Question on tube types. Wing C SED EL34 to replace stock tubes

[beaubrummels]

Re: Question on tube types. Wing C SED EL34 to replace stock tubes

Sometimes tubes with beam forming plates are called beam pentodes, instead of beam tetrodes or in Europe kinkless tetrodes. This is because the beam forming plates perform the essentially same function that a suppressor grid performs.

Strictly speaking a tube should have a suppressor grid to be a pentode. The suppressor grid is the 5th element. I guess we could stretch the definition a bit to say that beam forming plates are a 5th element as well. But this also why there is so much confusion about what is a pentode and what is beam tetrode.

They don't sound exactly the same. Beam tetrodes have more open mids, and pentodes have more dense mids.

I was reading up on the history of the 6CA7 and I’m starting to think the term ‘beam pentode’ may have came about to disguise the fact that the early Tung-Sol and Sylvania/GE 6CA7 was actually a true pentode with a suppressor grid, but had a beam power anode plate (which wrapped around and hid all the internals), possibly trying to get around the Philips pentode patent (marketing, as JMP pointed out). The 6CA7 was designed to be a drop in replacement for the EL34, as a cheaper domestic alternative and avoid the cost of import at the time.

 

[JMP/HBE]

Re: Question on tube types. Wing C SED EL34 to replace stock tubes

Well so, it went away when I disconnected it from the attenuator and plugged it right into the cab. so basically, it smelled a little when the vol was on 6 with the attenuator vs on 1-2 plugged into the cab where it didn't smell.

I'm going to test this again tonight. I will check the back for red plating and see.

I called my local music shop to see if they'd let me drop it off for biasing since their showroom is closed but they're still operating, but they're not taking any new jobs. stinks.

Also, I gotta be honest maybe what I was smelling was just the "Tube amp smell". Can't remember tbh, it was for like 2 seconds. Also how does the amp being made in Mexico factor in lol.

Now you're minimizing and downplaying your first response. If it smelled like hamburgers im sure you would have said so.
Then pretending hamburgers really smelled like pizza doesn't make it so.

Nothing on earth smells like "burning" but "burning".

 

[chillytouch]

Re: Question on tube types. Wing C SED EL34 to replace stock tubes

So I played for an hour with the amp hooked up to the waza. Master volume a little below noon. No burning smell. I looked through the back and the gray metal plate was not glowing, you could definitely see the filaments glowing orangeish/red underneath.

These tubes definitely sound awesome though. I think part is the tubes, and part is I also get the el34 breakup sound by using the waza cause I can raise the volume a bit more than I usually can.

Thanks again all I appreciate the feedback/help. I'll definitely get it biased when I can, who knows maybe a tech can get it hotter and make it sound even better.

 

[JMP/HBE]

Re: Question on tube types. Wing C SED EL34 to replace stock tubes

If you really like your amp & want to keep it i would not play it til you get it biased.
But ive got 4 decades of tube amp experience & bias my own.

What do i know ?

 

[dave74]

Re: Question on tube types. Wing C SED EL34 to replace stock tubes

Bias is like the amp's blood pressure. If it runs wild it can easily have a quick and deadly heart attack!
It's even more critical (I've been told) in an amp with multiple pairs of power tubes, due to the balancing issue, which I think relates to the transformer.

I know basically nothing on this, but get it biased accurately before using it anymore. it's too great of amp to risk stressing it.

 

[beaubrummels]

Question on tube types. Wing C SED EL34 to replace stock tubes

Thanks again all I appreciate the feedback/help. I'll definitely get it biased when I can, who knows maybe a tech can get it hotter and make it sound even better.

As others have tried to point out, bias is not chiefly about sound, it’s about getting all the components (particularly the tubes) to function at the correct operating levels and not do damage to the tubes and other components of the amp. If you run that amp with the tubes biased incorrectly, at minimum you are shortening the life of the tubes and possibly doing damage to the amp that is expensive to repair. It’s already running an amp hard when you’re using a power soak between the output and the speakers. You can do what you want, but if it were mine, I wouldn’t power it on again until getting it biased, and I certainly wouldn’t run it hot into a power soak.