Bass Cut Knob Wiring?

[thedirestrat]

Hey all,

I found this Premier Guitar article on a “focus knob” or just simply a bass cut knob, and I want to install it on my third tone knob of my Strat.

www.premierguitar.com/the-recording-guitarist-the-fabulous-focus-knob

Can anyone with more electronic knowledge explain this diagram for me and check if it’s right? The reason why I doubt the article is because there seems to be some contradicting information when explaining how to wire it:

“Push the wire leading from the volume pot (or pickup selector) through lug 3 of the new pot, along with one leg of the capacitor. (Remember, when the pot is viewed from the rear as in the diagram, lug 3 is on the left.)”

And now check the diagram on the website:


Here it says the output jack is on “lug 3”, not the pickup selector/switch!

I highly doubt they’re wrong though, I’m probably missing something. So here’s what I need: Would this work as a bass cut knob (10 to 1 cuts bass) and how do I wire it up connecting to the volume knob and pickup switch?

I really honestly rather have the output jack connected to the middle lug of the volume pot as usual. Can’t I just put a jumper from the volume’s middle lug to the lug in the basscut knob where the jack is supposed to go? And then do the same thing for the pickup selector?

I really appreciate it!! Thanks!!
You are some fine folks here

[unreg]

Aug 28, 2024 12:51:13 GMT -5 thedirestrat said:

The reason why I doubt the article is because there seems to be some contradicting information when explaining how to wire it:

“Push the wire leading from the volume pot (or pickup selector) through lug 3 of the new pot, along with one leg of the capacitor. (Remember, when the pot is viewed from the rear as in the diagram, lug 3 is on the left.)”

And now check the diagram on the website:


Here it says the output jack is on “lug 3”, not the pickup selector/switch!

Hi thedirestrat,

This situation forces me to check our always wise potentiometer orientation thread:

guitarnuts2.proboards.com/thread/6612/potentiometer-orientation

According to our wise thread, it seems that your site wasn’t specific enough. When the shaft is pointing up AND the lugs are facing toward you, lug 3 is on the right. Maybe they were assuming the shaft was pointing down, like it is when soldering to a potentiometer lug inside an upside-down guitar. But the pic, on the other hand, seems to be labeled as if the shaft is pointing up. So, lug 3 IS on the right, as you thought.


edit: Even though they labeled their pot-case portion of their pic as if the shaft was pointing down. Yes, it’s confusing since they made a mistake while thinking.

[unreg]

Or, maybe this bass cut pot is wired differently; and so maybe I’m wrong. Sry thedirestrat if they weren’t confused. Perhaps, you should simply wait for a reply with more knowledge; at least you can visit that potentiometer orientation thread now.

[thedirestrat]

Thanks!

That potentiometer guide really helped me out, I think I understand a bit more now.

They are wrong about the diagram.

Since it's "rear" up, the lugs are actually 3-2-1 from left to right.

What I don't understand is how I wire this to the entire Strat circuit.

I have a superswitch so that the tone knob only works on positions 1-3-5. So I can't wire it the G&L PTB way where the bass cut knob connects through the tone knob. I want the bass cut knob to work on all positions (2 and 4 included).

How would this work with respect to the volume, tone and superswitch?

Do I just put a jumper from the jack on the volume wiper to lug 3 (bass knob's)? Then another jump from the superswitch to lug 1 (bass knob's)?

Thanks!

[newey]

thedirestrat-

When he says " from the volume pot (or pickup selector)" this equates to "input from pickups" on his diagram. He really means the output from the pickups, but perhaps I'm being picky, since we could accurately calll it the input to the bass cut pot.

I really honestly rather have the output jack connected to the middle lug of the volume pot as usual. Can’t I just put a jumper from the volume’s middle lug to the lug in the basscut knob where the jack is supposed to go? And then do the same thing for the pickup selector?

Your jack will be connected through the middle lug of the volume pot, if this is a Strat-type of axe. When he says "or pickup selector, he's likely referencing an LP style where the pickup selector comes after the V and T controls.

The bass control is wired in series with the output, so what you were suggesting wouldn't work right.

But, we've had a lot of discussion and experimentation with bass-cut controls, and I think some of the other members here who have experimented with this, frets and ssstonelover have posted some schemes, and while I have never done this, the consensus seems to be that a 1M pot works best. If you search "PTB" "Bass cut pot" or similar search terms on the Board here, you should pull up tons of info.

[unreg]

Aug 28, 2024 12:51:13 GMT -5 thedirestrat said:

“Push the wire leading from the volume pot (or pickup selector) through lug 3 of the new pot, along with one leg of the capacitor. (Remember, when the pot is viewed from the rear as in the diagram, lug 3 is on the left.)”

They are wrong about the diagram.
Since it's "rear" up, the lugs are actually 3-2-1 from left to right.

So, it seems the diagram would be correct since lug3 is on the left, as they claimed.

I was thinking that since newey’s potentiometer orientation thread states: “ The CW lug, #3, will ordinarily be the "hot" input, unless one is using an alternate wiring. “, that meant that either the diagram is wrong with lug 3 on the right, since the right lug is “pickup input”, OR they were using an alternate wiring. But, I guess neither is the case, cause newey just said that by “input from pickups” they mean output from the pickups.

[reTrEaD]

Aug 28, 2024 18:58:44 GMT -5 thedirestrat said:

What I don't understand is how I wire this to the entire Strat circuit.

My first question for you: Do you intend to change your Strat's tone circuit so you have one "master" treble-cut tone control, or keep the existing two treble-cut pots and ADD another hole for the Bass-cut pot?

The second question I have for you: What kind of pot do you intend to use for the bass-cut?
--- If you'll be using a typical A-taper (audio taper), you'll want the capacitor to span between CCW lug on one end an the Wiper and CW lug on the other end. The "cut" will occur as you turn the knob clockwise (toward 10).
--- If you'll be using a C-taper (audio taper), you'll want the capacitor to span between CW lug on one end an the Wiper and CCW lug on the other end. The "cut" will occur as you turn the knob clockwise (away from 10).

In any case, you'll want the Bass-cut control to be AFTER the treble-cut tone control(s) and pickup selector, but BEFORE the CW lug of the volume control.

The thread in this link shows a schematic representation of how a bass-cut circuit is connected, using a single tone control and using a C-taper pot: guitarnuts2.proboards.com/thread/7172/bass-cut-ptb-system

[frets]

Newey had made a comment regarding the use of a 1M pot for the bass cut. I find that it does make a slight difference between a 500k. I always use the 1M for my bass cuts.

[thedirestrat]

Hey everyone,
I’m very grateful for all your responses as usual!
So here’s some clarification on my:
The schematic is right, the lug 3 is truly on the left— I still don’t think they worded it right though. Anyways that’s not important Ms
I have a 500k C-Taper (reverse) pot, so unfortunately no 1 Meg for me. What’s the different electrically between a 1 Meg and 500k pot for this application?
And reTrEaD, I do have a Strat-Style axe, and I do have a master tone knob.

I asked the same question on TDPRI before asking here, and Peegoo was kind enough to make a diagram for me to follow! Here it is:




He’s using a “B” linear 500k pot for this diagram. Would my C-Taper pot be a simple drop in to have the Max bass at 10 and least bass at 1?
Or would it have to be reversed?

thanks! reTrEaD I know you explained the CW stuff so I’ll take a better look at it. Thank you

[JohnH]

A 500k C-taper pot is a good choice. It will follow all of the same bass-cut tones that a 1M will do, just missing a few dB's of max cut in the very low bass. See this thread:

guitarnuts2.proboards.com/thread/7172/bass-cut-ptb-system

The first diagram plot illustrates it:




This plot is for a 1M pot, and labelled as if it's a linear pot. But log A or C taper will follow the same range of tones, just spread differently around the pot turn.

So at min bass cut (top red trace), they are all inactive letting all bass through. As you turn down, the max bass cut of a 500k pot is the same as that of a 1M when the 1M is at 50% resistance. Thats labelled as trace 'b5' on the plot (3rd liwest). So compare that to the lowest trace and you can see that there's only a difference in the lowest frequencies. At low E, it's just a 2.5dB difference in the bass cut range and that difference reduces as frequency rises

I disagree with the circuit diagram though. The bass cut circuit should be before the volume pot. So between the blue wires and the volume outer lug. The volume centre lug goes to output. This is to ensure that the volume pot forms part of the RC 'high-pass' filter which is what is making the bass cut happen.

[stevewf]

I, too, use 1M pots for bass cut. Also, they're pots with a "C" taper (aka "reverse audio" or "reverse logarithmic"). That way, you get to have smoother taper with a setup that's similar to a treble cut: knob at ten means less (or no) cut; knob at zero means more cut.


C1M pots have been hard to find. So I make them by physically opening Bourns dual-gang A1M pots ("normal audio" taper) and taking out the wafers that have the resistive tracks. I flip one of the wafers over and put it into the place where the other wafer used to be (note: I also flip the other wafer and put it back into the pot, where the other-other wafer used to be, but that's only as a physical place holder to make the pot continue to function). You have to be motivated to do that, as not only does it take time, but dual-gang pots cost more, too.

You could settle for a B1M (linear taper) pot, whose taper will be a little better than a A1M pot.

[frets]

I swear I can hear the difference on the Bass Cut between a 500k and 1M. I guess it’s just one of those weird “guitar effects”😺.

[ssstonelover]

I'm a little late to the party, sorry! I like to use the C1M pot to get the maximum bass cut so I don't cut' into other frequencies (if I don't want to). It can be hard to find as stevewf says, but it can be found.
--Mouser does have them. In fact they have several. I choose the Alpha splined version Alpha model C!M (RV16AF-10-15K-C1M-3LA) and have used it 3~4 times already. It's not fancy but it works fine.
--I have sent (just last night) a message to Bourns asking them if they can make a C1M pot (which would be PDB24 1 - GTR 01 - 105 C2 for the full size version). If I get a response I'll let the forum know.
--G&L sells a C1M pot and the pictures look nice. It's pricier than the Alpha but this could be a good option. They may or may not have stock....

Edit: 9/3/24 I called Bourns today and they just happened to have 1 of the C1M pots, PDB24 1 - GTR 01 - 105 C2, in sample stock. Their MOQ (minimum order quantity) is 1000 units.....no wonder none of the distributors has stock, it's a valuable part but would be a slow mover, at least until PTB systems catch fire! LOL.

[reTrEaD]

Aug 30, 2024 15:33:02 GMT -5 JohnH said:

I disagree with the circuit diagram though. The bass cut circuit should be before the volume pot. So between the blue wires and the volume outer lug. The volume centre lug goes to output. This is to ensure that the volume pot forms part of the RC 'high-pass' filter which is what is making the bass cut happen.

^this^

If the bass cut circuit is placed after the volume pot, the only resistance to ground after the bass cut cap is at the input of the amplifier, which is typically quite high. You will still get some bass cut, but not much. Below is a standard Strat modified for treble and bass cut:

[thedirestrat]

Aug 30, 2024 22:26:23 GMT -5 reTrEaD said:

Aug 30, 2024 15:33:02 GMT -5 JohnH said:

I disagree with the circuit diagram though. The bass cut circuit should be before the volume pot. So between the blue wires and the volume outer lug. The volume centre lug goes to output. This is to ensure that the volume pot forms part of the RC 'high-pass' filter which is what is making the bass cut happen.

^this^

If the bass cut circuit is placed after the volume pot, the only resistance to ground after the bass cut cap is at the input of the amplifier, which is typically quite high. You will still get some bass cut, but not much. Below is a standard Strat modified for treble and bass cut:

reTrEaD, thanks for the diagram!! Helps immensely. The Premier Guitar diagram had the capacitor wired to the two outer lugs, yours has it on the middle and on only one of the outer lugs. Is there any difference between the two ways of wiring the cap? I think I'm gonna trust yours lol

[reTrEaD]

Sept 1, 2024 17:04:49 GMT -5 thedirestrat said:

reTrEaD , thanks for the diagram!! Helps immensely.

You're welcome.

Sept 1, 2024 17:04:49 GMT -5 thedirestrat said:

The Premier Guitar diagram had the capacitor wired to the two outer lugs, yours has it on the middle and on only one of the outer lugs. Is there any difference between the two ways of wiring the cap?

Since the Wiper and CCW lug of the pot are tied together with a jumper, it doesn't matter if that end of the cap is connected to the Wiper or the CCW lug. Make sense?

[thedirestrat]

Sept 1, 2024 20:51:29 GMT -5 reTrEaD said:

Sept 1, 2024 17:04:49 GMT -5 thedirestrat said:

reTrEaD , thanks for the diagram!! Helps immensely.

You're welcome.

Sept 1, 2024 17:04:49 GMT -5 thedirestrat said:

The Premier Guitar diagram had the capacitor wired to the two outer lugs, yours has it on the middle and on only one of the outer lugs. Is there any difference between the two ways of wiring the cap?

Since the Wiper and CCW lug of the pot are tied together with a jumper, it doesn't matter if that end of the cap is connected to the Wiper or the CCW lug. Make sense?

Makes perfect sense! Thanks reTrEaD for the response!

Sorry for my late response... september got crazy and I still didn't do these wiring things. Gonna do it now!

[thedirestrat]

Hey guitarnuts,

especially reTrEaD, newey, I got my Strat all wired up, and I'm using this diagram: I apologize in advance, it's kinda messy.



There's a lot going on here: 5 way super switch, so that the tone knob/treble cut (middle pot) only affects the 1,3,5 positions, and not the in-betweens. Then there's a treble bleed on off switch on the mini switch furthest to the right. Then an S-1 switch acting as an arlo mod blower switch which takes one pickup and shoots it straight to output. I put a 250k resistor to simulate a loading from one pot because I don't want it to go outta control. Then the other mini switch selects which pickup is being solo'd by that S-1 blower switch (either neck or bridge). And lastly, the subject of this thread, I got a bass cut knob at the furthest away knob/pot. 

Now I tested everything I wired up using only sound. I didn't put strings on yet (there's no neck right now, just a body and then circuit). With the body connected to my amp, I could hear that lovely 60hz hum, and I tapped on the pickup pole pieces. Everything seems to work as it should, except for the bass cut knob. I don't hear a reduction in bass frequencies-- but maybe that's because I'm only going through listening how the 60hz hum changes.

I want to know: would the bass cut knob here work as planned? I would like a bass cut that works on each of the 5 positions of pickup configurations
reTrEaD, I couldn't follow your diagram to a T because your tone knob is connected to your bass cut knob, and I can't with mine since it has to be connected solely to 1,3,5 when I want my bass cut to work all the time.

A gentle reminder that I'm using this PremierGuitar diagram as a basis here:


And that I'm connecting the pot to the input lug of the volume pot instead of the output jack since it was established here that such a change would make a more meaningful difference when it comes to adjusting lower frequencies.

Thanks everyone!

[thedirestrat]

Hey all,
I finally finished the circuit and got the guitar stringed up. Everything worked as it should! Except… for the bass cut knob as expected. The 60hz hum doesn’t lie I guess. Can someone take a look at the rats nest diagram I posted above? Everything can be ignored except for the bass cut connections.

The bass cut literally did nothing. It seemed to not affect the circuit at all. I’ll be sure to check my connections once again.

Thanks again

[stevewf]

Hi. Sorry I don't have time to look carefully, but at a glance I'd say that the bass cut isn't affecting the signal because it's in parallel with another wire (the yellow one that connects 2 commons of the 5-way with the input lug of the volume pot).

Again, at a glance, the answer may be to eliminate that wire, and instead let the signal go only to the bass cut pot (and then onward to the volume pot) via the blue wires.

Edit for clarity: Remove the segment of the yellow wire that connects to the volume pot's input lug - only that segment - still leaving the two commons connected together.

[thedirestrat]

Hey Steve!

Thanks for the very clear explanation! That must be it!

I’m thinking of it as if it’s a tone knob (treble cut).
This bass cut thing is a SERIES connection. And instead of using the output of the jack— going from the output of volume through the pot and out the jack— I’m replacing the switch to volume input with the bass cut itself (in series so it’s like a wire).

I’m having troubles in other places now though… my 5 way Superswitch is getting me angry! For position 2, it turns on BOTH the 2nd and 3rd lug on two half wafers (so this is happening on two of the four groups of lugs).
It used to only happen to one group, now of course after soldering, another group of lugs has the same issue. This means for position 2, I don’t get the middle-bridge pickup iconic pairing (Dire Straits), I get all three pickups on at once, which in my opinion, sounds terrible.

Does anyone here know how to fix this issue with a Superswitch? Thanks!

[thedirestrat]

Hey forget about the switch, it’s a bit wonky but it ended up working anyway— the broken part by chance did not take anything away due to a redundancy!

And the bass cut works stevewf! Totally understand the circuit and it works like a charm.

I just want more bass cut so I’ll lower the capacitor value from 2 nanofarad to about 1 nanofarad if I have one. If not I have a 3.3 nanofarad that I can add to the existing 2 nanofarad cap I have already for around 1.3 nanofarad. Not too shabby at all.

Thanks everyone for all the help. This guitar really sounds great. I really recommend these mods, especially the Blower Arlo Switch! Let me know if you want details I’ll be happy to talk about them!