Best low-signal direct heated triodes?

[gentlevoice]

Hi DIYs,

I was wondering what - soundwise - is considered the all-time very best low-signal direct heated triodes?

Any of you have suggestions?

It doesn't matter if they are no longer available - I am mainly interested in comparing their physical design (materials used, positioning of grid, anode, cathode, etc.) for another purpose (plasma-like microphone).

I'll appreciate if you have also suggestions as to where I can find pictures of their physical design on the internet.

Thanks,

Jesper

[andyjevans]

I've been collecting small signal DHTs for over a year and now have boxes full of the stuff. My rank order would go something like

10Y

26 globe
201A

26 ST
01A

31
112A
30 globe


3a5
1G4G
1E4G

rest.

I didn't put in 71A, 45, 46 etc because these are primarily drivers. The 10Y is an incredible tube that can go anywhere in a system, even as input with lower voltage and current.

[gentlevoice]

Thanks! Looks interesting ...

Would you by any chance know where I can see pictures/drawings of their physical design? And maybe a description of materials used?

BTW I did a google search on the Y10 and found this website:

http://www.geocities.com/nikolic_lj_...ctronTubes.htm

Thought I'd mention it in case it is of interest ....

Regards,

Jesper

[ncc]

Hi,

Is there any difference between 10 and 10Y tubes?
I'm planning to make a #26 tube linestage but don't like #26 tube low voltage, hight current heater, so I'm probably going to make a 10/10Y linestage.

[andyjevans]

Datasheets say:
10Y - max voltage 350v 10 watts
10 - max voltage 425v 12 watts

They look pretty identical. The VT-25 is the thoriated filament 10 or 10Y

The VT-25A is a longer plate version.

[kenpeter]

I am seeing here (in spec sheets) astonishingly parallel Mu curves...
Very little lean to the right (if real tubes measure like the book).

As I've been studying, variances in Mu within the tube structure
cause the lean to the right as the lower Mu (remotest) parts of
the triode cut off last, with consequence of unenequal spacings
between curves along a resistive load line.

I see a trend: Flat sheet (rather than radial) constructed triodes
seem to have a lot less lean to the right (at least in the books).
And for the very same reason, the linearity is pretty good.

Any triode can have constant Mu with a constant current load.
Takes something special to have with other types of load lines.

[andyjevans]

It's true that my top three - 10Y, 26 and 01A all have flat plate structures. They do look fairly similar. I've always thought that flat plates were the way to go, though I've liked a few round plates in the past. These days I find the same round plates a little tubby.

[jlsem]

The Y in 10Y means it has a micanol base rather than a plain bakelite one. The VT-25A has a gold-plated grid to reduce secondary emission.

John