6L6 Taste Testing

Written by
Dave Hunter
Published on
January 21, 2021 2:27:11 PM PST January 21, 2021 2:27:11 PM PSTst, January 21, 2021 2:27:11 PM PST
The output tubes (aka power tubes) are the final muscle in any guitar amp, responsible for ramping up your pre-amplified signal into a high-wattage rendition of your precious tone that can be pumped out to the speaker via the output transformer. As such, these tubes play a big part in shaping the character and sound of any amp, and are the last tubes in the long and complex signal chain between pickups and sound waves transmitted through air.
Think “classic big American tone," and nine times out of ten you’re thinking of the sound made by 6L6 output tubes. These big American-toned bottles (and their equivalents) are the tubes of note in classics like Fender’s tweed Pro, Super, Bassman, and Twin of the ’50s -- and Super Reverb and Twin Reverb of the ’60s. They’re also used in plenty of other designs, including many high-gain legends from Mesa/Boogie, Soldano and Dumble, and several points in between.
The 6L6 is particularly known for its clear, well-balanced tone, which includes tight lows, a midrange response that’s not over-hyped, and firm, articulate highs. It might be thought of first and foremost as an archetypal “clean” output tube—given some of the vintage amps it has been used in—but it also exhibits a muscular, dynamic overdrive when pushed hard, and can beautifully translate preamp-tube-generated overdrive into punchy, aggressive output when needed.
Let’s investigate the characteristics and capabilities of three newly manufactured makes of this beloved output tube, all of which are currently available from Mojotone: the Electro-Harmonix 6L6GC, Tung-Sol 6L6GC STR, and JJ 6L6GC.
In addition to my own “live” impressions gleaned from playing each set of matched 6L6s in the same amp over a prolonged period, I’ve recorded several sample clips for the purposes of easy and comparable A/B/C comparisons. Please note, too, that the notes below were taken without any previous reference to the manufacturers’ or sellers’ promotional info, but are provided as an objective impression of these tubes’ individual strengths.
Guitar, Amp & Settings
Three samples of each tube were recorded using a ’57 Fender into a custom tweed Fender Pro-style amp through a 2x12 cabinet with Jensen C12Q speakers.
  • Each of the three clips begins using Telecaster’s bridge pickup with guitar volume and tone controls up full, and the amp set to clean-on-the-edge-of-breakup (these tweed amps are rarely entirely clean).

  • The second segment in each clip maintains the same amp settings, but switches to the Telecaster’s neck pickup, with both guitar knobs still up full.

  • The third segment returns to the Telecaster’s bridge pickup, with the amp’s volume control cranked up into the breakup zone, at about 7 on the tweed scale of 12.

Electro-Harmonix 6L6GCA reissue of the legendary British-made Mullard EL34 manufactured at New Sensor’s Xpo-Pul factory (aka Reflektor) in Saratov, Russia.

General Notes: This is a relatively tall-bottled 6L6 type which, nevertheless, combats microphonic rattle with a ruggedized grid structure, and increased power handling along with it. The manufacturer tells us it’s based on the legendary RCA “black plate” 6L6GCs, although it also displays constructional elements seen on classic Soviet 6L6 types, such as the graduated two-tier base and some internal elements as well. In any case, this is a great-sounding tube all around, particularly adept at “that American tone,” but just a confident, well-voiced 6L6 in general, with good balance and an appealing depth and richness.
Overdriven: When pushed into overdrive by the Telecaster’s bridge pickup, the E-H presents a classy snarl loaded with character and edge without getting nasty or harsh. As you hit it harder with aggressive lead lines further up the neck, the tube hints and sliding into some trashy grunge, but without ever losing its cool, retaining surprisingly good articulation and note separation amid that characteristically gnarly tweed breakup.
Clean-ish: The E-H 6L6GC elicits a meaty twang from the Tele’s bridge pickup, which is never harsh or spiky, and includes a juicy, succulent richness amid the punch and bite of the low and midrange notes. Highs remain silky and smooth, yet clear and, again, never ice-picky. From the Tele’s neck pickup, this tube delivers round, plummy lows with good firmness, and a very musical upper-midrange and treble response that gives character to the individual notes.
Good For: An impressive current-make 6L6GC all around, delivering sonic characteristics that can be both elegant and aggressive, as needed.

JJ 6L6GCAn Eastern-European tube Manufactured by JJ Electronic in Cadca, Slovakia.

General Notes: This Slovakian-made 6L6 has an extended glass envelope with a particularly tall double-halo getter structure at the top, and could at first glance be mistaken for an EL34. It’s a big, bold, clear sounding tube in use, with an impressive balance between lows, mids and highs -- excellent clarity all around. It segues into breakup at semi-clean amp settings a little less easily than the other makes tested here, and offers a lot of usable headroom as a result. Another confident 6L6 for that classic “American sound,” and a powerful 30-watt (per tube) variant as well.  
Overdriven: When overdriven in the tweed test amp, this tube is thick, muscular and authoritative, with a particularly fat and swaggering personality on the lower string twang runs, delivering a bold, characterful, and extremely appealing rock ‘n’ roll tone. Hitting jangly chords and single-note runs and bends higher up the neck elicits a little more bite and sting in the highs, with shimmering harmonics that only ever hint at harshness without ever quite tipping over into it.
Clean: The JJ is crisp, clear, and articulate when hit with the Tele’s bridge pickup, and although there’s a little clipping around the edges it doesn’t fold into breakup quite as easily as many other 6L6s (that inevitable “tweed hair” notwithstanding). And while it retains its composure well, it does exhibit appealing harmonic sparkle and depth in the process. From the Tele’s neck pickup, this 6L6GC presents a warm, round, woody-sounding jazz and ballad tone, with tight lows, and highs that have a nice little forward edge of cutting power in the attack, without being at all strident.
Good For: A very big-sounding 6L6, this is a good choice when you’re seeking significant headroom from a tube that also segues well into breakup without getting strident too quickly. Firm, clear, and balanced, it harks back to the more high-powered big-bottle American 6L6s of old.

Tung-Sol 6L6GC STRA Russian tube, manufactured at New Sensor’s Xpo-Pul factory (aka Reflektor) in Saratov, Russia.

General Notes: The “STR” in the name stands for “Special Tube Request," designating it was made to specifications requested by amp manufacturers back in the day (or, in this case, made to emulate such tubes). This Tung-Sol has a shorter bottle much like the American-made 6L6WGC types that remained more plentiful for several years after other NOS 6L6s were drying up fast; but those were lower-output tubes, whereas this is a relatively powerful 30-watt (per tube) 6L6 variant. Even so, it exhibits some of the softer, earlier breakup of those traditional smaller 6L6s, along with the slightly easier compression, while still delivering impressive output overall.
Overdriven: The slightly easier breakup and gently compressed attack help this 6L6GC STR segue nicely into overdrive, and it rewards when you dig in for more classic and straight-on rock ‘n’ roll or more retro-voiced blues tones in particular. There’s tasty harmonic shimmer amid the distortion when higher notes are pushed hard, and excellent high-end bite without ever issuing brash or strident overtones. Particularly impressive is that, while this tube has marginally less headroom, it’s segue into clipping is smooth and dynamic, rather than harsh or jarring.
Clean: This Tung-Sol 6L6GC has plenty of clarity and sparkle, yet a certain softness amid punchy clean tones that lends a somewhat more “vintage tube” character, as might be found in some of the lower-output, short-bottle 6L6s of the ’50s and ’60s. Hit by the Tele’s bridge pickup, the lows are tight without being particularly bountiful, and the midrange is balanced and musical, with some compression aiding an enjoyable playing feel. Highs jangle and crunch a little more, with sparkling overtones. Via the Tele’s neck pickup, this tube is articulate and well-defined, with a sweetness and richness that isn’t overly deep, yet is very appealing.
Good For: An excellent tube when you want to elicit classic output-stage-generated overdrive from an amp, and a non-master-volume amp in particular. It has a sweet and well-balanced voice over all, and a slightly compressed front edge that enhances touch sensitivity. Not ideal if you’re seeking the biggest, boldest possibly clean-de-la-clean tones, although it’s cleans are also very musical and appealing.