The Ultimate Metrix Combination Guide
20,873 tubes resolved live to their 9 main + 5 supplementary selectors. Type any reference, watch the panel reconfigure to the exact Metrix bench position with the expected plate current on the galvanometer.
How to read this
How a Metrix combination works
A Metrix tube tester has 9 main rotary selectors numbered 1 to 9 plus, on most models, 5 supplementary selectors numbered 10 to 14. Each selector position routes a specific tube pin to a specific bench rail (cathode, filament, ground, plate, screen, etc.). To test a tube you set every selector to the position the manufacturer specifies, apply the test voltages, and read the plate current on the galvanometer.
The corpus on this page resolves any reference to its full position vector in real time. The galvanometer shows the expected reading at the bench operating point — if your real Metrix lands close, the tube is healthy; if it reads way low, the cathode emission has dropped.
Models supported
Different Metrix models expose different physical selectors. The model toggle at the top of the page hides supplementary selectors when they don't exist on your unit:
- U61 — 9 main selectors only. The most common audio-shop unit. Selectors 10-14 are not exposed.
- 310 — Older predecessor of the LX109, same selector layout. Pre-1965 production.
Suffix conventions (k, f, m, •)
Some entries carry a suffix on a selector position to disambiguate which rail the pin is bonded to:
k— cathode rail (the bench common-K)f— filament rail (one of the two heater pins)m— ground / chassis (the bench mass)•— special-purpose pin (varies by model — consult the original tester manual)
Direct vs Indirect heating
The mode flag (D / I) tells the operator whether the test point uses the directly-heated convention (filament IS the cathode — 300B, 2A3, type-45) or the indirectly-heated convention (separate heater + cathode sleeve — 12AX7, EL34, KT88). Some Metrix units have a separate switch for this; on others it determines which selector position to use on rail F or K.
Sources & credits
JJD — compiled the original 733-page PDF recueil that catalogues the bulk of the corpus (20,814 entries marked PDF). The data was extracted via OCR — most of it is correct, some entries contain transcription errors. Always cross-check with the original tube datasheet before testing.
René Conseil — authored the verified U61 update in 2022 — 59 entries marked "U61 ✓" carry his hand-checked positions. His online resource at 6bm8-lab.fr ↗
Data provided as-is, no warranty. Always verify against the tube datasheet and your specific Metrix manual before applying voltages. Vacuum tube testing involves lethal voltages — discharge filter capacitors before working inside any tester.