ASV Tube Amplifier Kit KTA-50

There has always existed a large group of tube lovers who prefer to design and build their own tube amplifiers instead of simply buying them in a shop. Money has never been problem for them. It's the warmth of the soldering iron and the odour of soldering which attracts them. There is no greater happiness than to see tubes start glowing and to hear the warmly sounding music from your amplifier for the first time. Troubles finding suitable electronic and mechanical components are soon forgotten.
It has been our aim to help such audio enthusiasts by offering either a complete kit for a tube amplifier or only some vital components and parts. In this way we help them to avoid problems in finding these parts and still retaining the thrill of making something personal and unique.

The concept

The integrated tube amplifier ASV KTA-50 is at your disposal. It is the result of careful and persistent development and design. The ASV KTA-50 has been designed as a stereo 2x25W block fitted in the housing containing two power stages, a power supply and a passive preamplifier stage with inputs for CD, tuner and tape. A quality input switch and a stereo input potentiometer are fitted at the input. Thanking to a relatively high input sensitivity, no separate preamplifier is needed, except for phono cartridges. The housing is made of quality varnished steel sheet. The output transformers in metal cases, array of tubes and power supply capacitors on top panel contribute to an overall elegant look of the tube amplifier. Rear panel is fitted with all input and output terminals and the power switch.
In fact, housing of KTA-50 is very similar to SE amplifier STA-8, so they are some kind of "brothers". In the basic model the front and the rear nameplates are printed on special durable polyester self-adhesive foil. However, the black anodized and laser engraved nameplates will be available too.

The circuit

All components built in the ASV KTA-50 have been carefully selected: metal oxide resistors, ceramic tube sockets, toroidal power transformer, high quality electrolytics. In the basic design the simplified principles of Williamson topology have been followed. As active components in the input and the driver phase-splitter stage dual triodes ECC 83 (12AX7) are used. In the power stage the EL 34 (6CA7) pentodes are employed in the cathode bias circuit. They work in the push-pull AB1 ultralinear configuration with a quality EI-core output transformer. However, for sophisticated constructors it wouldn't be difficult to add a switch for selection between ultralinear and triode configuration of output valves.

The output transformer

A high quality output transformer is the heart of a tube amplifier. A poor output transformer fitted in a well-designed amplifier will spoil its performance.
Needless to say that the design and optimization of an output transformer takes high skill and know-how because performance requirements are complex and high. The transformer must deliver adequate and constant power without core saturation. It should provide wide frequency bandwidth at minimum distortion. Moreover, it should provide constant outstanding performance to retain the open, spacious qualities of recorded music. The sound quality of ASV output transformers is very good: low distortion and an extremely wide frequency and dynamic ranges.
The present AOT-25 transformers have been carefully wound on high quality EI laminations core, impregnated and tested.

Performances

The final results are very good and also confirmed by measurements. This provides a clean, airy performance and is capable of delivering truly classic and warm tube sound. It re-creates a glory of tube sound, it focuses well, has very good depth and transparency with fine image width. The ASV KTA-50 tube amplifier has been designed for assembling in the classical manner of manual soldering of all components and joints. All elements and connections are entirely hard-wired on the circuit assembly. No printed circuits are used in this amplifier. We believe that only such a design can together with a great degree of skill, know-how and enthusiasm provide the result: warm natural sound without disturbing, sharp transients.
The time invested in the assembling of this tube amplifier will be rewarded by an outstanding quality of reproduction that can be enjoyed for hours and hours.
Finally, in addition to comprehensive and detailed "Assembling Manual" you will receive an address of a special web page with a set of pictures. These photos show the most important steps of the assembling process.