You ALL Need To Try KT77's - (NO---I Am NOT a Salesman)

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You ALL Need To Try KT77's - (NO---I Am NOT a Salesman)

Postby pferrari » Mon Mar 20, 2006 1:59 pm

OK---to let you all know, I am fairly new to Shannon's diytube site.
This is great! I am already hooked on the brand new Poseidon driver board for the Dynaco MK4. I have been wanting to build up an old amp for a long time as a hobby, both for the experience and the fun.

I will post pictures and details as the project progresses. At this point I have gutted the amps COMPLETELY, and have sent the chassis out to be re-chromed along with the bell covers off the transformers. OK, OK---I want them to be pretty too.

What I really wanted to talk about were some tubes. The KT77 tubes being re-introduced by JJ Electronics:
http://www.jj-electronic.sk/pdf/KT77.pdf

In a word-------INCREDIBLE!!

Now for you younger generation, the KT77 was a little know tube mad for the military as a VERY RELIABLE and INDESTRUCTIBLE replacement for the EL34. Here are a few details: http://www.mclink.it/com/audiomatica/tubes/kt77.htm.

The other good news is it will withstand much higher plate voltages, is DEAD QUIET, and any "microphonics" problems are eliminated.

The great thing is this tube sounds FABULOUS, and better than any NOS Mullard! Go out and try to price some NOS KT77 tubes and it's enough to give you a heart attack.

The KT77 is designed primarily for use under ultra-linear conditions (43% taps, Class AB1 push-pull) and this connection is recommended. Similiar performance can be obtained in the tetrode connected mode, but the output impednace (zout) will be higher. Life expectancy=5000 hours when operated at maximum ratings of 32W, or 10,000 hours when operated at the 25W ratings of most Dynaco amps (MK2, MK4, or ST-70).

The original KT77 tubes are very rare, and are a direct replacement for the EL34 or 6CA7.
This tube was only produced Marconi-Osram Valve Co. (later Genalex). The early Genalex KT77 had a skinny bottle with a flat top similar to the Mullards and had a red Genalex decal on it with two halo getters on top in a "stacked" configuration. Later versions went to a black octal base similar to the XF4 Mullards---but NOT Mullards!! These are probably the rarest, and most expensive, of all EL34 types today. Usually, the early thin brownbase versions will cost the most due to their rarity, and the blackbase types will be a little less, but you will easily pay $180 or more PER TUBE!

These are all EXCELLANT tubes, and out perform the best Mullard XF1 tubes, but are so rare worldwide they are not often found.

Enter JJ Electronics!! Heros!!!
(OK- not really heros, but great guys.)
They bought the original Marconi Osram Valve equipment and have re-introduced this incredible tube by building it to the exact specs using the original manufacturing equipment.

I (being the ultimate sceptic because I remember the original KT77 tubes) recently bought 2 matched quads of thes new KT77's and popped them in my Conrad Johnson Premier 4 tube amp (100 WPC all tube using one quad per side). I COULDN'T BELIEVE THE DIFFERENCE!
These tubes were amazing right out of the box! I cannot wait until some "break-in" time goes by.

I had a set of 2 matched quads of Svetlana EL34 tubes and a set of 2 matched quads of the overpriced Valve Art "Cryo Stabilized" EL34 tubes to compare the new KT77's against. THERE IS NO COMPARISON!

I now have a lot of matched Svetlana and Valve Art EL34 tubes for sale if anyone is interested.
YES!-----They are that good.
At the current price of about $17 each (matched), you can't affort NOT to try them!!

I highly recommend that you try these tubes in place of your existing EL34 tubes. You will NOT be disappointed!

Sincerely,
-Pat
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Re: You ALL Need To Try KT77's - (NO---I Am NOT a Salesman)

Postby Francois_G » Fri Mar 24, 2006 3:39 pm

pferrari wrote:The KT77 is designed primarily for use under ultra-linear conditions (43% taps, Class AB1 push-pull) and this connection is recommended. Similiar performance can be obtained in the tetrode connected mode, but the output impednace (zout) will be higher. Life expectancy=5000 hours when operated at maximum ratings of 32W, or 10,000 hours when operated at the 25W ratings of most Dynaco amps (MK2, MK4, or ST-70).



Hi Pat,
Sshh! I tried to get a pair and AES is out of stock! BTW., Could you elaborate on the 32W dissipation you mentioned above. The JJ spec has 24 W only.

Francois
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Postby EWBrown » Tue Mar 28, 2006 1:58 pm

I just snared an MQ of the JJ KT77s on E-bay (jspht8338) for $70 plus 6.50 shipping.
Other sellers have them at around $25 each Yellow_Light_Colorz_PDT_09

I'll load these into the modded ST70 and see how they compare against "Old style" Svetlana Svetzalot EL34s. Yellow_Light_Colorz_PDT_11

The JJ Spec of 25W is one single tube's plate dissipation.

/ed B in NH
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Postby TomMcNally » Tue Mar 28, 2006 5:04 pm

I bought some tubes from jspht8338 last week and they arrived from California really quickly. I ordered some KT-90s from him for my new Poseidon MK-III clones yesterday, also have chassis, transformers and all the other stuff coming. Fun stuff !
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Postby mesherm » Wed Mar 29, 2006 5:05 pm

This site has KT77 matched quads for $64.

https://ssl.eurotubes.com/index.htm
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KT77 Tubes

Postby pferrari » Fri Apr 07, 2006 11:12 am

Hi Francois.
The 32 W operation is the absolute max that this tube is designed to handle, but it still boasts a 5000 hour life which says a lot about the quality of this tube. Remember, it was originally (and exclusively) designed and built for military application as a direct replacement for the EL34/6CA7. It was built to handle "tougher than normal" conditions and still operate within specs.

Now operating this tube within the normal, or more common parameters of standard Dynaco equipment----well----you will get a lot of listening time out of this tube at the usual 25 watts.

Of course, what is standard Dynaco equipment anyway??
Aren't we all here, at Shannon's website, to CHANGE the standards of the original Dynaco equipment and to find its true potential?

Sincerely,
-Pat
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KT77's---------The Feeling of This Tube

Postby pferrari » Fri Apr 07, 2006 12:23 pm

jeffreybehr;
I understand what you are asking, about "making comparisons", so I'll try to put my "apples and oranges" into a fruit salad for you.

I have three different sets of main listening amps in two different rooms (OK---OK---some people have Corvettes, and I have stereos).
I play through Vandersteen 3A Signatures, which are not very efficient speakers, hence I need some power.
My one amp is a Conrad Johnson Premier 4 at 100 WPC, and it takes a quad of EL34 type tubes per side, for a total of 8 pentodes!!
My other PAIR of amps are a set of Conrad Johnson Premier 5 monoblocks at 200 Watts each, and these take a set of eight (8) EL34 type tubes each amp, for a total of 16 pentodes!!
I also have a pristine Precision Fidelity M-7A+ that uses a quad of EL34's. (This is a sentimental piece because it was my very first tube amp, and I just can't get myself to sell it.)

Now you see I am virtually swimming in EL34/6CA7 type tubes!

Naturally, when I started reading about the new JJ Electronics re-introduction of the KT77 I was skeptical-------but curious.

I didn't want to blow a wad of money on 16 tubes for my pair of Premier 5's, and I did not want to mess with the tubes in my Precision Fidelity amp because I WAS very happy with its current sound at the time (more later). That left me the Premier 4 to play with.
I figured a set of 8 tubes to try isn't so bad---------ESPECIALLY at $16 per tube!

I ordered a set of KT77's, which actually came to $17.25 per tube to have all 8 tubes specially matched.
I removed the Valve Art EL34 Cryo stabilized matched pair of quads that were in the amp. The Valve Art tube were excellant tubes---don't get me wrong. I had recently rolled them in to replace the matched pair of quads of Svetlana tubes which were also nice. The Valve Art tubes were slightly better, but not worth the money I paid for the difference (IMHO).

Both previous sets of tubes were thoroughly broken in at several hundered hours. I did a LOT of careful comparison between those two sets.
Then I popped in the KT77's fresh out of the box!! There was NO COMPARISON, like I said before, and these tubes aren't even broken in yet!!

The soundstage was MUCH fuller and more stabil, with a more realistic depth of field to the music and the placement of the musicians.
The highs were cleaner and brighter without being harsh------It just felt right!
The bass was tighter, with greater punch, and there was no sloppy post resonance typical with a lot of low frequencies.
The midrange seemed to be a much more accurate balance between the highs and lows, and fit very naturally. (I play my music EQ'ed flat.)

In some of my more familiar music I could actually hear the wood resonate in Yo Yo Ma's cello.

Maybe I cannot put it into the words you would want to hear, but I can tell you this; At $16 to $17 a tube, give them a try. If you don't like them you can EASILY sell them.

Me personally!?!?.....Well, all I can say is that I have a lot of quads of Svetlana and Valve Art tubes, with very little time on them, now for sale!
THAT is how I feel about these new KT77 tubes that have been resurrected from the past.
Given a choice between NOS Mullards and a set of KT77's-----I'll take the KT77's anyday!! HANDS DOWN!

Oh!---The Precision Fidelity M-7A+ I have that I didn't want to mess with when I originally bought the KT77's to try..........It has NOS brown base Mullards in it. Since then I put a quad of the KT77's in the Precision Fidelity amp and it sounds much nicer. So, I will be selling the Mullards too.

I do NOT go for "name brands", or what is popular!
I go for what sounds the best--------and the most real.

-Pat
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Postby erichayes » Fri Apr 07, 2006 7:59 pm

Hi All,

It's been more years than I care to admit to since I heard an amp with KT77s (it was a pair of Fairchilds, if that gives you a hint), and, having graduated from EL34s to JJ KT88s for the big amps, the new KT77s are moot for me.

I do, however, have a few words to say about Eurotubes.

I met Bob at his house about five years ago after asking him if he'd like to hear the 1773. At that time Eurotubes had pretty much overtaken his day job, as far as time consumption. He also mentioned that his wife was probably going to quit her job to devote time to Eurotubes.

The reason so much time was needed was (and is) because Bob tests every tube he sells, not just output tubes, and he knows what certain test results sound like.

If you tell him you want to create a certain sound, he'll send you those types of tubes and make a note for future orders.

When I was there, his living room was full of JJ tubes (the only brand he sells) and there were a couple of Gm tube testers on the couch so he could test while watching TV or listening to the HiFi (also JJ). The numbers on the boxes actually mean something to him--that's how he can duplicate previous orders.

I haven't ordered anything from him for a while, and feel guilty about it. I'm just ordering in quantities that he'd be unable to supply with any kind of profit margin (he described Eurotubes as being "the pimple on the ass of the retail tube sales world"). Nevertheless, I consider him to be a second source, should something go awry.

In short: honest, with it, and on our side
Eric in the Jefferson State
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Postby craigtone » Sun Apr 16, 2006 6:09 pm

I just finished a complete rebuild of an ST-70 and decided to bite on this post and install a fresh set of matched quad KT-77's.

First impression is as stated ... good soundstaging, good imagery and VERY balanced response. I did notice a loss of extreme dynamic highs and lows with respect to my mix of NOS GE & Mullards before. I'm hoping they just need to burn-in a bit! I too run input with a flat response FWIW. Test system is an upgraded Rega P2 -> NAD PP-2 -> Axiom Passive Preamp -> Modified ST-70 -> Klipsch SF-2's. Not the best system, but better than SS!

Overall, I think it is a more neutral and balanced sound than the NOS tubes. It also is cleaner and more punchy in the mid-bass and midrange than before. Noise floor is cleaner but that is probably due to my excellent wiring job than the tubes! Yellow_Light_Colorz_PDT_09

Either way, if you are looking for new tubes for your EL34 amp, give these a shot! They were $64 for the quad c/o Eurotubes which I also highly-recommend. For that price, you can't go wrong! If you don't like, at least you have some nice spares laying around!
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Postby craigtone » Wed May 03, 2006 9:32 am

I just wanted to post an update now that I have maybe ~50 hours on the KT77's and my rebuild ST-70. The tubes DEFINITELY improved with break-in! Everytime I listen to it, the dynamics increase, detail increases ... they sound incredible!

I have been tube rolling my VTA driver board with some interesting results. I have Mullard 12AT7's in there now and I rolled some Sylvania 12BH7's and some Brimar 12AU7's. I noticed that the latter 2 tubes caused a loss of high-end and detail but improved bottom-end. The 12AU7 was better than the 12BH7 with respect to high-end and detail. After talking to some fellow tubeheads familiar with the VTA circuit, it appears that these findings are consistent with the fact that I run a passive preamp. If I had an active pre, the increased gain of the 12AT7's would make the amp too sensitive and thus the 12AU7's would sound more balanced. More testing to continue ...
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Watch out for those skinny pins...

Postby EWBrown » Wed Oct 11, 2006 6:32 am

One caveat with the JJ KT77s, the early release version has very "skinny" pins, when I first tried them in a vintage "stock" ST-70, the pin to socket contact was just about useless. They are OJK in new "virgin" sockets, but they rattle around like a BB in a boxcar, with older well-used sockets.
The skinny pins are OK in new (virgin) ceramic Russian or Chinese octal sockets, which seem to have a very tight "grip. (see last paragraph).

The newer ones (I got mine from Eurotubes) have the fatter, normal size pins, so contact isn't an issue, and yes indded they do sound very good.
The "fat pin" '77s are still just breaking in, but they are a noticeable upgrade, and given some more runtime, they should really "shine" Yellow_Light_Colorz_PDT_11

FWIW the "skinnies" are going into a Chinese made Meixing "Ming Da" EL34 amplifier that I am upgrading for a friend. Not a bad little unit, beautifully made, but they'll never replace a well-tuned ST70...
These amps are all point to point wiring, and are of decent quality for the price, but they do need better than Chinese "generic" no-name tubes and some decent coupling caps. This particular model uses adjustable fixed bias, and runs about 30 WPC.

FWIW, I learned that the Chinese 12AX7 equivalent is called 6N4

/ed B in NH
Last edited by EWBrown on Wed Jun 17, 2009 11:23 am, edited 1 time in total.
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Genelec re-issue KT77s?

Postby ezside » Wed Jun 17, 2009 12:17 am

I read all the good things said about the JJ KT77s & am wondering how they compare with the Gold Lion version (at twice the price!)...
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Postby mesherm » Wed Jun 17, 2009 10:38 am

I have yet to get a JJ KT77 or EL34 that wasn't built crooked. That gives me no confidence in their QC system.
Mike's N-1 Rule: When looking for N number of components to finish a job, you have a 95% chance of only finding N-1 of them.
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Postby EWBrown » Wed Jun 17, 2009 11:25 am

I've read that J/J has had QA problems over the past couple years.

Until recently I have had good results with them, but I haven't been impressed with the latest goods from them... (sick)

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