Vacuum Tube Gain Controlled Amplifier

A project book for the advanced builder, includes circuit diagrams and circuit descriptions to build a gain controlled amplifier also referred to as a compressor. This type of amplifier is used to prevent over-driving audio systems by maintaining an average output and keep levels in a more comfortable listening range. This particular design uses all triode vacuum tubes including a triode gain control stage, all stages are built around the popular 12AX7 tube. Triodes are used because they produce primarily second harmonic content when harmonic distortion occurs, the addition of low-level second harmonics enhances the sound. The design uses a variable compression ratio, the ratio becomes tighter as the input level increases past the compression threshold. This allows soft passages to retain high dynamics while imposing more control on loud passages. The amplifier uses broadband compression to maintain the original sound balance. A slow gain control is used as an average level reference on which a faster gain control rides, ratio between the two is adjustable. Gain control is non-intrusive and dynamics are maintained, this is not a brick wall processor. Useful gain control is a 30DB range.

This book is written for electronic hobbyist interested in working with vacuum tube circuits. A wide range of reference material related to vacuum tubes and audio are concise with examples and illustrations.Principles of vacuum tube operation includes function of grids, effect of tube capacitance, tube resistance, heat dissipation and voltage gain. A table of component values for the popular 12AX7 in various operating parameters simplifies amplifier stage design. Power supply sections cover vacuum tube and solid state rectifier conversion of AC to DC and DC filtering. A sample power supply is used to explain calculating loads, determining required transformer ratings and component values. Includes high voltage, bias and filament supplies.For the novice not versed in electronics several sections cover electronic basics. Includes how capacitors work, voltage, current, ohms law and reading circuit drawings.Working with electronics and vacuum tube circuits requires some math. Circuit calculations in this book use various forms of addition, subtraction, multiplication and division. Formulas are all solvable using a standard 12 digit calculator. Calculations are presented with examples.The last part of the book has amplifier project circuits with parts list and component layout drawings. Projects include a line amplifier with 25db gain, triode balanced-unbalanced input stage, tone control stage, turntable pre-amplifier, 6V6SE Class A stereo amplifier, 6V6SE Class A monoblock amplifier, 30 watt monoblock amplifier and a 5 watt guitar amplifier with adjustable overdrive. The 30 watt monoblock amplifier is designed for tube rolling using various type output tubes.Current version of book was updated in April of 2017.

The Text Is Based On The Ccir 625-B Monochrome (Black & White) And Pal-B And G Colour Television Standards As Adopted By India And Many Other Countries. The American And French Tv Systems Have Also Been Given Due Coverage While Presenting Various Aspects Of The Subject Starting From Television Camera To The Receiver Picture Tube. Keeping In View The Fact That Colour And Monochrome Telecasts Will Co-Exist In India For At Least A Decade, The Author Has Included Relevant Details And Modern Techniques Of Both The Systems.Conceptually The Book May Be Considered To Have Four Sections. The Initial Chapters (1 To 10) Are Devoted To The Essentials Of Transmission, Reception And Applications Of Television Without Involving Detailed Circuitry. The Next 14 Chapters (11 To 24) Explain Basic Design Considerations And Modern Circuitry Of Various Sections Of The Receiver. Topics Like Tv Games, Cable Television, Cctv, Remote Control, Automatic Frequency Tuning, Automatic Brightness Control, Electronic Touch Tuning Etc. Are Also Discussed.The Third Section (Chapters 25 And 26) Is Exclusively Devoted To The Colour Television Transmission And Reception. All The Three Colour Television Systems Have Been Described. Chapters 27 To 30 Are Devoted To Complete Receiver Circuits-Both Monochrome And Colour, Electronic Instruments Necessary For Receiver Manufacture And Servicing, Alignment Procedure, Fault Finding And Servicing Of Black White And Colour Receivers.The Complete Text Is Presented In A Way That Students Having Basic Knowledge Of Electronics Will Find No Difficulty In Grasping The Complexities Of Television Transmission And Reception.