What are Matched Valves and do I need them?
Each type of valve works within a set of electrical parameters. These include anode voltage, screen voltage (if applicable) and grid bias. When a signal is applied to the grid it is amplified by a designed amount. These values are termed the valve’s “characteristics” and are different for each type of valve. There is a tolerance in manufacture, which means that although they meet their type specification, they will vary somewhat between samples. Valves are normally checked on a valve tester, such as the AVO or Hickock range, against a set of “characteristics”. The fixed settings for the heater, anode voltage, screen voltage, and grid bias are set on the machine. A signal measured in mA current is applied and the resultant amplification read as mA/V. Thus 2 variables are recorded for each valve, current, in mA, and “slope” in mA/V. Although the valve is being measured at only 1 point on it\’s response curve this usually gives a good indication of it`s performance for the purpose of esta
