Simple Phono Preamplifier

Simple circuitry suitable for moving-magnet cartridges Passive high-frequency equalization. This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these webpages, featuring low noise, good RIAA frequency response curve, low distortion and good high frequency transients behavior due to passive equalization in the 1 to 20KHz range. Transistors and associated components provide ±18V supply to the op-amp, improving headroom and maximum output voltage.

Source:http://www.redcircuits.com//Page10.htm

Soundblaster Preamp

The Sound Blaster 16 PCI and Sound Blaster 16 ISA do not have a very sensitive microphone input. This little one transistor amplifier is powered directly from the microphone jack on the sound card and has LOTS of gain. Just put a 100uF bypass capacitor in parallel with the diode to increase gain even more.

Source: http://members.shaw.ca/novotill/SoundBlasterPreamp/index.htm

Phono Preamps For All

This is a collection of phono (black vinyl for the youngsters) preamps and equalisation circuits, one of which is sure to meet your requirements. These are not my circuits, but were contributed by a reader (see above), so I am not really in a position to make any specific recommendations. They are provided as a service to the experimenters out there, and may be found useful for other applications as well.

Source: http://sound.westhost.com/project25.htm

Intercom preamp - Universal high quality preamp

The circuit is so simple that there is little to say about it, but it gives very good results. Tr1 is operated in grounded base mode with input to its emitter to give low impedance input. The values shown give correct operation from 9v. If operating from other voltages you may wish to alter the 1K8 resistor to give symmetrical clipping at high levels. The third circuit is one I was working on as I left the audio company but is seems to be potentially very useful. It should be simple to use it as a low impedance mic amp or as a high input impedance preamp for mic or, with a suitable RIAA equalization, for phono pickup or similar. It can even be used as a balanced input mic preamp.

Source:http://www.4qdtec.com/preamp.html

Audio Preamplifier with Digital Volume

The circuit is a preamplifier with digital regulation intensity of sound. He is separated in three departments. In first schematic (Fig.1), is found the circuit of control of electronic potesometer. The control become from two pressing switches. The S1 (UP), that put up the intensity of sound and the S2 (DOWN), on the contrary, that lower the intensity, checking them two oscillator follow a bistable multivibrator R-S (ICIC-D), with that determined the direction of counter IC3.. The gate IC2B ensure deactivate the counter in the limits of region of regulation. With the S4 we have the possibility selecting the level of sound, in which it will come back after RESET or when we give supply in the circuit. This operation is very useful when we select null level of sound, then with switch S3 we have the possibility of going to situation MUTE, to rapid nihilism of sound.

Source : http://users.otenet.gr/~athsam/audio_preamplifier_with_digital_volume.htm

Microphone pre-amp

This is an image Schematic. No Description available.

Link : http://www.ee.washington.edu/circuit_archive/circuits/Micro.GIF

All transistor microphone pre-amplifier

The microphone has high sensitivity in the audio range, but in the ultrasonic range, the sensitivity decreases rapidly. The receiver is very sensitive. To prevent overdriving and feedback due to the high sensitivity of the microphone in the audio range, the gain of the amplifier should be low in the audio range and increase with frequency in the ultrasonic range.

Read More Source: http://bertrik.sikken.nl/bat/preamps.htm

Simple Preamplifier by Transistor

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Simple Preamplifier by Transistor

Cassette Preamp by transister

Read MORE and VIEW circuit Cassette Preamp by transister

Hi-Fi Preamplifier (transister)

Design: Graham Maynard
Email graham.maynard1@virgin.net

Notes:
This circuit was submitted by Graham Maynard from Newtownabbey, Northern Ireland. It has an exceptionally fast high frequency response, as demonstrated by applying an 100kHz squarewave to the input. All graphs were produced using Tina Pro.

Source :http://www.mitedu.freeserve.co.uk/Circuits/Audio/gmpre.htm