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EL84 and true pentodes interesting question

66.117.237.162

Guys,

I have noticed something interesting about the use of EL84s and a Russian variant that I'm using that is a true pentode (no internal cathode to grid 3 connection). I have my sockets connected to run either type of valve (grid and grid 3 wired together)

Here's the interesting part..

When using the Russian Pentode, I get a very loud thump/fart sound when I power down the amp. When using EL84s, no sound at all when I power down. Because of the socket wiring I can't imagine how they can be electrically different. I have not yet had a close look at the Russian pentode data to see if there is something significantly different from the EL84..

Thoughts??

Stuben

Follow Ups:

Pedantic note - Paul Joppa 19:21:15 04/25/14 (1)
A true pentode has three grids, whether or not the suppressor grid is internally connected to the cathode.

The alternative is a beam tetrode or "kinkless tetrode" such as the 6L6 or KT-66. The distinction was once important and patent battles were fought. Nobody really cares any more, since they work pretty much the same.
- RE: Pedantic note - Stuben 05:35:39 04/26/14 (0)
  Paul,
  
  Thanks for the clarity...I had the hear the term used prior for valves with out the internal connection.
  
  Stuben
RE: EL84 and true pentodes interesting question - Stuben 18:16:05 04/24/14 (0)
Sorry...Cathode to G3...typo
Why would you tie G1 & G3 together at the socket........ - vinylkid58 16:03:02 04/24/14 (1)
Shouldn't you tie G3 to the cathode at the socket to emulate the internal connection of the 6BQ5? We'll assume the Russian tube you're talking about is the 6p15p.

jeff
- RE: Why would you tie G1 & G3 together at the socket........ - Stuben 18:15:08 04/24/14 (0)
  Yep I tie the cathode to G3.
  
  Stuben
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