Question LUKE III preamp: what are the internal trimpots used for?

[Iperfungus]

Hi guys!

Since owning the LIII, I didn't mess with internal trimpots and I used the preamp/booster with factory settings.
I've to say I ignored trimpots until I joined the EBMM family here...ahahah!!!

Then I started reading here and there...and now I fucking know that those trimpots lie in control cavity and I cannot ignore them anymore.

Now someone MUST tell me the function of every single trimpot.
There are 5 inside...so I assume they are volume, gain, high, middle, bass controls?
Or something like that...
Or am I totally wrong??

I didn't find much information about this around...

 

[ruger9]

I think they are in 2 groups? 2 and 3?

the group of 2 is COMP (compensate) and BOOST (volume boost when depressing volume knob). Compensate adjusts the volume of the in-between positions (2 & 4) so they are the same volume as the standard positions (1,3,5).

Not sure what the other 3 are, I think I read the same board is used on different guitars, and in the Luke III those 3 pots are not used? I'm sure someone will correct me if I'm wrong. FWIW, my Luke III (2015) only has the 2 pots, not 5.

 

[Iperfungus]

I think they are in 2 groups? 2 and 3?

the group of 2 is COMP (compensate) and BOOST (volume boost when depressing volume knob). Compensate adjusts the volume of the in-between positions (2 & 4) so they are the same volume as the standard positions (1,3,5).

Not sure what the other 3 are, I think I read the same board is used on different guitars, and in the Luke III those 3 pots are not used? I'm sure someone will correct me if I'm wrong. FWIW, my Luke III (2015) only has the 2 pots, not 5.

Yes, they are in 2 groups...2 and 3.
My Luke III is from 2019.

I was wondering about the functions of the group of 3, indeed.
I've read around that they do change nothing in the Luke III and in MM specs no eq function is mentioned.
Maybe you're right about same board usage in different guitars/basses.

The COMP function sounds useful and something to mess not with, then (factory settings should be the best already).
Is that always ON or it's activated together with booster, with the push-push pot?
So, the only trimpot one could attempt to adjust is booster's volume.

 

[beej]

As noted, two of the trimpots are for pickup compensation and boost. Don't be scared to touch them- you can adjust to taste. (For example, on my HSS Luke I have the comp one turned all the way off.)

There should two other ones, for the Silent Circuit adjustments (which aren't relevant if you have an HH). Are you sure you have a 5th? Do you have a pic?

 

[Iperfungus]

As noted, two of the trimpots are for pickup compensation and boost. Don't be scared to touch them- you can adjust to taste. (For example, on my HSS Luke I have the comp one turned all the way off.)

There should two other ones, for the Silent Circuit adjustments (which aren't relevant if you have an HH). Are you sure you have a 5th? Do you have a pic?

Yep.
Here we go with some pics: there are 5 trimpots inside!
Mine is HH.

This could be some Rev. X of the wiring and circuit.
In 2020, when MM swapped pickups from Transitions to MM ones, they also added a PCB and other stuff, if I'm not wrong here.
Wiring should be the same but differently realized.
My LIII is from 2019, maybe they did with some different boards in previous years?

 

[GoKart Mozart]

This has been brought up a few times before; they did switch to a common board at some point but I can't recall exactly which other model(s) shared that same board. I've got a 2013 LIII with the original 2-trimpot board and a 2015 BFR LIII with the 5-trimpot one.

 

[beej]

Right- ok it's that one. The other three are bass/treble/piezo mix.

 

[Iperfungus]

This has been brought up a few times before; they did switch to a common board at some point but I can't recall exactly which other model(s) shared that same board. I've got a 2013 LIII with the original 2-trimpot board and a 2015 BFR LIII with the 5-trimpot one.

I assume other models would be JP6/7, Luke or Axis Super Sport with piezo, then.
The usage of a common board makes sense, but it's not that clear how/when trimpots are used and for what they're used for, since it seems to be not documented.
I found a couple of old threads here with the same questions/doubts.
About the COMP trimpot: is it active on the Luke III HH model as well, to compensate volume in 2 and 4 switch positions with splitted pickups?

 

[Iperfungus]

The other three are bass/treble/piezo mix.

Not used, then....if there's no piezo installed.

 

[GoKart Mozart]

I assume other models would be JP6/7, Luke or Axis Super Sport with piezo, then.
The usage of a common board makes sense, but it's not that clear how/when trimpots are used and for what they're used for, since it seems to be not documented.
I found a couple of old threads here with the same questions/doubts.
About the COMP trimpot: is it active on the Luke III HH model as well, to compensate volume in 2 and 4 switch positions with splitted pickups?

It must be just the JP6/7/Majesty (piezo + boost) & Valentine (boost) that shares the common board with the LIII; by the time of the PCB switch Music Man had eliminated the piezo option on most models like the ASS, Albert Lee, Luke II; that was also around the time that they pared down the color offerings as well.

Yes, the compensation pot is active on the HH as well; like you said, it allows you to adjust the volume of the split positions.

 

[Iperfungus]

It must be just the JP6/7/Majesty (piezo + boost) & Valentine (boost) that shares the common board with the LIII; by the time of the PCB switch Music Man had eliminated the piezo option on most models like the ASS, Albert Lee, Luke II; that was also around the time that they pared down the color offerings as well.

Yes, the compensation pot is active on the HH as well; like you said, it allows you to adjust the volume of the split positions.

This helps to better clarify many things!