250 ohm mic?

[Wizard200056]

Anyone try hooking a 250 ohm PA mic to a 500 ohm CB? How much difference will the R mismatch make?

 

[W5LZ]

A difference in impedance typically means a lessening in transferred energy. That typically means 'less' audio fidelity or strength. It may or may not make any significance for you, but it will mean a difference.
Lot'a help, huh?
- 'Doc

 

[Captain Kilowatt]

250 ohms into a 500 ohm load will not make any significant difference at all. The mismatch is not big enough to be an issue.

 

[Wizard200056]

Thanx

Thankyou gentlemen for your reply.I was afraid I would see 250 ohms worth of smoke puffing from the radio when I keyed.But just a poor sounding mic I can handle.Thanks again.

 

[Captain Kilowatt]

I doubt the mismatch will fegrade the audio quality very much at all. Wjen you start dealing with 5K or 1Megohm mikes into 500 ohm loads then you are talking some issues for sure.

 

[FuzzyTheBear]

Impedance / bandpass

Many devices offer low output impedance compared to the load.This is simply to allow for ex a mic to be able to be split to the FOH console and the monitor console without degradation in performance. We often see 200 ohm rated outputs on preamps / digital signal processors etc , what it means is that you can feed 3 600 ohm input amplifiers in parallel without signal degradation.
So .. if the output of a device has lower impedance than the load you're always ok .We are not talking about level , simply impedance here . As to connecting ex Shure SM-58 etc to transceivers , one of the things i'd be concerned is not level which can be compensated as required easily , it's bandwidth of the RF signal you transmit with the larger audio bandwidth. If you want to keep in line with the FCC guidelines for that spec i am certain that you will have to use a lowpass filter in the audio chain.