What are the operating voltages it subjects your outputs tubes to? If you don't know , what's the amp? Many amps need 7189 spec tubes as they are pushing voltages way above EL84 specs.
I've had good luck with JJ's so far and they are well priced. You can get them for $40 a quad. They are known to take some out of spec voltages too and sound really nice. From what I read on this form and others there is an agreement on this.
There are Russian EV etc. rated tubes which can take even more abuse according to many on the forms. You'll probably hear from many users on the these as they can be quite well priced.
New Sensor's Gold Lions are supposed to sound great for close to 3 times the price. May be best sounding of new production. Don't know if they can take out of spec voltages.
Shuguang Treasure Series has a Pavane T series in the upper price range about $95/Pr. just out which should be sonically great too as the other tubes in this series are well liked on the forms. Can they take out of spec V. is another unknown.
My question for the many amps that need 7189 or higher spec why not make tube adapters to plug in your amp which take the new production 7868 or 7591 tubes which are octals and apparently have close to the same drive requirements as the EL84/7189. Space could be a problem on some so they may have to be sky wired. EH ones go for about $80 a quad and should last for many more hours too at the lower voltages. Plus you could have fair bit more power with adjustments! HH Scott amps specified 7189 tubes and in the later seies went to 7591 tubes with larger output transformer. Their amps ranged from 30-40 W/CH. You would loose a bit in power because of the 7.6-8K ohms input load found on most EL84/7189 amps, but may gain in sonics. I don't think it would hurt sonics going from Tung-Sol's 6.6K spec. for fixed bias. Actually the spec. for Cathode Bias which many EL84 amps use is 9K for Pentode hookup of 7591's. The Tung-Sol specs 23-45W depending on setup and voltages. It is said they run nice and cool in the under 400V range too.
See attachment for specs.
Hope that helps!
Randy
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