In-Line pad for SDC microphones

[callgrlmusic]

More of a theory question than anything—say you wanted to build an in-line pad for high spl handling.

would you do that between the rest of the circuit and the capsule? guessing yes, lower the voltage to capsule, lower sensitivity etc. would it be essentially the same thing as you’d use for a speaker driver in a crossover?

i have seen off the shelf solutions in line between the mic and the preamp, but wouldn’t that work less effectively in terms of capsule “loading”?

 

[gyraf]

The common means are: Lowering polarisazion voltage, adding capacitance in parallel with capsule.

If you are looking for additions for existing microphones, I dont think that's realistic.

 

[callgrlmusic]

The common means are: Lowering polarisazion voltage, adding capacitance in parallel with capsule.

If you are looking for additions for existing microphones, I dont think that's realistic.

thank you gyraf—big fan by the way.

i saw this on another forum and wanted to pick it apart a little bit—im more trying to understand the optimal approach , but also WHY it’s optimal.

 

[pasarski]

I try to rephrase what David is saying there: If the preamp can't handle the the signal coming from the mic, it's better to use a pad between the mic and the preamp, and only if it's the mic that's distorting you have to use the microphone's pad, because the pads in mics worsen the s/n ratio.

IMO this applies only to a situation where the program material has very quiet and very loud parts, like in classical music. If the source is loud all the time the noise probably won't matter.

 

[callgrlmusic]

I try to rephrase what David is saying there: If the preamp can't handle the the signal coming from the mic, it's better to use a pad between the mic and the preamp, and only if it's the mic that's distorting you have to use the microphone's pad, because the pads in mics worsen the s/n ratio.

IMO this applies only to a situation where the program material has very quiet and very loud parts, like in classical music. If the source is loud all the time the noise probably won't matter.

if you don’t mind, let me ask you a practical question—i’m modifying some SDCs that will mainly be used as drum overheads, but not always. my main concern is clipping the mics themselves with high spl, so far as i understand it, the only kind of pad that can avoid that would be placed between the capsule and the mic circuit—am i wrong about that?

oktava used to have removable screw-in pads that sat between the capsules and the mic bodies in their sdcs and i really like that idea. does putting a pad between the mic and the preamp work the same way by dropping the voltage across the whole mic circuit including the capsule, though? any drawbacks to doing it one way versus the other for this application?

 

[ccaudle]

my main concern is clipping the mics themselves with high spl

That is usually a concern with close placement to drums, not overhead.

But you are correct, if the microphone circuitry is clipping, you have to reduce the signal from the capsule to the microphone circuitry.

 

[jp8]

if you don’t mind, let me ask you a practical question—i’m modifying some SDCs that will mainly be used as drum overheads, but not always. my main concern is clipping the mics themselves with high spl, so far as i understand it, the only kind of pad that can avoid that would be placed between the capsule and the mic circuit—am i wrong about that?

oktava used to have removable screw-in pads that sat between the capsules and the mic bodies in their sdcs and i really like that idea. does putting a pad between the mic and the preamp work the same way by dropping the voltage across the whole mic circuit including the capsule, though? any drawbacks to doing it one way versus the other for this application?

The Octava pad is just a capacitor, which reduces the capsule audio signal to the JFET buffer in the mic. It acts as a capacitive voltage divider (google for how it works). This prevents overloading the JFET.

An inline pad would not reduce the capsule audio signal, hence will not prevent JFET overloading. It will reduce the output signal from the JFET, not its input signal. Btw, you cannot just insert a resistive divider in the mic output as an inline pad, because it would also lower the phantom power voltage to the mic, either causing it to not work at all, or increasing its distortion and reducing its headroom.

Jan