Subject: Tube Amp safety
    I'm pleased to see that you did the article about Tube Amp safety. This subject and how to improve the reliability of the amp / gear are often overlooked.
    I feel however that you failed on one important issue, namely pots and trimmers. I've repaired guitar amps for years and the most common fault is one (or more) bad pot (or trimmer). More often than not you'll see that the wiper have no contact with the rest and almost as often that the soldering of the pins or the rivets assembling the pins to the rest of the pot. This is rather annoying when it's the controls, but when it happens to the bias circuit ...... well I'm sure you can imagine the consequence.
   This is the reason why all serious guitar amp makers all ensure that a failure (or complete removal) of the bias pot always results in max. bias voltage. This will save the amp and you can even finish the gig (with a bad sound, better than none).
   I hope that you'll continue to publish your excellent webzine.

-Per

   My attempt to list safety issues for tube circuits was not exhaustive. In fact, a thick book could easily be written on this topic.
   You are absolutely right about the danger of using potentiometers. It has become a fad to omit grid grounding resistors from line stage and power amplifiers. Just why this is happening eludes me. 
   Always try to imagine worst case scenarios and try to prepare for them. What will happen when someone toggles on the "on" switch back and forth? What will happen if someone removes a tube while the amplifier is in use? What will happen if the wrong tube is plugged into an amplifier? A good imagination helps make a safe project.
   Shown below is the wrong and right way to use grid grounding resistors.

Subject: Four things from
the Letters column of October
   1) Thanks for publishing my letter regarding the sort-of-unsafe-Loftin-White-kinda-thing I built, I would be interested in hearing from anyone who writes to you about the letter and I am grateful for your advice.
   2) Herb Jeschke's letter: having heard some of Herb's gear, if he says it sounds good, it sounds VERY good! He has terrific ears. He is also quite a friendly and warmhearted guy, I like him very much.
   3) Nixie tubes: there is a design on the Web for a Nixie clock, which uses no power transformer as your reader noted. I built this unit