Educate me on KT66's

[Transcend]

Has anyone used these?

What are the tonal qualities of them?

I'm growing tired of the EL34 sound so much i moved onto E34L's for that extra aggression and headroom.

Initially i am going to throw some 6l6's in my SLO (which should be finished tomorrow btw!) but i have never really liked the sound of 6l6's in the past so these may not last in there too long and i've accomodated the build to be able to take pretty much any octal valves.

[darkbluemurder]

Be careful if you want to swap 6L6s for KT66. A 6L6 needs 0.9A heater current. A KT 66 needs 1.3A. That means with a duet the power transformer will need to supply 0.8A more which may be too much. You (or your tech) should check the specs of the power transformer whether it will be capable of supplying the additional heater current.

If you are changing from EL34s you will be fine with the heater current but you should then check whether you have enough bias voltage available, and you will definitely have to rebias, otherwise the KT66 may melt.

Finally the KT66 are tall beasts - make sure that they fit and that the side by side spacing is appropriate.

Cheers Stephan

[Transcend]

I built the amp :) I know the transformers are more than capable if anything they're overspec'd.

I also checked the side clearance and the height clearance.

i was more wondering what the tonal qualities are as the internet seems to be very vague on the descriptions so i was hoping for someone with first hand experience

[Twinfan]

Did someone mention my favourite valves?  :D

KT-66s are big, round, warm and smooth with a decent sized bottom end.  If you're playing super-thrash-death-metal you'd probably be better off with EL34s (for their midrange crunch) or 6L6s (for their tightness).

For classic rock and hard rock bluesy crunch tones then I think they're great, and they don't need to be wound up to sound good (unlike EL34s).  When you do get them cooking, they break up in a very musical way (unlike 6L6s).

I use them in my Martamp M45/100 for my AC/DC band, and have had them in a couple of JTM45s and a Martamp Orion.  I'll end up with a set in my AFD100 once the stock 6550s need replacing.

Think of them as a warm 6L6...

[Transcend]

Sounds very interesting.

How is the tightness on the low end?

I don't need ultra tightness as i aren't into this whole modern metal malarky just some kind of early 80s sort of stuff but thicker is what im looking for.

[Twinfan]

They're not that tight to be honest - warm and fatt-ish.  Maybe 6550s might suit you better?

[HTH AMPS]

its tough to describe how KT66s sound, but I've yet to put them into an amp and not like them.  I think of them as somewhere between a 6L6 and 6550, they really don't have the snarly mids of EL34s, but do have more low end and weight behind them in general.

[Transcend]

Thanks for all of your help guys. I guess i'll get a pair of these when i need to change the power tubes.

[darkbluemurder]

I built the amp :) I know the transformers are more than capable if anything they're overspec'd.

I also checked the side clearance and the height clearance.

i was more wondering what the tonal qualities are as the internet seems to be very vague on the descriptions so i was hoping for someone with first hand experience

Well then go for it! I have a pair in my JTM45 RI - that one has a new power transformer - and that amp is so loud, clean and 3D it's almost unreal.

Cheers Stephan