PAD for a Sennheiser MKE2-Mic needed

Hi,

Today I´ve finished the work on my wireless system for my fiddle. It consists of a Sennheiser MKE2 Mic installed into the fiddle (soundlab symphonic microphone system) and a Sennheiser BF1083 UHF transmitter fixed under the back of the fiddle with a custom-made holder.

My problem: I even get clipping (caused by an overloaded transmitter-input) when the pad switch at the transmitter is switched to -20dB. That´s because of the high sound pressure inside the instrument. I know that the mic can easily handle this sound pressure (it worked fine without the transmitter).
So I´d like to build a pad between the mic and the transmitter. The problem: It is an unbalanced line that simultaneously carries the 9VDC and the signal (in german called "9V Tonaderspeisung"). Any idea, what I could do?? Perhaps a voltage-divider using two resistors? This will lower the signal, but the supply voltage as well... (At the moment I can measure 6.4 volts with a not very fresh battery... a guy from Sennheiser told me, that the mic will run from 5 to 12VDC)
Thanx & happy new year )
Sascha

can you get to the transmitter's audio input ?

if there is an op-amp at the front end
perhaps you can change the gain there

allowing the volts for the capsule to remain the same
but bring down the audio level through the circuit

where in the circuit does the transmitter PAD operate ?

Hi Kev,

I have not opened the transmitter yet. Tomorrow I will call the guy from Sennheiser again and ask him, if he perhaps can send me a schematic of this transmitter. Otherwise I will try to find the audio-in of the circuit.

But the best way would be to change something at the mic-line of this specific violin mic... I have good access there (without disassembling the transmitter), and I perhaps want to use the transmitter in other applications (with other MKE´s), where I´d need more gain.


Thanx, Sascha

Hmm... how about putting a capacitor in series with the shunt resistor? That would block the DC and keep the bias voltage from being drained off.

Yes, good idea...
But wouldn´t this behave like a HF roll off and have bad influence on the mic´s frequency-response, notably the high frequencies?

I need especially much roll off at about 200-250 Hz as this is the main resonant frequency of the violins body... But the transmitter also clips at other notes (higher freq´s; - as 200 Hz is around the lowest frequency produced by a violin apart from chairs being thrown by the audience :green: ).