the other remains at the 100% level.

If your blend pot is an A/C type, the level of each pickup at the center detent is less than 100%. As you roll off one pickup, the other gets louder than it was at the detent until it reaches 100%. So, as you go from Neck to detent to Bridge, your volume may go down, then up again.

[mmbongo]

I definitely don't have much volume loss on my Jazzman so something is wrong.

Does your preamp look like this?

[SGD Lutherie]

If the pickups are out of phase, you lose a lot of low end and volume. The sound is usually thin. Sometimes you have to back off on the volume of the louder pickup to really hit that thin sounding spot.

But passive basses also sometimes have some signal loss when blending two pickups because the impedance of one pickup will load down the other. This is especially true if they are somewhat mismatched in resistance/impedance.

[bassbenj]

Originally Posted by frits51

What type of blend pot are you using?

The Bourns type M/N blend pot gives you 100% of both pickups at the center detent. As you roll off one pickup, the other remains at the 100% level.

If your blend pot is an A/C type, the level of each pickup at the center detent is less than 100%. As you roll off one pickup, the other gets louder than it was at the detent until it reaches 100%. So, as you go from Neck to detent to Bridge, your volume may go down, then up again.

THIS ^

Check the blend pot. There are TWO TYPES. One is simply two stacked pots. In that case it is obvious that when you are at the mid point of rotation each pickup is at half volume (two stacked volume pots, remember)

What you want is a specific blend pot. With this one each pot goes from zero to full resistance as you go from one end to mid. This kind then gives BOTH pickups having full output in the mid position.

To test the blend pot you'll have to unwire it and use an ohm meter.

[SGD Lutherie]

Originally Posted by bassbenj

THIS ^

Check the blend pot. There are TWO TYPES.

Oh that's a good point... I did read the whole thread. You also have to wire the blend pot up the right way, or it will sound dull in the middle.

With a Bourns M/N you wire it like this:



If you get the wires mixed up, then when you are in the middle, you actually have the pickups turned down, and not up.

[Ian the bassist]

I took a picture of the cavity. This is more so for bongo. It looks similar, not sure if its the exact same, although since mines left its mirrored.

[Ian the bassist]

Seems the file didn't upload. Ill link you another way hold on one second

[Ian the bassist]

This is a video of the cavity. Bongo, you also have a jazzman so this is more so for you or for anyone who might be able to see something wrong from me posting this. I know I have a different pre amp to yours, as you replaced yours if I remember correctly. When I say the push pull is meant to set it into active, I meant to say passive ;P The video is a bit all over the place, but you can see the cavity in it.


http://www.youtube.com/watch?client=...k8Y&nomobile=1



This is a video just for sound comparison. Can you hear what I hear?

http://www.youtube.com/watch?hl=en&c...PWE&nomobile=1

Hopefully with these two videos, it should solve the issue. Thanks for taking the time guys.

[mmbongo]

I wasn't able to view either video, the thumbnail just sits there.

But the picture I posted is my stock MEC preamp. I did replace it at one point, but it is back totally 100% stock now.

[InternetAlias]

His links are to mobile, try these.

http://www.youtube.com/watch?client=...k8Y&nomobile=1

http://www.youtube.com/watch?hl=en&c...PWE&nomobile=1

[Ian the bassist]

Originally Posted by mmbongo

I wasn't able to view either video, the thumbnail just sits there.

But the picture I posted is my stock MEC preamp. I did replace it at one point, but it is back totally 100% stock now.

My apologies mmBongo. Luckily InternetAlias spotted that. Thanks for correcting that mistake.

[Ian the bassist]

Bumpity bump bump