Questions about using KT66's in place of 6L6's

mrid

The Duke Of Trades
Is there anything I should be aware of when swapping out 6L6's for KT66's? I know that the KT66's filament current is 1.4 amps and the 6L6's filament current is 0.9 amps, but I have no idea how that difference would affect an amp (I'd guess there would be a heat increase?). Also, I've heard that KT66's shouldn't be used in amps with plate voltages in excess of 450v. Am I correct in assuming that any amp designed for 5881/6L6 would work fine with KT66's?
 
Re: Questions about using KT66's in place of 6L6's

one thing to be aware of is the physical size of K66s ... the actual spec for the on center spacing is actually wider than Fender's spacing, although people swap them anyway
 
Re: Questions about using KT66's in place of 6L6's

mrid said:
Is there anything I should be aware of when swapping out 6L6's for KT66's? I know that the KT66's filament current is 1.4 amps and the 6L6's filament current is 0.9 amps, but I have no idea how that difference would affect an amp (I'd guess there would be a heat increase?). Also, I've heard that KT66's shouldn't be used in amps with plate voltages in excess of 450v. Am I correct in assuming that any amp designed for 5881/6L6 would work fine with KT66's?


You will have to increase the bias and you might have to add a filament transformer due to the extra filament draw...what amp are you trying to do this in? Also like Curly said the size of the tube it self might be a problem...in fact the 1st re-issue Marshall BluesBreakers were too small to use KT66 tubes!
 
Re: Questions about using KT66's in place of 6L6's

You might give Bob at Eurotubes a call or email regarding this. I know there's a section on his website talking about this very subject, and even if you're not purchasing anything from him he loves to talk about tubes and amps, and is a pretty knowledgeable guy.

Scroll down to the bottom for contact info.
 
Re: Questions about using KT66's in place of 6L6's

the guy who invented fire said:
You will have to increase the bias and you might have to add a filament transformer due to the extra filament draw...what amp are you trying to do this in? Also like Curly said the size of the tube it self might be a problem...in fact the 1st re-issue Marshall BluesBreakers were too small to use KT66 tubes!

The amp is a Yamaha T-50.
 
Re: Questions about using KT66's in place of 6L6's

Thats a great amp... You might want to E-mail Soldano about using KT-66's in that one...
 
Re: Questions about using KT66's in place of 6L6's

mrid said:
The amp is a Yamaha T-50.


those a really good amps for the money...I would contact either Yamaha or maybe Soldano...altough I called Soldano once about them and they acted like I was wasting their time. If memory serves me it has 2 6L6's and 7 preamps tubes...all 12AX7's I belive...the tranny might be pretty much tapped on the filament windings, and going to a set of KT66's might do the amp in...let me look through some schematics I have, and If I still have one for that amp I'll let you know what I find!
 
Re: Questions about using KT66's in place of 6L6's

I called Groove Tubes on this issue one time and they told me that their KT66HP's were just direct drop ins for 6L6 amps and not to worry. Your mileage may vary.
 
Re: Questions about using KT66's in place of 6L6's

the guy who invented fire said:
I would contact either Yamaha or maybe Soldano...altough I called Soldano once about them and they acted like I was wasting their time.
Wow. My experience was very different. I contacted them about a depth mod and they offered to do it for $75--pretty reasonable IMO. Bill Sundt (their support guy) then suggested that I could do it myself if I was comfortable with poking around in the amp. He emailed me the schematic and then answered a couple of follow-up questions.

Maybe you caught 'em on a bad day...
 
Re: Questions about using KT66's in place of 6L6's

Curly said:
one thing to be aware of is the physical size of K66s ... the actual spec for the on center spacing is actually wider than Fender's spacing, although people swap them anyway


Exactly how I just scooped a quad of KT-88s from a guy....they were too big for his amp; should fit nicely in the Hiwatt !!! :)

Hey MRID....if you don't have tubes yet, I was in Guitar Center last week & they had 3 matched sets of Groove Tube KT-66s in their clearance bin for $24.99. Let me know if you would wanna try them & I'll grab 'em for ya'.
 
Re: Questions about using KT66's in place of 6L6's

I put KT66HP's in my SLO-100. No sweat! The amp was very sensitive to bias adjustments, and early on I had it set too high at 42ma. It wasn't a problem technically, it just didn't sound as sweet as when we backed it down to 32.5ma. Call Soldano and ask about the plate voltage question to make sure, however.
 
Re: Questions about using KT66's in place of 6L6's

I don't know the answer, either, but I agree with the concensus to call Soldano. Mike & company have always been totally helpful with me.
 
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