DP

The Cossor D.P., indexed as DP in the archive, is a mains-apparatus output triode with indirect heating at 16 V and 0.25 A. The technical page highlights transconductance of 6 mA/V, described by the manufacturer as particularly high for a triode and associated with good sensitivity. This characterizes the device; it does not by itself specify available audio output power.

The sheet gives internal resistance 2,800 Ω, amplification factor 17 and transconductance 6 mA/V at plate 100 V and grid 0 V. For normal power use it instead specifies plate 200 V, grid bias −7.5 V and plate current 25 mA, with optimum load 3,500 Ω and bias resistance 300 Ω. These two sets of conditions remain distinct. Maximum plate voltage is 200 V; the page does not give output watts or a distortion figure associated with the load.

An additional application cited by Cossor is power grid or anode-bend detection. It is proposed when preceding stages develop a grid-to-cathode detector signal too large for a higher-impedance tube, risking overload distortion. Thus the DP is presented for this role as well as ordinary audio output. The graph provides plate-current families against grid voltage for plate voltages 50, 100, 150 and 200 V.

Archive information identifies a five-contact European B5 base. The primary page contains neither terminal drawing nor mechanical dimensions, so no numeric pinout or dimensions from other types are added. Documentation: Cossor, Cossor D.P. technical page, catalogue page 97, with data and curves. The available page has no publication date and is not used to establish a definite introduction year.