In the article you will learn how to make tube amplifiers with your own hands from improvised materials. It's no secret that tube sound is the most beautiful, its fans will exist at all times, despite the fact that the market is replete with a large number of small-sized proposals on transistors and microcircuits. Consider in more detail what you should consider when making a tube amp.
Nutrition is the main difficulty
Yes, it is the power supply that can cause problems, since you will need two AC voltage values: 6.3 V for powering the filament and 150 V for the anodes of the lamps. The very first thing you need to find out for yourself is the power of the future design. The power of the transformer for the power supply depends on this. Please note that the transformer must have three windings. Without such power, you can not make tube amplifiers with your own hands.
In addition to the above secondary, there must also be a network (primary). It should contain so many turns so that the transformer operates in normal mode. And even with a significant load (and power surges up to 250 V), the winding should not overheat. Of course, the dimensions of the power supply will be rather large due to the large size of the transformer.
Rectifier
You will need to make a rectifier to get a minimum of +150 volts DC voltage at the output. To do this, use a bridge circuit for connecting diodes. In the design of the power supply, diodes D226 can be used. If you need to make high reliability, then use D219 (they have a maximum working current of 10 Amps). If you make tube amplifiers with your own hands, then follow the safety rules.
Diode assemblies work well in power supplies. It is only necessary to choose those that are able to function normally at voltages up to 300 volts. Pay special attention to filtering the output DC voltage - install 3-4 electrolytic capacitors connected in parallel. The capacitance of each should be at least 50 microfarads, the supply voltage above 300 V.
Lamp preamplifier circuit
So, now closer to the circuit itself. If you make a tube guitar amp with your own hands, or for playing music, you need to understand that the most important thing is safety and reliability. The most common circuits contain one or two stages of the pre-amplifier and one terminal. Preliminary are built on triodes. Since there are radio tubes with two triodes in one base, you can save some space during installation.
And now about what elements contain tube amplifiers. With your own hands you will have to assemble everything into a single design. For a lamp in a pre-amplifier, it is best to use 6N2P, 6N23P, 6N1P. Moreover, despite the fact that all these lamps are analogues to each other, 6N23P sounds much nicer. This lamp can be found in the PTK block (TV channel switch) of old black-and-white television sets such as Record, Vesna-308, etc.
Terminal amplifier stage
As an output lamp, 6P14P, 6P3S, G-807 are usually used. Moreover, the first will be the smallest, but the last two are very impressive sizes. And the G-807 has an anode at all in the upper part of the cylinder. Please note that in tube VLF it is absolutely necessary to use a transformer to connect speakers. Without such a matching transformer, you can not make a tube amplifier yourself.
The TVK transformers used in personnel scanning work perfectly as output transformers. Its primary winding is turned on between the plus of the power supply and the anode of the output lamp. A capacitor is connected in parallel to the windings. And it’s very important to choose the right one! Firstly, it should be paper (like MBM). Secondly, its capacitance should be at least 3300 pF. Do not use electrolytic or ceramic.
Adjustments and stereo sound
Making stereo sound will be very simple. It is enough to make two identical amplifiers. You can find a stereo tube amplifier in old Soviet technology. With your own hands you can repeat the design. But you need to consider some features:
- The volume control is connected directly to the input of the amplifier. The variable resistor that is used for it, you need to choose such that in one case on the axis there are two elements. In other words, so that when the handle rotates, the resistance of two resistors changes at once.
- Similar requirements for the frequency controller. It is included in the anode circuit of the first triode of the pre-amplifier.
Amplifier housing
If you make a tube guitar amp with your own hands, then it makes sense to use a metal housing. He will not be afraid of strikes and other minor shocks. But if you are making an amplifier for use at home, for example, to connect to a player, a computer, then it is wiser to use a wooden case. But you need to consider that it is advisable to mount the power transformer to the case with rubber gaskets. With their help, vibration is reduced.
Much depends on what the housing of the tube amplifier will be. With their own hands, many craftsmen make cases from sheet aluminum. If even small vibrations affect the lamp, its grid will begin to oscillate. And these fluctuations will begin to intensify, and the result is a buzz in the speakers. You also need to make a common bus, which should pass near all the lamps included in the design. All wires that carry the signal should be shielded as much as possible - this will get rid of various kinds of pickups.
Transistor Circuits
And another interesting design is the tube-transistor amplifiers. With your own hands, you can do such literally in the evening. But here lamp designs, as a rule, are made by hanging installation. It turns out to be the most convenient and simple. And in case transistors will be used, it is necessary to apply printed wiring. In addition, a voltage of 9 or 12 volts is required to power the transistor stages. Moreover, transistors are used only to build a preliminary amplification stage. In other words, you only have one lamp left - in the output stage (or two, if it is a stereo version).