Single Ended Class A 6V6 6J5 Valve (Vacuum Tube) Amplifier Circuit

This is my first successful vacuum tube project.  The output of this small amplifier in which a 6V6GT output pentode is connected as triode is about 4.5 watts.

This project involves a single ended audio amplifier, which consists of a resistive input network, a driver stage, and an output stage to a typical 8 ohm loudspeaker load, all the while, using a minimum of supportive passive components for biasing and coupling duties. Power-supply voltage is provided by  full wave diode rectification of 230 VAC by a magnetic transformer. This design provides a quality audio amplifier.

Valve amplifier circuit diagram

The major factor involving the design of this single ended output stage is matching an available output tube to an available output transformer (OT) , which can provide the proper impedance matching. Using typical operating parameters, the 6V6 power tube, operating in triode mode, has an ideal load impedance of 5k Ohm, and generates about 4.5 watts of power. An OT was used, handling 8 watts and providing impedance matching from a 5k primary to an 8 ohm secondary, which is a common loudspeaker impedance.

Tube amplifier power supply

The amplifier uses a simple linear power supply to develop 300VDC. Heater voltages are supplied directly from the 6.3VAC taps on the secondary of the power transformer. The other secondary windings, rated at 230VAC are used for the DC supply. It consists of a 4 rectifiers, variety of smoothing capacitors and resistor.

Tube Datasheets

6J5 Datasheet

6V6 Datasheet

Several construction issues were considered in the building of this amplifier. High power supply voltages, large and leaky inductive components, and high temperatures are among these considerations. I used old tube amplifier chassis.

Magnetic flux is expelled from the transformers as shown by the red arrows above. By placing the output transformer (OT) and power transformer (PT) at opposite ends of the chassis, and rotating their axes 90° from one another, induction noise from PT to OT is reduced. Although this configuration sees flux from the OT directed at the 6V6, OT flux interference into the sensitive preamp stage tube is avoided. Beneath the chassis hum reduction is further achieved by winding all pairs of wire containing AC (filament heater wires, PT primary, and secondary wiring to the diode rectifier).

6V6 Tube amplifier Video

Due to the 300V power supply voltages used, components were carefully chosen to withstand peak conditions.

Connect amplifier ground and power supply ground to the chassis ground point.

Don’t touch any component when the tube amplifier connected to the power, because it used high voltage.

Please send your ideas, which are very important for our success…

Discrete Class AB Transistor Audio Power Amplifier Circuit Diagram

This is a class AB transistor power amplifier. It is a simple amplifier to build, uses standard parts and is stable and reliable.  The entire circuit utilizes commonly available components and may be simply built over a general-purpose board. But this amplifier has very good sound quality.

There are eleven transistors, including four in the output stage. Q1 and Q2 transistor must be between 3 and 5  amperes power transistors. Q4 and Q5 must be between 100mA and 500mA driver transistors. Other transistors are 10mA small driver transistors. Q1, Q4 and Q2, Q5 are complementary pairs, they make complementary darlington pairs.

Power output of the amplifier

10W is much enough for the day today home usage.

Amplification of this amplifier (A)

Volume control can be added to the circuit by connecting a 10KΩ  POT in series to the input of the amplifier.

Q1 and Q2 must be kept sufficiently cool, so it is mounted on a suitable heat sink. If you used single heat sink please use insulation between transistors and heat sink.

Please send your ideas, which are very important for our success…

CD4060 Timer Circuit 1 minute to 2 hours

This is a 1 minute to two-hour timer switch. The 14-stage binary ripple counter Type 4060, IC1, has an on-chip oscillator capable of stable operation over a relatively wide frequency range. In the present circuit, the oscillator frequency is determined by an external RC network connected to pins 9, 10 and 11.

When the power is on, the pulse at junction R6-C2 resets the counter and counting starts. When the counter reaches bit 14 (Q13), pin 3 goes high so that the relay, a 9V type, is turned on via driver Q1.

CD4060 Pinout

The time delay is set with the aid of VR1. Time delays of between one minute and two hours are possible by appropriate dimensioning of the timing components:

1-30 minutes: C1 = 220nF ; VR1 = 500KΩ.
1-60 minutes: C1 = 470nF ; VR1 = 500KΩ.
1-120 minutes: C1 = 470nF ; VR1 = 1MΩ.

The timer is powered by a 9V PP3 battery. Light-emitting diode D1 does not affect the operation of the circuit and is included merely to show that the timer works. Diode D1 and resistor R4 are , therefore, optional components.

Please send your ideas, which are very important for our success…

Low Ripple Regulated Power Supply Circuit Diagram

This circuit may be used where a high current is required with a low ripple voltage (such as in a high powered class AB amplifier when high quality reproduction is necessary ).

Q1, Q2, and R2 may be regarded as a power darlington transistor. D5 and R1 provide a reference voltage at the base of Q1. D5 should be chosen thus:
D5=V_out-1.2

C2 can be chosen for the degree of smoothness as its value is effectively multiplied by the combined gains of Q1/Q2, if 100µF is chosen for C2, assuming minimum hef for Q1 and Q2,

C=100×15(Q1)×25(Q2)

=37000µF.

Please send your ideas, which are very important for our success…

Electronic Coin Toss Circuit Diagram

This is electronic coin toss circuit using one CD4049 IC (Hex inverting buffer and TTL driver).  This IC has six buffers and it may be used independently. The buffers may be used as simple inverters, as voltage translators, or as current drivers for interfacing TTL or other logic.

The gate IC1 and IC2 of the IC and resistor  – condenser network from a relaxation oscillator. Gate IC3 of the IC is a buffer which isolates the oscillator from the load. Gates IC5 and IC6 are wired as a flip-flop. The LEDs will glow (either head or tail) when the corresponding gate’s output is high. The output of flip-flop will change states only when the input applied are compliment logic levels, example: high and low.For this gate IC4 is used.

Press the switch PB1 and release it. The LED will show for chance.

You can use a 7-segment common cathode display instead of LEDs to know the chance by reading the letters h and t.

Please send your ideas, which are very important for our success…

Power Amplifier Speaker Protection Circuit Schematic

While switching a power amplifier on, a loud thump sound is heard to sudden heavy discharge current through the speaker at the time of power on. This current may damage the speaker, especially in case of direct coupled amplifier.

The circuit given here protects speakers from the current surge. When the amplifier is off, relay switch is also off. When the amplifier is switch on, R1 and Ci provide delay of a few seconds to switch the transistor on which energizes the relay.

BC107 NPN TRANSISTOR

Delay time is proportional to value of R1.

Please send your ideas, which are very important for our success…

Two LED CMOS Flasher Circuit Diagram

This is a simple 2 led cmos robot ( flasher, multivibrator ) circuit using CD4069 six inverter IC.

Circuit Description

CD4069 six inverter CMOS IC

Inverters IC1-a and IC1-b from a multivibrator and IC1-c is a buffer. Inverter IC1-d is connected so that its output is opposite that of IC1-c; when  pin 6 is high, then pin 8 is low and vice versa. Because pins 6 and 8 are constantly changing state, first one LED and then the other is on since they are connected in reverse. The light seems to jump back and forth between the LED’s.

The R2 resistor limits LED current. Depending upon the supply voltage used, the value of the resistor may have to be changed to obtain maximum light output. To change the switching rate, change the value of capacitor.

Please send your ideas, which are very important for our success…

12V DC Light Dimmer Circuit Using 555 Timer IC

This is a 12 volt at 2 amp Lamp dimmer that can be used to dim a standard 25 watt bulb by controlling the duty cycle of a astable 555 timer oscillator.

When the potentiometer is at the up position, the capacitor will charge quickly through both 1k resistors and the diode, producing a short positive interval and long negative interval which dims the lamp to near darkness.

555 Timer IC PIN Configuration

When the potentiometer is at the lower position, the capacitor will charge through both 1k resistors and the 50k potentiometer and discharge through the lower 1k resistor, producing a long positive interval and short negative interval which brightens the lamp to near full intensity.

BC140 PIN Configuration

The duty cycle of the 200Hz square wave can be varied from approximately 5% to 95%.

You can drive more power light using 2 or more parallel 2n2955 transistors with good heat sink.

Please send your ideas, which are very important for our success…

Transmitter RF Output LED Indicator Circuit Diagram

This RF output detector circuit using a visual indicator can be useful for an RF indicator.

This circuit was used for a transmitter ON indicator.

2N3904 PIN Configuration

Transmitter output or other RF output is connected to the RF input in this circuit.

Please send your ideas, which are very important for our success…

VCR Camera Video Detector Switch Controller Circuit

This video detector switch controller circuit uses the video output from a VCR or camera to control a relay.

A1 = To video output

A2 = To circuit under control

Video turns on Q1, cutting off Q2, allowing Q3 to be forward biased, activating relay RL1.

2N2222 Pin Configuration

You can use the timer in your VCR and this unit to generate long time delays as well.

Please send your ideas, which are very important for our success…