Tubes are supposed to last for YEARS.
Are you in a hurry? I suggest you buy a full set of cheap used tubes, so, for the rest of your life, you don’t live without music, while searching/deciding on the next set you will use. Time is a luxury, time for research, find most comfortable source, wait for a great price .....
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2 matched pairs?
from your stock? or buy from a source with matched pairs ready to ship?
If they have matched pairs, they have a tester. Perhaps, for a small premium, they will test and find two pairs for you, if you can wait.
Ignoring all the other electrical measurements, for me, it comes down to left/right balance.
I just lost left channel, was a blown 6sl7. Happily, when I searched my boxes of randomly acquired tubes, I had two GE 6sl7’s, used, in my collection. I replaced the blown one, oh happy day, and, l/r balance was terrific. Time to search ....
GE 6sl7 is short, so, I decided, while waiting for the two matched pairs I ordered, to put the other short GE in right channel. Nooo, right channel volume way down. Original tall one back in, l/r equal. No way a matched pair, but ..... especially temporarily.
btw, I had 4 look alikes, 2 6sl7 and 2 6sn7. preamp tubes before KT88’s. I mixed them up inadvertently not long ago, left channel was weak, yanked for testing, realized they were different. They look identical. I purposely ordered chrome top 6sl7’s so I will never mix them up with the 6sn7’s.
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I have my own tube testers. The little cheapo one always gives the same relative strength answers as the big one.
not to buy this one, but this is the model
https://www.ebay.com/i/323712928966?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=323712928966&targetid=858380238160&device=c&mktype=pla&googleloc=9003512&poi=&campaignid=6470719340&mkgroupid=77931583832&rlsatarget=pla-858380238160&abcId=1140476&merchantid=115026223&gclid=CjwKCAiA98TxBRBtEiwAVRLquwrExfEjEkByy2tj4bjcKQGCxdmf1PYLG13wl2I98eSMoSUf7BXZoRoCMOsQAvD_BwE I love this little thing.
