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Topic: phantom power voltage range? |
Michael Maddex
From:
Northern New Mexico, USA
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Posted 20 Oct 2008 7:09 pm |
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I just acquired a small condenser mic (Shure Beta 98/S). According to the spec sheet, it requires 48V (+/- 4V) phantom power. Using a mixer with 48V phantom power, it works as expected. I also tried it with a PA with 15V phantom power. Just going by ear (no formal test) the mic seems to work fine with the lower power.
My question: Can continued use of the mic with the lower (15V) phantom power damage the mic or its pre-amp? Are there any other potential unwanted/adverse effects? |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 21 Oct 2008 4:44 pm
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Condenser mic elements have a really low output so these mics require an internal preamp to bring the signal up to a nominal mic level and the "phantom" voltage is used to power this preamp. If the voltage is too low the mic pre's headroom will be affected but if you are not using it to mic a kick drum or a trumpet you may get by just fine and never hear bad juju from it.Basically, as is so often the case, if it sounds good to you then it is.
Cheers
dg |
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Lynn Oliver
From:
Redmond, Washington USA * R.I.P.
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Posted 22 Oct 2008 8:11 am
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The phantom power is required not only for the internal preamp, but also to establish the capacitor (condenser) plate voltage that makes it work.
From the RaneNote "Selecting Mic Preamps:"
| Quote: |
| There is a huge myth circulating that microphones sound better running from 48 volts, as opposed to, say, 12 volts, or that you can increase the dynamic range of a microphone by using higher phantom power. For the overwhelming majority of microphones both of these beliefs are false. Most condenser microphones require phantom power in the range of 12-48 VDC, with many extending the range to 9-52 VDC, leaving only a very few that actually require just 48 VDC. The reason is that internally most designs use some form of current source to drive a low voltage zener (usually 5 volts; sometimes higher) which determines the polarization voltage and powers the electronics. The significance is that neither runs off the raw phantom power, they both are powered from a fixed and regulated low voltage source inside the mic. Increasing the phantom power voltage is never seen by the microphone element or electronics, it only increases the voltage across the current source. But there are exceptions, so check the manufacturer, and don’t make assumptions based on hearsay. |
FWIW, when I checked with Shure on other models I was told that 15V is fine. I have not tried a Beta 98. |
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Jon Light
From:
Saugerties, NY
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Posted 22 Oct 2008 12:14 pm
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From reading, not from experience:
Apparently a number of inexpensive mic preamps actually fall short of the 48 volts listed on their spec sheet. While this can potentially affect mic performance, it will not hurt the mic. So you can let the ears judge whether there is a problem or not. |
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Michael Maddex
From:
Northern New Mexico, USA
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Posted 22 Oct 2008 3:41 pm Thanks, gents ...
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Thanks for the good responses.
I already had the basic idea of how condenser mics work: plate polarizing voltage and integral pre-amp. On reflection, of course an internally regulated voltage is required. On this particular unit, the pre-amp is separate from the mic element, so unless the pre-amp gets unnaturally warm or the signal degrades in volume or quality, I'll go ahead with the 15V phantom power.
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"For every expert, there is an equal and opposite expert." -- Arthur C. Clarke |
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