Surge Protection for ARC Tube Amps

To protect from lightning surges, you might want to contact your power company and see if they offer surge suppression for the whole house. It normally costs about $4 per month, and they add a really large transorb device to your home's power box.

Most off-the-shelf surge suppressors have internal inductors that can play havoc with a high power amplifier, causing a ringing voltage effect on the AC power input of the amplifier. Also, they tend to be too aggressive in choking the input power when the amp draws high current like during boot up. This choking causes brown out and slow rise time problems with the primary power supply of the amp.

If you do want to experiment with off-the-shelf suppressors, choose one that is grossly over-rated. If your amp has listed draw of 30 amps, use a 100+ rated suppressor or higher. Amps have "rush current" that can be quite high, and those numbers of 30 amp and 100 amp are just the nominal current draw numbers. Rush peaks out to much higher current, and that's the problem.

It's true that the surge suppressors that use only MOVs or transorb devices are very unlikely to cause problems. Those devices are totally passive until the voltage reaches too high a level, then they kick in and clip the high voltage down.

The more expensive suppressors use not only MOVs and transorbs, they also throw in noise filtering by using inductors. It's the reactance of the inductor that causes the problems I described above. So... the cheaper surge suppressors that don't have filtering are most likely to be best for this application.

But again, remember to over-rate the current capacity of the suppressor, as I mentioned above. If you use too skimpy of a suppressor bar then you might get a voltage drop on the wiring or burn out the On/Off switch contacts. It has to handle the high surge currents without causing a voltage droop.

The current capacity of the bar is not the same rating as the surge current handling rating of the device. So an example would be that the bar can handle 30 amps, but during the surge/spike it can clip off 350 amps. That 350 amps is just for a tenth of a second during the spike. The 30 amps is average current over long term. The spike clipping is normally given as an energy number (such as Watts or Joules), rather than a current handling number, but sometimes they will mention current and people confuse that number with the nominal current handling capacity.

And with a high current device like this, watch out for the ones that have a built in circuit breaker. The breaker can cause a voltage drop during surge demands from normal running of the amplifier. If you use one with a circuit breaker, over-rate it by 3X over requirements.