Microphone Circuits

This low-power FM transmitter will take sound input from the Electret Condensor Microphone and transmit it to a nearby FM radio tuned to a unused area of the dial in the 100 - 108 Mhz region. The microphone is very sensitive and will pick up a wisper in a room.

No description available.

The 24 watt amp is easy to build, and very inexpensive. The circuit can be used as a booster in a car audio system, an amp for satellite speakers in a surround sound or home theater system, or as an amp for computer speakers. The circuit is quite compact and uses only about 60 watts.

A lot of friends me asked to draw a more shrunk circuit 2-ch mixer, which will contain also, operation CROSSFADER. The circuits can be modified and added also other channels, repeating basic that I give. It can are added channels stereo PHONO/line or even channels microphone with proportional modification of next stages. In the Fig.1 exist the input circuits of two channels and input of microphone channel. The two basic channels she is same between them. Thus that its go for a channel, the he is also go for the other. In each stereo channel exist two inputs, classic stereo input PHONO that is practical a correction filter RIAA and concerns the signal amplification of sound that emanates from the classic reproduction heads of classic disks LP.

FM Wireless Microphone with added microphone amplifier and power amplifier stage to increase the microphone sensitivity and range. * Microphone sensitivity is limited without a MIC preamp. * The maximum range is only 500 metres (in the clear). I had loads of success with this version of the circuit in the early 80s and had a range of about 2Km. I will build this version again later, after my present projects are complete, then present any possible changes to the circuit.

Here is one that uses a single IC (LM324 quad op amp) and a handful of parts. This circuit is for detecting one of those 3.6khz

Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area. The cable can be buried in a hosepipe or duct and is concealed out of sight. The mic is an ordinary dynamic mic insert and should be housed in a waterproof enclosure with the rest of the circuit.

The circuit is differential in and out and therefore requires a balanced to unbalanced buffer to give suitable output for the next signal stages of a channel in a mixing desk. This is provided by a high performance op-amp differential gain stage, which can be a TL071 or similar IC of your choice. The stage has a gain of six or 15 dB and that sets the maximum input level at about 1.5 volts rms before clipping. This equals an SPL of over 150dB with a typical microphone!

The design consists of differential compound pairs of transistors with a common mode (floating) gain control connecting the emitters of the pair. The compound pairs of 2N4403 and BC549s are far more linear than any single transistor. The circuit is differential in and out and therefore requires a balanced to unbalanced buffer to give suitable output for the next signal stages of a channel in a mixing desk. This is provided by a high performance op-amp differential gain stage, which can be a TL071 or similar IC of your choice. The stage has a gain of six or 15 dB and that sets the maximum input level at about 1.5 volts rms before clipping. This equals an SPL of over 150dB with a typical microphone!

Well, it's pretty much a PAiA preamp - usual input circuity followed by one half of dual op-amp rigged in fixed 20dB amplification circuity, followed by second stage which is adjustable for up to 40dB amplification, for up to 60dB total. The power supply is a simple affair, supplying +-12V using 7912 and 7812 regulators. As ECM8000 is happy with only 15 volts of phantom power, I added a 7805 which I referred to +12V instead of ground - resulting in 17V output which I used for phantom power.