Re: [Harp-L] EL84s

[Frank Evers <frank@xxxxxxxxx>]

Hi

Sorry, but this is simply wrong.

Am Montag, 22. Januar 2007 15:12 schrieb John Balding:
> A triode is a basic tube design which incorporates a cathode, a
> grid and a plate. Tri=three components. All power tubes (6L6, EL34,
> 6V6, etc.) are triodes. Older preamp tubes were also triodes.
>

All of 6L6, EL34, 6V6 (and of course also EL84/6BQ5) are pentodes. 
Pentodes have cathode, plate and three grids. The first cifer of the 
american name represents the tube heating voltage (dunno how this is 
correctly called in english). In 6L6 the first 6 means it´s to be 
heated with 6.3V. The last cifer is the number of used pins. L is 
arbitary.

Of course pentodes can be run as triodes and they are quite often.

> In the mid-to-late 50s, amp manufacturers started switching to the
> pentode PREAMP tube design. (power tubes have remained triodes).
> Pentodes incorporated "two tubes in one glass bottle". Each pentode
> has essentially two 6-Volt tubes residing within. (In the name
> 12AX7, for example, the "12" represents "12 volts", meaning that
> there are two 6-volt tubes in the glass. In the power tubes (6L6,
> 6V6, 6BQ5, etc.) The "6" means a single 6-volt tube. The older
> preamp tubes such as the 6SJ7, and 6SN7 were, as the name implies,
> 6-volt triodes.

The 12AX7 is a double triode, which means there are two triodes in one 
tube. They can be run mostly independently from each other. The tube 
needs a heating voltage of 12.6V (12).

Overall you can say, that preamp tubes are almost exclusivly triodes, 
while most power tubes are pentodes (not all, the 6AS7 is a double 
triode e.g.) that can be run as pentodes but also as triodes.

The 6SN7 is a double triode.

-- 
Gruß,Frank