Condenser Mics, Phantom Power, ETC redux

Jerry Overstreet · From: Louisville Ky

This is an old thread from 2014 that I'd like to boost with some other questions.

https://bb.steelguitarforum.com/viewtopic.php?t=274411

I have acquired this APEX 565 condenser mic. It requires phantom power. It's been enlightening discovering some of the behavioral characteristics of condenser mics and I'd like to expand this old thread to include some other questions.

I have one of those Boss record to CD units that has phantom power and this mic works well with that.

My concerns are using this mic minus the Boss unit to reduce clutter and gear in a stage situation going into FOH.

We have a Behringer Euro 8 ch. mixer at the barn which is used primarly for vocal mics. It only has one 48v phantom power button, but I'm thinking that's a global setting that would affect all the mics on stage which are all dynamic far as I know.

I have read here and other places that applying phantom power to dynamic mics could damage or destroy them. Is that an absolute given? Do only high end mixer units have individual PP for ea. channel?

I wouldn't want to risk damaging other equipment by using this mic which requires PP into this system if it's a real possibility.

I would like to use this mic with dobro and acoustic guitar into a Fishman Platinum pre unit between the instrument and the board so I'll have some control from my stage position.

Next question: The Fishman Platinum pre only accepts 1/4 input but has an XLR out. It also will accept PP from a mixer.

I also have an XLR balanced to 1/4 unbalanced transformer. Can I just run the transformered 1/4" plug into the Fishman input and connect it's XLR out to the house desk?

Howard Parker · From: Maryland

Phantom power has absolutely zero effect on dynamic mics. The "Global" phantom power is common on PA mixers.

Phantom power WILL effect ribbon mics..so!

yes..You can run the adaptor/transformer into the Platinum pro although I'm sorta at a loss why that would be desireable.

But heck..That's just me.

YMMV

hp
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Howard Parker

03\' Carter D-10
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Jerry Overstreet · From: Louisville Ky

Well Howard, the reason is so that I can control the eq, phase, effects etc. from my station on stage as there's not generally a sound engineer at the desk when we play.

Howard Parker · From: Maryland

OK..

You can certainly control what you hear on stage..which usually isn't what the audience hears from the front of house.

But, like I say..it's all my .02, ymmv and etc.

Have fun!

h

- edit , fwiw the Fishman unit isn't really designed for a mic input so I'd play with it before committing to the setup.

Dan Beller-McKenna · From: Durham, New Hampshire, USA

I also use a condenser on my reso (AT Pro 35). The only DI unit like the Platinum Pro I found that would accept an XLR is the Zoom A3. Ultimately, I decided it was one too many things cluttering the stage and too hard to adjust in performance (tiny knobs, small digital screen, etc.) and I felt I got just as good sound going straight into the board with the AT 35. (Th A3 did have a great feedback killer, though).

During this lost year, I picked up a Beard Deco 27 with the Fishman pickup. Hoping to add the Aura JD before gigs start up again. I'm guessing the condenser mic has a slightly better sound (based on the few Fishman "Nashville"/Aura JD rigs I have tried before), but there is A LOT to be said for the simplicity of the piezo out through a 1/4" into a more user friendly box like the Aura. Looking forward to trying the new rig....well, really, I'm just looking forward to making music again, period!!!

Jerry Overstreet · From: Louisville Ky

Howard, thanks for your input and technical explanations.
I'm just trying to cover all situations where I might be using these acoustic instruments. At times, I may want to go out of the Fishman unbalanced into an amp alone on stage, and it would be convenient to have control at the Platinum pre.

Until I get a chance to preview these things, I'm not going to really know how they perform. I'm just trying to gain a little knowledge in advance.

Howard Parker · From: Maryland

Jerry,

You might want to also check out a small mixer (2-4 mic inputs) Mic and instrument level inputs.

They can be quite flexible.

I have several rigs available, depending on the gig.

I do mic on the straight ahead bluegrass stuff. Typically my Americana gigs get too loud to mic without feedback so I use the Fishman "Nashville/Aura" based rig with the usual array of DI's and stage amp, if required.

I'll even go wireless if the situation requires mobility on stage.

Dobro playing in 2021! Very Happy

Jerry Overstreet · From: Louisville Ky

Richard Sinkler · From: aka: Rusty Strings -- Missoula, Montana

Here is some information from Shure. Straight from the "horses" mouth.

"7. Phantom power and bias voltage are the same thing.

False. Many users of professional audio equipment believe there is no difference between phantom power and bias voltage. Not true! Phantom and bias are not interchangeable.

Phantom power is a dc voltage (11 â€“ 48 volts) that powers the preamplifier of a condenser microphone. Phantom power is normally supplied by the microphone mixer, but may also be supplied by a separate phantom power supply. Phantom requires a balanced circuit in which XLR pins 2 and 3 carry the same dc voltage relative to pin 1. So if a mixer supplies 48 volts of phantom, XLR pins 2 and 3 of the microphone cable each carry 48 volts dc relative to pin 1. Of course, the mic cable carries the audio signal as well as the phantom voltage.

Mixers that supply phantom power contain current-limiting resistors that act as control valves. If the microphone or cable is improperly wired, these resistors limit the flow of current to the microphone and thereby prevent damage to the phantom supply circuit. A balanced dynamic microphone is not affected by phantom power; however, an unbalanced dynamic microphone will be affected. Although the microphone will probably not be damaged, it will not work properly.

Unlike phantom power, bias does not require a balanced circuit. Bias supplies power to a Junction Field Effect Transistor (JFET) connected to the output of an electret condenser mic element. The JFET acts as an impedance converter that is a necessity in any microphone design that uses a condenser element. A condenser element has a high output impedance (>1,000,000 ohms). The JFET input loads the output of the condenser element with an even higher impedance (>10,000,000 ohms) to minimize loss of signal level. Also, the JFET output provides a low source impedance (1,000 ohms) to feed the microphone preamplifier.

In some condenser microphones, the bias voltage must be supplied on the same conductor as the audio. Condenser elements with a built in JFET use this configuration and employ a single conductor, shielded cable. Other condenser microphones utilize separate conductors for bias and for audio. It's a good idea to consult the manufacturer's data sheet to determine the exact wiring configuration.

A dynamic microphone should not be connected to an input that supplies bias voltage (such as a wireless transmitter) because the audio and the bias voltage will travel down the same conductor. If this occurs, the frequency response of the microphone may be altered or the audio signal distorted. If a dynamic microphone must be connected to an input with bias voltage, a blocking capacitor must be used.

In a typical electret condenser microphone, it is the JFET that requires unbalanced bias and the preamplifier that requires balanced phantom power. This means that a condenser microphone requiring phantom power will not work with an input that only supplies bias, e.g. a wireless transmitter.

Phantom power and bias voltage are not interchangeable!"

Quoted from:

https://www.shure.com/en-US/performance-production/louder/top-8-microphone-myths-exposed#:~:text=Phantom%20power%20is%20a%20dc,preamplifier%20of%20a%20condenser%20microphone.&text=A%20balanced%20dynamic%20microphone%20is,it%20will%20not%20work%20properly.

Interesting reading concerning "balanced" and "unbalanced" dynamic mics.

https://taperssection.com/index.php?topic=85406.0
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Jerry Overstreet · From: Louisville Ky

Thanks Richard. So it's only unbalanced mics, say commonly a 2 conductor 1/4" phone plug, that is affected by PP. This was not pointed out in the other sources I found. They all just stated don't do it.

I think I'm beginning to understand it now. I'll read the entire article soon as time permits.

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