Dayton EMM6 bias voltage
The Dayton EMM6 microphone has a bias voltage rating between 15 to 48 Volts.
Sensitivity is given as 10mV/Pa .
Will this change with the bias voltage ? I think it shouldn't but would like some confirmation from someone who knows.
Apart from the mic capsule, what else is inside the mic body ?
No one appears to have read this thread or has no answer.
Well, I found that it appears to make no difference to sensitivity if the phantom voltage is varied. The mic usually has a built in zener that keeps the 'internal' voltage fairly stable within a range of external phantom voltages.
I rigged up a phantom supply for the EMM6 and got the following results.
Phantom voltage 41 volts .
Series resistor on pin2 and 3 = 6.74K
Voltage at the pins 2 and 3 = 32.1 V
Current flow into each pin = 1.32 mA
Phantom voltage 16 volts
Series resistor = 6.74K
Voltage at pin 2 = 8.99 V and pin 3 = 8.95 V
Current flow (average ) about 1.04 mA
That seems to be low as I expected to see about 4 mA based on data seen somewhere on the Net. Anybody else checked this ?
Looks attractive for the single battery split supply rails at +/- 9V.
With a lower phantom power voltage you should reduce the resistor values in the supply lines. The attached graph, taken from the "Handbook for Sound Engineers" has served me well with different mics. The sensitivity, with a well designed circuit, should not change
Thanks mickeymoose.( nice name !). Appropriate for Canada !
That chart should be useful. I will check sensitivity with different phantom voltages. Will also check with Dayton if they have a recommended chart of their own !
Phantom voltage from 9 V battery
I built a voltage tripler with a 7555 chip for getting the phantom voltage for the mic from a 9 V battery.
Here are the test results with a new battery. There is a 22 ohm resistor in series with the battery and the circuit . The resistor and a 100uF capacitor is just to filter the supply a bit.
On load battery voltage at the chip 9.6V
Multiplier output dc voltage 27.4 V without load.
Multiplier operating frequency 61.9 Khz
Multiplier output voltage on load ( mic connected) 18.9 V
Voltage at the mic pins 10.8 V
Resistor in series with the phantom voltage and the mic 6.8K ( x2)
Battery current with no load 1.2 mA
Battery current with mic connected 8.2 mA
Ra/Rb/C on the 7555 4.7K / 10 k / 2 x 470 pF ( 940pF).
The multiplier circuit uses 4 x 1uF ( mini box type ) and 4x 1N4148.
I will try it later with a bench supply at lower voltages and see what happens. Should be OK till about 7.6 V I think.
Wonder how low the mic will really accept without loosing sensitivity ......14V ?
Right now I'll be using two batteries to get +/- supplies for the mic amp. Will work on the -ve supply scheme from a single battery to make the whole system work off one 9 V battery.
I haven't drawn out a schematic but if anyone really wants it I can put one up later. Just a simple astable with a multiplier attached to the output.
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