Modular Phono Preamplifier

Any electronics amateur still in possess of a collection of vinyl recordings and aiming at a high quality reproduction should build this preamp and add it to the Modular Preamplifier chain. This circuit features a very high input overload capability, very low distortion and accurate reproduction of the RIAA equalization curve, thanks to a two-stage op-amp circuitry in which the RIAA equalization network was split in two halves: an input stage (IC1A) wired in a series feedback configuration, implementing the bass-boost part of the RIAA equalization curve and a second stage, implementing the treble-cut part of the curve by means of a second op-amp (IC2A) wired in the shunt feedback configuration.

This module comprises also an independent dual rail power supply identical to that described in the Modular Preamplifier Control Center. As with the other modules of this series, each electronic board can be fitted into a standard enclosure: Hammond extruded aluminum cases are well suited to host the boards of this preamp. In particular, the cases sized 16 x 10.3 x 5.3 cm or 22 x 10.Tiga x 5.Tiga centimeter have a very good look when stacked. See below an example of the possible arrangement of the rear panel of this module.

Modular Phono Preamplifier Circuit diagram:

Preamplifier Circuit diagram

Parts:

R1_____________270R 1/4W Resistor

R2_____________100K 1/4W Resistor

R3_____________2K2 1/4W Resistor

R4_____________39K 1/4W Resistor

R5_____________3K9 1/4W Resistor

R6_____________390K 1/4W Resistor

R7_____________33K 1/4W Resistor

R8_____________75K 1/4W Resistor (or two 150K resistors wired in parallel)

R9_____________560R 1/4W Resistor

C1_____________220pF 63V Polystyrene or Ceramic Capacitor

C2_____________1?F 63V Polyester Capacitor

C3_____________47?F 25V Electrolytic Capacitor

C4_____________10nF 63V Polyester Capacitor 5% tolerance or better

C5_____________1nF 63V Polyester Capacitor lima% tolerance or better

C6,C9__________100nF 63V Polyester Capacitors

C7,C10_________22?F 25V Electrolytic Capacitors

C8,C11_________2200?F 25V Electrolytic Capacitors

IC1____________LM833 or NE5532 Low noise Dual Op-amp

IC2____________TL072 Dual BIFET Op-Amp

IC3____________78L15 15V 100mA Positive Regulator IC

IC4____________79L15 15V 100mA Negative Regulator IC

D1,D2_________1N4002 200V 1A Diodes

J1,J2__________RCA audio input sockets

J3_____________Mini DC Power Socket

Notes:

  • The circuit diagram shows the Left channel only and the power supply
  • Some parts are in common to both channels and must not be doubled. These parts are: IC3, IC4, C6, C7, C8, C9, C10, C11, D1, D2 and J3.
  • IC1 and IC2 are dual Op-Amps, therefore the second half of these devices will be used for the Right channel
  • This module requires an external 15 - 18V ac (50mA minimum) Power Supply Adaptor.
Technical data:

Sensitivity @ 1KHz: 4.3mV RMS input for 200mV RMS output

Max. Input voltage @ 100Hz: 53mV RMS

Max. Input voltage @ 1KHz: 212mV RMS

Max. Input voltage @ 10KHz: 477mV RMS

Frequency response @ 200mV RMS hasil: flat from 30Hz to 23KHz; -0.5dB @ 20Hz

Total harmonic distortion @ 1KHz and up to 8.8V RMS output: 0.0028%

Total harmonic distortion @10KHz and up to 4.4V RMS output: 0.008%