EE1

The EE1 is a secondary-emission amplifier valve. Philips describes initial development for television wide-band amplifiers, followed by use in radio receivers and power amplifiers as a push-pull output-stage driver. It supplies two opposite-phase voltages without an interstage transformer while retaining gain useful for negative feedback. Indirect heating requires 6.3 V at 0.6 A, in parallel on AC or DC. A generic diode-tetrode description does not adequately represent this structure.

Besides the heated primary cathode, the EE1 contains a surface that releases secondary electrons when struck by primary electrons. The manual illustrates a secondary-emission coefficient of about five, so several electrons are collected by the plate for each electron reaching that surface. A construction detail is beam deflection around a shield: electrons follow curved paths while evaporated cathode material must not deposit on the secondary-emission surface. The design separates the useful electron path from a possible cause of emission deterioration.

The 1939 EE1 wide-band point uses plate 250 V, screen and secondary cathode 150 V, control grid −2.5 V: plate current 8 mA, screen current 0.7 mA, secondary-cathode current −6 mA, transconductance 14 mA/V and internal resistance 75 kΩ. Negative secondary current indicates conventional direction relative to the electrode, not a meaningless current. These are characteristics of that point and version; EEP1 figures in comparative documentation must not replace EE1 data.

Push-pull driving exploits opposite current changes at plate and secondary cathode. Suitable resistive loads yield signals 180° apart, capacitively coupled to output grids. Resistors must balance amplitudes, rather than simply being equal. The manual’s EE1 circuit at supply 275 V gives gain 70 to each output grid, total distortion 2.2% at 3 V RMS or 3.6% at 5 V RMS; at 300 V, gain 75 with 3% and 5% respectively. These belong to the specified circuit, not the tube independently of its load.

High transconductance requires careful biasing. Philips permits only automatic bias: the primary-cathode resistor must exceed the value needed merely to produce grid bias, while a divider raises the grid above ground but keeps it negative relative to cathode. This compensation limits operating-point changes. The manual warns of oscillation tendency and gives a 10 kΩ resistor before the grid as an example. For the driver circuit it recommends supply no lower than 275 V; that does not change actual plate-cathode voltage limits.

The 1940 EE1 sheets list maximum plate voltage 250 V and dissipation 2 W, screen 150 V and 0.1 W, secondary cathode 150 V and 2.5 W; zero-current voltage is 550 V for these electrodes. Primary-cathode current maximum is 20 mA in the 1940 sheets, but 10 mA in the German manual: the prescriptions remain distinct. Maximum grid-cathode resistance is 0.7 MΩ, external heater-cathode resistance 20 kΩ and voltage 50 V DC or RMS AC. EEP1’s higher plate-voltage limits are not transferred to EE1.

The base has eight side contacts, with control grid at the top cap; drawings distinguish primary and secondary cathodes, plate, screen, heater and metallization. Dimensions also vary by edition: the German EE1 manual gives maximum diameter 50 mm and height 115 mm; April and July 1940 EE1 sheets instead give 48 and 124 mm. These are separate observations, not an averaged envelope. Documentation: Philips, “EE1 Sekundäremissionsröhre”, pages 51–60; Philips Miniwatt EE1 sheets July 13, 1939, April 17 and July 17, 1940, with 1938–1939 curves; for comparison, Philips “EEP1 (EE1) Secondary-emission valve”, pages 51–60, and 1948–1949 EEP1 sheets. Comparative sources do not establish universal identity between versions.