microphone too hot - can I just insert a resistor?

mounted

resistor

I just thought of another thing - since the inputs are balanced, could I just insert the resistor between in the path to ground (thus using only 1 resistor, rather than 1 for each of the + and - in the balanced path)

Thanks again

You should use a pad -- a series resistor from the mic, followed by a parallel resistor to keep the resistance "seen" by the amplifier low.

Or use a pot, so you can experiment to find the right setting.

If you want to preserve the balance and avoid upsetting the phantom power then you'll need a pair of equal series resistors, one in each of the signal lines, followed by a shunt resistor between the downstream ends of those two resistors, with no connection to ground. The phantom-power voltage appears between the balanced pair of signal lines and the ground line.

Chris

distorting

Just to make sure I understand you Tim - the parallel resistor goes between pins 2 and 3 (i.e. + and - signal lines)? Also, I would need 1 for each of the + and - lines right? I'm also assuming the parallel resistor should be fairly low (less than a couple K)?

Thanks

How do you know where the problem lies?

Yes, you may be overloading the stage it runs into.

But, you may be overdriving the microphone itself, it being too close to the sound source.

You need to figure that out first.

Michael

mounted

distorting

resistor

That is something I've also considered, but I'm leaning towards the distorting my inputs theory for a couple reasons:

1. Manufacturer's specs are showing 0.5% at 145 dB SPL and a sensitivity of -34. It seems unlikely that the noise levels are hitting 145dB inside of a classical guitar.
2. Even with the input gain virtually off, the meters on my mixer are showing clipping without a lot of heavy strumming.
3. This mic has been successfully used for micing drums, and the 2.00 capsule I had in the guitar previously did not distort.

o------/\\/\\--o-----o | / in \\ out / | o------/\\/\\--o-----o

Ideally you'd figure out the impedance of the balanced line, and match that. Less than a couple of K is probably a good starting point, but I don't know what they do with guitar audio, so I can't say specifically what is best.

I'm surprised that switching in the mixer pad didnt fix it. Tried that? Maybe theres a bunch of DC from the phantom power biasing your preamp up near clipping. Any caps in the signal from the mic to the mixer preamp? If you have a nice hot mic signal, you can unbalance it. Might work into the line in then.

"tempus fugit"

Is there no "pad" switch ?

What mixer is it ?

...... Phil

distorting

your

The mixer is actually a mixer amp, and (I didn't find this out until I actually bought it) the phantom power isn't 48v, it's only 15. I tried recording with it, using my homebrew mic pre which actually has 48v phantom, and still got the distortion. Unfortunately, my mic pre doesn't have a pad. I agree though, it's kind of crazy that the output is that high, but even with virtually no gain on my mic pre, it still clips the VUs on my recording program. Now I did measure the resistance from pins 1-2 (on the mic) and got

Thanks Phil

"tempus fugit" "Phil Allison"

And why is this secret ?

Why it its identity a big secret?

Build it yourself maybe ?

Jeez people who REFUSE to post the most basic of details are annoying.

...... Phil

If I understand the above correctly, you are supplying 15V phantom power to a mic that expects 48V. That may be the entire problem, since it surely will affect clipping and distortion. Knowing nothing about your particular mic circuit, here's a couple of thoughts:

If this is an electret and not a true condenser, it runs at some specified fixed bias voltage which is less than the phantom supply. If the regulator for that voltage expects 48V at its input and is getting 15V, it may be biasing the mic with the wrong value. Even if it's still providing the right value (let's say 10V), the input stage of the preamp will then be running with only a 5V difference between its supply and its input. This would explain the clipping.

And if it is really a true condenser mic (which requires 200V bias or so) then running with a 15V supply instead of 48V might mean you have so little bias you have a ton of distortion just from that.

Best regards,

Bob Masta DAQARTA v4.00 Data AcQuisition And Real-Time Analysis

even

The mic is made by Karma Audio - I chose it for it's small size:

The mixer amp is made by Carvin:

phantom,

pad.

recording

got

I thought that might be the problem too, but, as I stated above

I tried

phantom,

from overdriving the inputs, as even with the mic pre gain almost off the VUs on my recording program are still pegging.

Look like that button next to the channel volume knob is a gain button.... or a pad if you like to use industry jargon..... I usually use a pad to kneel on when weeding the garden, or to crash in when visiting my hippy friends in the city.

What mixer ?

Graham

mounted

distorting

The mixer is here:

phantom,

pad.

recording

got

I've just tried putting about 15K worth of resistance in series with the output, and using a true 48v phantom power, and the sound is really quite good. I suppose I could hardwire the resistors and lug around the extra 48v supply to gigs, but I think I'm going to try going back to my original mic element and using the 15v phantom power from the mixeramp to power it. I'm pretty sure the mic is only rated for a 10v supply V+ though. Do you think that it would handle the extra 5v without going up in smoke, or should I build a voltage divider?

Thanks

Inadequate data. A pro mixer (even a Behringer) probably wouldn't grumble at the mic output level since they have variable gain input stages.

This Carvin is MI grade garbage. Sorry.

Graham