We’ve had a bit of a cold and rainy snap here which has prevented me from getting to the chassis work for the new 807 amp. But that doesn’t mean I’ve been totally idle.
I decided that if I was going to be stuck in the house, I should make the most of all the free time. A while back I asked people which tube should be the next in the series of SE-UL bias optimization investigations (before I get to the EL34). The conclusion was that I should check out the EL84.
The 6BQ5/EL84 is a smaller power tube akin to the 6AQ5. However, a major difference is that the 6BQ5/EL84 is a true pentode and not a beam power tube. This will be the first true power pentode I’ve thoroughly investigated so the results should be interesting. The EL84 is a lower power tube with a maximum plate dissipation of 12W. In SE-UL this means that maximum power out will likely only be a handful watts. The 6AQ5 (i.e. 6V6 limited to 12W Pd) peaked out at a little over 4W in the 6V6 SE-UL Bias Investigation. I am hoping for similar performance out of the EL84.
The test equipment has been deployed to my desk and I’ve calibrated the driver to start gathering data. Here is the test setup.
I’ve still got a lot of work to do but I should have some results to report in a week or two.
As always, questions and comments are welcome.