Yes, you can do this if you are already using an op-amp anyway, but there really isn't a great advantage that I can see. It uses a differential amplifier instead of reversing the windings.
Basically just 2 ways to accomplish the same thing.
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Magnets & Copper Wire: A Pickup Building Thread
- Thread starter Freekmagnet
- Start date
Yes, you can do this if you are already using an op-amp anyway, but there really isn't a great advantage that I can see. It uses a differential amplifier instead of reversing the windings.
Basically just 2 ways to accomplish the same thing.
The benefit is that you can load each coil differently, so the articles says. It widens the resonant peak at the expense of slightly less hum cancelling
No, because the coils are RP but not RW. So the hum is the same polarity in both, but the signal is inverted. When you diff that you cancel the hum and sum the signal.
Ah, that makes more sense. I hadn't noticed that R3 was actually 0 ohms. Most schematics would have represented a zero ohm resistor as just a wire!
RWRP is for a standard humbucker where you are adding (either series or parallel) the coil outputs.
With a differential amplifier you are inverting one of the signals (coil outputs) so you need the coils wound in the same direction for the hum signal to cancel out, with one magnet reversed so that when the string signals are added they are in phase.
With a differential amplifier you are inverting one of the signals (coil outputs) so you need the coils wound in the same direction for the hum signal to cancel out, with one magnet reversed so that when the string signals are added they are in phase.
Alnico 3 pickups tend to be a little darker and Alnico 5 tend to be a little brighter. Alnico 5 is pretty much the standard Alnico magnet for pickups.
Thanks. Any idea what gauss level is best? I'm making a pickup for fretless bass, will likely be active so don't need huge output but want maximum sustain...
Unless the magnet is absurdly strong, the pickup isn't likely to affect the amount of sustain. Sustain mostly comes from the structural framework of the instrument.
"Best" is kind of a relative term. It doesn't really apply to pickup magnets, because they all have different characteristics that have more to do with the sound of the pickup as opposed to the performance of the pickup.
If I was in your place, I would pick a magnet and a wire gauge and wind the pickup to the output level that you're looking for. AlNiCo 5 is a fairly middle-of-the-road magnet and #42 wire is commonplace as well. Both of those are a pretty good place to start.
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Thanks. I've already bought Alnico 3 magnets, might consider keeping them for another project and buying Alnico 5. Can you give me a gauss level to aim for please?
PS, trying to calibrate my diy gauss meter, have telecaster pickup that reads either 50, 500 or 5000, depending on my math - which would be correct?
PS, trying to calibrate my diy gauss meter, have telecaster pickup that reads either 50, 500 or 5000, depending on my math - which would be correct?
I don't have a gauss meter and I'll probably never own one unless someone gives one to me. I don't build pickups that way. I try to envision the magnetic structure and the shape of the magnetic field and go from there.
Haha yeah! They start to make sense after a while. It takes a number of failures to get there.
You'll be fine. You can pretty much wrap anything around an A5 magnet and it'll sound pretty good.
I'm struggling with this a bit. My humbucker picks up the signal, but it hums. What am I doing wrong?
I have an alnico 5 bar magnet with 2 rail pole pieces. I have my preamp, which is silent with no coils connected. I've tried two clockwise coils and I've tried one clockwise and one anticlockwise. I've also tried each coil as a single coil. Each single coil works as a pickup but hums. more so if you touch the rail or if you grip the coil between thumb and finger. Any two coils wired in series works the same but is louder (as you'd expect). Reverse either coil and the signal cancels out. All good but it still hums. One final test, I wired one pickup to the inverting input of the amplifier and one to the non inverting input. It does buck hum in that configuration, but is as quiet as a single coil.
Surely having two coils in series, one north up one south up should buck hum. Why might mine not be?
I have an alnico 5 bar magnet with 2 rail pole pieces. I have my preamp, which is silent with no coils connected. I've tried two clockwise coils and I've tried one clockwise and one anticlockwise. I've also tried each coil as a single coil. Each single coil works as a pickup but hums. more so if you touch the rail or if you grip the coil between thumb and finger. Any two coils wired in series works the same but is louder (as you'd expect). Reverse either coil and the signal cancels out. All good but it still hums. One final test, I wired one pickup to the inverting input of the amplifier and one to the non inverting input. It does buck hum in that configuration, but is as quiet as a single coil.
Surely having two coils in series, one north up one south up should buck hum. Why might mine not be?
Is it "humming" or "buzzing"? Those steel blades are going to act as antennae and attract a lot of interference - that will create a "buzzing" sound. Generally, when I finish a pickup, I ground the blade poles.
slowburnaz
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