[earplay]

Found the following warning on the Glow amp site's home page:

"European EL84s differ in design from their Chinese and Russian counterparts in one important respect:  On all European manufactured EL84s, pins 1 and 2 are connected together inside the tube envelope. Chinese and Russian EL84s do not internally link the pins 1 and 2.  Therefore, when a European manufactured EL84 is plugged into the '09 GLOW amp, the additional connection within the tube envelope in the European design is likely to cause premature failure of the tube.

For the above reason, it is highly recommended that you NOT use European tubes in the 2009 Amp One, as you will likely permanently damage your tube and possibly the amplifier.  All Russian and Chinese manufactured EL84 tubes are compatible with the Amp One."

I wrote Glow to ask if the above applied to amps manufactured prior to 2009, but no reply yet. Also, there is no mention of American made tubes. To further complicate matters, they use the term EL84 ambiguously.

Does anyone know what would actually cause such premature failures of EL84's? The site doesn't explain this?

[Niteshade]

Pins 1, 6 & 8 supposedly do not go to any internal components in an EL84. If these amps are point to point wired, the manufacturer could be using the unused pins to hold resistors, etc... That can cause allot of problems if some tube was paralleling pins internally not normally used.

[earplay]

Thanks, Niteshade,

Glow replied and said that the warning applies only to 2009 versions of the amp, not earlier versions.

Now, how would a pin on a tube "hold" another component? I mean, I don't see anything dangling from the pins. Yes, I'm that uninformed!   

I suppose you mean some kind of internal connection, but then I wonder why would you want to connect to an otherwise unconnected pin.

By the way, I've ogled your stuff more than once.   

[Niteshade]

I see what you're saying. Unused pins correspond to unused socket contacts underneath. Sometimes it is useful to use them as a place to attach components- like a terminal strip. Real estate is prime under there and anything that can be used to avoid clutter, such as an extra post to hook on to is a blessing.

[earplay]

Thanks, Niteshade,


Now I understand. Now it makes sense.

[Tubo]

I am glad I got a 2008 version of the amp! I am using RCA NOS EL84's and love the sound. They make my LS3/5A's sing!

[Ericus Rex]

I've seen a couple of amps use the connection for Pin 6 on an EL34 as a soldering post.  This is quite clever but possibly dangerous.  Doesn't Tung Sol (the reissues, at least) connect pin 6 on the tube to the metal base of their 6550 (or is it KT66...)?  If that is true they could inadvertently feed voltage to an exposed external tube part.  Am I wrong about this?

[Niteshade]

Some 6550's have pin 1 connected to the base. The only possible reason for this would be to use it as a shield by connecting it to ground.