JJ Electronic 6L6GC-DM Matched Quad

One Matched Quad of JJ Electronic 6L6GC-DM's. The "DM" stands for Double Mica. Back in 2005 our good friends at JJ worked with us to develop a 6L6GC that was more resistant to the vibrations when used in a Combo amp or torture chamber as we call them! The problem is that the expansion coefficient for metal is very high compared to the expansion coefficient of glass and the anode or plate structure must be able to move or expand inside the glass as the tube achieves operating temperature. Holding it too tight will kink the anode and other parts.

Several things were tried and in the end using double mica spacers in the top of the tube proved to greatly reduce rattle and still allow the expansion necessary for reliability. Since 2005 these tubes have been available exclusively from Eurotubes for Combo amps.

At Eurotubes there is no such thing as platinum matching or an upcharge for "closer matching" . All power tubes are matched within one milliamp period.

After a 24 hour burn-in all power tubes are tested for noise and matched at multiple operating points for plate current ( ± one milliamp) and transconductance. This is done on our custom made Kamna Matcher. The voltage is regulated to within a tenth of a volt and the high DC voltage is applied to all tubes simultaneously. The Kamna Matcher features individual readouts for each socket and each socket is fully active during the duration of the matching process which includes testing for current, transconductance and individual audio tests.

The video below shows both our preamp tube testing and power tube matching procedures here at Eurotubes which are second to none. We may not be the cheapest, but we are arguably the best.

Doing what other tube resellers say "can't be done" since 1998