OLP MM2 bass wiring

[servant]

Hi guys,

My son has an OLP/MusicMan MM2 StingRay bass "on spec." We're trying it out to see if he wants to buy it. It actually plays quite nicely, and the wood resonates better than I expected.

I knew that it had passive electronics and, like the EB MM StingRay, has three pots. On the web I read that they had 2 volume and one tone, which I was sure was a typo.

But, no, it is 2 volume! I was wondering how (and why!), as it only has one humbucker pickup. Turns out that one volume pot controls the front coil (I tapped with some needle nose pliers); the other controls the rear. Needless to say, there is not much difference in tone between the two.

Now, the sole tone pot seems to do nothing from about 3 all the way up to 10. 0 is an OK "bass" tone; up to three adds some brightness.

So - couple of questions about my ideas, and am open to fresh suggestions.

If we get this, I would probably go with one master volume, and would like to set it up with individual, passive treble and bass tone controls. I didn't think the latter would be possible until I learned, through another picker at church, about the G&L Legacy tone controls. With different value caps, I should be able to do this on the StingRay, right?

Even barring that, what do you think is causing the one tone control to do so little from 3 - 10?

[UnklMickey]

since i am not familiar with the wiring scheme and the pickups, i can only guess.

maybe the volume pots are fairly low value and are not allowing much in high frequencies from the coils to survive.

add to that, the fact that the fundamental frequencies a bass produces are of course lower than a guitar.

and the possibility that the tone cap might have a small value, and has little effect on the highest of the frequencies that are present, until it is almost "fully in the circuit" (tone pot near zero).

also, (probably the most biggest reason) if a tone pot has is a linear, rather than audio taper, the "activity" will be pushed toward the low numbers.

you will still have all the same tone effect at both ends, the same range of tone settings, it just has to do with how things are "bunched up" at one end.

if it is a linear pot and you replace it with an audio taper, it wont change any of the tones that you get. just where they occur on the knob.


hope i said that in a way that makes sense.




unk

[servant]

Well, I opened the control cavity. The pots are so tiny that the solder blob on the back of each obscures most of the printing/embossing. The tone pot starts with A5 so must be 500K; not sure about the volume pots.

Tone cap has sorta smeared white ink. Top line is 100V, second line has four characters. It is 6, 8, then what looks like an upside down U but could be an incomplete 0, then what looks like a J (with no top bar like I see here - more like the right side of this U ). So it could be "680J". Would that be 680pF, or is that "partial zero" some marking indicating 68pF?

So, in addition to getting some decent pots in there, what about the rest of my idea - 1 volume, 1 treble, 1 bass?

Or add a push/push or push/pull (volume?) to switch the pickup from parallel to series coils?

In addition to maybe copying the G&L tone circuit on this bass, I want to help the G&L owner put in a SuperSwitch so I'll be back with that one...

Thanks,
Dean

[UnklMickey]

Dean,

a series/parallel switch seems like a great addition here.

i would say a single volume and treble and bass controls are not a bad idea either. especially since s/p switching brings such challenges to implementing 2 volume controls.



measuring the total value of the tone pot and what kind of taper is easy. only one end of the pot (ccw) and the wiper will be used in the circuit. use that cheap little ohmeter (the one i've been encouraging everyone to buy) and measure between both outer terminals. that is the value of the pot.

step 2: set the tone to 5 and measure between either one of the outer terminals and the wiper (center). if its a linear it will be equal or nearly equal to half the total. if it's an audio taper, the measurement will be about 10~15% from ccw to wiper, and 85~90% wiper to cw.

i have always been a bit confused by the markings on capacitors. so i'll leave that one for someone else.


unk

[servant]

unklmickey said:

i have always been a bit confused by the markings on capacitors. so i'll leave that one for someone else.

unk

Maybe I've found it, right here on this very forum.

In the Schematic section, JohnH has "The LP Maximiser - Two humbuckers to the max"

guitarnuts2.proboards45.com/index.cgi?board=schem&action=display&thread=1138768962

On that page, he has photos of his buffer circuit, containing two yellow caps. On the caps themselves, I can see "39nJ 100" and "330nJ 63" Further down, he has a drawing of the board, and labels them 39nF and 330nF, respectively.

So, is this nanoJoule? Is this some universally recognized nomenclature for what we North Americans call nanoFarads? Here in Canada our electricity usage is measured in Joules, but I've never heard the phrase used in electronics. If I have to learn something new we might as well go back and call capacitors condensors!

If this is the case, this bass must have a 68nF tone cap. What is a typical value for an electric bass?

[mlrpa]

I personally would drop the one volume, and add a series/single coil/parallel switch.

[servant]

servant said:

Maybe I've found it, right here on this very forum.

In the Schematic section, JohnH has "The LP Maximiser - Two humbuckers to the max"

guitarnuts2.proboards45.com/index.cgi?board=schem&action=display&thread=1138768962

On that page, he has photos of his buffer circuit, containing two yellow caps. On the caps themselves, I can see "39nJ 100" and "330nJ 63" Further down, he has a drawing of the board, and labels them 39nF and 330nF, respectively.

Anyone?? Beuller?

I've also come across www.onlineconversion.com/electric_capacitance.htm which lists a conversion from/to a "jar" which, in this context, I have never heard of. Could this be the J on the cap in the bass? Is there a nanoJar?

[JohnH]

Hi servant

sorry I missed your post noting the LPmax. Those caps on mine are 39 and 330 nF. I dont know why they are stamped with a J! - it must mean something in chinese.

On your bass, the only sensible tone cap value with a 6 and an 8 would be 68nF, which is 0.068 microfarads. Is that possible? Its a bit higher value than on a guitar, reflecting the lower range of the bass tones.

John

[sumgai]

servant,

The 'n' is a temperature co-efficient - it means that the capacitance goes up as the temp goes down. The 'J' is a tolerance range, which in this case, is 5% . Neither are mission critical, but they do point to some care being given to parts selection.

Otherwise, what John said.

HTH


sumgai