KT-66 tubes... How do they sound?

[TrueTone500]

I'm thinking about trying a quad of KT-66 tubes in place of EL34's in my 100 watt amp. What can I expect? Do they sound more like a 6L6, or closer to EL34? Who makes (made) the best KT-66 tubes?

 

[rupe]

I simply don't understand posts like these. Why are you thinking about trying them if you know nothing about them and have no idea what to expect? I would think knowing a bit about them first is what would lead you to want to try them.

 

[TrueTone500]

I simply don't understand posts like these. Why are you thinking about trying them if you know nothing about them and have no idea what to expect? I would think knowing a bit about them first is what would lead you to want to try them.

I simply don't understand replies like this? Passive-aggressive, non-informative, and completely devoid of logic.

 

[Shark Diver]

I believe they are more 6L6ish. They are not as tight or aggressive as the 6L6s I've used. Higher headroom, more bottom end, smoother high end. The mids are not as pronounced. My experience with them in the SLOs is that they are the more vintage of the 5881s/6L6/Kt66s I've tried. Gold Lions are the only ones I've used based on internet love for them.

To me switching from a 5881 to the KT was like going from the Ruby 12ax7 to an NOS Mullard. Still plenty of gain, more musical and balanced. Much better for cleans and rock, but not as balls out for more modern voicing,

 

[Mr. Willy]

Shouldn't KT77's be used in place of EL34's?

 

[TrueTone500]

My amp has the option of running EL34 or 6L6 tubes.

Well, if it adds bottom-end, then it may not be a good idea. My amp has more bottom-end than I would ever use. I was going to buy a quad of 6L6's, but Steve39Stripes told me I should consider KT-66's instead.

 

[rupe]

I simply don't understand posts like these. Why are you thinking about trying them if you know nothing about them and have no idea what to expect? I would think knowing a bit about them first is what would lead you to want to try them.

I simply don't understand replies like this? Passive-aggressive, non-informative, and completely devoid of logic.

Not passive aggressive in the least...actually its very matter-of-fact. Devoid of logic??? Nice try, but it simply questions the lack of logic in your entire approach.
I see you have no answer for my question either

 

[TrueTone500]

I believe they are more 6L6ish. They are not as tight or aggressive as the 6L6s I've used. Higher headroom, more bottom end, smoother high end. The mids are not as pronounced. My experience with them in the SLOs is that they are the more vintage of the 5881s/6L6/Kt66s I've tried. Gold Lions are the only ones I've used based on internet love for them.

To me switching from a 5881 to the KT was like going from the Ruby 12ax7 to an NOS Mullard. Still plenty of gain, more musical and balanced. Much better for cleans and rock, but not as balls out for more modern voicing,

Thanks. My amp is similar to the SLO with exception to some cap values in the tone-stack. I'll just stick with the 6L6's I think. I definitely don't want to dull the mids since it's already a somewhat lower-mid voiced amplifier. It's closest relative would be a Soldano SLO, but with an extended amount of bottom-end.

Soldano SLO T/S

My amps T/S

 

[TrueTone500]

I simply don't understand posts like these. Why are you thinking about trying them if you know nothing about them and have no idea what to expect? I would think knowing a bit about them first is what would lead you to want to try them.

I simply don't understand replies like this? Passive-aggressive, non-informative, and completely devoid of logic.

Not passive aggressive in the least...actually its very matter-of-fact. Devoid of logic??? Nice try, but it simply questions the lack of logic in your entire approach.
I see you have no answer for my question either

How's the water? What's that taste like? Was the movie any good?

You're obviously looking to stir-up some shit... There are healthier forms of entertainment. I'm just say'in...

 

[rupe]

Not in the least. Still wondering what would lead a person to state "I'm thinking about trying a quad of KT-66 tubes in place of EL34's in my 100 watt amp" without having a clue what attributes they exhibit. A reasonable person would either state what they were looking for tonally and ask for suggestions, or have some idea of what a KT-66 brings to the party before considering the switch. I simply don't understand your approach. That said, I'll leave it alone since you still haven't answered the question.

As for a KT-66, its simply a 6L6 varient. It will exhibit different traits depending on the amp that its used in, but in general it has more clean headroom and power with bigger lows and smoother highs. In my experience, it also has stronger mids than a typical 6L6/5881 which contradicts Shark Diver's experience. I'll attribute that to different amps...my experience is with Fenders and Marshalls (I've never tried anything other than 6L6/5881 in an SLO). It's the sound of old (70's) AC/DC and Bluesbreakers era Clapton. A good modern amp that uses them is the Dr Z Rt 66...listen to some clips to get an idea.

Bottom line is to try them...it's ultimately the only way to truly satisfy a curiosity.

 

[TrueTone500]

As for a KT-66, its simply a 6L6 varient. It will exhibit different traits depending on the amp that its used in, but in general it has more clean headroom and power with bigger lows and smoother highs. In my experience, it also has stronger mids than a typical 6L6/5881 which contradicts Shark Diver's experience. I'll attribute that to different amps...my experience is with Fenders and Marshalls (I've never tried anything other than 6L6/5881 in an SLO). It's the sound of old (70's) AC/DC and Bluesbreakers era Clapton. A good modern amp that uses them is the Dr Z Rt 66...listen to some clips to get an idea.

Bottom line is to try them...it's ultimately the only way to truly satisfy a curiosity.

This would have been a great initial reply! No need for hating I say...

I love those older sounds, but how good these would sound in a high-gain amp, I did not know. I ask these questions simply because I don't have a ton of experience with high-gain MV amplifiers, and no experience at all with KT-66 power tubes. Would KT-66 tubes paired with Alnico speakers smooth the highs too much? A 'cart before the horse' situation I think... Based on your review, I think the KT-66's are worth a try. Thanks!

 

[stephen sawall]

Just to add to what Shark Diver has stated - Because they are KT - "Kinkless Tetrode" they do not have any cancellation and all frequencies are there. In some of my amps it can produce the best cleans & lead sounds ~ big & round. In some amps with the extended bottom it will not be as tight as EL34 or even 6L6. In a very tight amp this can be nice because it loosens up the sound a bit. Overall it is just a bigger sound in most amps .... huge actually.

I also agree with rupe about them having more midrange. But the difference's in what David is hearing might be explained by the amp circuit or the other gear being used.

Be aware that with some amps changing tubes can make a huge difference. Other circuits little change is made. What tube the circuit was designed around often is the best sound (taste). Also be aware every tube has it's own sound & property's. Two tubes made on the same day on the same run can react & sound very different. They are like snowflakes ....everyone is different.

Some of my favorite tubes are KT66 & 6CA7 ..... like stated the KT66 has more of a 6L6 sound - but it does have some of the crunch associated with amps designed around EL34. The 6CA7 is more like a EL34 - but has more bottom like a 6L6.

I would not worry about them over smoothing the highend - unless the cut in the mix you get with some amps that have a more brash sound is very important to you.

What amp are you planning on trying them in ?

 

[TrueTone500]

Just to add to what Shark Diver has stated - Because they are KT - "Kinkless Tetrode" they do not have any cancellation and all frequencies are there. In some of my amps it can produce the best cleans & lead sounds ~ big & round. In some amps with the extended bottom it will not be as tight as EL34 or even 6L6. In a very tight amp this can be nice because it loosens up the sound a bit. Overall it is just a bigger sound in most amps .... huge actually.

I also agree with rupe about them having more midrange. But the difference's in what David is hearing might be explained by the amp circuit or the other gear being used.

Be aware that with some amps changing tubes can make a huge difference. Other circuits little change is made. What tube the circuit was designed around often is the best sound (taste). Also be aware every tube has it's own sound & property's. Two tubes made on the same day on the same run can react & sound very different. They are like snowflakes ....everyone is different.

Some of my favorite tubes are KT66 & 6CA7 ..... like stated the KT66 has more of a 6L6 sound - but it does have some of the crunch associated with amps designed around EL34. The 6CA7 is more like a EL34 - but has more bottom like a 6L6.

I would not worry about them over smoothing the highend - unless the cut in the mix you get with some amps that have a more brash sound is very important to you.

What amp are you planning on trying them in ?

It's a Cornford RK100. The circuit was designed primarily for EL34 tubes, but can be switched to use 6L6 or EL34. My thought was to switch it to 6L6 mode, and load it with KT66's... As long as that's safe to do? Given the size of the PT, I don't think there's much it can't handle... I may still ask Martin before using them. Martin left Cornford three years ago, so he may not respond.

 

[stephen sawall]

Very nice amp .... I have never tried one. I imagine it would be fine / But I would ask also & ask for any advise on the various tubes that are in the two family's.

6L6 / 5881 / KT66 / EL34 / KT77 / 6CA7

 

[rlord1974]

I also agree with rupe about them having more midrange. But the difference's in what David is hearing might be explained by the amp circuit or the other gear being used.

It has nothing to do with the gear being used. David is just a little SLO......

 

[Shark Diver]

I also agree with rupe about them having more midrange. But the difference's in what David is hearing might be explained by the amp circuit or the other gear being used.

It has nothing to do with the gear being used. David is just a little SLO......

Sometimes it's hard for me to be good at knowing what is the actual cause of what. I am using the KTs in my Hiwatt/SLO. I put a couple of Mullards and Telefunkens in around the same time. But when I had the KTs in a regular SLO I still felt the mids were not as pronounced. Maybe It is just what Percieved because there was more low end ?

 

[stephen sawall]

KT66 have more bass than 6L6 / 5881 / EL34 / KT77 / 6CA7. Without being able to switch them fast like I can in my Bivalve it is harder to hear differences. Different circuits are going to react differently to tube changes. Individual tubes from the same batch can have a slightly different tonal balance. Tonal balance like everything else can be subjective.

 

[TrueTone500]

KT66 would definitely not be the tube I would run then. I run my bass at 1-2 as it is.

 

[stephen sawall]

5881 & 6L6 both have more bass than EL34's in my ears. The EL34 has the least of all from both family's of tubes.

I would just borrow a set of 6L6 and see if you like them or not....

 

[glip22]

I believe they are more 6L6ish. They are not as tight or aggressive as the 6L6s I've used. Higher headroom, more bottom end, smoother high end. The mids are not as pronounced. My experience with them in the SLOs is that they are the more vintage of the 5881s/6L6/Kt66s I've tried. Gold Lions are the only ones I've used based on internet love for them.

To me switching from a 5881 to the KT was like going from the Ruby 12ax7 to an NOS Mullard. Still plenty of gain, more musical and balanced. Much better for cleans and rock, but not as balls out for more modern voicing,

Thanks. My amp is similar to the SLO with exception to some cap values in the tone-stack. I'll just stick with the 6L6's I think. I definitely don't want to dull the mids since it's already a somewhat lower-mid voiced amplifier. It's closest relative would be a Soldano SLO, but with an extended amount of bottom-end.

Soldano SLO T/S

My amps T/S

Didn't love them in my MK50 when I had it. In that amp the 6l6 was my favorite.