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What wrong with my tone?

I have a Bronco modded into a Musicmaster with the following electronics:
o Custom 4 pole 7.6k noiseless Pickup by John Benson
o Wiring harness with 250k CTS pots, .047 orange drop cap by John Benson
o RotoSound Swing 66

The tone knob changes the tone so very little.
What could the problem be?

mm1.jpg


057912
 
Somebody messed up a connection along the way because a proper tone knob on a bass with one pickup changes the tone an enormous amount. You'd have more luck with a good picture of the wiring.

Agreed, that's why this is a mystery, it is wired correctly.
A pic of the wiring does make sense, since I'm asking for help.
But has anyone else had this problem?

057912
 
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A few weeks ago I picked up a like new Ibanez Artcore AGB 140 bass. It is the thin hollow body with F holes and a single pichup.

The instrument is beautiful and really easy to play, but the sound was not too exciting, very middy, and the tone control seemed to do nearly nothing. It did not cut the sound, it just changed it a little.

I expected that it was perhaps miswired or a wire broken loose, so I took all the controls out and found it perfectly wired in the same manner as a standard P bass. Meanwhile I find that another TBer has the same problem, and as I did some 'Net research - many others as well!

At the urging of 62bass here who has the same problem, I spent a good afternoon checking, measuring and double-checking everything, and the only thing I could find that seemed weird was that the DC resistance of the pickup seemed very low - around 1.4K Ohms instead of the usual 10-15K. I happened to have another of these same pickups in my part drawer, and measured that one, and wow! it was also 1.4K ! This is very strange.

I drew up a schematic and sent it to my genius engineer, and he said that the pup impedance was so low, that it would not work properly with the standard 500K pots and 0.05 Cap!

I ordered 2 x 50K pots and installed them with the 0.22 cap he suggested and voila! The bass sounds MUCH better and the tone control WORKS! My guess is that some engineer at Ibanez had the thought to design a low-impedance pup to reduce noise, but somehow the production engineers did not get the word, and used the same pots and cap as usual. Evidently Ibanez continued to make them WRONG for the entire production life of the product. They probably did not sell well for this exact problem.

The other possible fix is to replace the pup, which was reccommended by my engineer. He says no one has every made a good low-impedance pickup. I checked out the Bartolini M34C-B - this seems the one to get, and I found a review of it that was glowing. AND - guess where the reviewer put it - in an ARTCORE BASS!!! Too strange. See the review here - [Invalid or Expired Link Removed]

ANYWAY - if you have one of these fine basses, you can increase the sound quality by a huge factor by changing the pots and cap or the pickup and have a completely different bass.


@Bassamatic,
IBANEZ ARTCORE TONE PROBLEM SOLVED !!!

I just came from my luthier, and he said the tone pot is functioning,
but like in your case, my tone changes very little.

It is wired like a PBass, and wired correctly:
- 4 pole 7.6k noiseless Pickup
- 250k CTS pots
- .047 orange drop cap

He said putting a 1. Cap will make it muddier but might fix the tone problem.
Any thoughts on this?
Also, I don't know if the pots are linear/audio, would this make a difference?

057912
 
Switching from linear to audio will definitely help. And oh don't bother with the orange drop if you change resistor values. They no longer are made the way the original ones were. They are the same as the ones that cost one tenth as much.
 
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Switching from linear to audio will definitely help. And oh don't bother with the orange drop if you change resistor values. They no longer are made the way the original ones were. They are the same as the ones that cost one tenth as much.

Thanks,
I had another mod problem that was fixed by switching, that's why I asked.
So, I'll try an audio, but what value/brand cap do you recommend?

Seems, like a .047 would be what I need, but if a .1 will be too muddy, then maybe a .22?


057912
 
Hold on a bit here. .022, .047, .1, linear or audio taper - no matter what, if you turn the tone pot to zero, you should gear a clear difference. Changing parts values or tapers isn't your problem - a connection is likely broken in the tone signal path. Figure that out before you change parts.

Could be a wire, could be you lost the connection to ground, could be an open wiper on the tone pot.
 
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Hold on a bit here. .022, .047, .1, linear or audio taper - no matter what, if you torn the tone pot to zero, you should gear a clear difference. Changing parts values or tapers isn't your problem - a connection is likely broken in the tone signal path. Figure that out before you change parts.

Could be a wire, could be you lost the connection to ground, could be an open wiper on the tone pot.

Thanks

My skill level is limited to visual imspection. I can't tell if a pot or cap is bad.
Visually it looks like it's wired correctly.

057912
 
Then an audio taper pot would help some but If the value is the same, the change would be the same for the full sweep. Maybe a 500 k pot. Do you know what it came with originally? I ask because linear pots are not usually used for tone controls on a bass.
 
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Then an audio taper pot would help some but If the value is the same, the change would be the same for the full sweep. Maybe a 500 k pot. Do you know what it came with originally? I ask because linear pots are not usually used for tone controls on a bass.


- 4 pole 7.6k noiseless Pickup
- 250k CTS pots
- .047 orange drop cap


Could you educate me on the difference between 500K and 250K?


Edit: If I have this re-wired would I use a linear for vol and audio for tone?
I had a problem once before with a mod and re-wiring with audio fixed it somehow.
But I don't remember if I use two, or just the one for the tone.

057912
 
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