Groove Tubes GT-KT66HP

Im not a guitar player but I am an avid audiophile. I use the KT66HPs in my modded heath W5ms and they are simply stunning when played on my quad ESL63s electrostatic speakers.The amps are rated at 25 watts each but with the KT66hp tubes and the power supply mods its about 33wpc. The bass is phenominal and the midrange clarity is stunning and the high end is as a summer breeze.I have had these tubes for 2 years now and play them 2 hours per day and they show no signs of wear.This is by far as good or better than the Genelex tubes that were in the amp originally.Nice job GT.Im your customer for life.
mike samra

Reliabilty...I have played them 2 hours a day for two years and the flashing and effortless power the tubes produce has no equal.

You cant beat GT. They take a real interest in their customers no matter how big or small.
mike

I pay classical and jazz and country and rock. I play a lot of austrian strauss dance music.

Using the KT-66HP in a good Marshall top couldn't be much easier. I use a 1974 4 input style 50 watt top that used to be fitted with Tesla E34L output tubes. The bias needs to be made about 10 volts more negative to bias this tube properly in the circuit. You don't change the feedback loop attach point as you do when using 6550's vs EL34's, you leave it the same as with EL34's. They seem to run quite a bit cooler than the E34L's did in the same amp. They are very touch sensitive and sound great at all levels..

Being Groove Tubes, with their rating system all I'll have to do is just plug in a new set of the same number and go when they need to be changed, probably in a year or so (we were changing the E34L's every six months with our playing schedule and use)

Very fat full sound, excellent top end and clarity, perfect mix between 6L6 and EL34 tonewise. This Marshall is a very touch sensitive amp with EL34's and it's even better now with these, about the same total output but even better tone...

These have been tested under practice and performance situations and they seem to be very reliable, probably more so than the Tesla E34L's we've been using for years and those have been very good. If properly biased I think a set of these would be reliable and sound good for about a year of typical use, I'm thinking about 2 times as long as the E34L Tesla, they seem to bias easily and they run cool. Groove Tubes does pretty extensive testing before you get the tubes, so I think they will be quite reliable..

Groove Tubes answered my questions via e-mail very quickly. I asked them a few questions about biasing requirement, feedback loop tap etc.

For playing rock with a Marshall or Fender amp that's been using 6L6 or EL34's these are probably the ultimate, at least they are for us. We play blues, pop and rock tunes and these are the best output tubes we've ever used in our Marshalls. We have been playing for almost 20 years now with regular giging and recording. www.polarisband.com There are other companies offering KT66's but they are NOT the same as the GT HP version which is produced in Russia on GT exclusive tooling. I'm not a big Groove Tubes user but I would recommend their version of this tube very highly for anyone who uses the output section of the amp as a source of tone. These tubes are not all that expensive either. If you crank it through a Marshall Power Brake or Hotplate, give these a try, biasing the amp will take about 30 minutes of time well spent, rock on.

You plug them into your tube amp, that accepts 6L6's, in a matched pair, and you're ready to roll

KILLER! These tubes have great articulation to the tone, and very warm all the time. They have one of the most musical distortions I've ever heard (right behind Tung Sol 5881's and RCA blackplates). Simply these tubes are unbelievable, very warm, rich, full tone at all volumes. They also respond very nicely to boost pedals or overdrives, like the Barber Direct Drive and the Fulltone Fat Boost.

My first pair went in about 6 months, so now I'm on pair #2, but I them pretty hard, two boost pedals, a humbuckered guitar, and usuallly turning up the amp to a pretty healthy volume. I wish they would last a little longer, but the sound they produce is very consistent, and usually I have a backup, and with Groove Tubes numbering system its easy to throw in a new set. Have to knock a few points off because 6 months isn't real long, but for $50 a pair that's not bad either.

Company was very friendly and easy to deal with.

I play blues, boogie, and blues-rock. The tubes are great for these styles. I've been playing a bit over 5 years now, and own some pretty cool gear, Heritage 150CM, a strat, a JTM45, 1966 Vox cab, etc. I'll buy these again, because I don't want to shell out the money for GEC KT66's. I wished these would be a little more robust, but I can't really complain that much as they weren't that expensive.