Elektor Special: Tube Amplifiers and Electronics
Table of Contents
INFO
Foreword: Technology to Touch
In the digital age, technology is dominated by highly complex chips. They either work or they don't. Tube technology is quite different. It is truly technology you can touch, not referring to hot tube envelopes and resistors. With appropriate technical understanding, the user can follow the function of each individual component. Any defective component can be replaced individually, bringing the device back to life.
Tschüss Rainer: Obituary for Rainer zur Linde
NEUHEITEN
What's Happening: New from Tube Manufacturers
The last introductions of new tubes were about two years ago. Since then, much has happened. Particularly noteworthy is the well-made WE300B from PSVANE, which is finally a true replica of the Western Electric again. But other manufacturers have also been active.
GRUNDLAGEN
The Unknown Entity: Transformer Properties
The quality of a tube power amplifier depends heavily on the properties of the output transformer. Often, secrets are made about the materials used, the winding, and much more. In reality, it is solid physics that can be mastered within the given possibilities. This article clarifies what is important about the "transformer" component in tube amplifiers, how it is used, and how it reacts under different operating conditions. It also covers the parameters important for practical use and how they are measured.
What You Hear: Headphone Operation
Low-power single-ended tube amplifiers are often used for headphone operation due to their pleasant sound. Often, incorrect assumptions are made here, as impedance matching is performed instead of voltage matching. Based on Ohm's law and the datasheet information from headphone manufacturers, it is easy to see what is actually required.
TECHNIK
What is Good? Concerns with Lead-Free Solder
Since the EU Commission decided to ban lead in solder, there have not only been many treatises on this topic, but also massive frustration when soldering with lead-free solder types. For hobby electronics, the choice of whether to use lead-free or leaded solder remains available for private use. What is important is that the solder joints are good and durable. This article sheds light on the physical properties of solder types. It also clarifies why some solder alloys are easy to handle and others are not.
Up to Here and No Further: Tube Limit Data
Tubes are significantly less sensitive and more tolerant to overload than semiconductors. However, if some of the limit data are not observed, the circuit will function, but depending on the operating condition, it can lead to the destruction of the tube and surrounding components.
A Tube for Many Applications: The 300B - A Comparison
The 300B came onto the market in 1938 and was produced until 1988, its fiftieth anniversary. Production was then discontinued. However, it wasn't long before various manufacturers produced replicas of the successful tube. The author tested tubes from various manufacturers and presents his findings in this article.
PRAXIS
Is it Worth More? Line Preamplifier with Triodes
In principle, modern high-level signal sources can be connected directly to power amplifiers. However, if the volume needs to be adjusted or the level needs to be boosted slightly, the use of a preamplifier is recommended.
Old Refreshed: Single-Ended Class A Amplifier with KT 120
In the special issue on tube amplifiers 6, a power amplifier circuit with the EL 156 was presented. This can also be used for the KT 120. To do this, some dimensioning changes must be made to meet the requirements of the new tube type.
Little Powerhouse: High-Performance Push-Pull Class AB Amplifier with KT 120
The KT 120 is a higher-performance version of the well-known KT 88. Circuits designed for the KT 88 can be adapted for the KT 120. This allows high-performance power amplifiers to be built for a variety of applications in Hi-Fi systems, guitar amplifiers, and PA systems.
New vs. Old: Electronic Volume Control
In every amplifier chain, there is a volume control to adjust the listening volume. Mostly conventional potentiometers are used, with all their disadvantages such as poor channel separation, lack of tracking, and problems in the start-up range. Due to mechanical manufacturing tolerances, when turning the potentiometer, one channel may come in first, while the second becomes audible later. The volume control presented here does not have these problems and also offers the advantages of highest channel separation and best tracking.
Catch the Wave: Active Antenna with the EF 183 Tube
This tunable magnetic antenna uses the steep HF pentode EF 183 as its active element. With plug-in modules, the antenna can be used from LW to KW and enables very good reception.
Dancing Waves: Wobbulator for Aligning Radio Receivers
For HF circuits, such as intermediate frequency amplifiers or resonant circuits, a wobbulator is very useful for successful alignment. The complete construction manual is very extensive, so we have only briefly described the purpose, function, and use of this special generator here. The complete construction and alignment manual with all details is available for free download on the Elektor website.
