The EL84 output pentode was introduced by Mullard in 1954. To demonstrate its use and quality the Mullard applications lab produced an amplifier design. The now classic 5-10 high quality audio amplifier.
The performance figures given here refer to class A operation.
When used as a pair in an ultra-linear push-pull configuration with 43% distributed loading the output could reach 10 W with 0.9 % total harmonic distortion.
With ultra-linear operation the screen grids were connected to taps in the in the output transformer primary winding. The valve operating conditions so produced were intermediate between a triode and a pentode. The operation of the distributed loading was to introduce negative feedback directly within the output stage.
See also UL84 & PL84 produced for designs using AC or DC mains without a mains transformer and a series heater chain. The PL84 was used for TV frame output service.
By clicking the link from the exhibit name above, the full Mullard datasheet can be downloaded. Warning this is a very large PDF file.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 70 mm tall.
References: Datasheet & 1040. Type EL84 was first introduced¶ in 1953.
Pin Connections
B9A |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |

|
ic |
g1 |
k,g3 |
h |
h |
ic |
a |
ic |
g2 |
Absolute Maximum Operating Conditions¶
Pentode |
Vh |
Ah |
Va |
Vs |
Vg |
mAa |
mAs |
gm |
Pout |
Pdiss |

|
6.3 |
0.76 |
250 |
250 |
-7.3 |
48 |
5.5 |
6.7 |
2.2 |
12W |
Thanks to Frank Philipse for supplying the above PDF datasheet
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Click on the custom picture of the valve above to view more exhibits. There are plenty of valve photographs, descriptions, and datasheets that have been designed especially for those interested in learning more about the collection. Many have referenced the National Valve Museum, including avid collectors and clubs that go as far as to design custom t-shirts with pictures depicting the hobby, to others who are just being introduced to the world of valves. Don't fret if you're not one of those that design custom t-shirts with valves on them; all are welcome to puruse the museum!
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