Measuring Pickup Impedence?

[Baker69]

Can you accurately measure the impedence of a pickup while it's still on the bass?

I've heard that you can get a reasonably good measurement by simply connecting your meter to the guitar cable, but won't all the wiring, tone and pots influence the reading?

Also, the other evening I took the pickguard off and measured off the pickup connections on the pots and I think it gave me an accurate measurement, but then I tried this on another bass of the same type and identical wiring and it wouldn't give me a reading at all until I altered the position of the pickup toggle switch - weird!

To summarise, do you have to physically remove the pickup to measure its impedence?

 

[line6man]

There is no accurate way to measure the impedance of a pickup. Because of the complex part of the impedance, it is frequency-dependent.

I'm assuming that what you measured was DCR. This is the resistance to direct current, and does not account for the Inductive Reactance of the coil.

 

[Stealth]

If you measure it while it's still in the bass, you'll get a reading of everything in there because all of the controls partially connect some of the signal to ground even at everything maxed out.

To get a DC resistance reading you'll need to desolder the pickup off the first pot it's connected to (the lug) and the ground (which is usually connected to the back of that same pot).

To get the non-real parts of impedance, as in the inductive and capacitive properties, you'd need at least a 200 USD LCR-meter such as an Extech. The inductance and capacitance vary by frequency, though, and are usually measured at a few frequencies.

Why are you interested in the impedance of your pickup? Out of pure curiosity, to figure out its "hotness", its output level?

 

[line6man]

If you measure it while it's still in the bass, you'll get a reading of everything in there because all of the controls partially connect some of the signal to ground even at everything maxed out.

To get a DC resistance reading you'll need to desolder the pickup off the first pot it's connected to (the lug) and the ground (which is usually connected to the back of that same pot).

To get the non-real parts of impedance, as in the inductive and capacitive properties, you'd need at least a 200 USD LCR-meter such as an Extech. The inductance and capacitance vary by frequency, though, and are usually measured at a few frequencies.

Why are you interested in the impedance of your pickup? Out of pure curiosity, to figure out its "hotness", its output level?

Actually, there is a way to figure out the DCR of each pickup without desoldering. You just have to do a little math.

Assuming there is a VVT setup, for instance, first turn down both pickup volumes all the way and turn the tone control all the way up, then measure the resistance at the output jack. This will give you the resistance of the controls, which you can call R1​. Next, turn the neck pickup up all the way and measure the resistance at the jack again. This will give you the neck pickup's DCR parallel to the resistance of the controls, which you can call RTotal​. To determine R2​, which is the DCR of the neck pickup, use the following formula:

R2​= 1/([1/RTotal​]-[1/R1​])

Now that you have determined the DCR of the neck pickup, you can repeat the process for the bridge pickup.

 

[Baker69]

If you measure it while it's still in the bass, you'll get a reading of everything in there because all of the controls partially connect some of the signal to ground even at everything maxed out.

To get a DC resistance reading you'll need to desolder the pickup off the first pot it's connected to (the lug) and the ground (which is usually connected to the back of that same pot).

To get the non-real parts of impedance, as in the inductive and capacitive properties, you'd need at least a 200 USD LCR-meter such as an Extech. The inductance and capacitance vary by frequency, though, and are usually measured at a few frequencies.

Why are you interested in the impedance of your pickup? Out of pure curiosity, to figure out its "hotness", its output level?

I have a spare Ric Toaster pickup that I want to use with a Ric high gain bridge pickup which I think is going to be too hot for the Toaster pickup. Need to measure them both accurately to make a final decision as to whether it will work satisfactorily.

 

[line6man]

I have a spare Ric Toaster pickup that I want to use with a Ric high gain bridge pickup which I think is going to be too hot for the Toaster pickup. Need to measure them both accurately to make a final decision as to whether it will work satisfactorily.

DCR and impedance are not indicators of output. People make that assumption because if you have identical pickups and put more wire on one, you will get a higher output, and the DCR and impedance will also go up because there is a greater resistance from the extra wire. Change wire gauges or alter the magnets or winding, and everything changes drastically.

 

[ClassicAmps]

I have a spare Ric Toaster pickup that I want to use with a Ric high gain bridge pickup which I think is going to be too hot for the Toaster pickup. Need to measure them both accurately to make a final decision as to whether it will work satisfactorily.

Baker69, just measure the DCR it will be your simplest way to determine if the two will balance.

...Assuming there is a VVT setup, for instance, first turn down both pickup volumes all the way and turn the tone control all the way up, then measure the resistance at the output jack. This will give you the resistance of the controls...

Only if your bass is wired so the pickups are connected to the wiper of the pot.


Anyway, in the OP's case, having a couple Ric pickups which will (99% probability) be the same wire gauge, one would think it's ok to simply use DCR readings as a good indicator of comparing relative output, and if they were both hi-gains that would be fairly true.

But the OP having a 6-pole "Toaster" the construction difference (magnets being so close together) the output is effected a bit.

 

[Baker69]

I think I will de-solder the pickups as you suggest, I was kind of hoping this wasn't necessary but I think for simplicity and for what I need it is the best course.

If I can't get a balance between the Toaster and the High Gain I will just have to adjust the volumes accordingly.

 

[ClassicAmps]

...If I can't get a balance between the Toaster and the High Gain I will just have to adjust the volumes accordingly.

That's the way musicians have been doing it for years.

 

[iiipopes]

I think I will de-solder the pickups as you suggest, I was kind of hoping this wasn't necessary but I think for simplicity and for what I need it is the best course.

If I can't get a balance between the Toaster and the High Gain I will just have to adjust the volumes accordingly.

I know, old thread. But having worked on both, the high gain and toaster do not necessarily have different outputs voltages, because they have relatively low inductances compared to their DC resistance figures because of the 44 gauge AWG wire they use.

I'd try the high gain in the bridge and the toaster in the neck first to see what it sounds like.

Remember -- with the .0047 capacitor to the bridge pickup in vintage wiring, that's what a 5th knob is for on the neck pickup: secondary volume control to balance the pickups.