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Tube Match question for Tekton Speaker & Dennis Had Inspire Firebottle

Hello fellow ’Goners,

For the past eighteen months and until last week, I had been running a pair of Golden Lion KT88’s in my Dennis Had Inspire Firebottle KT88 SEP. Over the months of reading various sources on tubes, I discovered many kind reviews of the GL KT77 and so I bought a pair a few weeks ago. Installed about seven days ago, I was immediately impressed with the KT77’s enhanced bass, both more full and more nuanced, not to mention the improvement in instrument separation throughout the sound field. Soundstage is also more palpable and some instrument sounds have finally found their "place," if that makes sense.

So, moments ago, I decided to review the spec sheet for the recommended tubes, provided by Mr. Had. Therein I discovered Dennis has sorted his recommended tubes into 8ohm and 4ohm categories. The KT88 is recommended for 4 ohm speakers. I have Tekton Moabs, running at 4ohms, so the KT88 is a good fit. I also noted that the KT77’s are listed in the category for 8ohm speakers. Wow. Not good? I’m not sure. Is this simply a recommendation or are there technical limitations that I’m running through that will damage amplifier, preamplifier (by referential impacts?), or speaker parts in the near or long term?

I’m not sure if I can post a link here, but there is a datasheet download available for the Golden Lion KT77 at the tube store dot com. I will see if I can post the link herein, but I figured one of your techies might have some useful comments and insights into this matter of concern.

https://www.thetubestore.com/lib/thetubestore/genalex-kt77.pdf

Thanks for your time.
listening99
millercarbon's avatar
millercarbon
12,531 posts
 
I would think it would be similar to the situation with 4 and 8 ohm taps where one sounds slightly better than the other but other than that it doesn't really make any difference. Speaker impedance is as I'm sure you know nominal. Not fixed, it varies, sometimes all over the place. So hard to see having anything resembling a problem, but instead only a small sonic preference for one over another, like the way it is with the taps.
oldhvymec
5,101 posts
 
It's the way the valve is voiced. KT88 are just better at deep bass and EL34s are renowned for silky smooth midbass, mids and highs.. Good valve to 60 hz or so and they really start to struggle.  It's harder on the amp too 4 vs 8. Try the 8 ohm tap, won't hurt a thing. Might sound better still. 

Second that little amp may not have the oomph to push KT88 they way they need to be pushed. Two KT88 can hit almost 90 watts when set up in a push pull amp.

Regards
listening99 OP
172 posts
 
The "Firebottle" only has one 'tap.' Dennis claims the unit can drive speakers from 2 to 20 ohms. 

This amp runs low wattage: KT88's push 11 wpc; KT77's push 9wpc.

I assume this could prolong tube life. Also, the Moabs are known to be easy to drive, even at 4ohms. I had them on a Nuforce STA200 for several months and that amp isn't rated for 4ohms, and yet it had little trouble with the Moabs, barely ever growing warm.
oldhvymec
5,101 posts
 
Oh, single tap, early VTL was the same way. They settled on 4.9. The difference is push pull. It is still 9 watts class A I guess. 9 watts can get pretty loud pretty quick..

I'm running Mr. Hads V12r and Six Pac, both fairly low wattage considering the number of valves.

They will run 6V6,6L6,EL34,6550,KT88,KT90,KT99. 2-6 valves per rail, just have to bias at 25-35 mA per valve. 10-110 watts per rail. A or A/B, I love the way they sound pretty simple. I run small planars and ribbons, they are a push pull design, very fast. The speaker and amp are a great match in UL (push pull).. 

KT77 should make those domes sound pretty good. Your running the bass too on that little amp? Your Moabs aren't bi-amp/able?
A lot of drivers to push, wow..:-) I'm guessing they don't dip to low  and are a pretty easy load at close to 4 and maybe rising a bit..

Enjoy.
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