EL34, 6CA7, KT77 Difference?

Related: see EL34, 6CA7, KT77 tubes we stock


EL34, 6CA7 and KT77

EL34 - European Invention

Mullard in England developed EL34 in the 1950's. EL34 handled lots of power in a small envelope. EL34 became very popular in audio amplification. The market expanded. And many European tube manufacturers soon started manufacturing EL34.

6CA7 - America's Answer

Not to be outdone, Sylvania introduced fat-bottled 6CA7 in US soon after. 6CA7 was not a copy of EL34, it was a design of its own. 6CA7 is drop-in compatible with EL34, but it sounds closer to 6L6 because of this.

GEC KT77 - Ultimate EL34

GEC in West London, England introduced KT77 as the ultimate medium power audio tube. KT77 employed an internal construction resembling 6CA7. GEC optimized KT77 for use in audio application. This makes KT77 the ultimate EL34 for audiophile.

Then they were the same

As years passed, tube manufacturers consolidated worldwide. EL34 and 6CA7 came to be treated the same because they were interchangeable. This is why you see some NOS tubes marked as EL34/6CA7.

KT77 all but disappeared when GEC stopped production in the 80's.

Back to the Roots

Today, tube manufacturers returned to the roots of these great tubes.

Current production EL34 tubes are true to the original Mullard pentode design. Likewise, current production 6CA7 are beam forming tetrode like the original Sylvania design. Tube manufacturers also re-issued KT77 in recent years. The internal construction of current production KT77 resembles that of classic KT77.

This makes current production EL34, 6CA7 and KT77 all sound noticeably different. This allows us to try and pick the one that suits our tastes.



How they stack up

Guitar amps

In guitar amps, EL34 is all about mids and upper-mids. You get more of that brown tone with your rhythm work. You also get smoothness with good note separation. And with EL34, you get that complex harmonics with sparkle that fills the room.

6CA7 and KT77 are more about bottom end. You can get much darker and with more drive, more high end harmonics. If the EL34 sound is a bit boxy, KT77 or 6CA7 will give you more open sound with heaviness on demand.

Audio application

In audio amps, the velvet smooth mids of EL34 is hard to miss. If you like listening to classical, opera or jazz, with horns and vocals, EL34 tube is the perfect fit.

6CA7 and KT77 have more sizzle and pop, in a pleasant manner that doesn't get in your way. KT77 is especially good at handling contemporary sound sources even at lower volumes.

As a side note, we have had the most number of positive feedbacks from our customers who bought KT77.

Freedom of choice

All this gives you a wide range of tonal landscape and a freedom to choose what fits you best. Feel free to check out EL34, 6CA7, KT77 tubes we stock, and see which one suits you best.