TREE

Dual preamplifier 

This little project came about as a result of a design job for a client. One of the items needed was a mic preamp, and the project didn't warrant a design such as the P66 preamp, since it is intended for basic PA only. Since mic preamps are needed by people for all manner of projects, this little board may be just what's needed for interfacing a balanced microphone with PC sound cards or other gear. Unlike most of my boards, this one is double-sided. I normally avoid double-sided PCBs for projects because rework by those inexperienced in working with them will almost certainly damage the board beyond repair. I consider this not to be an issue with this preamp, because it is so simple. It is extremely difficult to make a mistake because of the simplicity. As you can see, the board uses a PCB mounted XLR connector and pot, so is a complete mic preamp, ready to go. Feel free to ignore the terminals marked SW1 (centred between the two electrolytic supply caps), as they are specifi...

High Quality, Discrete Components Design, Input and Tone Control Modules To complement the 60 Watt MosFet Audio Amplifier a High Quality Preamplifier design was necessary. A discrete components topology, using + and - 24V supply rails was chosen, keeping the transistor count to the minimum, but still allowing low noise, very low distortion and high input overload margin. Obviously, the modules forming this preamplifier can be used in different combinations and drive different power amplifiers, provided the following stages present a reasonably high input impedance (i.e. higher than 10KOhm). Main Module: If a Tone Control facility is not needed, the Preamplifier will be formed by the Main Module only. Its input will be connected to some sort of changeover switch, in order to allow several audio reproduction devices to be connected, e.g. CD player, Tuner, Tape Recorder, iPod, MiniDisc etc. The total amount and type of inputs is left to the choice of the home constructor. The output of th...

In recent years, following CD's introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these web pages, featuring low noise, good RIAA frequency response curve, low distortion and good high frequency transients behavior due to passive equalization in the 1 to 20 KHz range. Simple Phono Preamplifier  Circuit Diagram: Parts: R1 = 47K R2 = 100R R2 = 6.8K R4 = 68K R5 = 2.7K-1/2W R6 = 2.7K-1/2W R7 = 2.2K R8 = 39K C1 = 100uF-25V C2 = 100uF-25V C3 = 100uF-25V C4 = 47nF-63V C5 = 47nF-63V D1 = BZX79C18 D2 = BZX79C18 Q1 = BC337 Q2 = BC327 J1 = RCA Jack IC1 = LM833, Opamp Notes: R2, R3, R4, R7, R8, C4 & C5 should be low tolerance types. Schematic shows left channel and power supply. For stereo operation R1, R2, R3, R4, R7, R8; J1; C1...

This is a Simple Phono Preamplifier Circuit Diagram . In recent years, following CD's introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these web pages, featuring low noise, good RIAA frequency response curve, low distortion and good high frequency transients behavior due to passive equalization in the 1 to 20 KHz range. Simple Phono Preamplifier Circuit Diagram Parts: R1 = 47K R2 = 100R R2 = 6.8K R4 = 68K R5 = 2.7K-1/2W R6 = 2.7K-1/2W R7 = 2.2K R8 = 39K C1 = 100uF-25V C2 = 100uF-25V C3 = 100uF-25V C4 = 47nF-63V C5 = 47nF-63V D1 = BZX79C18 D2 = BZX79C18 Q1 = BC337 Q2 = BC327 J1 = RCA Jack IC1 = LM833, Opamp Notes: R2, R3, R4, R7, R8, C4 & C5 should be low tolerance types. Schematic shows left channel and power supply....