Depends upon total dissipation, mainly.

Posted by drlowmu (M) on February 6, 2016 at 18:46:34

In Reply to: Life of a 45 tube posted by PaulF70 on February 6, 2016 at 15:02:55:

Paul,

I learned ( from Dennis Fraker, Serious Stereo.Com ) to set up my DHT finals tubes at a " Golden Ratio " plate dissipation in my DIY amps.

The Golden Ratio is about 62%. So, think of it as a car that can do 100 MPH maximum speed, and run it on the Interstate at 62 MPH. The car will last " for a long time " at THAT speed, as will a 10 Watt rated Type 45 globe, when operated at 6.2 Watts total.

On a 2016 DIY DC two stage Type 45 SE amp, I have calculated 473.11 VDC on the plate, and 236.6 VDC on the cathode, so I am dropping 236.51 VDC P-K at 0.026 A., which is 236.51 times 0.026 A. or, 6.149 Watts plate dissipation, for a 10 Watt ( maximum ) rated plate. Can I get 10,000 hours use? Sure !! How about 20 or 40,000 hours?? I don't know, possibly so.

But run it 250 P-K at 0.035 A. , and you are pulling 8.75 Watts out of the Globe 45....stressful as running your sedan down the Interstate at 87.5 MPH.

My point is this .... YOU can decide how long it lasts, AND ALSO how it sounds, by selecting the op point. I can tell you this, the 8.75 Watt op point, besides wearing the tube out perhaps TWICE as quickly ( as a Golden ratio dissipation ), will negatively SOUND **** STRESSED **** AS ALL GET OUT!!, because the tube IS thermally-stressed.

You are likely a caring and a responsible person, pick your own poison, with the guidelines I follow and have outlined herein.

Have fun.

Jeff Medwin

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Follow Ups Full Thread

Topic - Life of a 45 tube - PaulF70 15:02:55 02/06/16 (10)

RE: Life of a 45 tube - PaulF70 19:29:34 02/09/16 (2)

RE: Life of a 45 tube - drlowmu 08:42:27 02/10/16 (1)

RE: Life of a 45 tube - PaulF70 09:45:29 02/10/16 (0)

Depends upon total dissipation, mainly. - drlowmu 18:46:34 02/06/16 (6)

Yep - Chip647 07:35:45 02/07/16 (5)

Please send me a check for $1,000 Chip - drlowmu 10:35:41 02/07/16 (4)

RE: Please send me a check for $1,000 Chip - Caucasian Blackplate 13:11:02 02/07/16 (3)

RE: Please send me a check for $1,000 Chip - charles1dad 10:52:57 02/09/16 (2)

Yep. (The bet was to the original post, not Jeff's) - Chip647 13:38:05 02/11/16 (1)

RE: Yep. (The bet was to the original post, not Jeff's) - drlowmu 20:16:57 02/12/16 (0)

Follow Ups

Depends upon total dissipation, mainly. - drlowmu 18:46:34 02/06/16 (6)

Yep - Chip647 07:35:45 02/07/16 (5)

Please send me a check for $1,000 Chip - drlowmu 10:35:41 02/07/16 (4)

RE: Please send me a check for $1,000 Chip - Caucasian Blackplate 13:11:02 02/07/16 (3)

RE: Please send me a check for $1,000 Chip - charles1dad 10:52:57 02/09/16 (2)

Yep. (The bet was to the original post, not Jeff's) - Chip647 13:38:05 02/11/16 (1)

RE: Yep. (The bet was to the original post, not Jeff's) - drlowmu 20:16:57 02/12/16 (0)

Depends upon total dissipation, mainly.

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