Difference betweeen Aragon 4004 Mark I and Mark II

One thing is the replacement of the fire prone carbon emitter resistors to a non flamable type.

Thanks for the response. I am thinking of getting a used original 4004. Based on your response, I should be looking for the Mark II version then. I can live with a lower performance amp but I don't want to worry about resistors damage.

If the emitter resistors are "flaming", the amp has a LOT more problems to worry about than just a few smoked resistors. That's because those resistors will only "flame" when the transistors are damaged / on their last leg. As such, you can replace the resistors if / when you have to replace the transistors. Granted, this is a problem that should have been addressed with the original design, but at the same time, it will only happen under specific "high stress" situations. Sean
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What effect does it have on the sound if any and why can you not do the replacement yourself if it's only a few resistors before the output?

Just thinking?

Another difference is the use of a bias system that adjusts itself to changes in line voltage in the Mk II.

This is the first I've heard of flaming resistors!