Input impedance question(SM7b) ?

[Zombietakeover]

I Read a thread in Gearslutz and i wanted to ask a question.....

It was a guy talking about an SM7b and his Steinberg MR816.....And he was talking about his Input impendence's we're mismatched

the SM7b having 150ohms and my ONYX 400F is 2.4K
so that's a huge mismatch correct?

I also seen that they have a transformer you can buy on the shure site.
http://store.shure.com/store/shure/en_US/DisplayProductDetailsPage/productID.104215200

My question is how big of a problem do you think this could be causing.
the transformer description mentions that it prevents high-frequency loss, level loss, and pickup of noise and hum......hmmm

any thoughts

 

[John_C]

Impedance
Microphone impedance rating is 150 ohms (150 ohms actual) for connection to microphone inputs rated at 19 to 300 ohms.

this is a good article to read, it's about the sm57 but the same idea applies http://www.recordingmag.com/resources/resourceDetail/330.html

basically if you're confident with a soldering iron, then wire yourself up a resistor as detailed in this article. Or spend the cash on the shure gizmo, it comes to the same thing in the end

 

[Metaltastic]

Or realize that the higher the input impedance, the more tone is preserved (especially highs), hence why we like direct boxes with input impedances like 10 times as great as the guitar output impedance So in other words, you're fine Josh!

 

[Omega_Void]

Rule-of-thumb is the mic should be loaded with two to four times it's output impedance. Hence why mic inputs usually present 1.5k to 2k ohms, expecting dynamic mics to normally show 400-600 ohms output Z.

the higher the input impedance, the more tone is preserved (especially highs), hence why we like direct boxes with input impedances like 10 times as great as the guitar output impedance

With dynamic microphones 10 times is too high. Something to do with current in the voice coil I think. I haven't read very deeply in the subject, but too much Z = too little current = don't work right. Or something.

Bear in mind with guitars, the circuit from the pup is loaded mainly by the volume and tone pots - the current drawn by the DI box's input resistance is only a fraction of the current flowing through the pots. With a dynamic mic there's normally no circuit inside the mic, so all the load is external.

 

[John_C]

Or realize that the higher the input impedance, the more tone is preserved (especially highs), hence why we like direct boxes with input impedances like 10 times as great as the guitar output impedance So in other words, you're fine Josh!

a mic isn't a pickup. It works differently, and shure do specifically say "for use with low impedance inputs" in the details for many of their mics

again i'll refer to the article above for backup.


We like DIs to have high impedance, but if that high impedance was what we wanted for all mics, then mic preamps would be the same as DIs just with more gain