Since the vinyl record have passed, modern audio amplifiers and mixers do not have any phono inputs. However, turntables have always been popular among audiophiles and music lovers. There are many people still enjoying the time spent in playing a vinyl record and the interaction with the music and the album art. If you are looking back to enjoy the sound from your beloved vinyl record collection, all you need is a classic turntable with a moving magnet or a moving coil cartridge and a phono preamplifier (known also as a RIAA preamplifier). There is always the option to purchase one phono preamp for around 30 to 100$, but many will agree that building from scratch has more fun. Below there is a small collection of some excellent phono preamplifier circuits.
A phono preamplifier's primary task is to provide gain (usually 30 to 40 dB at 1 kHz) and accurate amplitude and phase equalization to the signal from a moving magnet or a moving coil cartridge. In addition to the amplification and equalization functions, the phono preamp must not add significant noise or distortion to the signal from the cartridge. Phono preamps follow the RIAA equalization curve, established by the Recording Industry Association of America (RIAA). TheRIAA equalization curve was intended to operate as a de facto global industry standard for records since 1954.
The presented electronic circuits require ±15V symmetrical power supply in order to operate normally. Click here to learn how to build the required power supply unit.
Most phono preamplifier circuits in commercially available audio products are based on the topology of the 1st preamplifier. There is not any specific set of component values for that topology. There are many equivalent sets that give equivalent results. With the recommended set of components, the voltage gain of the 1st RIAA preamplifier is about 30db at 1KHz. The input sensitivity is about 2mV and the signal to noise ratio is better than 80db. Using low tolerance components, the expected maximum deviation from the ideal RIAA curve could be less than 1db.
The voltage gain of the second RIAA preamplifier circuit is 40db at 1KHz. The harmonic distortion is less than 0.01% for the entire audio spectrum as long as the input signal is kept below 25mV, 150mV and 500mV at 50Hz, 1KHz and 6KHz respectively.
The third phono preamplifier is a precise two-stage RIAA phono preamplifier. That circuit has a very accurate RIAA response. It is derived from Texas Instrument's application notes on High-Performance Audio Applications of The LM833.