I think the better choice for bridging the grounds across the two channels in the control cavity is across the volume pots and not the tone pickups, because the volume pots are the signal source (pickup) connections. It could also be argued that you do not need a ground jumper between the two channels in the control cavity because the cross connection (single point ground) is made at the selector switch from the two channels (if you keep all of the grounds separate so shields (grounds) do not cross connect as they route through the guitar). With passive guitar electronics without a PCB the goal is to plan out how the grounds are connected and establish them a only one point (single point ground). The single point ground really means we are minimizing wiring loops, where any loop actually can act like an antennae to pick up noise. Grounds: (All ground types should ideally only connect at one point, meaning they are gathered and then all terminate at a single solder connection or node) Chassis Ground: With Gibson Les Pauls (LPs) that use a metal pot plate the plate is considered the chassis ground (grounds the pot housings), which also includes the selector switch housing and the output jack housing and connection to a metal jack plate (if not made from plastic). Basically, anything the user can touch is considered chassis ground. This also includes the tail piece ground, which ground the strings. Signal Ground: The signal outputs originate at the pickups where the ground is the braided Gavitt wire. We want the signal grounds to connect together at one point and then connect to the single point ground node. What is interesting is Gibson in production used the plate to act as a signal return for the tone pot to the volume pots, which essentially violates the single point ground best practice. Technically, using the pot rear covers as a ground solder point and the plate together also violates the single point ground best practice. I think at minimum Gibson should have made the signal ground connection between the tone and volume pots with a direct bus wire and not rely solely on the plate. Power Ground: The guitar in the video is passive circuitry only. So there is not power ground used. Connect all the grounds together at a single point (single solder connection), this will minimize any antennae loops. More stuff: Usually with single pickup swaps you should verify the polarity of the new pickup as compared to the one remaining as well as the DC resistance (looking for a shorted pickup). Some clone pickups are actually wired with the polarity reversed even though they use Gavitt wire (which somewhat assumes a consistent industry magnetic pole orientation for a dual pickup guitar like a LP, established essentially by Seymour Duncan and Gibson as to how the coil is wound and the magnets oriented). I use a Simpson 260 (Series 8) Analog VOM to check polarity. Upgrades: (depends on the specific guitar and how it is used). Warning: Expensive. 1) Insulate each Pickup push back wire from the control cavity to the pickup with Teflon sleeving so no pickup shields touch other grounds as they route through the guitar (use of single point ground). 2) Use Teflon single conductor with braided shield (with outer jacket) instead of the pushback wire from the selector switch. This has several advantages: It insulates the braid as the cable is routed through the guitar. It will not absorb moisture like the Gavitt cloth. It is high temperature so you can position all of the shields and other connections on the back of the pot together and solder all in one operation (we want to minimize the heating of the pot rear cover). The stranded center and braid are silver coated copper which has a better appearance (shiner solder joint) when used with tin/lead/silver wire solder and additional liquid flux. When excess flux is removed with IPA the joint is very shiny. The actual outer diameter of the Teflon wire is very close to the Gavitt wire of the same gauge (20AWG Standard) because Teflon jackets and insulation can be ultra thin. 3) Insulate the bus wire pot rear cover ground cross connections with Teflon sleeving (very thin wall, will not melt, will not absorb moisture and attractive). 4) Insulate the capacitor leads with Teflon sleeving. 5) Use Mica tone caps. MICA capacitors are commonly 5% tolerance, ultra stable, very long life, excellent for passive filter circuits and very effective if you pair them with 5% tolerance CTS guitar pots (TAOT or similar or custom order). Gibson CTS pots from the factory are +/- 20% tolerance and don't seem to be matched in sets of four for a LP. Some are so poor that I wonder if they are actually made by CTS (even though there is CTS stamped on the pot). The inaccuracy in electrical behavior is very noticeable for experienced players. For best positional accuracy and channel to channel matching it is best to use +/- 5% Tolerance pots that are matched sets of four, with 5% tolerance caps.
There’s certainly a lot here, and I appreciate it. The one thing that stood out to me that I wanted to engage with is tolerance. My understanding is that tolerance in a resistor or capacitor is the difference in the actual value versus the nominal value at the time of manufacture. It’s basically the factory saying a 500K pot might actually be 400K or 600K in your 20% example. The difference in actual versus nominal value will change with age, but it’s slow to do so. Therefore, I think it’s less important to get 5% tolerance pots over 20% tolerance ones than it is to simply measure the pot resistances to create a matched set. If I’m missing anything, I’d be curious to hear about it. Anyway, I do try to match pots many times, but more frequently, I decide to replace passive components based on whether they have drifted outside of their tolerance range, which I take as a sign of failure or impending failure, and that’s why I’m curious.
@@hacksguitarhobby The following is a little long, but there is really no short answer to your question. Tolerance with pots are little different than discrete resistors or capacitors in how they effect the control of the guitar settings (volume and tone knob position). With guitar pots from CTS what we are really trying to understand is their transfer function (resistance), usually referenced to the ground leg, relative to rotational position, commonly called the taper for audio curves. What is really needed is to match pots relative to a reference rotational position, which is up to the builder, usually at 50%, 60%, or 70% of total rotation from 0%. If you look at the CTS 450G guitar pot data sheet the tapers are called: Linear; Std. D Spl. D Audio; C, A, B, BD, H, and J. Most LP guitar pots as sets all have the same pot taper and are generally either A, B, or BD. TAOT uses the A taper or very close to it. If you order custom pots from CTS, like TAOT, you can specify your taper and many other specs, but your have to have a large buy. The 5% pot tolerance gives you a better matching taper shape from pot to pot. With the shape consistent, you can now match pots resistance based on your reference rotational position. The +/- 20% tolerance pots are all over the place, the shapes don't seem to match and matching rotational values is futile. If new pots do not rotate easily you can use Deoxit D5 to clean and lubrication them. Which I generally do as a matter of course before testing them. To make matching easy it is best to make up a jig where you can place a pot set it to 0% mechanical (this is at the low mechanical stop). Rotate the pot until the resistance starts to change (low inflection point) make a note of the rotational position. Then determine the maximum inflection point. Then verify the maximum stop position. The stops are established within the pot itself, and for the same CTS part number at 5% tolerance the inflection points and the stops should be very consistent. Then measure the resistance at your reference rotation (for example, 70%). You can use a degree wheel to line up the zero mark (low stop), establish the max stop, then inflection points and then the matching 70% rotation resistance. Then sort based on a batch, usually 100 pots. Once the above is completed when the guitar knob positions are set to the same value for volume and tone (if the tone caps are 5%) they should behave similarly for a LP with a matched set of pickups. Some LP guitars actually have indicators (pointer mounting washers) on the pots to help set the pot value more accurately. You can add them to any LP you rebuild with speed knobs or bell knobs. This helps the player consistently set their knob settings which for some players is very important. If you use 5% MICA tone capacitors, which are expensive, they will outlast the guitar owner and the guitar. For current production Gibson LPs with hand wiring, Gibson uses film (orange drop) capacitors from China, which is really unbelievable. Just think, you buy a brand new LP Custom Ebony for several thousand dollars and it has Chinese caps. The above really depends on the guitar you are rebuilding, its market value, purpose and budget available. Obviously, a matched pot set cost more than 4 pots purchased from one vendor with the hope that they will be close. Some vintage LP guitars, 1950s or 1960s, are worth several thousands of dollars for an excellent playing example (no warped neck or other major problems) but the electronics and wiring are just worn out. If the owner wants to keep the guitar in playing condition, the guitar electronics are usually rebuilt. You have to explain to the owner what is going to be done and why, and what materials are going to be used. It is good to have your own LPs (good to have a VINTAGE LP and a MODERN LP wiring example) properly setup, with your upgrade mods so the customer can see your improvements and actually play the guitar. Obviously, the pickups determine much of the tone, but the owner will understand how the controls work and why the mods are an improvement. For the older guitars this usually means adding a tail piece ground. So some luthier skills are needed on the bench. Most professional players want consistency between their LP guitars for a similar set of pickups and are willing to pay to upgrade the guitar electronics and wiring to make the control and tone behavior consistent.
Yes, I lumped them together, but my comment was more so directed at the 490T. I like a 490R/498T combo much better. Also this particular 490R was a PCB version and something was making it weak. May have been a flaw in the PCB.
@@hacksguitarhobbyIt's more of a question of taste and style of music played, and of course the guitar it goes into. 490r/490t is a great combination in an ES guitar but maybe not so much in an LP.
@@hacksguitarhobbymy bad man. So a ground loop is not what is happening here if you solder the same bare wire to the case of all pots. Electrically they become the same point if you do it that way or the way you did it in a “C” pattern. A ground loop is when there is a difference in potential between a “ground” and another “ground” between each other. In a a perfect circuit, all negatives would be tied to the same ground headed to earth and there would be no potential between them. However, if something happens that lifts one ground to say a little more positive than another ground in the system, the potential to get shocked by completing the circuit as a human exists. When I was in the Air Force, we would be working on a test set that was supposed to be grounded to a ground bar heading to earth ground but somewhere across the building there would be another circuit that would be tied to the positive of the outlet we’d be using and it would be tied to a different grounding rod in the ground that was in a more dry area or some other factor than the only our outlet was attached too. The result would be that there might be a slight difference in potential between our ground and a ground in the wall using a different outlet but the same positive as ours (in a 28vdc or something like that circuit) and somebody would get shocked. ANYWAYS….all that to say that if you mate a wire to all the backs of those pots, there is no way for them to have differences in potential causing a ground loop. They all go through the same negative on the jack. In fact, many Les Pauls through the years used a solid metal plate for all the pots to be mounted to. I hope I didn’t confuse you. Thanks for being humble instead of nasty.
Thank you for the explanation. In my Tele builds you’ll probably have heard me debate whether to use a ground wire connecting the back of the pots, because of the same issue. Perhaps “ground loop” isn’t the right terminology for me to use because it has another meaning? I’m using it as shorthand for a phenomenon that I’ve read creates a one turn coil that can receive EMI. This is the best representation I can find of what I’m trying to communicate in the video(s): www.fralinpickups.com/2018/11/12/understanding-guitar-grounding/
@@hacksguitarhobby thanks for the reply my friend. All you need to know about the guy writing that article is that he tells the reader to select DC Resistance. There is no such thing, there are alternating and direct current voltages settings on a multimeter, but resistance is just resistance. Anyways, it’s a well, put together article. However, dude is just wrong. You can’t over ground something. Otherwise the shielded/braided cables inside the cable to the pickups would create a million “ground loops” or as this guy calls it “single turn pickup”. This isn’t real. Just my opinion. Maybe you could test it both ways and make a video showing the results.
Interesting point about the shielded cable! I certainly don’t understand the science enough to know why they aren’t a problem but rather are preferred for noise reduction… or cavities that are fully encapsulated in shielding for that matter. It is very common advice though… here is another article that mentions that even the C shaped ground is close enough to a loop/coil to cause a problem, to the point that they recommend a star ground in an LP: humbuckersoup.com/proper-guitar-grounding/ I feel like there must be something to the antenna phenomenon that is real but certainly beyond my grasp, so I just do the star grounds as a “can’t hurt” sort of thing.
I think the better choice for bridging the grounds across the two channels in the control cavity is across the volume pots and not the tone pickups, because the volume pots are the signal source (pickup) connections. It could also be argued that you do not need a ground jumper between the two channels in the control cavity because the cross connection (single point ground) is made at the selector switch from the two channels (if you keep all of the grounds separate so shields (grounds) do not cross connect as they route through the guitar).
With passive guitar electronics without a PCB the goal is to plan out how the grounds are connected and establish them a only one point (single point ground). The single point ground really means we are minimizing wiring loops, where any loop actually can act like an antennae to pick up noise.
Grounds: (All ground types should ideally only connect at one point, meaning they are gathered and then all terminate at a single solder connection or node)
Chassis Ground:
With Gibson Les Pauls (LPs) that use a metal pot plate the plate is considered the chassis ground (grounds the pot housings), which also includes the selector switch housing and the output jack housing and connection to a metal jack plate (if not made from plastic). Basically, anything the user can touch is considered chassis ground. This also includes the tail piece ground, which ground the strings.
Signal Ground:
The signal outputs originate at the pickups where the ground is the braided Gavitt wire. We want the signal grounds to connect together at one point and then connect to the single point ground node. What is interesting is Gibson in production used the plate to act as a signal return for the tone pot to the volume pots, which essentially violates the single point ground best practice. Technically, using the pot rear covers as a ground solder point and the plate together also violates the single point ground best practice. I think at minimum Gibson should have made the signal ground connection between the tone and volume pots with a direct bus wire and not rely solely on the plate.
Power Ground:
The guitar in the video is passive circuitry only. So there is not power ground used.
Connect all the grounds together at a single point (single solder connection), this will minimize any antennae loops.
More stuff:
Usually with single pickup swaps you should verify the polarity of the new pickup as compared to the one remaining as well as the DC resistance (looking for a shorted pickup). Some clone pickups are actually wired with the polarity reversed even though they use Gavitt wire (which somewhat assumes a consistent industry magnetic pole orientation for a dual pickup guitar like a LP, established essentially by Seymour Duncan and Gibson as to how the coil is wound and the magnets oriented). I use a Simpson 260 (Series 8) Analog VOM to check polarity.
Upgrades: (depends on the specific guitar and how it is used). Warning: Expensive.
1) Insulate each Pickup push back wire from the control cavity to the pickup with Teflon sleeving so no pickup shields touch other grounds as they route through the guitar (use of single point ground).
2) Use Teflon single conductor with braided shield (with outer jacket) instead of the pushback wire from the selector switch. This has several advantages: It insulates the braid as the cable is routed through the guitar. It will not absorb moisture like the Gavitt cloth. It is high temperature so you can position all of the shields and other connections on the back of the pot together and solder all in one operation (we want to minimize the heating of the pot rear cover). The stranded center and braid are silver coated copper which has a better appearance (shiner solder joint) when used with tin/lead/silver wire solder and additional liquid flux. When excess flux is removed with IPA the joint is very shiny. The actual outer diameter of the Teflon wire is very close to the Gavitt wire of the same gauge (20AWG Standard) because Teflon jackets and insulation can be ultra thin.
3) Insulate the bus wire pot rear cover ground cross connections with Teflon sleeving (very thin wall, will not melt, will not absorb moisture and attractive).
4) Insulate the capacitor leads with Teflon sleeving.
5) Use Mica tone caps. MICA capacitors are commonly 5% tolerance, ultra stable, very long life, excellent for passive filter circuits and very effective if you pair them with 5% tolerance CTS guitar pots (TAOT or similar or custom order). Gibson CTS pots from the factory are +/- 20% tolerance and don't seem to be matched in sets of four for a LP. Some are so poor that I wonder if they are actually made by CTS (even though there is CTS stamped on the pot). The inaccuracy in electrical behavior is very noticeable for experienced players. For best positional accuracy and channel to channel matching it is best to use +/- 5% Tolerance pots that are matched sets of four, with 5% tolerance caps.
There’s certainly a lot here, and I appreciate it. The one thing that stood out to me that I wanted to engage with is tolerance. My understanding is that tolerance in a resistor or capacitor is the difference in the actual value versus the nominal value at the time of manufacture. It’s basically the factory saying a 500K pot might actually be 400K or 600K in your 20% example. The difference in actual versus nominal value will change with age, but it’s slow to do so. Therefore, I think it’s less important to get 5% tolerance pots over 20% tolerance ones than it is to simply measure the pot resistances to create a matched set. If I’m missing anything, I’d be curious to hear about it. Anyway, I do try to match pots many times, but more frequently, I decide to replace passive components based on whether they have drifted outside of their tolerance range, which I take as a sign of failure or impending failure, and that’s why I’m curious.
@@hacksguitarhobby The following is a little long, but there is really no short answer to your question.
Tolerance with pots are little different than discrete resistors or capacitors in how they effect the control of the guitar settings (volume and tone knob position).
With guitar pots from CTS what we are really trying to understand is their transfer function (resistance), usually referenced to the ground leg, relative to rotational position, commonly called the taper for audio curves.
What is really needed is to match pots relative to a reference rotational position, which is up to the builder, usually at 50%, 60%, or 70% of total rotation from 0%.
If you look at the CTS 450G guitar pot data sheet the tapers are called:
Linear; Std. D Spl. D
Audio; C, A, B, BD, H, and J.
Most LP guitar pots as sets all have the same pot taper and are generally either A, B, or BD. TAOT uses the A taper or very close to it. If you order custom pots from CTS, like TAOT, you can specify your taper and many other specs, but your have to have a large buy.
The 5% pot tolerance gives you a better matching taper shape from pot to pot. With the shape consistent, you can now match pots resistance based on your reference rotational position. The +/- 20% tolerance pots are all over the place, the shapes don't seem to match and matching rotational values is futile. If new pots do not rotate easily you can use Deoxit D5 to clean and lubrication them. Which I generally do as a matter of course before testing them.
To make matching easy it is best to make up a jig where you can place a pot set it to 0% mechanical (this is at the low mechanical stop). Rotate the pot until the resistance starts to change (low inflection point) make a note of the rotational position. Then determine the maximum inflection point. Then verify the maximum stop position. The stops are established within the pot itself, and for the same CTS part number at 5% tolerance the inflection points and the stops should be very consistent.
Then measure the resistance at your reference rotation (for example, 70%). You can use a degree wheel to line up the zero mark (low stop), establish the max stop, then inflection points and then the matching 70% rotation resistance. Then sort based on a batch, usually 100 pots.
Once the above is completed when the guitar knob positions are set to the same value for volume and tone (if the tone caps are 5%) they should behave similarly for a LP with a matched set of pickups. Some LP guitars actually have indicators (pointer mounting washers) on the pots to help set the pot value more accurately. You can add them to any LP you rebuild with speed knobs or bell knobs. This helps the player consistently set their knob settings which for some players is very important.
If you use 5% MICA tone capacitors, which are expensive, they will outlast the guitar owner and the guitar. For current production Gibson LPs with hand wiring, Gibson uses film (orange drop) capacitors from China, which is really unbelievable. Just think, you buy a brand new LP Custom Ebony for several thousand dollars and it has Chinese caps.
The above really depends on the guitar you are rebuilding, its market value, purpose and budget available. Obviously, a matched pot set cost more than 4 pots purchased from one vendor with the hope that they will be close.
Some vintage LP guitars, 1950s or 1960s, are worth several thousands of dollars for an excellent playing example (no warped neck or other major problems) but the electronics and wiring are just worn out. If the owner wants to keep the guitar in playing condition, the guitar electronics are usually rebuilt.
You have to explain to the owner what is going to be done and why, and what materials are going to be used. It is good to have your own LPs (good to have a VINTAGE LP and a MODERN LP wiring example) properly setup, with your upgrade mods so the customer can see your improvements and actually play the guitar. Obviously, the pickups determine much of the tone, but the owner will understand how the controls work and why the mods are an improvement. For the older guitars this usually means adding a tail piece ground. So some luthier skills are needed on the bench.
Most professional players want consistency between their LP guitars for a similar set of pickups and are willing to pay to upgrade the guitar electronics and wiring to make the control and tone behavior consistent.
Thanks for explaining all the things you did to investigate and verify the pickups, that is very helpful for future purchases.
You bet!
The 490r is a great pickup
Very much so.
@@hacksguitarhobbyyou said in the video that it’s not good… correct?
Yes, I lumped them together, but my comment was more so directed at the 490T. I like a 490R/498T combo much better. Also this particular 490R was a PCB version and something was making it weak. May have been a flaw in the PCB.
@@hacksguitarhobbyIt's more of a question of taste and style of music played, and of course the guitar it goes into. 490r/490t is a great combination in an ES guitar but maybe not so much in an LP.
I took them out of my LP and put a set of Duncan's In and put the 490s back in . I LOVE 490s@@adrianguggisberg3656
Man, some of that work you do is really fast!
✌️🤣🎸🎶🎵🎶🎵🎶
I work in fast forward :)
@@hacksguitarhobby -✌️🤣👍
omg why havent i thought of the capo trick thats genius
Love it!
Thanks for the video. That’s not what “ground loop” means. But love the video man
Thank you, but please explain?
@@hacksguitarhobbymy bad man. So a ground loop is not what is happening here if you solder the same bare wire to the case of all pots. Electrically they become the same point if you do it that way or the way you did it in a “C” pattern. A ground loop is when there is a difference in potential between a “ground” and another “ground” between each other. In a a perfect circuit, all negatives would be tied to the same ground headed to earth and there would be no potential between them. However, if something happens that lifts one ground to say a little more positive than another ground in the system, the potential to get shocked by completing the circuit as a human exists. When I was in the Air Force, we would be working on a test set that was supposed to be grounded to a ground bar heading to earth ground but somewhere across the building there would be another circuit that would be tied to the positive of the outlet we’d be using and it would be tied to a different grounding rod in the ground that was in a more dry area or some other factor than the only our outlet was attached too. The result would be that there might be a slight difference in potential between our ground and a ground in the wall using a different outlet but the same positive as ours (in a 28vdc or something like that circuit) and somebody would get shocked. ANYWAYS….all that to say that if you mate a wire to all the backs of those pots, there is no way for them to have differences in potential causing a ground loop. They all go through the same negative on the jack. In fact, many Les Pauls through the years used a solid metal plate for all the pots to be mounted to. I hope I didn’t confuse you. Thanks for being humble instead of nasty.
Thank you for the explanation. In my Tele builds you’ll probably have heard me debate whether to use a ground wire connecting the back of the pots, because of the same issue. Perhaps “ground loop” isn’t the right terminology for me to use because it has another meaning? I’m using it as shorthand for a phenomenon that I’ve read creates a one turn coil that can receive EMI. This is the best representation I can find of what I’m trying to communicate in the video(s): www.fralinpickups.com/2018/11/12/understanding-guitar-grounding/
@@hacksguitarhobby thanks for the reply my friend. All you need to know about the guy writing that article is that he tells the reader to select DC Resistance. There is no such thing, there are alternating and direct current voltages settings on a multimeter, but resistance is just resistance. Anyways, it’s a well, put together article. However, dude is just wrong. You can’t over ground something. Otherwise the shielded/braided cables inside the cable to the pickups would create a million “ground loops” or as this guy calls it “single turn pickup”. This isn’t real. Just my opinion. Maybe you could test it both ways and make a video showing the results.
Interesting point about the shielded cable! I certainly don’t understand the science enough to know why they aren’t a problem but rather are preferred for noise reduction… or cavities that are fully encapsulated in shielding for that matter. It is very common advice though… here is another article that mentions that even the C shaped ground is close enough to a loop/coil to cause a problem, to the point that they recommend a star ground in an LP: humbuckersoup.com/proper-guitar-grounding/ I feel like there must be something to the antenna phenomenon that is real but certainly beyond my grasp, so I just do the star grounds as a “can’t hurt” sort of thing.
Man, you really don't know what you're doing buddy lol
Thanks for the comment. Perhaps an explanation though?