Just add a cap 0.0033uf (I used a PIO just for the mojo) between the two lugs where the wires are soldered on the fifth knob. It will now work as a bass cut for the neck and middle position and gives a lot of nice combinations!

The whole story:

I have spend the whole week to read about mods for the fifth knob and bassy neck pickups at the internet. Today I spend the whole day today to find out some easy and simple 5:th knob mods by my self.

My guitar is a 340 with High-Gains in neck and middle position. Bridge is a HB-1. The guitar is built1991 and it looks like the HB-1 is added at some point later. In middle position there is a normal bridge pick up (according to the spacing of the poles). But I don´t know actually, it could be done this way from the beginning.

Anyway.

This is what I came up with:

To start with I just bypassed the tone and volume knobs completely. It added some volume and fullness to the guitar, but it was quite bassy in middle and neck position, too much actually. It also appeared to be some loading issue. At least it felt that way and it didn´t get along with my pedalboard that well and was a little spikey in the highs as well. Did not like it and went on.

Second I soldered the two wires at the fifth knobs lugs together so only the fifth knob was out of the wiring. Still a little bassy and it felt a little odd once again. I think that it is the loading thing.

After that I just removed the two wires completely at the other end. One from the switch and one from the middle lug on bass volume pot. Then I added a cap (0.01uf) from the switch to the lug. It took some bass out but it still felt wrong and didn´t get along with my pedals.

Then I found the winner!

I soldered back the wires to stock wiring, but added a cap (0.0033uf) between the two lugs that is used on the fifth knob. Now it felt right and the fifth knob acts like a bass cut on the middle and neck pickups. The other knobs are working as it works best (if you ask me) and you can dial in all tones and volumes you want. It only affects the neck and middle position. The bridge is untouched.

I know that there are lots of good mods out there, but I have not found this one that was so easy. I really think it´s worth a try!

I mentioned a loading issue earlier. I´m not sure if that is what happens, it just “felt” that way and the guitar behaved like if there was. I have no proof of it and have not measured anything.

What you really have is a version of the "bright" circuit that has been done to the volume controls for decades, especially those guitars that folks want to stay really bright when turning the volume down. Here is another example:

http://www.ratcliffe.co.za/articles/volumepot2.shtml

I agree. On some of the older overwound neck high gains, for those players who want to retain brightness and definition in the neck pickup position, this is a good mod.