Old Metal (envelope) tubes

[Masco]

I have no experience with these, but I’ve run across some NIB 6v6 and 6l6. Would love to hear your thoughts about using these. TIA.

[martin manning]

They’re fine. Just be aware that max dissipation limits may be lower than the newer glass envelope versions, so check the data sheets.

[pompeiisneaks]

I had some issues with a pair once, but they were bought at a ham radio fest and cheap and I knew they weren't NOS, just OS. They were a bit harmonic, and I thought someone said the metal ones tended to be more so than glass, but I may have just gotten a bad pair. (I used them in a Gibson EH-185 clone I built)

~Phil

[Stevem]

I think there may also be limits in how they could possibly be mounted in horizontal potions also.

[Tony Bones]

Be aware that the metal case is connected to pin 1, so it's not safe to use that pin as a tie point for grid or screen resistors.

[tubeswell]

Be aware that the metal case is connected to pin 1, so it's not safe to use that pin as a tie point for grid or screen resistors.

The case pin can be used for an earth connection to shield the tube.

[pompeiisneaks]

In fact it's mandatory on the 6SQ7 metal envelope tubes i had in that gibson and highly recommended with any of them, they added to the microphonics.

~Phil

[Andy Le Blanc]

There used to be metal type calibration tubes, keep your eyes out for those, a calibration set is a pretty penny.

The grounding pin on metal pentodes , 6sj7 can be very useful. They can be microphonic and NOS can be leaky .

But every now and again I've found strong and nice sounding metal types, I almost have enough for an all metal guitar rig.

They accumulate at tube retailers too, if they test well and you use design center voltages, as opposed to design max, they're fine.