Texas Amateur Radio
AARC Pages

Home

Site Map

Net Controls

AARC Photos

AARC Roster

Technical Articles

Skywarn

Live Weather

Emergency Preparedness

ARES

Solar Activity

Become a Ham

Contact Us

AARC By-Laws

Membership Form (PDF)

Area Repeaters

Our Neighbors

Area 2M Nets

Ham Links




Ham Radio Accessories - Microphone Preamp


Please see KV5R’s how-to articles on KV5R.COM, too!
Camera StabilizersHomemade SoapHomemade BreadWebsite Development — etc.


Microphone Preamp

Text and schematic by Anthony Gargasz, KB8WOW

This nifty little audio preamp can be used for just about anything you can dream up, from microphones, QRP rigs, even guitars.

An emitter resistor value of 390 ohms works well in most cases.

All resistors should be 1/8 watt, 5% tolerance. Regular carbon composition types are OK. Use metal film types if you require ultra-low noise operation.

The emitter bypass capacitor can be eliminated for low source impedance devices such as dynamic microphones and guitar pickups. High impedance devices such as crystal and electric condenser mics will require the capacitor. Although a 10 mfd. electrolytic is a good starting value, you may use up to 100 mfd. to get maximum AC gain. Be judicious, however, too much gain in a single stage invites hum and oscillation instabilities. The capacitor should have a 35 VDC rating.

Want to experiment with the frequency response? For low impedance sources try reducing the value of the input capacitor (not past 0.01) for more treble. Increasing the output capacitor (up to 4.7 mfd.) will boost the bass. There is allot of gain interaction when you change the capacitor values, so be prepared for some trade-offs.

Construction is not critical, perf board works great. There is only one rule-of-thumb, keep all component leads that attach to the transistor as short as possible.

photo


Next Page: Headset Adapter and Footswitch

 

Please see my articles on KV5R.COM, too!
DIY Camera StabilizersHomemade SoapHomemade BreadWebsite Development — etc.

Articles

Repair Membrane Buttons

Icom 706MkIIG

Mic Preamp

Headset/Footswitch Adapter

DC Buss

LF Converter

Noise Bridge

CW Key Base

2 Meter Dipole

Sleeve Dipole

Super Portable

Shortwave Antennas

NVIS Antennas

Vertical Antenna Project (PDF)

Digital Modes

Digital Sounds

Rabbit-Ears

ladder-line

Balloon Repeater

Shortwave Freq.

Scanner Freq.

Freq Alloc/Plans

Coax Ratings

GMRS/FRS

Grounding

Mobile Antennas

Other topics by KV5R

DIY Camera Stabilizers

Homemade Bread

Homemade Soap

Christian

Web Development

Windows

Linux

Ham Radio

Classic Books




Valid HTML 4.01 Valid CSS