Telecaster bridge plate testing; brass, steel, thin, thick
Feb 4, 2019 16:10:46 GMT -5
sydsbluesky1 and pj like this
Post by antigua on Feb 4, 2019 16:10:46 GMT -5
(I know most of the explanatory stuff below is redundant in the context of this forum, I've tried to write it for non-regulars)
One of the aspects of vintage guitar pickups that gives their their characteristic tone is LC resonance. Resonance causes there to be a bump in the treble range, which is often the cause of "ice pick" tones when it's too great, but also makes for "dull" sounding pickups when it's too low. The reason 1 meg ohm pots make pickups sounds brighter is because they increase resonance, while low value pots decrease resonance. Another cause of low resonance is eddy currents, such as those caused by cheap metal covers. But it can also be caused by any other conductive metal, such as AlNiCo magnets and steel pole pieces. Since virtually all pickups have conductive metal parts (not counting the coil itself), some degree of eddy current related resonance loss is inherent in all guitar pickups.
One definite cause of eddy current attenuation is the metal bridge of a Telecaster. I've analyzed three actual Tele bridges, as well a piece of aluminium foil cut to the shape of a Tele bridge in order to compare the differences they cause with respect to eddy current attenuation.
The test subject are:
Fender vintage style bridge plate, made of steel, is magnetic, thickness is 1.10mm
Fender modern style bridge plate, made of brass, is not magnetic, thickness is 2.32mm
Reynolds Wrap, made of aluminum, is not magnetic, thickness is 0.022mm
Fender Standard Series steel bridge plate, made of steel, is magnetic, thickness is 2.50mm
Obviously the foil is the thinnest, followed by the vintage ashtray bridge at about 1mm, and then the modern style bridges which are over 2mm thick. You can see their thickness by looking at the lower lip where the intonation screws pass through.
The ashtray and Standard Series bridges are made of steel, the Reynolds Wrap is aluminum, and the late 90's stock bridge is made of brass.
The test pickup is a Fender NoCaster bridge with the base plate still attached underneath the pickup.
The first plot is without added load. The only load is that of the USB oscilloscope, which is far lower than that of a guitar setup.
The plots shows that all of the base plates cause only a slight reduction in resonance, except one, the Fender brass bridge plate, the second bridge plate in the pictures above. The bridge was taken from an American made Telecaster, built in the late 90's or early 00's. The eddy currents cause the resonance to drop by a whopping 4.7dBV, as well as causing the inductance of the pickup to drop and the resonant peak to rise by about 700Hz.
The Fender Standard Series steel bridge plate, fourth in the picture, is actually thicker than the Fender brass bridge, and it shows almost as little eddy current attenuation as the much thinner steel ashtray style bridge.
Telecaster Bridge Plate Test
No plate: dV: 14.1dB f: 7.46kHz black
Fender vintage: dV: 11.5dB f: 7.54kHz blue
Fender brass: dV: 9.4dB f: 8.17kHz red
Reynolds Wrap: dV: 12.2dB f: 7.37kHz green
Fender Std. Ser.: dV: 11.1dB f: 7.54kHz pink
Here is a plot that adds a representative load of 470pF capacitance and 200k ohms across the pickup to mimic the effects of a guitar cable and control pots. This causes the resonant peak and the peak amplitude to drop significantly.
In this context, the Reynold Wrap bridge plate becomes indistinguishable from no bridge plate at all. The vintage ashtray style bridge and the thicker steel bridge overlap very closely, while the brass modern style Fender bridge once again shows significant attenuation.
For the vintage ash tray and the thick, unknown steel bridge, the reduction at resonance is only 1dB, which is right at the threshold of what human hearing can detect. The modern Fender , on the other hand, shows an amplitude drop of 3.2dB, and a peak frequnecy increase of almost 300Hz, both of which make for audible differences.
Telecaster Bridge Plate Test w/470pF & 200k ohm load
No plate: dV: 5.4dB f: 3.24kHz black
Fender vintage: dV: 4.4dB f: 3.24kHz blue
Fender brass dV: 2.2dB f: 3.51kHz red
Reynolds Wrap: dV: 5.4dB f: 3.24kHz green
Fender Std. Ser. dV: 4.4dB f: 3.24kHz pink
This is not to say the tested brass bridge plate sounds bad. The taller resonance creates a distinct sound, a pointed treble that is sometimes described as "shrill", where as the flatter response, caused by the eddy currents, causes the treble to sound a bit darker overall, but at the same time clearer, like an acoustic guitar. Rolling back on the tone knob slightly has a near identical function. If you have this brass bridge in your Tele, it's as though the tone knob is maxed out at 8 or 9, instead of 10. Since a lot of players like the tone knob rolled off anyway, some intrinsic attenuation can be a welcome feature.
Given that the aluminum and brass are similar, both being non-magnetic, and highly conductive, this result shows that thickness matters to some extent, otherwise the foil and brass would have shown similar plots. On the other hand, the 1mm and 2.5mm Fender steel bridge plates showed very similar plots, suggesting that in that context, where the material is both conductive and highly permeable, the thickness doesn't matter nearly as much.
I'm not sure which Telecasters on the market today have a brass bridge plate, and I've only tested the one I have on hand, so I don't know if all modern Fender bridge plates are brass, but if the bridge plate looks like the one above, and a magnet will not stick to it, my guess would be that it is brass. If a magnet does stick to it, it must be made of steel, and it will perform like other steel bridge plates, regardless of whether it's vintage ashtray or the modern six saddle type.
Pics:
That's Ken Willmott's integrator in the back ground, v4 IIRC.
Ashtray bridge:
Reynolds Wrap:
Brass bridge with some of the brass exposed:
One of the aspects of vintage guitar pickups that gives their their characteristic tone is LC resonance. Resonance causes there to be a bump in the treble range, which is often the cause of "ice pick" tones when it's too great, but also makes for "dull" sounding pickups when it's too low. The reason 1 meg ohm pots make pickups sounds brighter is because they increase resonance, while low value pots decrease resonance. Another cause of low resonance is eddy currents, such as those caused by cheap metal covers. But it can also be caused by any other conductive metal, such as AlNiCo magnets and steel pole pieces. Since virtually all pickups have conductive metal parts (not counting the coil itself), some degree of eddy current related resonance loss is inherent in all guitar pickups.
One definite cause of eddy current attenuation is the metal bridge of a Telecaster. I've analyzed three actual Tele bridges, as well a piece of aluminium foil cut to the shape of a Tele bridge in order to compare the differences they cause with respect to eddy current attenuation.
The test subject are:
Fender vintage style bridge plate, made of steel, is magnetic, thickness is 1.10mm
Fender modern style bridge plate, made of brass, is not magnetic, thickness is 2.32mm
Reynolds Wrap, made of aluminum, is not magnetic, thickness is 0.022mm
Fender Standard Series steel bridge plate, made of steel, is magnetic, thickness is 2.50mm
Obviously the foil is the thinnest, followed by the vintage ashtray bridge at about 1mm, and then the modern style bridges which are over 2mm thick. You can see their thickness by looking at the lower lip where the intonation screws pass through.
The ashtray and Standard Series bridges are made of steel, the Reynolds Wrap is aluminum, and the late 90's stock bridge is made of brass.
The test pickup is a Fender NoCaster bridge with the base plate still attached underneath the pickup.
The first plot is without added load. The only load is that of the USB oscilloscope, which is far lower than that of a guitar setup.
The plots shows that all of the base plates cause only a slight reduction in resonance, except one, the Fender brass bridge plate, the second bridge plate in the pictures above. The bridge was taken from an American made Telecaster, built in the late 90's or early 00's. The eddy currents cause the resonance to drop by a whopping 4.7dBV, as well as causing the inductance of the pickup to drop and the resonant peak to rise by about 700Hz.
The Fender Standard Series steel bridge plate, fourth in the picture, is actually thicker than the Fender brass bridge, and it shows almost as little eddy current attenuation as the much thinner steel ashtray style bridge.
Telecaster Bridge Plate Test
No plate: dV: 14.1dB f: 7.46kHz black
Fender vintage: dV: 11.5dB f: 7.54kHz blue
Fender brass: dV: 9.4dB f: 8.17kHz red
Reynolds Wrap: dV: 12.2dB f: 7.37kHz green
Fender Std. Ser.: dV: 11.1dB f: 7.54kHz pink
Here is a plot that adds a representative load of 470pF capacitance and 200k ohms across the pickup to mimic the effects of a guitar cable and control pots. This causes the resonant peak and the peak amplitude to drop significantly.
In this context, the Reynold Wrap bridge plate becomes indistinguishable from no bridge plate at all. The vintage ashtray style bridge and the thicker steel bridge overlap very closely, while the brass modern style Fender bridge once again shows significant attenuation.
For the vintage ash tray and the thick, unknown steel bridge, the reduction at resonance is only 1dB, which is right at the threshold of what human hearing can detect. The modern Fender , on the other hand, shows an amplitude drop of 3.2dB, and a peak frequnecy increase of almost 300Hz, both of which make for audible differences.
Telecaster Bridge Plate Test w/470pF & 200k ohm load
No plate: dV: 5.4dB f: 3.24kHz black
Fender vintage: dV: 4.4dB f: 3.24kHz blue
Fender brass dV: 2.2dB f: 3.51kHz red
Reynolds Wrap: dV: 5.4dB f: 3.24kHz green
Fender Std. Ser. dV: 4.4dB f: 3.24kHz pink
This is not to say the tested brass bridge plate sounds bad. The taller resonance creates a distinct sound, a pointed treble that is sometimes described as "shrill", where as the flatter response, caused by the eddy currents, causes the treble to sound a bit darker overall, but at the same time clearer, like an acoustic guitar. Rolling back on the tone knob slightly has a near identical function. If you have this brass bridge in your Tele, it's as though the tone knob is maxed out at 8 or 9, instead of 10. Since a lot of players like the tone knob rolled off anyway, some intrinsic attenuation can be a welcome feature.
Given that the aluminum and brass are similar, both being non-magnetic, and highly conductive, this result shows that thickness matters to some extent, otherwise the foil and brass would have shown similar plots. On the other hand, the 1mm and 2.5mm Fender steel bridge plates showed very similar plots, suggesting that in that context, where the material is both conductive and highly permeable, the thickness doesn't matter nearly as much.
I'm not sure which Telecasters on the market today have a brass bridge plate, and I've only tested the one I have on hand, so I don't know if all modern Fender bridge plates are brass, but if the bridge plate looks like the one above, and a magnet will not stick to it, my guess would be that it is brass. If a magnet does stick to it, it must be made of steel, and it will perform like other steel bridge plates, regardless of whether it's vintage ashtray or the modern six saddle type.
Pics:
That's Ken Willmott's integrator in the back ground, v4 IIRC.
Ashtray bridge:
Reynolds Wrap:
Brass bridge with some of the brass exposed:
