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How much current can a 26 tube take?

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Posted on October 20, 2020 at 14:56:43
andy evans
Audiophile

Posts: 4378
Joined: October 20, 2000
 The book ratings are 180v maximum, but I can't see a maximum for current or dissipation. Under characteristics we have 180v, 6.2mA, -14.5v. So dissipation here is 1.1W.

But this is a tube with 1 amp filaments. So I'm asking myself why it won't take more than 6.2mA of current? I've used it long-term with 7mA. I'm just wondering how much more is possible when using it as a driver tube?

By accident I drove a pair of 26 at 120v, 13mA, -0.12v for 20 minutes. Sound was a little overloaded but mostly OK. Admittedly a very odd operating point, but there was 13mA going through the tube. I'm not sure what this says about taking the current above 6.2mA. The tubes are fine and now working normally.

 

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RE: How much current can a 26 tube take?, posted on October 20, 2020 at 21:05:30
Paul Joppa
Industry Professional

Posts: 7295
Location: Seattle, WA
Joined: April 23, 2001
 At that time (introduced in 1927), maximum ratings were not generally specified, other than plate voltage. I would not want to exceed that rating on such an old, classic tube!

It's basically an 01A with a bit more transconductance - the filament power is nearly the same, but it's oxide-coated, not thoriated tungsten. Oxide filaments were pretty new in 1927 - the 12A had the same filament power in 1925. By 1930 the Type 30 (another near-clone of the 01A but with 180v max plate voltage) consumed 1/10th as much power.

In any case, the plate resistance limits the plate current in practical applications.

 

RE: How much current can a 26 tube take?, posted on October 21, 2020 at 14:16:13
drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003
 Would be great if you could get more drive (Mu ) ? out of them ....
.... without losing any of it's clarity !!

Willie

 

RE: How much current can a 26 tube take?, posted on October 22, 2020 at 04:53:37
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 THE factor that controls μ is geometry. Change the geometry and it's not a #26 any more.

JMO, if you want more gain combined with high linearity, use the triode found in the 6SN7 and several other types.


Eli D.

 

go Big, posted on October 23, 2020 at 04:53:07
PakProtector
Audiophile

Posts: 12360
Joined: May 14, 2002
 and Thoriated. Type HY40. Mu is 25, cathode current and plate dissipation are off the scale compared to the 26.

So is cathode heating power for that matter...:)
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: How much current can a 26 tube take? ,,,,Sorry Eli ...., posted on October 23, 2020 at 13:26:34
drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003
A 6SN7 or like doesn't sound like a 26 ...

Willie




 

RE: How much current can a 26 tube take? ,,,,Sorry Eli ...., posted on October 23, 2020 at 19:32:31
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 I didn't say it did. However, it's linear.

Some folks like euphony and other people like honesty. My preference is for the tiniest hint of euphony. I dislike both "icy cold" and "syrupy".


Eli D.

 

RE: How much current can a 26 tube take? ,,,,Sorry Eli ...., posted on October 26, 2020 at 11:17:00
Cleantimestream
Audiophile

Posts: 7550
Location: Kentucky
Joined: June 30, 2005
 sigh, this linearity is markedly less important than the speaker distortion and the venue/room. Why this is not brought forward more often escapes me.

A compression driver typically has ten times less distortion than a cone or dome. These are mere facts. Cones and domes are getting much cleaner if one has 70,000 usd on hand. If I did not prefer to listen in a realistic fashion I would be quite content with Quad ESL 63's which I owned for many years. Because music listening is so subjective and personal I do not question those whom use traditional cones and domes... they LIKE more distortion which is fine with me.

The enjoyment of music is paramount.


The Mind has No Firewall~ U.S. Army War College.

 

or slightly smaller, posted on October 28, 2020 at 03:43:25
PakProtector
Audiophile

Posts: 12360
Joined: May 14, 2002
 The Eimac 24G is only 25W plate dissipation. Takes a bit of power to warm up its TT filament. Mu is ~20 delivered...and plate resistance is about what a 26 has, or an 01A.

http://www.tubecollectors.org/eimac/archives/3c24-24g(44).pdf

Again, if the gain of ~10 is tolerable, there is another TT option; type HY75 by Hytron.

http://www.tubecollectors.org/hytron/archives/hy75.pdf
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

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