Retubing dilemma

@rodman99999
@hilde45

hilde, rodman is right... kt77 is an el34 variant, kt88 is a 6550 variant, very different tubes different output power different sound - some amps can run both but most amps are made for one or the other -- as a generality, el34’s are less powerful but sweeter sounding, 6550’s have about 40-50% more output capability and better bass control generally a bit less tubey sounding

both are tetrodes/pentodes but can be run in pseudo triode mode for less power and more sweetness

agree modern russian made gold lion kt77's are among the best el34 variants, with the also russian made mullard reissue el34b's or tungsol el34's (same tube different labelling) a close second

Thanks for the correction. OP, ignore what I said unless your amp can run those GL KT-77s.

Still learning...

+1 for the Gold Lion KT77’s; and here’s how I got there:

I was looking for an alternative to stock EL34’s, so first contacted Kevin Deal at Upscale Audio to get a recommendation. I explained my sound objectives … the ability to convey emotion, natural tone, with good low-end slam and transparency. Was there such a tube?  Oh yeah. The KT77 was the clear choice, but I still spent time checking out a bunch of reviews – first on Upscale, and then on TubeStore.com  

Since I have a drawer full of “spares” from tube rolling, I wanted a bit more validation. This review sealed it.  It reviews the “EL34 Family” of tubes. https://wallofsound.ca/audioreviews/tubes/el34-tube-comparison-with-tubes-supplied-by-www-thetubestore-com/

Installed the KT77’s and haven’t looked back since. I concur with all those 5-star reviews. 

The 6SN7 tubes are another story. @jkontuly my suggestion is to put in the Gold Lions. If you basically liked the overall sound you were getting before, compare that and then decide if KT77's give you enough of an improvement in sound quality. If not, and you want more of what the Shuguang Black Treasures offer, go ahead and get the full set. Hope that helps.

Happy Listening!

@strateahed Great link. It seemed from what others said that this tube won't substitute? (Or maybe needs to be checked?)

In the link you provided, I liked this paragraph:
"1st Place (tie):  Genalex Gold Lion KT77   ($49.95 each. All prices in USD) Essentially, a perfect tube. Quiet and unfussy. It works with every musical genre. The sound quality is right up there with the Shuguang black bottles but this comes at half the price. This tube does it all–huge reserves of power and headroom, a massive airy soundstage but in this case airiness is not a sign of thinness or an unsaturated midrange. For hard rock and complex orchestral music, here’s your tube. It’s no slouch with jazz but tone freaks seeking an even more saturated midrange might prefer the Mullards or the Tung-Sols. Highs are unusually detailed and well defined but never glassy or edgy. This tube excels in scraping up micro details. The bass is deep and dry, not quite as punchy and elastic and ripe as the SED Winged C or the Tung Sol EL34B, but bone dry. There is a touch of warmth but this tube is not a tone freak’s dream. It’s more neutral. This is the only serious challenger to Shuguang and Psvane’s best offerings, and again, it’s half the price. My vote for the King of the EL34-family."

Aren’t Red Ruby, Shuguang rebranded? I’m telling you the Red Ruby is a true KT77 killer.. 1/2 the price and every bit the quality. Never had a flame out yet.. LOL. They will scare the crap out of ya.. LOL I had a cable drop, that caused a tube failure.. LOL dog was barkin’ rabbit was jumpin’, wife was screemin’. I was laughin’. Still brings a smile to my face.. 15K cable drop..The words I said that day.... Every commandment, less killing...was broken.. I say that with great reverence.

Regards