Prety new to this cbg thing and wanting to put power to my first creation.
Got a piezo kit and am pretty good at soldering, so that's not a biggie.
But i'm trying to wrap my noodle around the concept of impedance and what effects it will have on my wiring projects? I get that piezo's have higher impedance from the sstufg i've read here, and from past experience and my first foray w/ a clamp-on piezo the extra "sensativity" it has.
Basically where my noodle gets knotted is putting this into planning future stuff to counteract ect the effects of the higher imp...
Does it require a different type of speaker/amplifier? I vaguely remember getting a bass speaker for a higher ohm rating ye are ago. Is this do to a similar effect as using a piezo?
How about using a preamp? How does it "filter/tame" the higher impedance I've read of w/ piezos?
Any answers, thoughts, suggestions will be greatly appreciated(ESP ones that don't require an EE ;)
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Good, I hoped it would be taken with the original intention of good humor. I was going to go into more detail but the wife was pushing me to get going on something else.
Don, I loved your answer. It cracked me up. When I get into over thinking some things it always helps to have a good friend bring me back to the real world with a statement similar to the last line... "just ignore the above and plug the pickup into an amp and play like everyone else." That's not to dismiss the original question. It's a valid point to consider in the design/re-design stage.
Wow! That's great guys! Thanks!
Dr. Steve, been thinking about that preamp...
Don, that's great info for the circuit. Thanks for sharing the guts-side view!
Wondering about what you said w/ the capacitance... not sure how to phrase the question right now, but will ponder it a bit. Again, thanks for the schematics, don't know by wrote all the numbers but think I can handle it now I know what i'm looking for at the e parts store...
Y'all rock!
General Definition of impedance: The AC value of resistance of an AC circuit. (in simplest terms). The variable here is that an AC signal or circuit is associated with a frequency (wave form, duty cycle) and is unlike a DC circuit where the voltage is a constant.
I'll use a speaker to explain. Defined an loudspeaker is generally consists of a magnet and coil. Voltage is applied to convert electrical energy to moving air. When you take a piece of wire and wrap it around (air, stick loudspeaker bobbin) you create a resistor. But a coil of wire also is what consists of an inductor. So this loudspeaker has both a resistive value and a self inductance value. There is also one other variable. The coil of wire also consists of conductors separated by a thin insulating coating. A capacitor is made from two thin conductive film layers separated by a dielectric insulator. So this coil has a resistive value, inductive value and capacitive value. These three values reacts to a AC signal with varying resistance depending on frequency. So an 8 ohm speaker is summed average or nominal resistive value of a speaker.
Now to how this relates to pickup and input. It really doesn't The sensitivity of the piezo pickup is because of the type of pickup it is. The preamp is there to increase the very low voltage signal from the device into something more useable. So just ignore the above and plug the pickup into an amp and play like everyone else.
Sorry but the only way to define impedance in layman's terms is to just say piezos are high impedance tranducers in the range of megaohms and your amp doesn't like that, they were not designed to handle that imput load.
The science really isn't needed just the understanding the two, piezo and amp are not a good fit. Hence the benefit of a buffer that lowers the piezo's impedance that your amp can correctly amplify correctly. The reason passive tone controls will not work with piezos is both the high impedance plus the high capacitance they also possess and which on forums such as this are ignored. Simply put piezos are completly different transducers than magnetic pickups electrically.
The main effect of the high impedence is that the signal degrades more quickly with cable distance to your amp. It is recommended to have about a 5 foot cable from guitar to amp with the piezo. And yes, the usual way to address this is to insert a preamp, a short distance (within 5 feet) from the piezo. The output of the preamp is lower impedance, so a cable out of that can be much longer before the signal degrades (drops in power/gain/volume). A good solution is the built-in preamp plus rod piezo you can get from our own CB Gitty. I've built with these and they are fantastic.
Replies
Don, I loved your answer. It cracked me up. When I get into over thinking some things it always helps to have a good friend bring me back to the real world with a statement similar to the last line... "just ignore the above and plug the pickup into an amp and play like everyone else." That's not to dismiss the original question. It's a valid point to consider in the design/re-design stage.
Thanks Don for the explanation as well, I too sometimes have a bit of trouble understanding these ideas.
Wyndham
Dr. Steve, been thinking about that preamp...
Don, that's great info for the circuit. Thanks for sharing the guts-side view!
Wondering about what you said w/ the capacitance... not sure how to phrase the question right now, but will ponder it a bit. Again, thanks for the schematics, don't know by wrote all the numbers but think I can handle it now I know what i'm looking for at the e parts store...
Y'all rock!
General Definition of impedance: The AC value of resistance of an AC circuit. (in simplest terms). The variable here is that an AC signal or circuit is associated with a frequency (wave form, duty cycle) and is unlike a DC circuit where the voltage is a constant.
I'll use a speaker to explain. Defined an loudspeaker is generally consists of a magnet and coil. Voltage is applied to convert electrical energy to moving air. When you take a piece of wire and wrap it around (air, stick loudspeaker bobbin) you create a resistor. But a coil of wire also is what consists of an inductor. So this loudspeaker has both a resistive value and a self inductance value. There is also one other variable. The coil of wire also consists of conductors separated by a thin insulating coating. A capacitor is made from two thin conductive film layers separated by a dielectric insulator. So this coil has a resistive value, inductive value and capacitive value. These three values reacts to a AC signal with varying resistance depending on frequency. So an 8 ohm speaker is summed average or nominal resistive value of a speaker.
Now to how this relates to pickup and input. It really doesn't The sensitivity of the piezo pickup is because of the type of pickup it is. The preamp is there to increase the very low voltage signal from the device into something more useable. So just ignore the above and plug the pickup into an amp and play like everyone else.
Sorry but the only way to define impedance in layman's terms is to just say piezos are high impedance tranducers in the range of megaohms and your amp doesn't like that, they were not designed to handle that imput load.
http://www.scotthelmke.com/Mint-box-buffer.html
The science really isn't needed just the understanding the two, piezo and amp are not a good fit. Hence the benefit of a buffer that lowers the piezo's impedance that your amp can correctly amplify correctly. The reason passive tone controls will not work with piezos is both the high impedance plus the high capacitance they also possess and which on forums such as this are ignored. Simply put piezos are completly different transducers than magnetic pickups electrically.