KT77 fans??

[boneyguy]

I've got a pair of JJ KT77's on the way and I'm pretty excited about the possible changes to my amps sound.

I've got an old Traynor Custom Reverb that runs on a pair of EL34's. I've been wanting to get more of a 6L6 type sound from it and I was initially planning to put 6L6's in it and then rebias etc. But when I called Eurotubes and spoke to Eddie he mentioned the KT77's so I did some reading and listening (YouTube) and decided that's my best choice.

From many reports it sounds like they fill a nice middle ground between the sound of EL34's and 6L6's. I'm feeling quite hopeful at this point that they'll get me closer to the sound I'm hearing in my head.

Anyone here a fan of the KT77's?

[marshman]

I've never tried any, but they do have my curiousity piqued, that's for sure. I only have one amp that runs 34s right now, and it's not the flavor of the month right now, so it doesn't get a lot of work.

I'm actually contemplating a set for a bass amp build, believe it or not.

Let us know how it turns out.

[boneyguy]

Originally Posted by marshman

I've never tried any, but they do have my curiousity piqued, that's for sure. I only have one amp that runs 34s right now, and it's not the flavor of the month right now, so it doesn't get a lot of work.

I'm actually contemplating a set for a bass amp build, believe it or not.

Let us know how it turns out.

Hey marshman. I''ll post my impressions after I've played them for a day or two.

[eugenedunn]

I have a cool old Kalamazoo Bass 50 amp that uses EL34's and I thought about going the KT77 route after swapping 6L6GC's for KT66's in another amp with great results.....

Then, I started reading up on 6CA7's......especially the new ElectroHarmonix 6CA7EH. They might strike a happy medium between the EL34 and 6L6GC tone....

What I've really been curious about is a comparison between a KT77 and 6CA7

[boneyguy]

Originally Posted by eugenedunn

I have a cool old Kalamazoo Bass 50 amp that uses EL34's and I thought about going the KT77 route after swapping 6L6GC's for KT66's in another amp with great results.....

Then, I started reading up on 6CA7's......especially the new ElectroHarmonix 6CA7EH. They might strike a happy medium between the EL34 and 6L6GC tone....

What I've really been curious about is a comparison between a KT77 and 6CA7

Cool. I haven't investigated the 6CA7's at all. I know I've seen them mentioned but like the KT77's I don't really know anything about them. I just learned about KT77's yesterday!! More reading to do.

[cobra94]

I have a Traynor YCV50 Blue that had EL34's which I found a little too dark. I installed KT-77's and biased a little hotter and it did brighten up the sound closer to a fender.

I guess I'll have to fire up the amp tonight and see how it sounds again.

[boneyguy]

Originally Posted by cobra94

I have a Traynor YCV50 Blue that had EL34's which I found a little too dark. I installed KT-77's and biased a little hotter and it did brighten up the sound closer to a fender.

I guess I'll have to fire up the amp tonight and see how it sounds again.

That's what I'm hoping for, to move the sound a bit more toward a Fender tone. My amp is already very bright. It's normally EQ'd with the treble on 2 and the bass on 3 or 4.

[marshman]

I guess the big problem I have is my cynical state...I do find myself wondering if JJ and Sovtek are REALLY making different tubes, or just changing the bottle shape and labelling of their EL34s and callin' 'em KT77s. Last time I looked, the Sovtek empire had no less than 6 EL34s, can they really ALL be different?

That said, a glance at a JJ spec sheet for their KT77s suggest that they might just be up to task of subbing in my Eden WTB300V all tube monstrosity. I'll hafta get someone more 'in the know' to check my specs for me. I'm guesstimating that 300 watts from 6 6550s means something like 600 volts on the plates, but I don't have a schematic.

http://www.eden-electronics.com/prod...v/wtb300v.aspx

If anyone's curious:
http://www.jj-electronic.com/pdf/KT77.pdf
(can't find Gold Lion spec sheet)

[boneyguy]

Originally Posted by marshman

I guess the big problem I have is my cynical state...I do find myself wondering if JJ and Sovtek are REALLY making different tubes, or just changing the bottle shape and labelling of their EL34s and callin' 'em KT77s. Last time I looked, the Sovtek empire had no less than 6 EL34s, can they really ALL be different?

That said, a glance at a JJ spec sheet for their KT77s suggest that they might just be up to task of subbing in my Eden WTB300V all tube monstrosity. I'll hafta get someone more 'in the know' to check my specs for me. I'm guesstimating that 300 watts from 6 6550s means something like 600 volts on the plates, but I don't have a schematic.

http://www.eden-electronics.com/prod...v/wtb300v.aspx

If anyone's curious:
http://www.jj-electronic.com/pdf/KT77.pdf
(can't find Gold Lion spec sheet)

Here's Bob's blurb about the JJ KT77 from his website.


"The story behind this tube is that it was made by JJ at my request after meeting with them. I quietly sacrificed a pair of my original GEC KT77 for them to test and then break apart (while I wasn't looking) to reverse engineer. The result is a stunning new production KT77 that has all the qualities I coveted in the original. The JJ KT77 has a slightly deeper low end than the JJ E34L and they have a nice sizzle on the top end without getting brittle and the mid range harmonic structure is very complex. The clean tone is very fat and full and the when driven to saturation the crunch has more of a chunk to it."

So it would appear that the KT77 is not just a 34 in a different bottle. I should be recieving mine early next week and I hope they live up to my expectations.

[ThermionicScott]

One difference between the EL34 and the 6CA7 or KT77 is that the former is a true pentode with a suppressor grid, and the latter two are beam tetrodes with beam-forming plates instead of a suppressor grid. If you look closely at pics of the Sovtek 6CA7 and the JJ KT77, you can see the beam-forming plate structure inside the plate:




EL34 just has grids, so it's not sharing guts with the other tubes:


(All images poached from thetubestore.com. I'll take them down if need be.)

Lots more pictures of real old KT77s here: https://www.tubeworld.com/kt77.htm You can spot a beam tetrode by the bent-over tabs rather than an extra pair of grid support rods toward the edge of the top mica.

- Scott