Homebrew Superlite II scratch build: Got a couple questions

[mojoboldt]

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Hey guys! LONG time lurker: First time poster here.
So, I recently built this amp using the Superlite II layout with the mosfet source follower. I love the amp and thinks it sounds amazing! I'm super excited!!
Well, I was re-reading some posts about the Superlite II schematic and now I see that folks on this site are saying that the 100 ohm resistors on the screens of the el84s should be replaced with 1k ohm resistors to increase tube life. I built mine with a 1k ohm resistor coming off the cap and then its splits to one 100 ohm resistor going to each of the el84s.

Dumb question: Do I simply replace the two 100 ohm resistors with two 1k ohms while still leaving the 1k ohm coming off the cap as it is?
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[Bieworm]

Why would you want to do that?. Just run 2 1k resistors from B+2 (2nd filter cap) like the schematic indicates. The idea behind this is that there should be a significant voltage difference between the plates and the screens (about 20V) to protect the tube to draw excess current. Ideally those resistors are 3 watts. In fact, 2 watts is better than 5 watts. This way you get some protection in case the tubes go bad, for the resistors will act like a fuse.

[JMPGuitars]

I built mine with a 1k ohm resistor coming off the cap and then its splits to one 100 ohm resistor going to each of the el84s.

The way you described it is perfectly fine as long as the resistors are at least 2W.

If you want to consider any modifications, you should start by reviewing your voltages first and see if any tweaks are actually needed. If it sounds good, go play.

Thanks,
Josh

[JMPGuitars]

Why would you want to do that?

Look at some older schematics and you'll see what he's referring to. It's a larger resistance than your suggestion. His wiring: 1k to 100Ω to screen. Your suggestion was 1k to screen. That 100Ω gives a slight additional drop. Either method is valid.

The screen resistors, besides helping keep the screen voltage below the plate voltage (how much doesn't matter that much), also act as screen grid stopper resistors. This is why the screen resistors are supposed to be close to the tube. Using two 1k resistors at the socket, done. Use only one 1k resistor, then put the 100Ωs at the sockets.

[mojoboldt]

Hey! Thanks Josh!
I checked the voltages as soon as I got it finished and they are in spec with the grids right at 20 volts below the plates.
I really appreciate your response. It sets my mind at ease as I play!
Thanks again.
Chris