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Old 01-25-2022, 03:27 PM
Rudy4 Rudy4 is offline
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Quote:
Originally Posted by Mbroady View Post
First, I want to thank Doug Young. He had an older k&K power-pro blend 3 channel preamp that he sent to me.

Second, my understanding of electronics is that of a 5th grader, so keep that in mind when responding (open to an education).

I already have a guitar with the K&k Mini and mic installed and wanted to experiment with adding the 3rd source, a UST

According to the folks at K&K, both the mini and UST channels are 1 meg with a low ohmic output

Should I be concerned about using another brand UST (fishman, LR baggs, etc)?
..are there other USTs that match the 1 meg and low ohmic spec?

Thanks, looking forward to learning something new
Your inquiry was titled "Question about UST Input impedance & ohmic output..."

One of the reasons why you won't find manufacturers of piezo transducers listing a specific "impedance" figure is that it's not really the correct verbiage to use as a parameter specification for the device. Impedance, within the field of electronics is "opposition to AC current flow", and the only time you would normally see a piezo material with that description used is when it is used as a speaker.

Yes, if you excite a piezo transducer with an electrical signal it works fine as a speaker. A raft of all those early piezo disk musical instrument pickups were often re-purposed "speakers" or vibrating alarms.

Since piezoelectric musical instrument transducers are operating to PRODUCE electricity as they are physically stimulated the transducer has an OUTPUT.

Since the piezo material usually has an impedance of 1 meg ohm (or often FAR higher) when used as a speaker, you'll find the same general values used to specify the INPUT impedance for the device that it is attached to. The reason for this is simple. Although the output voltage of a piezo transducer is really quite high, that counts on the load seen by the transducer (what it is plugged into...) being low. When we talk about circuit loading, the higher the impedance (in ohms) of the device the transducer feeds the less it serves as a load to the transducer's output.

If all of that is confusing, here's an easier way to understand it. If NO wire is attached the impedance seen by the transducer is essentially infinite, so there's no load. If you could attach a measuring instrument with a very high input impediance you'd see a very high voltage produced by the transducer.

I've been working with electricity and electronics for close to 60 years and I have never seen the term "ohmic output" used anywhere so I'm of no help there.

If your preamp specification is 1 meg ohm or greater you can plug any piezo transducer into it, although some may offer a higher output if the preamp impedance is higher.
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