Is rectifier tube arcing a problem?

I did some research and couldn’t find a definite answer.  I have an amp that I tried 6 different pairs of 5U4G and 5U4GB. 3 pairs has arcing (RCA 5U4G, TungSol, Svetlana 5C3S) and 3 pairs don’t (RCA 5U4G with hanging filament, EH 5U4GB, Sylvania 5931).  I took the amp to a technician and he checked everything, he can’t find anything wrong.  The problem is, I like the sound of the TungSol and Svetlana which both have arcing.  The technician said it is ok to keep using them, but honestly I am not too comfortable.  But I like their sound.  Is it really ok to keep using the arcing tubes?  Will it damage the amp?




Some/most of it is beyond my tech knowledge as well, but I do understand the basics of it.

I've relied upon techs/friends to update my tube gear in the past and I gleaned a tiny bit of understanding from doing so

This would be good info for your local repair person to read/consider.

Until 10 years ago I did not know what the tiny transformers a friend installed on my Dynaco ST70's, being used as mono blocks, were for (power supply chokes).

He performed the modifications in 1979, and said that the stock mono/stereo switch/circuit was a bad joke.

The improvement in sound quality from the mod was not a slight one.


Soft start will help, you also can add an UF4007 to the plate of rectifier tube to removes negative half cycle voltage and it halves the total time of voltage that feeding the arc.

@imhififan thank you. This seems something small and won’t change the sound.

min the diagram, I need to add two diodes per tube, am I correct?

I need to add two diodes per tube, am I correct?


BTW, do not reuse the arced tube! Usually once a tube has arced It will continue to arc at that same spot on power up.


Finally, some real help for this problem. Thanks for helping to solve problems that the wannabees simply cannot.