Monday, January 26, 2015

Bass Cut Tone Pot. Get Some Clarity out of Those Heavy Riffs!



For the years I've been around heavy music and the metal scene back in Portland, one thing rules above all.  Heavy riff-age.  Down tuning has become more and more common in the heavy music.  Hell, Drop D is the basically the common vernacular of metal music.  I've been using multiple tunings even a drop G tuning with a bass string for years now.    One thing I do see less of, is the usage of the Treble Cut tone knob that is on basically every passive guitar.  I do use it here and there and I have my secret tricks with it, but it seems to be in less use these days, compared to the days before dirty boxes. 

After searching the internet for some easy cure to my Drop G cheapo guitar with muddy pick-ups.  (Even more accentuated by the low tuning.)  I came across a wiring that was standard on a lot of G & L guitars and Reverend guitars.  A BASS CUT TONE POT!  This was the answer, and super easy and cheap to do.  Seems like a really good option with all my guitars.  I usually just use a master, or global tone pot for the treble cut, so why not put a bass cut for the other tone pot on my Les Paul styled guitar?  I don't like resetting my EQ for every different guitar I use on stage, and this gives me a lot of control to make my guitar dialed in.  Also, as many know, especially in a studio, bass on a guitar can just add a lot of clutter in the mix.  When I down tune in a band setting, I'm encroaching on the kick and bass territory.  And I lose some of my definition.  Instead of using a boost pedal to push some other high-end or mid, I can simply cut the low-end and get a similar effect.      

Wring #1 The Simple Bass Cut Tone Pot
I came across a few different wirings for this tone pot.  The basic idea is the same as the input cap in almost all guitar pedals. Depending on the value, we can use the cap, in-line, to filter out bass frequencies.  The simplest wiring, is just this.  A cap between the middle lug  receiving the hot signal, and the top lug that goes to the output jack.  (wiring chart #1)
Wiring #2 Another Variation
The other wiring I found ended up in my guitar.  The cap is in-line, just wiring a little differently, and there is a 1M resistor going to ground after the cap.  The BIGGEST difference in the behavior of the tone pot was the cap value.  I found a good medium with a .0022uF cap.  However I tested it with a .001uF cap and got even more bass cut.  I didn't try the .0047uF cap other suggested as well, but it should cut less bass.  Those caps seem to work in a good range. 


Les Paul wiring with Neck Volume, Bridge Volume, Master Treble cut, and Master Bass Cut.
Lastly, I haven't seen a wiring diagram for a Les Paul styled guitar.  So here we are.  This diagram will give you a Neck Volume, Bridge Volume, and a Master Treble and Bass Cut Tone Knobs.  (As a side note, I recommend adding a "Treble Bleed Mod"  on both the Volume Pots)  The only re-wiring you should have to do, is the change the order of where the pickups get routed to the 3-way switch.  Run the pickups to the volume pots first, then to the 3-way switch, and from the middle lung of the 3-way switch, you go to the treble cut pot, to the bass cut pot, to the output jack.

Hope that helps some people.  It's brought new life to a few cheap guitars with bad pickups and it's improved the versatility of my nicer guitars.  I'm feeling like this should be the new tone law for guitar makers. 

24 comments:

  1. rad man, i'll try it with my basswood shelter les paul with seymour duncan pickups

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  2. Hi. This is very helpful at least for the LP neck HB. What if I want to leave the bridge tone alone and do the Bass Cut for the neck tone only. What I mean is, instead of having global tone controls, have the usual low pass for bridge only and a high pass for neck only? The guitar is a LP with 50s wiring. Should I do the same as per the Wiring #2 schematic but run the lug 3 on the tone pot to the switch instead of the output jack? Obviously, that will mean that I need to remove the connection between lug 2 of the volume pot and the switch (as per the 50's wiring). Will that work? Thanks!

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    1. Yeah you got it. Also keep you bridge tone pot as you have it wired currently.

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  3. What is the functional difference in wiring #1 and wiring #2? I have a Epiphone EB 0 bass (mudbucker) that needs the bass frequencies tamed a little. Would you suggest one wiring over another for this application? Thank you, and thanks for posting this too!

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    1. I don't really have the right tools to tell you the difference in frequencies. So, try them both. Yeah most people have that problem with that bass. Give it a try!

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  4. I just tried the wiring#2 and got a fail.

    What I'm trying to do differently though is keep all 4 controls on an SG and ADD a master bass roll off. To do this I took the wiring#2 diagram and ran the hot and ground from the SWITCH rather than the master tone in the diagram. Any reason why that shouldn't work? It doesn't.

    Fully open I get a horribly REDUCED output from both pickups. Roll it off a bit and the output goes altogether.

    What can be happening? Grounding too much signal?

    And what IS that resistor for anyway?!

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  5. Update. The output doesn't QUITE go altogether when rolled off. It's just even more massively reduced! I can only hear it against the unamplified guitar itself if I turn up my amp's reverb. THEN I can hear that there is a VERY quiet signal getting through.

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    1. You're on the right track, however the green line in my diagram is a hot signal, not a ground. The middle lug of the selector switch should go to the pot lug of the bass cut pot. There might be a separate ground wire on the switch, and that should be connected to all other grounds. If you're not sure if all your grounds are connected then buy a multimeter and set to continuity and start poking around and testing. However you should be able to see it. Make sure all hot wires and ground wires are not connected. Again, also make sure every ground is connected.

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  6. Thanks for the response Lum. I've done continuity testing and all the grounds are working. Using diagram#2 the hot from the switch goes to the middle lug on the bass pot from which I have a jumper wire to the bottom lug where the foot of the cap is.

    I get continuity from the switch to the jack tip with the bass control open (but remember, already severely reduced output from the pickups) and as soon as I roll that bass knob off a bit I lose continuity (and very VERY quiet pickup output). So something seems to be wrong at the pot. Unless that's exactly what reading I SHOULD get? Surely not?

    That jumper wire between the middle lug on the bass roll off pot and the bottom one that the cap is attached to. Is that correct?

    I'm flummoxed!

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    1. Man weird. Have you tested another pot? Pots can be cracked or bad. You seem to have the wiring right. Also maybe try diagram 1. Alligator clips helps save time instead of soldering. Standard log or audio pot?

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  7. I haven't tested another pot but I did test this one before it went in. I did wonder about trying diagram #1.

    I even wondered is maybe the resistor is CAUSING the problem. What is that resistor meant to achieve that is not achieved using diagram #1. I've looked at Reverend's bass contour and it doesn't use the resistor.

    Then again, you say diagram #2 is on your guitar and is your preferred method. Perhaps my resistor IS shot.

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  8. #2 will work without a resistor. Give it a try. It&s certainly not mandatory. I honestly can&t remember how the resistor effected it, but it should determine the depth of cut.

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  9. Hi, I tried this mod with my SG and tried it either with a 2,2nf and finally a 1,5nf because bass cut wasn't enough. I tested it 2 days and was a bit desapointed with the result. Bass cutting wasn't so musical to my ear. Tested with 2 amps and different distortions. even if the possibilities of combinations are more important, the most disturbing is that I felt that I could not get the full saturated sounds that I love on my SG. the feeling of having the microphones permanently clamped with a narrow harmonic rendering and not very musical. I returned to the original wiring and I am very disappointed because this idea of bass cut would be welcome in many cases. anyone else have this experience? other tracks would it be possible to preserve the original rendering roof by bringing more versatility?

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    1. Man, I never thought this mod would cause so many issues. There is really only so much you can do with passive guitar controls. Mostly only cutting sounds and frequencies. The only mod I could see you doing would be replacing the resistor in the second mod for a trim pot to change the curve. This mod plus a standard low past time control both turned down, will give you a band pass or notched like effect. Much like you described. Have you thought about active electronic controls? You'll get much more EQ control and boost on hand. Frank Zappa did this with many of his SGs for more control. If higher gain and bass cut is what you want, give a treble booster s try. Myself and many others have posted about them on this site and others. Good luck!

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    2. I've just ordered some 0.001uF (1nF / 1000pF !) caps to see if I can get ANY bass cut at all. I'll post my findings.

      That resistor diagram did nothing for me at all. Wonder if it would work in conjunction with the new cap? But what would it do? Nobody knows!

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    3. Put the 0.001uF cap in and still no noticeable difference. I can hold it in place with clips and roll on the full 'bass cut'. Then play a big fat low E and quickly pull the clips off and hear no difference at all.

      The pot itself is of course a 500K, so that is having its own effect. Probably best to just take it out of the signal path and forget about the whole sorry saga! All things are worth a try though.

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  10. Just a quick update to my situation. I snipped the resistor out and my sound came back. However the capacitor is hardly affecting the sound at all. I think I may JUST be able to discern a tiny change at the beginning of the roll off but nothing worthwhile.

    I'll try using the other diagram which I think is the way Reverend do it, and see if that wins. Failing that I'll have to find another use for this spare hole!

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  11. Nope. Did nothing! Just to be absolutely certain, can you confirm I am using the right capacitors? They are sold as 2.2nF - 0.0022uF - 2200pF 50V. Are these about right? Can I check them with a multimeter?

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    1. Tried again, this time with a 0.001uF cap, and still no useful difference that my ears can hear. I can hold it in place with clips and roll on the full 'bass cut'. Then play a big fat low E and quickly pull the clips off and hear no difference at all.

      The pot itself is of course a 500K, so that is having its own effect. I can roll that and the signal will go muffly in exactly the same way with or without that cap. I'm beaten. I'll just take the pot out.

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    2. All I can ask is, are you using a real amp with a full sized 10 or 12" speaker? If not, or if you're using headphones, you might not be getting a real representation of the bass response. My guitar has this wiring. I used the same theory as almost all effects pedals input caps and Reverend Guitars use the same tone control. Test your cap maybe? Other than that, I don't know what's going on for you.

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    3. I used Orange Drop .0022uf 600v cap.. it was fine. Also used a 1meg 1 watt resistor. Also, this may be a dumb question but how are your soldering skills? A cold solder joint will not let the resistor go well to ground.

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  12. I know this is an old post, but thanks for the info
    I did v3 on my Les Paul with Seymour Duncan P-Rails, which was pretty muddy and awful before. This brought it to life. I used .0022uf on both pots. Sounds killer now. I found the .o22 to be kind of sterile in the high pass filter. But when I swapped it out it became infinitely tweakable. Now I can even turn both pots down on the rails and get a more Strat-like tone. Thanks a lot.

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  13. Thanks for posting the wiring pictures. I've been thinking about doing this mod for a while.

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