phantom voltage mic-preamp

[Marrrrris]

Hello,

(sorry - bad English)

I have an mixer with talkback, wich is possible intern or extern. On the extern-Mic-In there is an automatically phantom power. But I think, there is not using a good electronic. On the speaker the audio-signal is some "noisy", "sizzles". I can not found the root cause and I guess, it can be a bad phantom power. Is it possible to make a external additionally phantom-power source --> so finally there are two phantom-sources: the "bad" internal and the additionally external? Or shouldn't I do that?

Maris

 

[PRR]

I would suspect a bad microphone pre-amplifier, not bad Phantom power.

 

[Pano]

I would suspect that too. The easiest way to test is use a mic that does not require phantom power. Any dynamic mic will do, such as the Shure SM57 or SM58.

 

[Marrrrris]

Is it possible to make a external additionally phantom-power source --> so finally there are two phantom-sources: the "bad" internal and the additionally external? Or shouldn't I do that?


Maris?

 

[mchambin]

It needs a 48V power supply, 2 capacitors, 2 resistors and a switch.

Look at this first
,https://www.google.com/url?sa=t&sou...FjANegQIBBAB&usg=AOvVaw3x67vVeeS8a4AxRQj1wq7S

to fully understand how it is implemented in microphone pre amplifiers.

 

[Pano]

Yes you can make one, but before you do you should follow the advice given to test if your phantom power is really the problem.

 

[Mark Tillotson]

Could be bad connection, bad cable, leaky capacitor - the DC offset with phantom power will highlight any fault like this, since poor connections modulate the DC current flow and make noises.


In a passive mic circuit poor connections only modulate the signal itself and don't make noise.