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Hey,
Has anyone used the Groove Tubes KT66-HP in a 6L6GC amp? Has it worked okay? I'm looking at getting a pair of KT66's for my Hot Rod Deluxe. However, 6L6GC's only require 0.9A heater current, while KT-66's require 1.3A Ih. According to Justin Holton (of the Unofficial Hot Rod Deluxe Owner's Guide):

Originally Posted by Justin Holton on KT66'sNormally these tubes draw more heater current (KT66 Ih = 1.3A, 6L6GC Ih = 0.9A), so they could overload the power transformer. I've heard that Groove Tube's GT-KT66-HP draw the same amount of Ih as a 6L6GC, though it's impossible to say for sure since Groove Tubes do not supply spec sheets for their tubes. Still, I haven't heard any problems from the Hot Rod users who use them.

Can anyone confirm this? I went to the Groove Tubes site, and found out that their KT66-HP is a copy of the G.E.C. tube and can take up to 525V on the plates (more than normal KT66's IIRC). I couldn't find a spec sheet for the GT, but I found one for the G.E.C. which says that the approx Ih is 1.3A, like normal KT66's.

I'm not quite sure if the transformers could handle an Ih of 1.3A. Also from Holton's site:

Originally Posted by Justin Holton on the HRDx's transformersWhat is known is that because the Hot Rod uses a bridge rectifier instead of a full-wave tube rectifier, Fender can get away with using less copper in their transformers. This translates into lower thermal tolerance, and means the transformer is prone to overheating if the specs are exceeded, even by a narrow margin.

Would it be safe to use tubes that run even .4A over the 6L6GC's Ih?

Thanks,
Pras.

im interested in this too

Bump.

I'm curious also, what do those tubes do to the tone of a HRDx. I just put some JJ 6V6's and ECC83S's in mine and it sounds pretty sweet.

somebody help?

dont know about the hot rod, but in my '82 jcm 800 i replaced the 6550s with gtkt66hp running hot!! 475v or so and i havent had any problems, not sure about a newer fender design. ive heard of plenty of people doing it and ive never heard of anyone having a problem

... given the HRD and most of Fender's current lineup...which is already based upon the quot;barely adequate enough to do the jobquot; theory....I would highly suggest avoiding trying this.....

Why????.... look at it this way, replacement tranny for a HRD is about $65...(not bad, huh?) while a tranny that would actually handle the current goes for about $150.....
I can assure you, the price difference reflects quot;capabilityquot;...

As far as tone.....that is subjective...I've heard Kt66's sound both really good and really bad!

FWIW...
...and no offense meant for current Fender owner's...like all amps, they're not what they used to be!

Jeff Seal

I've used KT66HP's in a Fender Bassman RI, an older Pro Reverb, and several boutique amps that have crossed my path. I ran this buy myles at Groove Tubes, he says they're a direct drop in for any amp running 6L6 big bottles.

They sure did warm up the Bassman RI. Your mileage may vary, but I'd trust Jeff since he works on amps for a living.

I think I've got a book that talks about a mod to achieve it... Let me check it when I arrive home.


Originally Posted by Jeff Seal... given the HRD and most of Fender's current lineup...which is already based upon the quot;barely adequate enough to do the jobquot; theory....I would highly suggest avoiding trying this.....

Why????.... look at it this way, replacement tranny for a HRD is about $65...(not bad, huh?) while a tranny that would actually handle the current goes for about $150.....
I can assure you, the price difference reflects quot;capabilityquot;...

As far as tone.....that is subjective...I've heard Kt66's sound both really good and really bad!

FWIW...
...and no offense meant for current Fender owner's...like all amps, they're not what they used to be!

Jeff Seal

Exactly why I asked...thanks for the response.Originally Posted by Scott_FI've used KT66HP's in a Fender Bassman RI, an older Pro Reverb, and several boutique amps that have crossed my path. I ran this buy myles at Groove Tubes, he says they're a direct drop in for any amp running 6L6 big bottles.

They sure did warm up the Bassman RI. Your mileage may vary, but I'd trust Jeff since he works on amps for a living.

Hmm...if the Bassman RI is an accurate RI, it should probably have good transformers that can handle the extra current if necessary. I'm not so sure about the HRDx.

The thing that worries me is that GT says they're a copy of the GEC KT66, but that has a 1.3A Ih. If it really were .9A, wouldn't they want to advertise that?

I'll run an email through GT and see what they have to say. In the meantime, any HRDx owners on the board use these tubes? How've they worked out (not in terms of sound, but in terms of quot;have they workedquot;)?

I have heard that GT dosen't supply any specs about their tubes. If I'm right then I guess you will never know until you try them out. Drop some 6V6's in their anyway.

arent the GT kt66's the gimmick one's that are 6L6's with a coke bottle glass? The real one's are made by Saratov i think.