Bass-cut and the G&L PTB system

[newey]

Sept 17, 2020 23:11:08 GMT -5 carlsoti said:

does this look right for a 6-way switch, with the N+B past the neck position, push-pull cap changes for treble and bass?

I didn't check through the rest of your diagram, but the 6-way switch wiring is fine. For the treble bleed switch, just think that, without the switch, the treble bleed would be wired between the wiper of the pot and the CCW lug (the lower one with the pot oriented as it is in your diagram). SO, your switch will simply be switching the treble bleed cap and resistor in/out from between the wiper and the lower lug. In the position with no treble bleed, the switch connects nothing.

[carlsoti]

Thanks, newey. I think I've got all the parts I need to get this slapped back together. Thought it's been my luck as of late that I should expect my DMM battery to be flat.

[carlsoti]

I finally got my guitar put back together. Everything functions as it should, right off the bat. On initial listen, the bass roll-off of the PTB circuit isn't as pronounced as I had expected, however, I've only played it at "Person-in-the-next-room-on-a-tele-conference-call" volume levels. I suspect it will be more functional when the amp is moving more air.

I also fully expect my hap-hazard over-shielding might bite me in the butt, but that's an issue for a different day. 

Thanks to everyone posting diagrams, checking them, etc. It was all of your work that helped me through this project.

[newey]

Nice looking job! I wouldn't worry about your shielding, if it's working fine now it should continue to do so.

I think that everyone we've had who has tried the bass-cut scheme has said that the effect is not as dramatic as they had hoped. The expectation is that it will cut bass the same way a regular tone control cuts treble, and it doesn't. That may be why more manufacturers haven't followed G&L's lead.

[carlsoti]

I did get a chance to play it some more.  With more volume, it works much closer to what I expected, and I really like it. I certainly didn't expect it to act like an active shelving EQ one might find in the studio, but others may have and that might be why it's not what they expected. I did find that something is awry with my middle pick-up now. Like it's got a wet blanket over it, in any position that includes the middle pick-up, but it's bright and sparkly in every setting that doesn't have the middle pick-up on. I'm at a loss as to what's causing that.  I'll probably play it as is until I get frustrated enough so solve the issue.

[skern49]

Hey everyone. I've got the PTB system installed in my Strat which has regular single-coils. I currently have

250k volume, linear
250k treble cut with .047uF cap, audio
500k bass cut with 1nF cap, audio

I plan on updating the electronics and am curious what effect moving to a 1M pot for the bass cut will have. Will it simply give me more available cut at the lower end of the knob? Would the tone of the guitar when the knob is at 10 remain unchanged?

I'm fairly satisfied with how things are working right now, but if this change will simply give me more range, I can't see how it would hurt.

[JohnH]

hi skern49

That sounds fine. A 1M bass pot will give you a bit of extra range of bass cut, but at max (ie most bass), these circuits have no effect so there's nothing lost from having a different pot value.

[skern49]

Jun 12, 2021 18:10:19 GMT -5 JohnH said:

hi skern49

That sounds fine. A 1M bass pot will give you a bit of extra range of bass cut, but at max (ie most bass), these circuits have no effect so there's nothing lost from having a different pot value.

great, thanks!

[stevewf]

I tried adding a 1MΩ resistor to partially short-circuit the whole bass cut control, and it increased the effect. I didn't notice any change in volume and tone; I see, though, that in theory some must exist, and that it would be a permanent, global effect. Maybe I don't notice it because it's pretty small -- 1MΩ is a pretty tight squeeze in passive guitar signal speak, isn't it? -- or because I used a crappy amp while comparing (and/or crappy ears).

Here's an attempt at a wiring diagram:
[edit: 1.0nF]

The added resistor is at the bottom-right of the drawing.

Why did adding the resistor to ground increase the effect of the bass cut signal? Or, was I just hearing things? I did this a long time ago, before I got GuitarNutz2 (and therefore, a universe ago), and I was desperately looking for a bass cut, ended up rabbit-holing through EE glossaries online, found RC circuits, tried a few, hit the above, and sutured the patient . Now that I've been Nutzed, next time I open up, I can be smarter about testing.

Info, in case of need:
Pickups are GFS Dream-90 (neck) and stock TheFretWire 'Tron-bucker (bridge).
Master Vol is A500K with V-Treb bleed (trim pot pretty much center, I think);
Treble cut is also A500K with 2.2nF 22nF capacitor;
Bass cut is C1M with 0.1nF 1.0nF and 1MΩ resistor
Both Treble cut and Bass cut come after the Master Volume; this choice was driven by the physical layout of the guitar's control mounting holes (pics on Flickr) and my desire to avoid "pool laps" of back&forth wiring given the Master Vol's location.

[Deleted]

I still think need 250K in front if not using a C1M.

When I tried to use a 500K (Lin) I got to half way till I notice a change. It would explain the Rec Log used on G&L , C1M isn't easy to come by.

I'd suggest trying (and I need to try it myself really) cutting just above the silver side on Lug 1.
220K to Lug 3 and the other end to Lug 1 and Output. Input to Lug 2, now you can use a A1M

[bubbaleeevilgenious]

I have wired my Rogue Generic Pbass this PTB system. I used a 100K pot for the volume, a 250K pot with 1000uF Cap for the treble cut, and a 1 meg pot with a 2200uF Cap for the bass cut. I should have my generic Pbass sounding amazing. While the highs stay were they're supposed to be, and the lows. Will definitely rattle the house next door 😁.