RO4404 Triode Vacuum Tube
High-power directly-heated triode for single-ended amplification
Visseaux / Televisso
Visseaux maker equivalence table · 1 pp · FR
PRIMARY source documenting RO 4404 = P 460. Single row from the Visseaux equivalence table printed by the maker; promotes RO4404 from third-party-table inference to the strict D404 / RE604 / P460 / 4K60 / LK460 core.
TeKaDe (RVF Roehrentaschenbuch M1, 1947)
RVF Roehrentaschenbuch, Band M1, 1947 · 1 pp · DE
CALCULATOR DEFAULT. Single cleanest operating point in the whole family: 250 V / −45 V / 40 mA, S = 2.5 mA/V, D = 29 % → μ = 3.45, Ri = 1.4 kΩ. Maker-printed equivalences on the card: D404 / RE604 / P460 / LK460.
Philips / Miniwatt (A40 base)
Philips / Miniwatt D404 sheet 13/6/33 · 1 pp · FR · EN
Two-anchor bias table: 250 V / −40 V = 40 mA and 200 V / −30 V = 30 mA. μ = 3.5, S_max = 3.5 mA/V, S_norm = 2.7 mA/V, Ri_norm = 1.3 kΩ. Capacitances Cag 7 pF / Cak 5.7 pF / Cgk 5.2 pF. Soft grid-current onset near Vg = −2 V. Pa max 10 W, VaL max 250 V, Va0 max 500 V, Ik max 60–65 mA, Wo = 1.7 W @ Vg_eff 27 V into 3.5 kΩ.
Telefunken
Telefunken RE604 maker sheet · 1 pp · DE
Maker bias table 100 V / −6 V, 150 V / −15 V, 200 V / −25 V. μ = 3.5, S ~ 3.5 mA/V, D ~ 27 %. Va max 200 V, Pa max 12 W. Note: Telefunken allows 12 W; AmperaTubes applies the 10 W conservative ceiling family-wide.
Tungsram (Hongrie)
Tungsram Memento, 1937 (160 p.) · 160 pp · FR · HU
Highest-value next acquisition. Now that the Visseaux table fixes RO4404 = P460, the Tungsram P460 entry in this Memento is the missing fourth independent maker anchor — would enable a RO4404_TUNGSRAM_P460_1937 SPICE variant. OCR of the P460 operating point still pending.
MU=3.5 EX=1.95 KG1=20717.27 KP=369.37 KVB=15 VCT=0MU=3.5 EX=1.95 KG1=22847.01 KP=212.61 KVB=15 VCT=0MU=3.45 EX=1.6893 KG1=6758.86 KP=400 KVB=15 VCT=0Ia vs Vg at Va = 250 V — each manufacturer Koren fit overlaid. The de-rated French families (μ=30) read lower than the Philips/1966 high-gm family (μ=32) at the same grid voltage.
The RO4404 is the Visseaux / Televisso branding of the strict pre-war European 4 V directly heated low-power output triode (c. 1930), a confirmed sibling of the Philips-Miniwatt D404 / Telefunken RE604 / Tungsram P460 / TeKaDe 4K60 / Valvo LK460 family on the European 4-pin B4 base. RO4404 = P460 is documented by the Visseaux maker equivalence table itself — promoting RO4404 from third-party-table inference into the strict equivalence core. Three primary-source manufacturer datasheets agree on the same physical tube under different measurement conventions: TeKaDe 4K60 (RVF Roehrentaschenbuch M1, 1947) carries the single cleanest operating point in the whole family at Va = 250 V, Vg = −45 V, Ia = 40 mA, S = 2.5 mA/V, Ri = 1.4 kΩ, D = 29 % → μ = 3.45 (Ampera load-line calculator default); Philips / Miniwatt D404 (13/6/33) gives μ = 3.5, gm_norm = 2.7 mA/V, Ri_norm = 1.3 kΩ with a two-anchor table 250 V/−40 V = 40 mA and 200 V/−30 V = 30 mA; Telefunken RE604 publishes μ = 3.5, S ~ 3.5 mA/V at the same physical envelope. Single-ended Class A output at 250 V / 40 mA delivers about 1.7 W into 3.5 kΩ. SPICE status: model not bench-verified — fits are anchored on the well-documented D404 / RE604 / 4K60 maker data, and the pre-war wide-spaced geometry pushes the Koren EX exponent high (Philips / TFK variants at EX ≈ 1.95), so the model is accurate at and around the published operating points but should not be trusted for fine prediction far outside them or for Class A2 grid-current behaviour. The Visseaux 602 is treated as a probable mechanical / construction sibling (operator note: same construction and same plate as the RO4404), exposed in the SPICE deck as the provisional RO4404_602 alias pending a confirmed 602 datasheet. The E406 is NOT an equivalent (4 V / 1 A heater, μ ~ 6) and must never be swapped in via PX4-style adapters. Plate-dissipation ceiling held to the conservative 10 W family figure even though the Telefunken RE604 sheet permits 12 W.