What about JJ KT88 tubes?

Try the SED 6550. I like the JJ, but the sound of the 6550 is even better. The GL is a bit compressed sounding with my amps. Not a bad sound, just a little un-dynamic. I like the SED 6550 first, next the JJ, next the Sovtek KT88.

I've been really enjoying the blue glass JJ KT88 power tubes in my Jolida JD-502P amplifier. I've paired them with a pair of Mullard CV4024 type 12AT7 tubes and JJ 5751s. Very clean tone and wonderful bass.

I hope others can give this power tube a try in their amps. They aren't the most expensive tube out there so I'm guessing they may get overlooked by the audio community.

One thing I'm wondering about with these tubes when they are biased. With my Jolida amp as soon as I turn it on the bias lights on the Jolida turn on within minutes. With other KT88/6550 tubes and even the Tung Sol KT-120 power tube the Jolida would reach proper bias in about 20 minutes to 1/2 hour. Has anyone experienced this as well with their amps and JJ KT88 tubes?

I've used Gold Lion KT88s for years with no reliability issues.

I've used JJs (not 88s however, mostly El84s and 6V6s) in guitar amps for years and they're great.

Jedinite24...my 502 bias LEDs vary mightily depending on what time of day it is and what is going on in my house (laundry, dishwasher). None of my tubes drift much but those LEDs have become something of an "available juice" sensor, even though none of my tubes are dying yet. I check things with a meter just to be sure and it's never changed more than a tiny fraction and always well within the Jolida recomended range, regardless of tube type.