6AU6

[Justin Thomas]

If I suspect a tube being a problem at stage volume, I put a loop in the amp & check it at stage volume. And even then I will always try it in a "function" slot before trashing it.

Power tubes are more problematic obviously; the other ones I have a lot of issues are tubes made for switching. Usually those are the 4-digit "industrial " types where the specs SEEM "identical" to a 12AX7, 12AT7, or 12AY7. But if you plug it in an amp, it's terrible. I've learned to check the datasheet for the particular type instead of trusting a vendor who says it's a direct substitute for a 12A_7. 5814s as 12AU7s I recall being especially problematic.

Jusrin

[Chuck H]

If I suspect a tube being a problem at stage volume, I put a loop in the amp & check it at stage volume. And even then I will always try it in a "function" slot before trashing it.

This^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Good tubes are expensive. If I have an old Sylvania or Mullard tube that I know will live for almost the life of the amp, but doesn't play well in the early gain stages I will usually at least try to find a home for it where any marginal microphony won't cause a problem. New production tubes don't hold up as long as the "golden age" tubes. So I try not to be cavalier about discarding them.

[J M Fahey]

A Brazilian friend of mine makes Guitar amps using **only** TV tubes.

This one is an 8W head using 2 x PCL84 + 1 "mystery tube". (lettering erased but it works)

[Chuck H]

A Brazilian friend of mine makes Guitar amps using **only** TV tubes.

This one is an 8W head using 2 x PCL84 + 1 "mystery tube". (lettering erased but it works)

That looks like a lot of iron for 8 watts. Not "my" tone per se but it's definitely doing what tube amps do



EDIT: I was trying put my finger on what I meant by "doing what tube amps do" and while I don't have a proper technical description I'd like to bounce it off members here and see what happens.

Tube amps have more of a tendancy to "get under the note" (or chord) if that makes any sense. Like they grab the input in an excited way and it sounds more dynamic and lively. Most tube amps do this, more or less. The above amp does it well. I think it has some to do with tube preamp circuits usually being self biased and the way voltage swings change operating conditions. But somehow it goes beyond mere compression. That is, instead of exited dynamics being made more subtle, subtle dynamics seem to become exited. And I haven't heard a SS or digital amp that does this like tube amps do. I know that anything can be technically explained if observed under test. Somehow I don't feel like everything that makes tube amps special has been caught on the bench yet. Which helps lend an air of alchemy to the genre that I like. Tube amps have held on as the top choice for a VERY long time and I don't think it's just habit or nostalgia. There's a real (if subtle) difference that players can at least feel even if listeners don't notice. Like instead of just playing through the amp, the amp is your buddy and actually helping you play.