Got my KT77

organ

I've been very busy lately and have been missing in action for a while.

If you're planning to order some, go to www.thetubestore.com It seems like thetubestore is the only North American store that have them in stock. Eurotubes.com is still waiting for the next batch of 1000. They seem to be very limited in supply right now.

I got my quad today. Still breaking them in. I know they burn them in at the JJ plant for 24hrs but according to Eurotubes, they need about 50hrs.

Initial impressions.... THIS IS A KICK **** TUBE! I'm sure some of you remember my post about preferring KT66 over El34 in my Dynaco. Well, the KT77 has all the things that I love about KT66 and even more. The HF extension is much better and a lot more refined. The mids is to die for. Bass is about the same. Much more powerful than any EL34 tube.

So yeah, JJ was right, this is the ultimate EL34 replacement.

I'll do a longer write up once they're fully broken in. God I love tubes!:)

I've never heard the original GEC KT77 so I can't comment on how close they sound to the original.

Maurice

BlueMDPicker

Hi Maurice,

Interesting. With respect to specifications, how do the 6CA7, KT66 and KT77 differ? What bias voltage do you use for each?

Since acquiring a pair of Polk RTA 12C from doro, I've really gotten back into the ST-70. This combo has the most astounding synergy of anything I've wired together in nearly 40 years at the hobby. It sounds so great that I haven't even rolled any tubes (I'm using a quad of Dynaco/Mullard EL34) -- but, it would be fun to try the KT66 or KT77 sometime.

Tube gear can certainly keep your interest level up. A friend recently sent me a pair of Amperex 7308 for my EE MiniMax tube output CDP. I thought I was perfectly content with the vintage RCA badged Siemens 6DJ8 I'd been running for awhile. Wrong. The 7308's took it to another level with air, HF extension and bass musicality. What a pleasant surprise!

Mike

fredv

The Mullard EL34's (xf1, xf2) seem to be perceived as the best of the EL34's. The current ongoing prices simply prohibit me to try them. Mike, since you have the Mullard's, it can be difficult for you to find something better :-) Maurice, did you try Mullard's before on your st-70? If so, how do the KT77's compare (based on your memory, haha, the other fun thread)? Anyhow, I ordered a quad, it is even cheaper than the Mullard reissue!!!

organ

Mike,
Yeah, the ST-70 can be the most magical amp when you've got system synergy going. That's how I feel about it with my RF-35. I just haven't found anything else I like better with the speakers. I also find the same thing with Polk's RT series speakers. Glad you've found the perfect combo for your system. If you plan to keep using your ST-70 you should try to stock up on 7199. They're getting rare and very expensive.

The KT77 was designed to be a direct replacement for EL34, the KT66 wasn't. Actually, I got lucky on my KT66. I got a quad that worked within my ST-70's bias range. Later on when I ordered a quad of Saratov KT66, it biased way too high even on the minimum setting on the pots. KT66 need more negative bias voltage. So if you want to try the 66, you have to change the values of the two resistors on your bias circuit on the ST-70. That's an easy 5 minute job with the solder iron. The new resistors will still work with EL34. I'll look up the value of the resistors if you want to do it.

They all bias the same as EL34. I keep mine around 1.4V because the bias fluctuates depending on the line voltage.

I know exactly what you mean with the Ampex 7308. When I got mine, I was floored. Those tubes are amazing. I'll have to say the same thing about the Tele 12AX7 smooth plate. Those two tubes have the ability to make a huge step up in performance.

You won't be dissapointed with the KT77.

Fred,
All the current production EL34 (Sovtek, EH, new Mullard, JJ, SED) are copies of the old Mullard. Some people prefer SED or the JJ E34L over any vintage Mullard.

Sorry, I don't know the difference because I haven't been lucky enough to stumble upon a quad of vintage Mullard.

One thing to keep in mind, the KT77 is a completely different animal than EL34. The EL34 is a pentode (usually run as an Ultralinear in a lot of amps) and the KT77 is a "Kinkless Tetrode". The only other tube I've heard from the KT family is the KT66. So the sound is very different among the two families of tubes. To me, the EL34 sound more lush and romantic and sacrifices a bit of detail for the smoothness. The KT tubes are hardcore. Plenty of dynamics and slam, better speed and a lot more detail. They also give a bigger soundscape than EL34. They have this "presence" that I haven't heard on any EL34.

Let me know what you think of your 77's when you get them. If you like them as much as I do, I doubt you'll be going back to EL34. Remember to let them break in. Mine didn't sound very nice for the first 4-5hrs. Mine still need a lot of time to break in.


Update.....

Ok, I let them burn in all day and night and I can say they sound much better now. It's more open sounding and the bass is really kicking in. This is one serious tube. I didn't get enough sleep for work today because I was listening all night. The mids and highs they produce is Pure F*cking Magic! No joke.

I'll wait until they're fully broken in before I do a longer write up.

Maurice

organ

Ok, I think I should mention this. Under "Similar Threads" below, BMC mentioned that he got a quad of KT77 from the dealer to try out on his Rogue with a few pics attached.

I just took a good look and those are NOT JJ KT77. They're actually Shuguang EL34B in his amp. I can tell from the construction (I have a quad of those). One dead giveaway is the plate. The JJ KT77 have no rectangular holes on the plate, even the very first run. The plate is completely enclosed.

I did some reasearch on audioasylum and found out that some companies have KT77 stamped on their EL34 tube (in this case, Rogue purchased the Shuguang EL34B and stamped their logo and KT77 on the tube).

RuSsMaN

I wonder if these will physically fit in my Anthem? I know it will run them, I'm just worried about space (and heat maybe).

organ

Russ,
No problem there. They're the exact same size as the JJ E34L. They generate the same amount of heat as any EL34.

Here's a pic... http://www.thetubestore.com/teslakt77.html

:cool:.

Maurice

BlueMDPicker

organ wrote:

If you plan to keep using your ST-70 you should try to stock up on 7199. They're getting rare and very expensive.

I have several good pairs: 2 pair of Hammond, 1 pair Sylvania, 1 pair Realistic, and a NIB pair of HH Scott that the same friend (7308's) recently sent me as a get well present.

I have a quad of Tesla (original, pre-JJ) EL34 from madmax that I need to try in the Dynaco one of these days. It's just hard to mess with something that sounds so good.

Morningstar

Just received my JJ KT77's and this is one very clean sounding tube as the highs seem very extended and the mids are just right. Haven't put on enough hours yet so burn in needs to take place but I found that in the EE M520's running them in Ultra Linear is preferred mode of operation until they break in a bit.
For all those who can substitute EL34 to the KT77 you will be in for a treat. Just initial comments and not etched in stone yet but

organ

Mike,
You have enough to last you a loooooooong time there. I have 3 RCA black plates and a pair of JAN Philips.

That's an interesting tube there. Do you know where Scott sourced it from? It could be a Sylvania. The ST-70 designer, David Hafler, actually prefered the Sylvania. They shipped ST-70's with RCA later on because Sylvania stopped producing them.

Morningstar,
That's definitely good news. Just wait until you get about 15-20 hours on them the mids and highs will really open up. While listening last night, I noticed the dynamics is improving. I wonder how much more time they need.

Which EL34 were you using before getting the KT77?

Maurice

BlueMDPicker

organ wrote:

That's an interesting tube there. Do you know where Scott sourced it from? It could be a Sylvania.

I don't have a clue who actualy made them for Scott. Maybe I can get a better picture of the internal construction and you could tell?

I also received a pair of NOS Tele 12AX7 smooth plates in my care package. My friend knew I was talking about trying the EE MiniMax phono stage (I ended up purchasing a PS Audio GCPH instead), so he sent those along. Now, I need to find something to use them in! Might be time to re-work the near mint PAS 3X and give it a whirl.

Did you know I replaced the bias circuit and stacked, can cap in my ST-70 with the SDS board? WOW, what an improvement! From that point on, I've listened to it almost exclusively.

BlueMDPicker

Morningstar wrote:

For all those who can substitute EL34 to the KT77 you will be in for a treat. Just initial comments and not etched in stone yet but

Hi Bill. Man, you guys are gonna' make me buy MORE tubes with these glowing reviews!

Morningstar

Hi Maurice,
Was using a matched octet of the EI 6CA7 fatbottles which I liked very much. They have nice weight on the bottom end and the highs are clean without any grain.
Before that the SED Winged C EL34's which are very musical and also have a beautiful midrange and high end but the bottom just wasn't as full as what I like to hear.
The Groove Tube E34LS have great tone and also carried the weight in the bottom end but seem just a tad fuzzy as compared to the SED Winged C's.
I had one of my very good friends loan me a quad of the Gold Lion KT77's and these have such a tight deep bottom on them , I'm hoping that the JJ's bloom a bit and I'm almost positive that they will with some hours so by the end of next weekend hoping to have a better feel for their sonic character.

fredv

I have been using the EH 6CA7's since I restored my amp (originally came with 4 EL34's, 4 different brands, 2 tested garbage!!) 3 weeks ago. I ordered a quad of JJ from tubedepot.com Thursday evening and then KT77 Friday morning. It is going to be a lot of fun to have 3 sets of tubes to roll next week especially these 3 types seem to have very different characteristics.

organ

Aaaaah sheeeeat. I just posted a long reply and it didn't get through and I lost it. I'll get back to this later.

fredv

Ding, I still don't have the KT77 yet
But the JJ EL34 arrived. They have been burning in for 10 hours so far.
Comparing to the EH 6CA7, the JJ is more tube sound, couldn't think of other description. The EH sounds like a warm sound SS amp. Even with only 10 hours, the JJ's mid is already smoother than the EH. However, the EH seems to have more lowend punch than the JJ. More later!!

organ

That's what I hear between the two. Did you get the JJ E34L or EL34? The E34L is a better tube. It's my fav EL34. They will sound more tubey if you're used to the 6CA7. The SED =C= EL34 is the smoothest I've heard. Don't worry. Enjoy your JJ for now. I can guarantee that the 77's will be worth the wait. Remember to really break them in.

Are you using the 4 or 8 ohm output taps on your amp? It's better to go by the speaker's lowest impedance dip than nominal. The 4 ohm gave me a lot more bass. But the 6CA7 will always have more bass than EL34.

Maurice

organ

I'll re-type my lost response to the other posters later when I have more energy. It was very long and I'm too lazy right now.

fredv

organ wrote:

That's what I hear between the two. Did you get the JJ E34L or EL34? The E34L is a better tube. It's my fav EL34. They will sound more tubey if you're used to the 6CA7. The SED =C= EL34 is the smoothest I've heard. Don't worry. Enjoy your JJ for now. I can guarantee that the 77's will be worth the wait. Remember to really break them in.

Are you using the 4 or 8 ohm output taps on your amp? It's better to go by the speaker's lowest impedance dip than nominal. The 4 ohm gave me a lot more bass. But the 6CA7 will always have more bass than EL34.

Maurice

How igorant I am, I had to look at the invoice to find what did I ordered It said
JJ / Tesla E34L / EL34. So, I believe they are E34L.
I am using the 8ohm tap because that's the DQ-10's is rated.
The weekend is coming up, so I will be able to pump another 20 hours into
the tubes. It was very interesting that there is a huge improvement from the
1st 5 hours and the 2nd 5 hours. For both the EH and JJ, the 1st 5 hours
were rally nothing to talk about or listen to, but there was very noticeable change
after 5 hours or so. However, I wasn't very sure that was due to the 5 hours
burn-in, or all the tubes were in fully operating temp ... The reason probably
is not important because they all eventually sound good