I am picky about things, but the twins are not going to be rigs I will use a great deal and probably seldom. No doubt the Sherwood updates are top-notch but it just wouldn't be worth it to spend the time and money the way I would operate the receiver. I will leave that to the next guy. I did update the power supply and audio amp which are probably the first things someone with an R4C should tackle.

As for the filaments, I did add a self wound resistor to reduce the voltage by about .5 volts. It is now sitting at about 6.5 @ 122 line volts. From what I have read, you don't want to run the filament voltage too low, but too high by a volt is not a good idea either. This greatly depends on your line voltage. Typical today is 120-122, but in some areas it can vary greatly. I remember in the old incandescent light bulb days seeing a chart that showed a bulb would last 10 times longer with 10% less rated voltage and 1/10 the time with 10% more. I don't know if that is true, and tube filaments would probably not directly correlate to the old bulbs.

There is a lot of misinformation on the Internet so it is hard to get accurate information since tubes other than in hobby stuff are rarely used anymore. I saw many posts that warned of permanent loss of emission after running low filament voltage, and others saying that tube gain actually improved at lower filament voltage. Of course, we are talking about greatly lower. Keeping filaments between 6.0 and 6.5 volts is a good range to shoot for. It is also a good thing that Drake did not blast the hell out of plate voltage limits like Heath and other manufacturers. There are a couple of miniature tubes in the KWM2 that would give you a burn as bad as touching a soldering iron just by briefly touching. Heath often ran tubes at or higher than maximum ratings. There is no reason to run a receiving tube at 250-300 volts.

Many tubes are a limited resource so we need to take care of them!
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Doug, WA3DSP