PTB Wiring

[joelorigo]

Hi! This is my first post.

I have spent a couple years building pedals. I started as a completely clueless noob and have learned a lot, with the help of a free awesome message boards. Now I want to focus on some long thought about guitar upgrades and mods. I recently just finished replacing the pickups in a 87 MIJ Squier Strat and installed jumpier so the bridge is connected to the lower tone. Yay!

Now I want to try the PTB wiring in this guitar. I have been researching and have come across the attached diagram which doesn't look too hard for a beginner like me.

How does it look? Any opinions / tips to do this?

Forgive me for what are noob questions but here they are. The diagram doesn't specify but I have seen the pots needed are exactly A250 for volume, A500 for treble and C1M for bass. Why does the bass pot need to be reverse taper?

The guitar is left handed so it came with reverse pots. If I wanted to have the knobs operate in the same direction I am used to, the pots I would need C250K, C500K and A1M, correct? If not the operation will be opposite to what is currently on the guitar? (which isn't really a big deal for me since my left handed Gibson guitars operate opposite of my fenders - it's frustrating, even after all these years, mid-song to reach down and forget which way to turn the volume pot)

On the diagram, what is the ground symbol on the 1M pot? is it just pointing out that it is grounded?

[JohnH]

Hello and welcome to GN2

That PTB diagram looks all ok to me. You can use your current V and T pots if you want, which might be a 250k for tone. With bass fully up, it should give the usual tones with no change. But if you are getting new ones then I agree with your pot types and values for left-handed.

When you wire it up, you would swap all teh outer pot lugs
.
The ground symbols can be thought of as a bare wire that joins all the pot backs, with the main ground to the jack as shown. there would normally be another ground too, to go to your bridge/saddles to ground the strings

The 'volume kit' shown is a treble-bleed circuit. I use a 120k and 1000pF in parallel with a 250k pot,

[joelorigo]

Thank you.

I think I would purchase new pots at the recommended values. I was going to replace the electronics in this anyway. And the more I think about it I will use not worry about the left-handed rotation issue and get the recommended type. I read that the 1M needs to be reverse or a nice gradual taper on the bass cut circuit. 

I do have another wire that is connected to the claw (I believe). It would connect to the volume pot, right? There isn't any reference to this wire in the above diagram. 

Also, where is a good place to buy the pots, caps, etc.? I know of Stew Mac. And from building pedals Mouser, Small Bear, Digi-Key, and a few others.

[newey]

If you've already discovered Mouser and Digi-Key, you know where to go for the parts. StewMac tends to be pricier.

JohnH said this above, but I'm not sure he was clear. A reverse log (i.e., "C") taper is recommended for the bass cut for smoother operation across a wider range of the pot's rotation. This has nothing to do with wiring pots for left handed operation. Left-handed guitars use the same pots as regular guitars (although reverse-log pots are sometimes used). To wire a pot for left-handed operation, just swap the right and left lug wiring around. For example, on a volume pot for right handed use, we would typically wire the input from the pickups or switch to the counterclockwise ("CCW") lug, the wiper to the jack +, and the CW lug to ground. If you reverse those, wiring the CCW lug to ground and the input to the clockwise lug, you reverse the operation for lefty use.

[joelorigo]

Ah, I see. It wasn't clear. Now I get it. Thank you. Now I could re-wire my lefty Gibsons to make them "normal."

[joelorigo]

Finding the C1M pot is proving to be difficult btw

[newey]

If you can't find an antilog pot, you can use a regular taper pot, it's just a question of better control over the bass cut through more rotation of the knob.

[joelorigo]

I found the C1M pot. G&L sells it in their online shop

[joelorigo]

Quick question, I am looking at Orange drop caps for the .0022 and .022 needed. Is this correct or the type not important? I saw a photo of a G&L Doheny and they were not orange drops.

[frets]

Hi Joe,

Yes, the traditional values per G&L are .022 (22nF) for the Treble Cut Pot and .0022 (2.2nF) for the Bass Cut Pot. You can use just about any construction type of a tone cap although I would avoid ceramics or electrolytic. You can use polyester (greenies), polypropelene (Orange Drops), PIO (paper in oil), or wax caps.

[joelorigo]

Thank you

[blademaster2]

Jan 25, 2021 16:14:14 GMT -5 frets said:

Hi Joe,

Yes, the traditional values per G&L are .022 (22nF) for the Treble Cut Pot and .0022 (2.2nF) for the Bass Cut Pot. You can use just about any construction type of a tone cap although I would avoid ceramics or electrolytic. You can use polyester (greenies), polypropelene (Orange Drops), PIO (paper in oil), or wax caps.

Definitely agreed about avoiding ceramic caps (poor tolerance, varying value as they age, intermodulation but to a lesser extent), although I have seen Gibson Les Pauls that used them, and other brands like Hagstrom. I have used polyester in my guitars.

To be honest about it, however, I probably myself could not hear what type was in a guitar I was playing.

[frets]

Blade,
The excitable topic of cap construction has caused some lively debates. And I’m not going to beat a dead horse. I did a blind test with friends a long time ago and could not differentiate between polypropelene, styrene, or polyester. I could pick the PIO most of the time. I could tell a ceramic and definitely wax paper. I have a favorite Gudeman PIO that has followed in my favorite guitars over the years. It is one sweet cap. I bet others on here have their one favorite cap.

[joelorigo]

I have ordered the A250, A500 and C1M pots, a new switch, caps, and some wire. 
I found this description of the wring on another board:

- Your pots go V/T/B = 250K A, 500K A, 1M C (A = audio taper; C = reverse audio taper).
- Your caps are .022uF treble and .0022uF bass
- The pickups hook up to the switch like a Strat
- The output from the switch goes to lug 1 on the treble pot, then from there to lug 2 of the bass pot
- The treble pot's cap goes between lug 2 and the back of the pot
- The bass pot's cap goes between lugs 2 and 3
- A wire runs between lug 3 on the bass pot and lug 3 on the volume pot
- Your output wire runs between lug 2 on the volume pot and the jack's hot lug

Now for the grounds:

- The p/u grounds, the claw ground wire, and lug 1 of the volume pot all connect to the back of the pot
- A ground wire runs from the back of the volume pot, from there to the back of the treble pot, from there to the back of the bass pot, and from there to the ground lug of the jack


That seems to match the above diagram except for the grounding. The diagram doesn't show of a ground wire from the volume pot, to the treble pot. And it is missing the claw wire. Do I need to run a grounding wire connecting all the pots together? The current wiring does have have this

[unreg]

Jan 26, 2021 18:07:13 GMT -5 joelorigo said:

That seems to match the above diagram except for the grounding. The diagram doesn't show of a ground wire from the volume pot, to the treble pot. And it is missing the claw wire. Do I need to run a grounding wire connecting all the pots together? The current wiring does have have this

hi joelorigo, ashcatlt told me he doesn’t solder anything to the backs of his pots. I have a star ground paperclip, newey’s idea, screwed into the painted cavity wall. After reading ash’s advice, I removed all ground wires from the backs of my pots and routed/soldered them to my star ground.

Ash said never to ground through shielding. That works wonderfully!


So, no, you don’t need to run a ground wire connecting all pots together. Though, I’m not an expert guitar hardware guy; I don’t know if all the pots need to be grounded, but that currently seems like a wise idea to me. Each pot has a ground lug, so it makes sense.

Plus, a star ground works exceptionally well in a guitar bc, in a guitar, ground loop problems don’t exist.

[blademaster2]

Jan 26, 2021 16:14:49 GMT -5 frets said:

Blade,
The excitable topic of cap construction has caused some lively debates. And I’m not going to beat a dead horse. I did a blind test with friends a long time ago and could not differentiate between polypropelene, styrene, or polyester. I could pick the PIO most of the time. I could tell a ceramic and definitely wax paper. I have a favorite Gudeman PIO that has followed in my favorite guitars over the years. It is one sweet cap. I bet others on here have their one favorite cap.

Oh, I do know that. The fact that *I* would not expect to hear a difference does not say that others do not or cannot.

Having said that, I generally until recently keep my tone knob at full, so there was little likelihood of hearing any differences anyway. Lately I turn it down to 40-50% (since I installed "ice-pick single coils" in two of my guitars in the neck position and it needs the top end shaved off when playing clean) so I might be at a point where I could experiment and see if I can hear it myself.

The first thing would be to ensure that the values of the two type of caps were essentially the same before any other comparison would hold water.

How would you describe the difference of tone of PIO compared against, say, a ceramic or wax paper?  If I were to be a skeptic, I might first assert/suspect that the tolerance of the capacitance for the ones where you could hear a difference might still have dominated the result more than the dielectric material - but I would never claim that with any certainty.

[joelorigo]

I do see in photos of the G&L Legacy Specal and Doheny wring, that there is a black wire from volume to treble, and one from treble to bass. I guess my question does the above diagram assume that one would connect all the pots? I mean, it does show grounding symbols on the treble and bass pots. And it doesn't have the wire to the claw drawn, and this is needed right? Or is it saying "wire it like this and the bass and treble pots will be grounded." Sorry, I'm new to all this.

[unreg]

Actually, each pot DOES need to be grounded via its ground lug or claw. (Sry for being unsure earlier.) Grounding through shielding is the worst type of grounding bc that can cause hum/buzz problems. Also, skipping soldering to the backs of pots can also be beneficial bc that way heat can NOT damage one of your pots. (I believe I’m going to need to order a replacement pot to cure my current volume pot’s heat damage.)

[joelorigo]

I'll take that as a "yes" to connecting the 3 pots and the claw. Ha ha. My knowledge level and the implications of grouding, shielding and ground loops are low.

[newey]

Let's clarify a few things. Ideally, the cases of pots and switches should be grounded as there is some chance that not doing so would cause some noise, particularly if one is playing in an electrically "noisy" environment. Traditionally, this has been done by "daisy-chaining a ground wire between the backs of the pots.

But soldering to the backs of pots can be problematic. Back "in the day", when Fender, Gibson, et al. were daisy-chaining gorund wires, it was harder to wreck a pot by soldering to it. Now, the insides of your typical pot are often plastic, and excess heat can fry the pot.

Note that, when one is grounding the shells of pots or the frames of switches, this is a shielding ground- it is not carrying signal from your pickups. We want (again, ideally) our signal grounds to be separate from the shielding grounds until the point where both attach to the output jack, or close to that point.

If one is shielding the cavity of one's guitar (and the underside of the pickguard, if the guitar is so equipped), then there is no need to daisy chain the pot shells, and therefore no need to solder to the backs of pots. The switch frames and pot shells will be grounded by contact with the shielding (where the shaft pokes through the shielding). The shielding is then grounded, in turn, via one's grounding point, whether that be a "star ground" or not.

If one is not shielding one's cavity (which is tough to do on semi-hollow or hollow-bodied guitars), then one should ground the shells of one's pots for the potential benefit in noise reduction. That grounding will then necessarily involve soldering to the pots, whether or not one is daisy-chaining the ground wires or using a star grounding scheme.

A ground wire should be run from the bridge/trem/strings to the grounding point where it is possible to do so (again, some semi-hollow and hollow-bodied electrics being the exception). This wire is understood to be needed, and is therefore omitted from many wiring diagrams to avoid clutter.

unreg said:

Grounding through shielding is the worst type of grounding bc that can cause hum/buzz problems.

That can be an issue if we are using the shielding to carry signal. Here, we are not talking about any signal-carrying connections, just grounding the shells of the pots and/or the frames of the switches for shielding purposes.

[joelorigo]

Jan 26, 2021 23:45:10 GMT -5 newey said:

Let's clarify a few things. Ideally, the cases of pots and switches should be grounded as there is some chance that not doing so would cause some noise, particularly if one is playing in an electrically "noisy" environment. Traditionally, this has been done by "daisy-chaining a ground wire between the backs of the pots.

But soldering to the backs of pots can be problematic. Back "in the day", when Fender, Gibson, et al. were daisy-chaining gorund wires, it was harder to wreck a pot by soldering to it. Now, the insides of your typical pot are often plastic, and excess heat can fry the pot.

Note that, when one is grounding the shells of pots or the frames of switches, this is a shielding ground- it is not carrying signal from your pickups. We want (again, ideally) our signal grounds to be separate from the shielding grounds until the point where both attach to the output jack, or close to that point.

If one is shielding the cavity of one's guitar (and the underside of the pickguard, if the guitar is so equipped), then there is no need to daisy chain the pot shells, and therefore no need to solder to the backs of pots. The switch frames and pot shells will be grounded by contact with the shielding (where the shaft pokes through the shielding). The shielding is then grounded, in turn, via one's grounding point, whether that be a "star ground" or not.

If one is not shielding one's cavity (which is tough to do on semi-hollow or hollow-bodied guitars), then one should ground the shells of one's pots for the potential benefit in noise reduction. That grounding will then necessarily involve soldering to the pots, whether or not one is daisy-chaining the ground wires or using a star grounding scheme.

A ground wire should be run from the bridge/trem/strings to the grounding point where it is possible to do so (again, some semi-hollow and hollow-bodied electrics being the exception). This wire is understood to be needed, and is therefore omitted from many wiring diagrams to avoid clutter.

unreg said:

Grounding through shielding is the worst type of grounding bc that can cause hum/buzz problems.

That can be an issue if we are using the shielding to carry signal. Here, we are not talking about any signal-carrying connections, just grounding the shells of the pots and/or the frames of the switches for shielding purposes.

Ok. Great information. Thank you.

Do the current CTS pots have plastic in them? The C1M is from Mighty Mite, do you know if it has plastic?

[joelorigo]

I drew a few things on the diagram to make it easier for me, fi more cluttered. Look ok?

[newey]

Looks fine.

[joelorigo]

Thank you. And I follow this even though this is a lefty guitar, correct? The switch will just be on the other side?

[newey]

Looks to me like you have the tone pot wired lefty but not the volume pot. This is assuming that we are looking at the undersides of the pots.

For the bass cut pot, which way you wire it depends on which way you want the cut to operate and also whether a "C" taper pot is being used.

[joelorigo]

I'm actually just going to follow the diagram as is and not worry about compensating it for a left handed guitar. To keep it as simple as possible. I'm ok if the pots operate the opposite from normal because that's what I'm used to on my left-handed Gibsons. I also am assuming it is looking at the underside of the pots. I do have the C1M for the bass pot. But, I didn't change anything in the diagram make it for a "lefty," that's how I found it. In the one couple of posts ago, I only added pot numbering, a wire to the claw, and the grounding wire between the pots. So I'm curious that you say "the tone pot wired lefty but not the volume pot."

[joelorigo]

I found a photo of a G&L Legacy wiring that seems to match that diagram.

[newey]

No, I guess it's equivalent, looking again. I'm just used to seeing the tone pot signal in to the wiper, the out from lug 1 to the cap and to ground. This is wired "backwards" from the usual way, but still righty.

[joelorigo]

Jan 27, 2021 22:44:45 GMT -5 newey said:

No, I guess it's equivalent, looking again. I'm just used to seeing the tone pot signal in to the wiper, the out from lug 1 to the cap and to ground. This is wired "backwards" from the usual way, but still righty.

Looking at a regular strat wiring diagram, I see what you are talking about.

[joelorigo]

I have all the parts and I'm going to start the re-wire this week.

I bought some non-shielded and some shielded wire (because that's what the Stew Mac Premium upgrade kit contained). Links below.

I have found some different opinions about the shielded wire. One source said to use it on longer runs, like to the output jack. Another said it is not necessary at all. What should I do?


guitarelectronics.com/gavitt-cloth-covered-vintage-style-stranded-guitar-wire/
guitarelectronics.com/gavitt-vintage-style-guitar-wire-w-braided-shielding/