From our review: "Overall a nice balance of tone in bass, midrange and treble. The breakup is earlier than a 6L6 with more compression but not as compressed as the EL34. If you have a Marshall amp and find EL34’s too compressed and 6550’s too crunchy the JJ KT77 may be just the ticket."
The now rare KT77 tube was introduced by MO-Valve in the late 1950's and has recently been brought back by JJ. They use the same base and biasing as any EL34 tube so they are a great option for substitution in any EL34 amp.
If you are curious about how these fare in a hifi stereo amplifier be sure to read the Wall of Sound EL34 tube comparison for details.
Other JJ Electronics tubesEL34 Tube Types
Additional Information and Downloads
EL34 Tube Review for Guitar Amplifiers
EL34 Tube Review for HiFi Audio
Tube Matching Information:
Power Tube Matching FAQ
Perfect Pair System
JJ KT77 Datasheet (PDF)
Download Adobe Acrobat PDF reader
Warranty Information and Return PolicyWarranty Period: 3 months
All our tubes are guaranteed for 3 months from the date of purchase. (Any exceptions will be noted on that tube's Warranty tab)
If you receive a tube that does not perform to the manufacturer's specifications, please do the following:
- contact us to get a return authorization
- return it via regular mail within 90 days from when we shipped it, and we will provide an exchange or refund of the full purchase price of the tube.
Returns not related to warranty or defect will be considered at our discretion, and are subject to a 15% restocking fee.
We can not accept returns that don't have an authorization, are past 3 month, or are returned improperly.
These guidelines may be updated without notice.
Ratings & Reviews
Very Good Sounding EL34 Variant
by TubeHead Johnny
If you like the sound of the JJ EL34, the KT77 has more headroom and bass than a standard EL34. A little closer to a 6L6. I use these in my medium powered home-brew hi fi amplifier with 30 watt Hammond output transformers. My favorite JJ tube!
Great tube for modern hard rock and metal.
I love the aggressive mids EL34's possess, but in some amps EL34 tubes don't have enough low end for my taste. These KT77's have a similar type and amount of low end compared to a 6L6, an extended high end that is pleasant to listen to, and the mid presence of an EL34. It's the perfect blend for me. Pretty much the best of both worlds. The cleans are very nice as well. Plenty of thump and sparkle. They can sound boxy at first. Give them about 20 hours to break in and they will really start to bloom.
by Rob O'Donnell
Just got my quad of JJ KT77 tubes delivered, just over a week to NZ which is awesome, thanks!��I am using the JJ KT77's in a Line Magnetic LM-21IA EL34 integrated and right out of the box they are detailed, energetic with an awesome punch and sizzle.��I swapped out a set of New Sensor Mullard EL34 tubes which I still like for their smooth, lush presentation, but for now I'll keep the JJ's in rotation.��For the sound of these JJ's the price is insanely cheap. Recommended for HiFi in my books.
Great tube for Hi-Fi use
I've tried just about every current production EL34 and its variants over the past few years in my custom Bill Baker built Jolida 302B. This amp sounds just awesome with the right tubes pushing my KEF iQ90 towers. My favorite up until now was the "Winged C" EL34(I can't afford NOS power tubes!!!), but I've had two tubes out of my past two quads red plate on me. This has only happened with the "Winged Cs". I thought I'd give the JJ KT77 a try. WOW!! Glad I did!! In my rig, the KT77s are the best sounding power tubes I have tried. Soundstage grew in width and depth and these tubes are very articulate. They are very detailed without sounding the least bit harsh or hard, and they still retain that "in the flesh" 3D texture and realism of the EL34. Bass is tight and strong and highs are clean and airy. Cymbals have that nice sheen on fine recordings. VERY nice. I'll be sticking with these - they are my new favorite! Give them about 15-20 hours for them to sound their best. Highly recommended.
What a tube this is!
by Bob J.
I am typing this while listening to my Jolida JD502CRC integrated that uses (normally) an EL34 tube. I recently purchased four JJ KT77 tubes and just installed them in my amp tonight. With a mere four hours on them, these are unlike any other tube I have heard. The have a glorious midrange like an EL34 but slam and tight bass like a 6550 tube, and a light and airy top end like my Gold Lion KT88 tubes. Others have stated this tube is like a hybrid of a 6L6 and an EL34. I feel that yes, a hybrid is a good descriptor, but more like a great 6550 blended with the EL34. I am most impressed, and if you have been thinking about trying the JJ KT77, as the ad used to say, "Just do it". The soundstage increase, detail, punch, midrange magic and top end clarity will leave you smiling and tapping your toes, just like I am right now.