New KT77 Tubes by JJ

[astravitz]

I recently got my first Tube Amp (Jolida 302B), which I'm extremely happy with; but I was looking to replace the stock chinese tubes. Then I came across different threads and learned that the EL34's are equivalent to the 6CA7 and KT77. Then I noticed that JJ tubes is reintroducing the KT77. I'm not an electrical engineer by any means, but I was wondering if this tube is better in design then the current EL34's?

Below is a link to the specifications:

http://www.eurotubes.com/KT77-Spec.jpg

[kevinkr]

Based on the information provided it's not really a drop in for the EL34.
IMHO both the EH EL34 and JJ EL34 are good sounding current production tubes and are acceptable substitutions.

Kevin

[richwalters]

Have a look at Frank's electron tube site, http:/ frank.pocnet.net and compare with EL34....

richj

[edl]

http://frank.pocnet.net/sheets/086/k/KT77.pdf

http://frank.pocnet.net/sheets/129/e/EL34.pdf

http://www.jj-electronic.sk/

[kevinkr]

I would go straight to the JJ site as I did and compare, the differences are subtle but there. I wouldn't make that substitution although arguably there are some (many) who would.

Actually the curves shown did not look all that great for either tube..

Perhaps I have screw loose.. (Used to 300B)

Kevin

[richwalters]

Although slightly more powerful than the EL34 cat, however, these days I cannot see the point of reintroducing this tube unless physical contraints and heater current which avoid the use of a KT88 which is far more readily available and would last much longer in the same circuit. Substituting a 77 to an 88 in UL circuit can nearly tweak a circuit to run in close class A. There are alot of benefits doing this, i.e lower thd and a bit more o/p power..

To comments which downngrade a tube because of "non brilliant curves" is to me inexperience on part of the user.....this tube was designed specifically for UL operation and was used by millions. I'm sure that the designer of this tube certainly wouldn't give the orders to produce if it was a duffer.

richj

[Majestic]

Original KT-77's were considered by some to be one of the finest sounding output tubes, ever. Sadly, due to me being a relative tube young un, and the fact that they go for silly money today, I never got a chance to try them in my own system

Given that the EL34 is also a very fine sounding type (though I haven't auditioned all of the most latest manufactured versions), this reintroduction might make for an interesting comparision.

[kevinkr]

Yeah, I'm a little under 50 and have never heard KT77's in any amplifier, although I have heard most of the other suspects. My out and out preference these days would be either the 45 (NOS) or the JJ300B.

I used to sell a mod kit for the Dyna ST-70, and did the retrofit on about half of them. I found the JJ EL34 to be an excellent performer in this application - most were strapped for triode operation. More recently I have been also offering the EH EL34 as replacements because some of my old clients indicated that they thought they sounded even better.

I am sure the JJ KT77 will be a good performer, but for the moment I would guess they are going to be the sole "legitimate" source for this type. I just wonder whether there is a real demand for this type or did they just succumb to the mystique?

I used to have an octet of MO KT88's and they were wonderful in my heavily modified Citation II, but ultimately I ended up preferring the KT90, and got a good penny for the six (two were so heavily used I didn't put them up) I ultimately sold on eBay. The MO KT88 had this ethereal sound quality that is hard to describe, but I don't think it was accurate... Both the Winged C (real Svetlana) KT88 and JJ KT88 are good too.

[Stuben]

I just took a look at the KT77 specs at the JJ site. The tube specs are very close to the EL34 but the Plate curves look more like a KT88. I agree, this tube should be a good perfromer. It's nice to have decent new production tubes out there. So far Tesla/JJ has impressed me with their EL84, the ECC803 and the sweet ECC99. Go JJ....

Thanks for the tip on the KT77s...I didn't realize that JJ had reissued them.... I have a friend that has recently purchased a pair of used Quad IIs. They came with 6L6 power tubes. Depending on how Quad II biased the original KT66, the new KT77 might be a nice option.

Stuben

[Majestic]

Originally posted by kevinkr
Yeah, I'm a little under 50 and have never heard KT77's in any amplifier, although I have heard most of the other suspects. My out and out preference these days would be either the 45 (NOS) or the JJ300B.

Yes, "best sounding" was in the context of 'modern' tubes of the era. A good 300B or other good genuine power triode should still whip it! But the KT-77 reputedly did have lots of 'the magic' that we love tubes for.