The following schematics are the circuit diagram ofÂ RIAA tube preamplifiers based ECC83 valve. These three circuits equalization RIAA, for enhancing low signals turntable cartridges, following a different solution, each as far as the balance.

**Circuit 1**

**Components List:**

R1 = 47K ohm R2,R3 = 220K ohm R4,R5 = 2.2K ohm R6 = 1M ohm R7 = 820K ohm R8 = 27K ohm |
C1 = 33-470pF mylar C2 = 100nF/400V C3 = 22nF/400V C4 = 10nF/100V C5 = 3.3nF/100V V1 = ECC83 |

**Circuit 2**

**Components List:**

R1 = 47K ohm R2,R3 = 330K ohm R4,R5 = 2.2K ohm R6 = 470K ohm R7 = 100K ohm R8 = 2.2M ohm |
C1 = 33-470pF mylar C2 = 100nF/400V C3 = 220nF/400V C4 = 3.3nF/100V C5 = 750pF mylar V1 = ECC83 |

**Circuit 3**

**Components List:**

R1 = 47Kohm R2,R3 = 220Kohm R4,R5 = 2.2Kohm R6 = 1M ohm R7 = 10K ohm R8 = 8.2K ohm R9 = 91K ohm R10 = 910K ohm R11 = 82K ohm |
C1 = 33pF-470pF mylar C2,C3 = 470nF/400V C4 = 4.7nF/100V C5 = 2.7nF/100V C6 = 1nF/100V C7 = 2.2nF/100V C8 = 4.7uF/100V C9 = 10uF/100V V1 = ECC83 |

In the circuit of PHONO 1, we de-emphasis on passive filter placed between the two departments of tube V1. In PHONO 2, followed the classical solution of active de-emphasis. In PHONO 3, finally there is a combination of the two above solutions, the passive for the high frequencies and active at low frequencies.

The capacitance of the capacitor C1, can be modified to match the technical characteristics of the head, which the mark will have to reinforce each preamplifier.