Tube Line Preamplifier Project      

Fig.1

Fig.2

In the Fig. 2, you see the department that concerns the control of input sel. relay and the circuit of time delay. The drive of inputs choice Relay becomes from selector S2, that drive the corresponding Relay (Fig. 1), via the JF3/1�..6. Simultaneously we have optical clue of choice from corresponding Led (D1�. D5). The circuit is exceptionally simple. In the second department of Fig. 2, exists the circuit of time delay, round the IC1. The first delay time (10��), with R6, C2, concerns the control of RL7 that give the high voltage, in the circuit of line preamplifier. This becomes in order to is applied the high voltage, after first, heat the filament of tubes. The control of RL7 becomes from the Q1, JF3/9-10 and the optical clue becomes from LED (D10). After close the RL7 and is given the high voltage then, after a time delay that is determined by the R8, C3 (20��), the Q2 conduct and drive the RL6 via the JF3/7-8, in order to it connect the exit of preamplifier in the final amplifier. Optical clue of this operation becomes from LED (D11). With switch S3, when it needs, drive the base of Q2 to 0V, it open the RL6, so that is cut the sound signal to the exit, without close preamplifier (MUTE). The circuit is supplied by two voltage. The voltage + 12V, that supplies the Relay and the voltage + V DELAY, which supplies the IC1. This segregation will be explained in the circuit power supply.

Fig.3

In the Fig. 3, appears the circuit of power supply. He�s also simple in the design. We can him separate in the department that are reported in the benefit of high voltage and the department benefit of low voltage, for the filament of tubes and the circuit of delay and control Relay. Exist two transformers, for high voltage and low voltages (in plate). This solution was preferred for reasons of tumor. In the department of high voltage, we have the separation of voltage in two parts. To the line preamplifier and the other to preamplifier PHONO. This becomes, because somebody it can want use in his preamplifier unit PHONO. In line with the high voltage supplies exist contacts of RL7, what are drive by the circuit of delay and they close that exists the essential time delay in order that filament reach in good temperature. In the department of low voltages, exist and here separation of control of filament, with regulated continuous voltages [ IC1-2 ]. This becomes clearly for reasons of resolution of provided power. The IC�s that regulates the voltage of filament, it should they are placed without fail in heatsink. Their regulation should become first without load, in the exit (after we place a resistance 1.5K 1W as load, which we remove afterwards the end of regulation) and afterwards with complete the load of filament. In the department supply of Relay and delay exist resolution of voltages, in two parts. A part via the regulator + 12V [IC3 ], supplies the Relay. A other sector via the D7, R7, D8, C20 supplies the IC1 [ Fig. 2 ], with a voltage + 12V, stabilised from zener D8. This resolution becomes because the voltage [+ V DELAY ], should '' fall '' very fast, in order that cut also the Relay fast, when we close the main line of supply. This is the reason that the C20 is small in capacity. The block diagram of connections of mainer voltages, appear in the Fig.3. A point that it will be supposed you are careful they are, that the lines of 0V, are separated and are not met between them, in no point, neither are drive to the earth, only that the 0V of high voltage. The choice of unit of preamplifier PHONO can become from you.

My proposition is: Tube PHONO Preamplifiers with ECC83