Are KT66 tubes worth the cost?

[Chicago Slim]

NAD, yesterday I took a drive to Nashville to checkout a couple of used Dr Z amps. The DR Z amps were nice but you could tell that they had seen a lot of hard use. So, looking at other amps, I was surprised that a Tone King Gremlin actually sounded better. So, I came home with the Tone King. It uses a KT66 power tube. When I compared it to a good sounding 6L6, that I had been saving in a drawer, I couldn't hear the difference.

My questions are, do the KT66 tubes seem to be worth the added price? If so, what brand KT66 do you recommend?

Thanks.

 

[Timbresmith1]

The KT stands for “Kinkless Tetrode”.
The “Kink” reportedly a kink in the frequency response or bias curve of the early tetrodes
Depending upon the amp design, pickups or speaker used, the difference may not be noticeable.
I love the kt-66. Seems less spiky in the top end. If you love blackface clean, stick closer to the 6L6 family, imo.

 

[Swirling Snow]

Depending on the mix of harmonics you prefer, the 6L6 might be a better choice.

KT66s sound good in Plexis and older Marshalls.

 

[Chicago Slim]

The KT stands for “Kinkless Tetrode”.
The “Kink” reportedly a kink in the frequency response or bias curve of the early tetrodes
Depending upon the amp design, pickups or speaker used, the difference may not be noticeable.
I love the kt-66. Seems less spiky in the top end. If you love blackface clean, stick closer to the 6L6 family, imo.

Thanks. My main amp is a Bad Cat Cougar 15, set for Vox type sounds. Both amps are capable of good Tweed type sounds, but I guess I'm leaning more to the brighter, clean tones. I just expected to hear more of a difference between tubes, as the KT66 is a different construction and about twice the size and price of the 6L6.

 

[W.L.Weller]

When I compared it to a good sounding 6L6, that I had been saving in a drawer, I couldn't hear the difference.

My questions are, do the KT66 tubes seem to be worth the added price?

Based on this, I'd say that for you and that amp, definitively not. The post-6L6 innovations in beam tetrodes seem to focus on fixed bias, Class AB performance.

 

[Swirling Snow]

The cost of the KT66 is due to it's accuracy for audiophiles. But "flat response" is meaningless to a guitar player.

Also, the 6L6 was designed for use in B52s. Do you gig?

 

[Chicago Slim]

The cost of the KT66 is due to it's accuracy for audiophiles. But "flat response" is meaningless to a guitar player.

Also, the 6L6 was designed for use in B52s. Do you gig?

I used to be a working musician. Now that I've retired, I'm thinking that the smaller Gremlin would be a better amp for me, than the DR Z, Maz18.

 

[Cali Dude]

The cool thing about the Gremlin is that you can change power tubes and experiment. I have the Gremlin too. I've tried kt66s, kt77s, el34s, and 6v6s in that amp. I think I prefer the kt66s. It has a fuller low end. I have tried Gold Lions and the stock kt66s. I honestly didn't notice a huge difference between them.

 

[SnidelyWhiplash]

Depending on the mix of harmonics you prefer, the 6L6 might be a better choice.

KT66s sound good in Plexis and older Marshalls.

Didn't Claptons Bluesbreaker combo amp run on KT66s???

 

[Chicago Slim]

Didn't Claptons Bluesbreaker combo amp run on KT66s???

Yes, and SRV used them in Fender amps. I was surprised how good the Gremlin sounded, compared to other amps. But it sounds equally good with other tubes.

 

[NTC]

The KT stands for “Kinkless Tetrode”.
The “Kink” reportedly a kink in the frequency response or bias curve of the early tetrodes
Depending upon the amp design, pickups or speaker used, the difference may not be noticeable.
I love the kt-66. Seems less spiky in the top end. If you love blackface clean, stick closer to the 6L6 family, imo.

A beam power tube, or beam tetrode, IS a kinkless tetrode. Tetrodes have a "kink" in the bias curve due to electrons bouncing off the plate and going back to the cathode. Pentodes and Beam power tubes fix this problem and have more linear response.

Also, the 6L6 was designed for use in B52s.

The 6L6 was designed and released to the public in the mid 1930's. B52's were most likely designed in the 50's, being jet aircraft. 5881's are ruggedized 6L6'S that were used in servo systems in aircraft, but they also make a fine audio tube.

"KT" is a British designation, of course.

Edit: and for completeness, THE B52'S were formed in Athens, Georgia in 1976.

 

[jackal]

Had a newer model twin that someone put the KT66s in. Really preferred the 6L6s. Nice added midrange, but lost some highs.

 

[Fluddman]

Love my Gremlin but have never felt the need to change the original tube. It's a great amp for small gigs and at home.

Cheers

 

[Swirling Snow]

The 6L6 was designed and released to the public in the mid 1930's. B52's were most likely designed in the 50's, being jet aircraft. 5881's are ruggedized 6L6'S that were used in servo systems in aircraft, but they also make a fine audio tube.

You are, of course, correct. My bad. I forget how easy it is to look things up, these days. I was thinking of the bombers over Dresden, actually. Guess those weren't B52s.

For anyone that wants the whole story:

https://worldradiohistory.com/Archi...-Vacuum-Tube-Valley/Vacuum-Tube-Valley-04.pdf

 

[dom ray mustang]

Hi Chicago Slim,

One KT66 draws 1.3A of heater current in comparison to the 0.9A of a 6L6GC.
So checking out the the PT rating is always a good idea if the heater secondaries are able to provide that additional current.
As other's have mentioned, KT is referred to the absence/flatter kink in the load line diagrammes (plate/screen voltage correlation) near the saturation point. The amplification factor (U/I) is flatter while the tube is doing it's AC voltage swing.
As for current production tubes, the chinese ones (Sino/TAD) are closest to the old GEC KT66.

Dom

 

[VintageSG]

If you like them, if you enjoy them, then they're for you.

I couldn't tell the difference between a KT66 and a 6L6 without very careful listening, and slow, clean arpeggio playing. I'd rather listen to the whole than focus on minutiae. Amp used was a WF-55, a single-ended wonder that makes discerning changes easy, at the expense of exposing poor technique

If I didn't know what was in there, I couldn't tell which was which.

If you enjoy the sound, a few £/$ here and there spread over a few years is nothing compared to the personal pleasure you get from your setup. Be guided by your own ears.

 

[MuddyWolf]

If you are going into the amp straight in it might make a difference. If you are using drives and fuzzes, no not worth extra money.

 

[schmee]

I have a pair of Gold Lion KT66's in a drawer. They are probably 10 years old or more. I put them in a Pro Reverb for comparison and kinda thought they were smoother and less spiky on the high end than 6L6GC's were. I took them out and have never tried again though.

 

[Tim S]

FWIW, the Gremlin’s circuits were designed for the KT66, so results you get with it may not be the same when used in other amps.

Mark Bartel tuned his amp designs for current day tubes because he believes there are too few good NOS tubes available these days. Of course, the Gremlin came to market after Mark sold Tone King to BAD, so I don’t know how accurately they implemented his design. (They tended to make changes)

Anyway, enjoy that amp!

 

[String Tree]

NAD, yesterday I took a drive to Nashville to checkout a couple of used Dr Z amps. The DR Z amps were nice but you could tell that they had seen a lot of hard use. So, looking at other amps, I was surprised that a Tone King Gremlin actually sounded better. So, I came home with the Tone King. It uses a KT66 power tube. When I compared it to a good sounding 6L6, that I had been saving in a drawer, I couldn't hear the difference.

My questions are, do the KT66 tubes seem to be worth the added price? If so, what brand KT66 do you recommend?

Thanks.

View attachment 1121306

Many years ago, I had my JCM800 modded with KT66's.
Instant Angus Young!!!
Low End from Hell!!!

If you want Clean with all kinds of Headroom, I don't think they are what you are looking for.