DIY Vacuum Tube Amplifiers

DIY Vacuum Tube Amplifiers

Designing An Amplifier

For Tube Rolling
EJ Jurich

The best amplifier performance and lowest distortion come from an amplifier that has been designed for a specific type of output tube. Because of this, tube rolling is generally not suitable for audiophile high fidelity amplifiers. The distortion harmonics produced by different output tubes tend to suit a guitar amplifier where tubes can be swapped for a particular sound.

There is some risk involved with swapping tube types, particularly power output tubes. Most vacuum tube amplifiers are designed and built for use with specific tubes. Randomly swapping out tube types comes with the danger of overloading the amplifiers' power supply, causing the power transformer or other components to run too hot. It is also possible that different tube types may have lower maximum ratings than the amplifier design tubes and could be subject to failure causing component damage. Reading through the sections below, you will see that an amplifier designed for tube swapping must take many things into consideration.

Design Considerations

Tube Characteristics

Plate/Screen Dissipation

Power Transformer Loading

Design Description

Filament Load

Maximum Plate and Screen Voltages

High Voltage Supply

Output Transformer Impedance

The Amplifier Circuit

High Gain Pre-amplifier

Volume Control

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