I have a problem with these pairs. Every 3 months I have to replace them because I find Chinese material that at the slightest discharge even just touching a connected rca they burn out. I was thinking of replacing with 4 transistors. Has anyone already done a test?
I have two 2SC2291 that I harvested from an old Akai amp. They aren't better matched than what you can get buying a bunch of, say, KSC1845 and selecting them, if you have a DMM that measures Beta and Vbe. Thermals won't be as good but you can join them with a cable tie and some thermal paste in between to improve things. What's the application?
the problem is that if you go to measure them they are perfect it does not give me an error. I have the problem after a few minutes of listening. I think that all this old Pioneer generation is defective or just cheap. Unfortunately the problem is that it is a 220 device but we have about 240 V now, so all the voltages are slightly higher and there is no way to lower them unless you restudy the entire pre area