Finally I finished my Green Mic Preamp.
The project is slowly dyeing off, since the source files are hard to obtain.
I plan on making a better simplified SMD version which I will share.
Category Archives: Preamplifier
High Performance Microphone Preamplifier
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I build this primarily to use with my Tascam DR-40, since it doesn’t have enough gain for dynamic microphones, and it turned out great. I have couple of boards and components bundled together as a kit. Battery not included.
If anyone is interested, drop me a line.
Op-amp is: AD8648 ARUZ
High Gain about 43dB, set by a trimmer.
Balanced input, unbalanced output.
Very simple, mainly for field use. Very low battery consumption below 6mA.
SNR about 94dB
Trimmers are bottom mouneted now.
Green LED to indicate ON/OFF.
Fetboy Microphone Preamplifier
The famous Fetboy (Hamptone) Microphone Preamplifier.
Layout updated with 2k multi-turn trimmers to set the working point of the J-FETs. MPSA14 and BD139 used in working prototype.
Layout was made for transformers I had laying around.
Coupling capacitors can be changed to anythin from 10uF-47uF electrolytes. The poly capacitor is really not necessary.
About 26dB of gain.
Set 4V at the 100Ohm resistors (R8, R14) with the 100k trimers (R7, R13). Then set working point using a generator and osciloscope and the 2k trimers (R19, R20).
FETBOY (Hamptone) Microphone Preamp
Eagle 5 files availible for download. Supply PCB for a 24VAC transformer included.
Class A MOSFET Headphone Amplifier
Here is an adaptation of basic Class A MOSFET Headphone amplifier. Below schematic and the board layout. Its designed as a single sided PCB board. It`s always a good idea to use a low ESR coupling capacitor. Also use a ceramic capacitor in the supply and a good heat-sink for the transistors, at least one for a 5 Watt heat dissipation.
The described MOSFET Class A amplifier. One channel shown.
Amplifier is for use with pretty common 32 Ohm headphones. For input I used RCA connectors, and for output the preffered 6.35 mm TRS (Tip-Ring-Sleve) Jack!
At the bottom you can find a link for with EAGLE .brd & .sch and an exported .pdf. I will later add a tutorial on exporting your boards from EAGLE, so you can really do all by yourself. For link to EAGLE software go to “Links” section of the site
Headphone amplifier`s board layout, for illustration.
http://www.sendspace.com/file/4qutiw
