Pre-MIC | Electronic Project Circuits

Posts Tagged ‘Pre-MIC’

Dynamic microphone Amplifier for earphones

I decided to make this circuit so that I could listen to faint noises. It is a simple two-stage transistor amplifier design. The circuit was designed to use the input from a dynamic microphone but I am sure that with some modifications it would be possible to use an electret microphone. The 2N3053 transistors used in the design don’t have a particularly high gain so other types could probably be used as long as they are NPN.
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Source: http://www.geocities.com/electronics3456/soundamp.html Thank you.

Be the first to comment - What do you think? Posted by admin - April 25, 2008 at 10:58 am

Categories: Pre Amplifier Tags: Head phone amplifier, Pre Amplifier, Pre-MIC

ECM Mic Preamplifier by BC549

A microphone amplifier that may be used with either Electret Condenser Microphone (ECM) inserts or dynamic inserts, made with discrete components.
Both transistors should be low noise types. In the original circuit, I used BC650C which is an ultra low noise device. These transistors are now hard to find but BC549C or BC109C are a good replacement. The circuit is self biasing and will set its quiescent point at roughly half the supply voltage at the emitter of the last transistor.

Read More Source:Andy Collinson http://www.mitedu.freeserve.co.uk/Circuits/Audio/ecmmic.html

Be the first to comment - What do you think? Posted by admin - April 19, 2008 at 5:05 am

Categories: Pre Amplifier Tags: BC547, microphone preamp, Pre-MIC

Microphone Preamplifier by LM837

The mike preamp itself is based on the LM837 Low-noise audio opamp from National Semiconductor. The first stage is a noninverting 26dB gain stage (fixed). Note the use of the 33pF capacitor in the feedback loop, this reduces the tendency of the LM837 to oscillate (it has a large bandwidth of 17MHz). Two 5.1V Zener diodes are connected back-to-back across the input, to protect the amplifier from large voltage transients at the input.
The next stage is an inverting variable gain stage (-âˆž to 60dB), again with a 47pF capacitor across the gain-control resistor. The pot used here should be of high-quality to prevent crackling, etc. Also, the wires should be tightly twisted and shielded to prevent noise and mains-hum pickup. The last stage is an inverting buffer (unity gain), to correct the inversion caused by the variable gain stage.

Read More Source: http://wiredworld.tripod.com/tronics/mixer.html Thank you.