Tube Line = Preamplifier Progect 1=20 English

3D"Tube_line_preamplifier_1.gif

Fig.1

The=20 interest for circuits of tubes, remains big. Thus I = will give=20 completed in enough big degree, circuit of = preamplifier. It=20 is mainly constituted by the department of main=20 preamplifier, the department of input=20 selector, delay=20 of application voltage and connection output of = preamplifier=20 with the final amplifiers and the department power=20 supply. The department of mainly preamplifier = appears in=20 the Fig.1. Deliberately it does not have something = revolutionary in=20 the designing. In the entry exists a simple circuit=20 constituted from relay that is drive from input = selector [S2].=20 The signal afterwards drive to the next stage that is = constituted by a circuit cascade S.R.P.P (shunt regulated = push=96pull)=20 and a circuit cathode repeater, in the exit. As = S.R.P.P used=20 the double triode ECC82 (U1a-b), in connection = =91=92series =91=92 of=20 two triode, with characteristically pentode . The = circuit was=20 used as department of input R.F, in the old televisions with = tubes,=20 offers big input impedance and very good response in = the high=20 frequencies. In the circuit preferred use capacitors = with big=20 capacity in various points and capacitors of polypropylene = or MKT. =20 in the exits of tubes, for better quality of sound and = response=20 in low frequencies. Exists a simple circuit for the = VOLUME=20 and BALANCE potesometer, that is should be very good = quality.=20 In the exit exists a circuit Cathode Repeater, that is = constituted=20 by the half department of tube ECC81 (U2a). Here = exists a=20 particularity. Whoever wants it can use the one of = half tube=20 for a other channel and half for the other channel. We can = however=20 use his other half tube of channel, leaving him = inutile,=20 placing a output tube for each channel. This becomes = in order=20 to we avoid his effect of channel in the other, if we use = the=20 same tube ,for two channels. It=92s known that the tubes, do = not have=20 very good separation, when find itself the two = departments,=20 in the same integument. The choice is yours. In this = stage=20 are found also the contacts of RL6,=20 who connect the exit of line preamplifier in the = final=20 amplifier, with such certain time delay, so that are = not=20 heard annoying noises, when open or close the preamplifier. = The RL6 =20 closes after have been stabilised and applied, all the = voltages of circuit. All the relay of SEL. and = OUTPUT, should=20 be very good quality. The circuit of control appears in = circuit =20 SEL - DELAY, (Fig.2).=20 . =20

	Part =20 List

R1-7=3D1Mohm

R12-13=3D100ohm

C9=3D4.7uF = 250V*

R2=3D100Kohm = 1W

C1=3D220nF 250V*

U1=3DECC82

R3-8=3D1Kohm = 1W

C2=3D220pF ceramic or = mylar

U2=3DECC81

R4=3D1.2Kohm = 1W

C3=3D2.2uF 350V*

RV1=3D2X100Kohm = =20 log.

R5-11=3D5.6Kohm = =20 2W

C4=3D1000uF 16V

RV2=3D2X100Kohm = =20 lin.

R6=3D100Kohm

C5-6=3D2X50uF = 450V

RL1....6=3DRelay 12V 2X2 [1A]=20

R9=3D22Kohm

C7=3D1uF 250V*

R10=3D100Kohm

C8=3D220nF 630V

*polypropylene or = MKT

Input =20 Selector - Delay=20 Drive

<= /TD>

3D"Tube_line_preampl_sel_delay_1.gif

Fig.2

In=20 the Fig. 2, you see the department that concerns the = control=20 of input sel. relay and the circuit of time delay. = The drive=20 of inputs choice Relay becomes from selector S2, that = drive=20 the corresponding Relay (Fig.=20 1), via the JF3/1=85..6. Simultaneously we have = optical=20 clue of choice from corresponding Led (D1=85. D5). The = circuit=20 is exceptionally simple. In the second department of Fig. 2, = exists=20 the circuit of time delay, round the IC1. The first = delay=20 time (10=92=92), with R6, C2, concerns the control of = RL7=20 that give the high voltage, in the circuit of line =20 preamplifier. This becomes in order to is applied the high = voltage,=20 after first, heat the filament of tubes. The control = of RL7=20 becomes from the Q1, JF3/9-10 and the optical clue = becomes=20 from LED (D10). After close the RL7 and is given the high = voltage=20 then, after a time delay that is determined by the = R8, C3=20 (20=92=92), the Q2 conduct and drive the RL6=20 via the JF3/7-8, in order to it connect the exit of =20 preamplifier in the final amplifier. Optical clue of this = operation=20 becomes from LED (D11). With switch S3, when it = needs, drive=20 the base of Q2 to 0V, it open the RL6, so that is cut = the=20 sound signal to the exit, without close preamplifier (MUTE). = The=20 circuit is supplied by two voltage. The voltage + = 12V, that=20 supplies the Relay and the voltage + V DELAY, which = supplies=20 the IC1. This segregation will be explained in the circuit = power =20 supply.

	Part =20 List

R1.....5=3D1.2Kohm

C2=3D10uF 25V

Q1-2=3DBD679

R6-8=3D1Mohm

C3=3D22uF 25V

IC1=3D4081

R7-9=3D10Kohm

D1......5=3D3mm Red = LED

S2=3DSEL 1X6 = step

R10-11=3D1.2Kohm

D6......9=3D1N4148

S3=3D1X2 mini = switch

C1=3D100nF 100V

D10-11=3D3mm Green = LED

Power = Supply

<= /TD>

3D"tube_line_preampl_power_supply_1.gif

Fig.3

In=20 the Fig. 3, appears the circuit of power supply. = He=92s also=20 simple in the design. We can him separate in the = department=20 that are reported in the benefit of high voltage and the = =20 department benefit of low voltage, for the filament of tubes = and the=20 circuit of delay and control Relay. Exist two = transformers,=20 for high voltage and low voltages (in plate). This = solution=20 was preferred for reasons of tumor. In the department of high=20 voltage, we have the separation of voltage in two = parts.=20 To the line preamplifier and the other to = preamplifier PHONO.=20 This becomes, because somebody it can want use in his = preamplifier unit PHONO. In line with the high voltage = supplies=20 exist contacts of RL7, what are drive by the circuit = of delay=20 and they close that exists the essential time delay = in order=20 that filament reach in good temperature. In the department = of=20 low voltages, exist and here separation of control of = filament, with=20 regulated continuous voltages [ IC1-2=20 ]. This becomes clearly for reasons of resolution of = provided=20 power. The IC=92s that regulates the voltage of filament, it = should =20 they are placed without fail in heatsink. Their = regulation=20 should become first without load, in the exit (after = we place=20 a resistance 1.5K 1W as load, which we remove afterwards = the=20 end of regulation) and afterwards with complete the load of=20 filament. In the department supply of Relay and delay = exist=20 resolution of voltages, in two parts. A part via the=20 regulator + 12V [IC3=20 ], supplies the Relay. A other sector via the D7, R7, = D8, C20=20 supplies the IC1 [ Fig.=20 2 ], with a voltage + 12V, stabilised from zener = D8. This=20 resolution becomes because the voltage [+ V DELAY ], = should=20 '' fall '' very fast, in order that cut also the Relay fast, = when we=20 close the main line of supply. This is the reason = that the=20 C20 is small in capacity. The block diagram of = connections of=20 mainer voltages, appear in the Fig.3. A point that it will = be=20 supposed you are careful they are, that the lines of = 0V, are=20 separated and are not met between them, in no point, = neither=20 are drive to the earth, only that the 0V of high voltage. = The choice=20 of unit of preamplifier PHONO can become from = you.

My=20 proposition is: Tube PHONO Preamplifiers = with=20 ECC83

	Part =20 List

R1=3D2.2Kohm = 5W	C8-13=3D10uF 16V	IC3=3D7812 =20 [1A]
R2-4=3D100Kohm = =20 2W	C10-15-19-20=3D47uF = 25V	T1=3D230Vac / 200V = 0.15A
R3=3D680ohm = =20 5W	C16=3D470uF 25V	T2=3D230Vac / 12V = 3A
R5-6=3D220ohm	C17-18=3D100nF = 100V	F1=3D0.2A = slow
R7=3D470ohm = =20 1W	BR1=3D4 X 1N5408	F2=3D0.1A = fast
TR1-2=3D4.7Kohm = =20 trimmer	BR2=3D4 X 1N5408	S1=3D Switch 2X2 = 10Aac
C1=3D33nF 630V	BR3=3D4 X 1N4007	RL7=3D12Vdc Relay 2X2 = 10A
C2.....5=3D2X50uF = >350V	D1.....7=3D1N4007	EMI RF Filter = 230Vac/6A
C6=3D4700uF 25V	D8=3D12V 0.5W = zener	* with = heatsink
C7-9=3D100nF 100V	IC1-2=3DLM317*

Sam=20 Electronic Circuits 12/01

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