6AW8

The 6AW8 combines a high-mu triode and a sharp-cutoff pentode in one envelope. RCA’s 1955 sheets describe a nine-pin miniature intended for equipment with series-connected heaters. Separate cathodes provide two distinct amplifying systems within one valve. The heater requires 6.3 V at 0.6 A, AC or DC; stated average warm-up time is 11 seconds. The sheet dates document these specifications, without by themselves establishing the type’s introduction year.

For the triode, RCA gives a typical class A1 point of anode 200 V, grid −2 V and anode current 4 mA: amplification factor 70, approximate anode resistance 17.5 kΩ and transconductance 4000 µmho, or 4 mA/V. The design-center anode limit is instead 300 V and maximum dissipation 1 W. Approximately −5 V refers to anode current 10 µA, a near-cutoff condition rather than a signal-amplifying operating point. Maximum grid-circuit resistance is 0.5 MΩ with fixed bias and 1 MΩ with cathode bias.

The pentode has higher transconductance: the typical point with anode 200 V, screen 150 V and cathode resistor 180 Ω gives anode current 13 mA, screen current 3.5 mA, approximate anode resistance 0.4 MΩ and transconductance 9000 µmho, or 9 mA/V. Distinct limits are anode 300 V, screen supply 300 V and anode dissipation 3 W. Allowed screen input is 1 W up to 150 V; between 150 and 300 V RCA refers to a general chart absent from these seven pages, so that watt must not be extended across the entire range. Control-grid limits are 50 V negative and 0 V positive; maximum grid resistance is 0.25 MΩ for fixed bias and 1 MΩ for cathode bias.

Capacitance and shielding are particularly well documented. RCA compares measurements without an external shield and with a JE.TEC 315 shield connected to the cathode of the section under test. For example, maximum triode-grid to pentode-anode capacitance falls from 0.03 to 0.008 pF; anode-to-anode capacitance from 0.2 to 0.05 pF. Not every capacitance falls: triode-anode to cathode-plus-heater capacitance rises from 0.32 to 1.7 pF. Measurement conditions must therefore be retained when comparing data. Four curve pages describe the systems separately, with pentode screen at 150 V. For both sections, heater-cathode peak voltage is limited to 200 V in either polarity; with heater positive the DC component must not exceed 100 V.

The nine-pin Noval base is JE.TEC E9-1, bottom-view 9DX: 1 triode cathode, 2 triode grid, 3 triode anode, 4 and 5 heater, 6 pentode cathode with suppressor grid and internal shield, 7 pentode control grid, 8 screen grid, 9 pentode anode. Any mounting position is permitted. RCA maxima are overall length 2 5/8 inches, 66.675 mm; seated height 2 3/8 inches, 60.325 mm; diameter 7/8 inch, 22.225 mm. Base seat to bulb top excluding tip is 2 inches ±3/32, or 50.8 ±2.38125 mm: a toleranced dimension distinct from overall length. Documentation: RCA 6AW8, seven pages, tentative data March and July 1955 and curves June 1955; the two archived copies were compared without counting them as independent sources.