Allynmey wrote:Fischerman, congrats on the build. Here are a couple of things to try...
100 Ohm screens (the way KF built them).
NOS Russian military EL84's from the early '80's (KF again).
If you like more girth in the sound, use the higher voltage tap and a 68 Ohm Cathode resistor. It takes away a slight amount of jangle but, adds midrange "girth" (courtesy of a Rocket owner).
Allyn
Fischerman wrote:Hi Allyn, thanks for the suggestions. Why 100ohm screen grid resistors? I know that's what KF copied from the Vox AC30...but I've had several people tell me that 470ohm is easier on the tubes and they didn't notice any tonal degradation. Some suggested that be the only thing I change.
Hey guys,
I have been doing quite a bit of reading regarding the Rocket and could not find a resolution to Allyn’s statement. Allyn states that the real Rocket used 100R/5W screen resistors and I confirmed this on the 1960 AC30 schematic.
On the Trainwreck Rocket Version A0 schematic in the Rocket Files however, the screen resistors are shown at 1k/5W. I found a “Rockit” layout which shows this value as does the graphical layout of the A0 Rocket.
Can anyone shed some light on the choice for the higher value? Is the consensus that the higher value is easier on the [EL84] power tubes but does not compromise the overall sparkle/chime/jangle of the amp? Hopefully this isn't a point of contention or will stir up a commotion, but I'm just trying to sort it out.
Hello!
Sometimes in HI-FI amps they "tie" the screens to the plates with 100 ohm resistors. I've always thought this was a "triode connected" pentode. The 100 ohm resistors would not drop the voltage very much at all. Just a thought.
