Globes only, directly or indirectly heated. Highest I've noticed is the 56 which has a mu of 13.8. I've seen pentodes with much higher mu but only when used as pentodes and when triode wired their mu is lower than the 56. Can't say as though I've done an exhaustive search, though.
Wondering if there's anything between 13.8 and, say 100 mu.
Wondering if there's anything between 13.8 and, say 100 mu.
What do you mean by "Globes only"? I know the word globe as a spherical scale model of Earth or some other planet.
Early vacuum tubes used glass shapes developed for incandescent lamp "bulbs". Globe to shine all around.
102D and 102F may work though the envelope may be considered to be ball shapes rather than globe.
Back 90 years ago, they would use transformer coupling to get more gain out of the early tubes.
Some globes are offered in ST shape to avoid the microphonics. Not having the top supported caused some problems.
Back 90 years ago, they would use transformer coupling to get more gain out of the early tubes.
Some globes are offered in ST shape to avoid the microphonics. Not having the top supported caused some problems.
I recalled the Rice-Kellog amplifier used an early hi-Mu tube. I had to crawl and beg at a university library annex to see a copy. It's on the Web now.
http://www.one-electron.com/Archive...nt of a New Type of Hornless Loud Speaker.pdfTube is P.R.1-c. Perhaps related to this guy:
https://www.radiomuseum.org/tubes/tube_pr1.htmlMy digging at the time suggested it was really an experimental type, not production, specs not published.
If you are intensely curious, the amplifier was preserved in Schenectady. The museum has confused the voice coil and field coil, so...
https://edisontechcenter.org/CWrice.htmlExperimental tubes may not have permanent markings.
http://www.one-electron.com/Archive...nt of a New Type of Hornless Loud Speaker.pdfTube is P.R.1-c. Perhaps related to this guy:
https://www.radiomuseum.org/tubes/tube_pr1.htmlMy digging at the time suggested it was really an experimental type, not production, specs not published.
If you are intensely curious, the amplifier was preserved in Schenectady. The museum has confused the voice coil and field coil, so...
https://edisontechcenter.org/CWrice.htmlExperimental tubes may not have permanent markings.
If a somewhat bigger sized triode also counts, than the TA08/10 transmitting triode (μ = 50):
TA08/10 Radiomuseum
TA08/10 Philips
If triodes with a top connection also count, than the A235/A435/A635 (μ = 35):
A235 Radiomuseum
A235 Data
A435 Radiomuseum
A435 Philips
A635 Radiomuseum
A635 Data
TA08/10 Radiomuseum
TA08/10 Philips
If triodes with a top connection also count, than the A235/A435/A635 (μ = 35):
A235 Radiomuseum
A235 Data
A435 Radiomuseum
A435 Philips
A635 Radiomuseum
A635 Data
Early high mu triode usually has high plate resistance.
For example my beloved 841/VT51 (mu:30) has 40..63k (recommended load 250k).
Globe version ones are more prone to microphonic than ST version ... and nowadays expensive as hell. :-(
For example my beloved 841/VT51 (mu:30) has 40..63k (recommended load 250k).
Globe version ones are more prone to microphonic than ST version ... and nowadays expensive as hell. :-(
The 2A6 has a triode section with a gain of 100. There is also a directly-heated triode with very high gain but I can't track it down right now...
Was the 2A6 ever made as a globe? The earliest data sheet I've seen is dated 1941. Although I didn't look closely, it seems to resemble the octal 6SQ7 - a single 100 mu triode with two diodes - except that it's in an ST bottle with a top cap.
Is there a list of "Globes" somewhere? Obviously some folks are not clear on the term and others can't remember all the types ever made.
High gain:
Cascode or positive Fdbk around 2 tubes.
Could also make a positive Fdbk ( less than unity loop gain ) cross-coupled splitter. (two triodes)
Cascode or positive Fdbk around 2 tubes.
Could also make a positive Fdbk ( less than unity loop gain ) cross-coupled splitter. (two triodes)