You can directly connect the BM-800 microphone to the icom IC-7300 without problems and it works very well getting good audio reports.
These mics even work well with the 5 volts coming from the Yaesu FT-450AT
The preamp is built into the microphone, no external one is needed. The IC-7300 microphone input cable is 8 VDC and the blocking capacitor is built into the radio.
In fact, the Icom IC-7300 already comes with a fist microphone that is of the electret type. KF8RM
BM-800 mic for ham radio
Here is the schematic for the ic-7300
bm 800 icom 7300
The BM-800 (NW-800) mics are ELECTRET mics not condenser mics.
The Electret mic element only need’s 2v to 10v to operate. The BM-700, BM-800, etc. are all karaoke ELECTRET mics designed to run off Computer +5v. They will run on +48v because of the Zener diode circuit but that is OVERKILL for an Icom. The +48v will be dropped to the +2v/+10v level that is required.
The BM800 audio output level should be fine for the Icom but what if it isn’t what are you going to do? Use GOOGLE to do more research.
Icom wiring; pin 1 is AUDIO and +8v; pin 2 is +8v only; pin 7 is AUDIO ground; pin 5 is PTT; pin 6 PTT ground
BM-800 XLR; pin 1 is ground; pin 2 is + AUDIO; pin 3 is – Audio.
The audio output on the BM800 is pin 2 & 3, gnd is pin 1. That is a balanced output, the Icom is unbalanced input, in other words you only need audio & gnd. Which would be on the XLR pin 2 & pin 1.
So how do you get audio & power to the electret microphone; Icom pin 1 to XLR pin 2; Icom pin 7 to XLR pin 1.
You should be able to leave XLR pin 3 unconnected but if you have RF or distorted audio try XLR pin 3 as gnd.
Some folks like to ground XLR pin 3 but that is grounding the output of one half of the audio circuit, which may work. Some high-end microphone manufactures use a method called Impedance Balancing if there mics are used in an unbalanced situation.
They take XLR pin 3 and go through a 100 ohm to 600 ohm resistor to ground. The resistor value matches the impedance of the mic output, I think the BM800 is 150 ohms.
What do you do if you have RF or distorted audio? Check out W1AEX website site he has excellent info on homebrew Electret mics. I had to employ his +8v filter design for my TS590 and it worked perfectly. GOOGLE is your friend.
I converted 2 BM-800 mics for use with my IC-7300 & SDR radio. The easiest conversion was to use a PUI HD 1024L Electret mic element & W1AEX’s pre-emphasis circuit. The conversion was inexpensive and easy to build.
The mic level output is high, my IC-7300 mic gain is set to 15. The 2nd conversion was more work and much more money; $50. You can see both mics on my QRZ page. The mic with the BLUE heat shrink is the PUI electret element & the pre-emphasis circuit.
The mic with the large condenser element is my latest mic and is used with the SDR. I use the $50 mic with my Anan7000DLE MKII SDR radio. The mic that’s is marked em1a is a studio quality mic that requires +48v to operate. The EM1A mic, the circuit board & element on the left is the original, the middle is my board & element.
Also I prefer to use Heil microphone cable & Heil 8 pin Foster mic connectors both very high quality. The only drawback to the Heil mic cable is very thick. It has 2 wires for PTT, I only use vox so they are wasted on me.
Dave, k4em – “We’re Hams, we’re supposed to built stuff”
Difference between electret condenser and true condenser microphones
What is the difference between a condenser and electret microphones? My son and I have a difference in opinion. I said that they are very much the same. Except one needs a bias supply for the elements and the electret has a charge on one of the plates there for not needing the bias supply. I guess there maybe some other differences and that is why he thinks the condenser mike is better.
The electret is a type of condenser microphone. There are two types of condenser microphones: a permanently biased condenser, usually called an electret condenser, and an externally biased condenser, usually called a true condenser. These days, when people say “condenser microphone”, they usually mean, “electret condenser microphone”. Probably ninety-five percent of the condenser microphones on the market are the electret type.
The electret has a charged backplate that is created when we manufacture the microphone. A true condenser, on the other hand, continuously requires an external charge. This external charge may come in the form of any external box attached to the microphone, or it may come from the electronics built into the housing of the microphone.
Which is better? There are excellent microphones on the market that use both types of construction. They are simply different ways to achieve the same goal.
One last note, do not get the bias for a true condenser element confused with the bias that is supplied by a wireless transmitter. The bias supplied by a wireless transmitter is needed to power up a small transistor located near an electret condenser element. These two types of bias voltages are completely different.
|BM-800 Condenser Microphone 3.5Mm Wired Microphone for Computer Karaoke KTV||Neewer NW-800 Condenser Microphone 2.5M Wired Microphone for Computer Karaoke KTV|