Are all GZ34's born equal?

[Mike Watterson]

Totally Agree Andy.
The equipment was designed for a valve rectifier and really should always have one.
There are big disadvantages with silicon, obviously the surge then adding limiting resistors to tame the running HT which defeats the purpose of silicon as the resistors have to dissipate waste through heat, the big issue for me is the peak voltages that shorten the life of smoothers and of course breakdown on paxolin tag strips and even valve bases
A good indirectly heated rectifier removes all of the aforementioned issues.

I'm happy to replace metal rectifiers with Silicon because the peak HT before the valves heat up is the same. I've seen ECH42 etc flash-over from too high HT before rail loaded on sets meant to take a valve rectifier, resistors in series don't fix that. Also good luck getting any reliable NOS selenium replacement! I've always been able to find a valve rectifier.