Soft Fail...rectifier tube

[FunkyE9th]

So I was reading Premiere Guitar mag. They have an article on modifying amps with tubes rectifiers. The idea is to add 2 diodes in series with the 2ndary of the PT (i.e. essentially a SS rectifier) so that in the event that the tube rectifier fails as a short, the diodes will act as the rectifier. Thereby protecting the PT from the short and at the same time also preventing your polarized filter caps from seeing AC. The side effect is if the rectifer does fail as a short, your B+ of course will rise a little bit. I'm thinking of adding this to my amps from now on. Any opinions on this mod?

[rooster]

This comes from a Dave Funk book published some 10+ years ago. It sounds like a good idea doesn't it? The only problem I have with it is the fact that - since the AC will be pre rectified before going to the rectifier tube - how can it sound and perform like an amp with just the rectifier tube? It seems to me that the sag of the rectifier, if sag exists, comes in part from the rectifier tube doing its business. If the diode does the business, how can the rectifier tube offer anything unique? Why not just skip the recifier tube at this point?

But it is a failsafe. If you do not trust the rectifier tube, try the mod by all means.

[Phil_S]

My reaction is that life is too short to live in the slow lane all the time. If you want a tube rectifier, accept the remote possibility that it will fail, and when it does, it is probably only 50-50 that something bad will happen.

[Tubetwang]

FWIW, i had rectifier tubes popping on me several times over the years...and on each occasion, the fuse blew, with no harm done...

Twang

[FunkyE9th]

Thanks guys. My orginal thought was the fuse should blow if the rectifier does fail as a short. But the article said it might not blow fast enough so your PT could get hosed. Anyway, after much thought, I'm not doing the mod.