Buy a quad of Penta Labs' solid-plate Shuguang KT88's. This is a copy of the famous Genelex KT88. Price was $29 each, last time I checked, and it's a wonderful tube for the SLI-80.
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Actually the Svetlana KT88's are known primarily for their warmth. I have been using the Svetlana KT88's and EL34's in my Prima Lunas. After these, I would try the Electro-Harmonix. Tried the the JJ Teslas (blue glass no less) and did not like the sound ... not warm at all. The Chines Genelex copies are nice as well, not as warm sounding as the Svetlanas, but pretty nice.
I use the JJ Tesla KT88 and like them a lot. I would suggest trying the EH KT88. I have not tried them, but all the other EH tubes I've tried (12AX7, 6922) have been over-achievers. The 6922 gold pin was better than my Siemens NOS tubes that they replaced. The JJ's are excellent all around, but I think they are more dynamic and fast than warm, which is what you're looking for. The EH KT88's are much less expensive. I plan to try them next, myself.
Does Cary have a recommendation? They'll know if a certain tube is a better match.
If You have tried the JJs EL34L then I take it your amp can take EL34s. If so, then you might want to try the JJ KT-77s despite whatever controversy over quality you may have heard, they have worked well for me and my friends. I find that they are very big and rich sounding. It may be the warmth you are looking for. Then again I like the Blue Glass JJ EL34L, I am using them right now. Try www.eurotubes.com he has them in matched quads for a low price and lightening quick delivery. I have no affilation with him just a happy customer.
Thanks to all. I have heard of the JJ Tesla KT-77s as an EL34 alternative. When I was trying EL34s (which turned out not to have enough power for my system's needs), a dealer suggested I try the KT77s. I'll go back and look them over, see what the power ratings are. If I use the lower-powered tubes, I can perhaps compensate by switching the amp to ultralinear mode, which allows for more power though it usually doesn't sound as good as triode. Regarding the issue of KT88s--Cary ships this amp with the Electro-Harmonix tubes and I've heard some on their staff (and Kevin Deal of Upscale Audio) likes them a lot. I'll call them Monday for a view. Very nice of all of you to respond with your suggestions.
Aloha Artmaltman! Actually, I had the EL34s in the Cary while using three different players--the CAL CL-15, a Modwright Sony 999ES (Tung-sol tubes), and a Lector 0.6T. The edginess/glassiness occurred with each of them (though less so in the CAL than the other two), which is one reason I thought to switch back to KT88s in the Cary.
Regarding power tubes, I've spoken with one dealer, eurotubes.com, who said emphatically the KT77 JJ Electronics tubes ARE NOT "JJ Tesla" as I have been used to calling them, but are made in Slovakia in a factory using some old Tesla equipment. He also said that the JJ Electronics E34L is the tube with more power--about 15%-20%--than the EL34 and not the KT77 they make, which is based on a GEC KT77 and has the same power rating as an EL34. I'm just reporting his comments, though, as I have tried none of these.
I've tried Chinese EL34s (stolen from my own PrimaLuna One) and RFT EL34s. I wouldn't say those were warmer, but they did create interesting changes in spaciousness of sound and air--particularly the RFTs. Like I said above, the drop in power also caused glassiness in massed trebles, so I switched back to Svetlana KT88s. Kevin Deal, though, of Upscale Audio gave the same recommendation regarding warmth, as he says the Svetlana Winged "C" KT88 is the warmest of its kind and the only way to improve on it is to go to Svetlana (SED) EL34s. Thanks for the view.
Art Maltman's observation that the glassiness in my system I thought I was hearing with Svetlana KT88s was not the power tubes but rather the sound of the CD player provoked me to reconsider my entire approach to the issues of warmth and glassiness. Since we exchanged messages in the thread, I've made many changes in my system. I'm still using the Svetlana C KT88s, but I bought a new Cary 303/300 and rolled Mullard longplate 12AU7s into it (replacing stock EH tubes). I've also switched input tubes in my Cary SLI-80 to Bugle Boy 6DJ8s and NOW I have the sound I've been after--a warm midrange with a clear, airy top-end in the massed vocals of choirs. The Bugle Boys are the most recent change, and they replace a whole sequence of fine input tubes (Mullard 6DJ8, Siemens & Halske 6DJ8, Philips 6922 SQ, Philips 7308, Mullard E188CC/7308)--all very good, but not as airy and spacious as the BBs. Art Maltman's observation that I may have been describing the sound of the Cal player rather than the KT88s was entirely correct--it was the CDP that was the limitation of the system (also with JoLida, Lector 0.6T, and Modwright Sony 999ES). I decided to upgrade my target price-point therefore, and I couldn't be happier. His suggestion/criticism/observation was the critical point at which I began to reconsider my approach, and the resulting chain of changes has given me a system that pleases me a great deal. [As a side-note, I want to mention I've acquired a quad of 50s Tung-Sol 6550s that are wonderful with operatic voices, especially with lyric sopranos; and I have also read that Western Electric is planning a re-release of the Genalex KT88 once made by Marconi-Osram.] Many thanks to all for your feedback. It's a perfect demonstration to me how well Audiogon works as a site for hobbyists who seek help and then, like magic, receive it.