Can A Resistor Be Used To Reduce A Pickups Output?

[vintage guitars]

Need help with this one. I installed 3 Red Lace Sensors in my strat. I have a humming noise now. Well according to Lace I cannot have 3 hot lace pickups together. They suggested I replace my middle and neck pickup to a lower output pickup to reduce noise. Instead of replacing the neck and my middle pickup can I just bring down the 15K output of the Lace Sensors using resistors? Or that will not work? Please HELP.

3 Red Lace Sensor Pickups Single Coil size

[JoeAArthur]

Need help with this one. I installed 3 Red Lace Sensors in my strat. I have a humming noise now. Well according to Lace I cannot have 3 hot lace pickups together. They suggested I replace my middle and neck pickup to a lower output pickup to reduce noise. Instead of replacing the neck and my middle pickup can I just bring down the 15K output of the Lace Sensors using resistors? Or that will not work? Please HELP.

3 Red Lace Sensor Pickups Single Coil size

I've read this several times. For the life of me I can't come up with any reason (other than you might not like the sound) why you can't have 3 reds in the same guitar. Certainly no reason why having 3 reds in and of itself would cause you to have more hum.

Do you have this hum in all pickup positions? If you do, then I would suspect something like bad grounding - like maybe the string ground is no longer connected. After all, one lace sensor ain't gonna know it's got two brothers when only one is selected.

To answer your question about reducing output using resistors, yeah, you can. But the resistor would probably have to be a real high value to have any real reduction effect - like a 250K if your're using 250K pots would only reduce the output by 6db - like the difference between the #1 and #2 input jacks of a Fender amp. Trying to come up with an appropriate value would be a lot of hit and miss experimentation, and might even increase your noise.

You could connect a trimmer pot internally to those two pickups in a volume control configuration.

But I still can't see why having 3 reds causes more hum.

[Paul Marossy]

Adding resistors will also change the frequency response...

[Samba Pa Ti]

this could be a bad grounding lace sensors are not that noisey

[lovekraft]

I'm with them - I believe that if you correct the wiring error(s), get your grounds sorted and make sure the guitar is shielded, the hum will go away (for the most part).

[KeithHowell]

"Adding resistors will also change the frequency response..."

No it won't. Resistors are non reactive components! However you should make sure you match your input and output impedances ie input from pickup and output to amp. To do this you would need to make a "T" pad. I can't remember all the calcs to do this it's been many years since I studied line transmission!

Keith

[JoeAArthur]

"Adding resistors will also change the frequency response..."

No it won't. Resistors are non reactive components! However you should make sure you match your input and output impedances ie input from pickup and output to amp. To do this you would need to make a "T" pad. I can't remember all the calcs to do this it's been many years since I studied line transmission!

Keith

Yes it will, by changing the time constant of the reactive components. As an example, a series resistance from the pickup will decrease the rolloff frequency of the tone control capacitor.

Matching an output impedance to an input impedance is necessary only if you're interested in a maximum POWER transfer. That's why we match output impedance of amplifier to speaker impedance.

The usual case with pickups and amps - the lower output impedance of the pickup (roughly 50-70K) is feeding the higher input impedance of the amp (roughly 1 meg for a typical tube amp). This insures a maximum VOLTAGE transfer - which is what we're primarily interested in accomplishing.

"Adding resistors will also change the frequency response..."

No it won't. Resistors are non reactive components! However you should make sure you match your input and output impedances ie input from pickup and output to amp. To do this you would need to make a "T" pad. I can't remember all the calcs to do this it's been many years since I studied line transmission!

Keith

Yes it will, by changing the time constant of the reactive components. As an example, a series resistance from the pickup will decrease the rolloff frequency of the tone control capacitor.

Matching an output impedance to an input impedance is necessary only if you're interested in a maximum POWER transfer. That's why we match output impedance of amplifier to speaker impedance.

The usual case with pickups and amps - the lower output impedance of the pickup (roughly 50-70K) is feeding the higher input impedance of the amp (roughly 1 meg for a typical tube amp). This insures a maximum VOLTAGE transfer - which is what we're primarily interested in accomplishing.

[perhellion]

Simply, what would adding a resistor do to the sound of a pickup (without the electrical engineer info)? And are there any examples of somebody famous and recorded using a resistor like this? Is this use of a resistor somehow different than turning a tone pot down?

[guitar2005]

Simply, what would adding a resistor do to the sound of a pickup (without the electrical engineer info)? And are there any examples of somebody famous and recorded using a resistor like this? Is this use of a resistor somehow different than turning a tone pot down?

I have a degree in electronics. By adding a minimum of two resistors, you could divide the voltage going out to the amp by any given amount. I don't understand why anyone would do this though....

What will this do to the sound? It will do the same as reducing your volume control. The higher the resistance values (just like with the volume control), the less impact you will have on the overall tone.

If you are having noise problems, your shielding or wiring have to be revisited first.

As for reducingthe amount of signal that goes to the amp, that's what a volume control is for (variable resistor).

[Paul Marossy]

Thanks for backing me up on that guitar2005. Did anyone mention shielding or the lack thereof? Maybe your guitar needs to be shielded better and your new pickups are making that more evident.

[JoeAArthur]

The higher the resistance values (just like with the volume control), the less impact you will have on the overall tone.

Are you sure about this? By using two resistors to reduce the voltage level, one will be in series and the other will be in parallel.

The series resistor forms a low pass filter with the parallel capacitance of the cable. As that series resistor increases in value, the cutoff frequency of that low pass filter decreases. Assuming a typical cable capacitance of 500-600pf total, a 1 meg series resistance would have that low pass filter cutting treble frequencies somewhere between 250-320 hz.

That wouldn't sound like less impact to the tone.

[Paul Marossy]

The bottom line is that you can not change the DC resistance of a pickup by adding an external resistor. That will only mess up the tone.

[jnewman]

The higher the resistance values (just like with the volume control), the less impact you will have on the overall tone.

Are you sure about this? By using two resistors to reduce the voltage level, one will be in series and the other will be in parallel.

The series resistor forms a low pass filter with the parallel capacitance of the cable. As that series resistor increases in value, the cutoff frequency of that low pass filter decreases. Assuming a typical cable capacitance of 500-600pf total, a 1 meg series resistance would have that low pass filter cutting treble frequencies somewhere between 250-320 hz.

That wouldn't sound like less impact to the tone.

As I understand it, the way the whole shebang in a guitar actually works is that it is a high-pass filter - to ground. As a result, increasing the series resistor increases the cutoff frequency, therefore decreasing the amount of high frequency signal passed to ground, therefore increasing the amount of high frequency signal that goes to the amp. This is why a 1 MOhm volume pot sounds brighter than a 500 KOhm pot sounds brighter than a 250KOhm pot.