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The G&L S-500 is like many Strats. It has three SC pickups and a 5-way switch system. Three positions select a single SC pickup and they sound great but hum like all SC pickups. The two humbucker positions put the reverse-wound mid pickup in parallel with either the neck or bridge pickups to give a signature "strat quack" tone with minimal hum. It is really important to leave those "quack" tones unaltered while reducing the hum for the single pickup settings.
The G&L S-500 is like many Strats. It has three SC pickups and a 5-way switch system. Three positions select a single SC pickup and they sound great but hum like all SC pickups. The two humbucker positions put the reverse-wound mid pickup in parallel with either the neck or bridge pickups to give a signature "strat quack" tone with minimal hum. It is really important to leave those "quack" tones unaltered while reducing the hum for the single pickup settings.
First I tried to find data about the G&L pickups. This turned out to be fruitless. There is very little on the web about G&L pickups other than opinions about their tone - most of which is positive. I measured my pickup's dc resistances as Neck = 5.04k, Mid = 5.08k, and Bridge = 5.2k. The mid pickup is reverse wound and used for hum cancelling in switch positions 2 and 4. It makes sense to treat all the pickups as the same since hum cancelling works best when coils are matched. I don't know the number of turns or wire gauge, but if I assume 42 gauge wire, it takes ~3300 feet of wire or ~6000 turns of wire to accumulate 5k ohms of resistance. That's the best assumption I can make, although I didn't base my coil on these figures.
First I tried to find data about the G&L pickups. This turned out to be fruitless. There is very little on the web about G&L pickups other than opinions about their tone - most of which is positive. I measured my pickup's dc resistances as Neck = 5.04k, Mid = 5.08k, and Bridge = 5.2k. The mid pickup is reverse wound and used for hum cancelling in switch positions 2 and 4. It makes sense to treat all the pickups as the same since hum cancelling works best when coils are matched. I don't know the number of turns or wire gauge, but if I assume 42 gauge wire, it takes ~3300 feet of wire or ~6000 turns of wire to accumulate 5k ohms of resistance. That's the best assumption I can make, although I didn't base my coil on these figures.
I considered two coil placement options. One is the back plate (hiding the vibrato springs) as used by Suhr and Ilitch for their cancelling coils. A picture with measurements is shown below. The plate area is about 18 square inches, but it's not easy to actually use that space due to the minimal clearances from the hardware and the routed recess for the plate. I don't know how Suhr can get a coil into that space unless they use very fine wire, which will alter the pickup tone. (See discussion on the tele page about minimizing coil resistance and inductance.) I want to use relatively heavy wire (30 gauge) for my coil to minimize its resistance and impact on pickup tone. I estimated that I need about 1/4 inch clearance for my coil and this back plate area just doesn't provide that much room.
I considered two coil placement options. One is the back plate (hiding the vibrato springs) as used by Suhr and Ilitch for their cancelling coils. A picture with measurements is shown below. The plate area is about 18 square inches, but it's not easy to actually use that space due to the minimal clearances from the hardware and the routed recess for the plate. I don't know how Suhr can get a coil into that space unless they use very fine wire, which will alter the pickup tone. (See discussion on the tele page about minimizing coil resistance and inductance.) I want to use relatively heavy wire (30 gauge) for my coil to minimize its resistance and impact on pickup tone. I estimated that I need about 1/4 inch clearance for my coil and this back plate area just doesn't provide that much room.
The other option is to locate the coil under the pickguard. An image of the routed area under the pickguard is shown below. This is a "bathtub" route that is common with strat-style guitars. In this case I've already done the copper foil shielding. The main cavity for the pickups has about the same area as the back plate, but the cavity is deep enough to allow ~0.2 inches of clearance to the pickups with similar clearance to the side walls. In addition, the control cavity is connected so that the coil loop could extend into that area as well.
The other option is to locate the coil under the pickguard. An image of the routed area under the pickguard is shown below. This is a "bathtub" route that is common with strat-style guitars. In this case I've already done the copper foil shielding. The main cavity for the pickups has about the same area as the back plate, but the cavity is deep enough to allow ~0.2 inches of clearance to the pickups with similar clearance to the side walls. In addition, the control cavity is connected so that the coil loop could extend into that area as well.
Based on noise factor estimates (similar to the Telecaster design) I arrived at some target figures for the coil. I estimated the coil as 3x5 with an area of15 sq inches, allowing for clearances in the cavity and thickness of the coil. The coil wire is 30 gauge to minimize resistance. The noise factor I assumed was ~7500, meaning I would need about 500 turns of wire, and a length of ~800 feet.
Based on noise factor estimates (similar to the Telecaster design) I arrived at some target figures for the coil. I estimated the coil as 3x5 with an area of15 sq inches, allowing for clearances in the cavity and thickness of the coil. The coil wire is 30 gauge to minimize resistance. The noise factor I assumed was ~7500, meaning I would need about 500 turns of wire, and a length of ~800 feet.
The standard S-500 wiring diagram is below. The 5-way switching is typical of Stratocasters, although the tone controls differ. This tone section has both treble and bass controls. The G&L circuit also has a "combine" switch that parallels the neck and bridge pickups, but this can be ignored. Each pickup can be selected alone, or the two humbucker settings parallel the mid pickup with the bridge or neck pickup. Unfortunately, the standard pickup switch is insufficient for hum cancelling since the cancelling coil needs to be switched in/out of the circuit depending on the pickup selection.
The standard S-500 wiring diagram is below. The 5-way switching is typical of Stratocasters, although the tone controls differ. This tone section has both treble and bass controls. The G&L circuit also has a "combine" switch that parallels the neck and bridge pickups, but this can be ignored. Each pickup can be selected alone, or the two humbucker settings parallel the mid pickup with the bridge or neck pickup. Unfortunately, the standard pickup switch is insufficient for hum cancelling since the cancelling coil needs to be switched in/out of the circuit depending on the pickup selection.
The wiring diagram below requires a "super switch" that has four poles and five positions. This is a standard Fender part sold by many dealers (see http://www.themusiczoo.com/product/1659/Fender-Stratocaster--Telecaster-5-Way-Super-Switch/ as one example source). The switch arrangement below puts the cancelling coil (L1) in series with the selected pickup for the three single-coil positions, and bypasses the coil for the two humbucker positions. This ensures that the humbucker position tone is unaltered, while the single coil positions are hum-cancelled. In addition, the cancelling coil polarity is flipped for the middle pickup since a reverse-wound pickup produces an inverted hum signal and therefore the hum cancelling coil needs to be flipped to cancel that hum. The tone circuit is unchanged and I left in the "combine" switch as well. The super switch is a bit larger than a standard 5-way switch, but it fits without any difficulty and there is no change to the guitar's appearance or operation.
The wiring diagram below requires a "super switch" that has four poles and five positions. This is a standard Fender part sold by many dealers (see http://www.themusiczoo.com/product/1659/Fender-Stratocaster--Telecaster-5-Way-Super-Switch/ as one example source). The switch arrangement below puts the cancelling coil (L1) in series with the selected pickup for the three single-coil positions, and bypasses the coil for the two humbucker positions. This ensures that the humbucker position tone is unaltered, while the single coil positions are hum-cancelled. In addition, the cancelling coil polarity is flipped for the middle pickup since a reverse-wound pickup produces an inverted hum signal and therefore the hum cancelling coil needs to be flipped to cancel that hum. The tone circuit is unchanged and I left in the "combine" switch as well. The super switch is a bit larger than a standard 5-way switch, but it fits without any difficulty and there is no change to the guitar's appearance or operation.
I altered my method for winding the coil and opted to use a 4-post frame shown below. A wood base has 4 screws inserted and each screw has a smooth round spacer over it to ensure the wire is not damaged during winding or removal. The screws are slightly angled outwards so that the wire is forced to the base of the frame during winding. I created taps (a loop with a knot) every 50 turns to provide a lot of flexibility in optimizing the cancellation once the coil is inserted into the cavity. I used all 800 feet of wire and ended up with 516 turns. Removing a screw from the frame allowed for easy removal of the final coil.
I altered my method for winding the coil and opted to use a 4-post frame shown below. A wood base has 4 screws inserted and each screw has a smooth round spacer over it to ensure the wire is not damaged during winding or removal. The screws are slightly angled outwards so that the wire is forced to the base of the frame during winding. I created taps (a loop with a knot) every 50 turns to provide a lot of flexibility in optimizing the cancellation once the coil is inserted into the cavity. I used all 800 feet of wire and ended up with 516 turns. Removing a screw from the frame allowed for easy removal of the final coil.
The heavy wire makes the coil easy to handle and shape to fit the cavity. I just used scotch tape to hold the coil together and pressed it into the lower cavity edges. The excess length was shaped to spill into the control cavity and shaped to avoid interference with the switch and pots. The final coil position is shown below. Precise coil position and shape is not that critical, and the wire tension is sufficient to hold it in place. Once the pick guard is attached, the pickups press down on the coil and also hold it in place.
The heavy wire makes the coil easy to handle and shape to fit the cavity. I just used scotch tape to hold the coil together and pressed it into the lower cavity edges. The excess length was shaped to spill into the control cavity and shaped to avoid interference with the switch and pots. The final coil position is shown below. Precise coil position and shape is not that critical, and the wire tension is sufficient to hold it in place. Once the pick guard is attached, the pickups press down on the coil and also hold it in place.
In spite of my care to put taps every 50 turns, there was no need for them. The pickups all produce about the same noise level (~1mV pp) and the full 516 turn coil canceled that nicely. I didn't notice any improvement by using the taps. Pole 4 of the super switch can use a different tap for each of the pickups, but it turned out to be unnecessary, so all the connections are tied to the same point. The only coil connections are made with the red and green wires connecting the coil ends to the super switch. The final coil has a measured resistance of 90 ohms. The final wired pick guard and coil arrangement is shown below.
In spite of my care to put taps every 50 turns, there was no need for them. The pickups all produce about the same noise level (~1mV pp) and the full 516 turn coil canceled that nicely. I didn't notice any improvement by using the taps. Pole 4 of the super switch can use a different tap for each of the pickups, but it turned out to be unnecessary, so all the connections are tied to the same point. The only coil connections are made with the red and green wires connecting the coil ends to the super switch. The final coil has a measured resistance of 90 ohms. The final wired pick guard and coil arrangement is shown below.
The results are excellent, I'm happy to say. There is no visual change to the guitar and it plays no differently after the modification - except the hum is gone.
The results are excellent, I'm happy to say. There is no visual change to the guitar and it plays no differently after the modification - except the hum is gone.
I made some simple measurements with the guitar in a laying position on my floor, which is a worst-case for hum pickup in my environment. The measurements are approximate from looking at a scope trace.
I made some simple measurements with the guitar in a laying position on my floor, which is a worst-case for hum pickup in my environment. The measurements are approximate from looking at a scope trace.
Nominal signal output is +/- 200mV as a sustained level after a modest open-string strum.
Nominal signal output is +/- 200mV as a sustained level after a modest open-string strum.
Humbucker-mode noise is +/- 0.2mV - observed as small sparse high-frequencey (HF) spikes barely visible on the scope. Actual 60 Hz hum signal is invisible on scope.
Humbucker-mode noise is +/- 0.2mV - observed as small sparse high-frequencey (HF) spikes barely visible on the scope. Actual 60 Hz hum signal is invisible on scope.
Single coil mode noise is +/- 1mV - also observed as sparse HF peaks (narrow spikes with little signal amplitude between the spikes). A 60 Hz hum amplitude was barely visible and estimated as +/- 0.2mV. This is about the limit of something I can see on the scope.
Single coil mode noise is +/- 1mV - also observed as sparse HF peaks (narrow spikes with little signal amplitude between the spikes). A 60 Hz hum amplitude was barely visible and estimated as +/- 0.2mV. This is about the limit of something I can see on the scope.
All these signals were measured at the output jack with full volume and tone settings while laying the guitar on its back.
All these signals were measured at the output jack with full volume and tone settings while laying the guitar on its back.
The signal-to-noise ratio for my measurements is SNR = 200/.2 = 1000:1 = -60 db hum levels. Again, this was worst case; once I pick up the guitar and hold it in a normal sitting or standing orientation, the noise signals drop considerably. Subjectively speaking, I no longer hear the noise. I switch between single coil and humbucker pickups without any noticeable noise levels. I used to mainly play the humbucker positions on this guitar because they were quiet. Now, I use all the 5 pickup options without concern. A slight noise is now audible with the "combine" switch on since it parallels the neck and bridge pickups and there is a small level of noise in that case. I rarely used that switch before since it was also the noisiest option without the cancelling coil. Now it is perfectly usable. I can not detect any change to the tone of the SC pickups other than the loss of noise. The middle pickup is really sweet and the bridge pickup has a nice twang, and they are all quiet.
The signal-to-noise ratio for my measurements is SNR = 200/.2 = 1000:1 = -60 db hum levels. Again, this was worst case; once I pick up the guitar and hold it in a normal sitting or standing orientation, the noise signals drop considerably. Subjectively speaking, I no longer hear the noise. I switch between single coil and humbucker pickups without any noticeable noise levels. I used to mainly play the humbucker positions on this guitar because they were quiet. Now, I use all the 5 pickup options without concern. A slight noise is now audible with the "combine" switch on since it parallels the neck and bridge pickups and there is a small level of noise in that case. I rarely used that switch before since it was also the noisiest option without the cancelling coil. Now it is perfectly usable. I can not detect any change to the tone of the SC pickups other than the loss of noise. The middle pickup is really sweet and the bridge pickup has a nice twang, and they are all quiet.
Not counting all the time I spent thinking about this and considering design options and buying the wire and super switch (waiting for UPS), the actual modification was done is less than a day. If you have a bathtub route in your Strat, this is pretty simple and painless.
Not counting all the time I spent thinking about this and considering design options and buying the wire and super switch (waiting for UPS), the actual modification was done is less than a day. If you have a bathtub route in your Strat, this is pretty simple and painless.
Results are everything. I have a video clip that shows me switching the PUs while I record audio straight from the guitar into a UA-25 USB interface. This is the raw guitar signal into the high-impedance input and right into the computer - no amps or mics are involved. I think the compression on my web-cam record software makes this less than ideal for critical evaluation, but it's all I can do right now. I'll get set up to do an A-B comparison at some point, but I'll have to wire in a switch to bypass the coil and that may take me some time. This does show that the noise level is pretty low. If you crank your audio you'll hear slight hum and noise level changes as I switch between PUs. There is very little difference between the humbucker positions (2 and 4) and the single coils (1, 3, 5). You'll also get a sense of how low the noise is relative to the decaying notes. S-500 volume and tone are set at max.
Results are everything. I have a video clip that shows me switching the PUs while I record audio straight from the guitar into a UA-25 USB interface. This is the raw guitar signal into the high-impedance input and right into the computer - no amps or mics are involved. I think the compression on my web-cam record software makes this less than ideal for critical evaluation, but it's all I can do right now. I'll get set up to do an A-B comparison at some point, but I'll have to wire in a switch to bypass the coil and that may take me some time. This does show that the noise level is pretty low. If you crank your audio you'll hear slight hum and noise level changes as I switch between PUs. There is very little difference between the humbucker positions (2 and 4) and the single coils (1, 3, 5). You'll also get a sense of how low the noise is relative to the decaying notes. S-500 volume and tone are set at max.
UPDATE 10/21/16
UPDATE 10/21/16
This isn't about hum or coils, but I recently had a chance to play a G&L Legacy and noted how different it sounded compared to the S-500. After poking around a bit I found that the S-500 is the only G&L guitar to use a cap (C3) across all the pickups. It shunts highs to ground (like a treble control turned down). On a whim I disconnected it and - wow - the guitar just wakes up. The change is not that surprising in hindsight. What is surprising is that G&L added that cap in the first place. There is nothing about the S-500 that warrants it, IMO. It's not used in any of their other guitars with the same SC pickups. Fortunately, its easy to try if you're feeling adventurous. I'm very happy with the cap removed - it's made a good guitar even better.
This isn't about hum or coils, but I recently had a chance to play a G&L Legacy and noted how different it sounded compared to the S-500. After poking around a bit I found that the S-500 is the only G&L guitar to use a cap (C3) across all the pickups. It shunts highs to ground (like a treble control turned down). On a whim I disconnected it and - wow - the guitar just wakes up. The change is not that surprising in hindsight. What is surprising is that G&L added that cap in the first place. There is nothing about the S-500 that warrants it, IMO. It's not used in any of their other guitars with the same SC pickups. Fortunately, its easy to try if you're feeling adventurous. I'm very happy with the cap removed - it's made a good guitar even better.
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