The 5V4 is my favourite rectifier valve too - and by NOS standards, not yet that expensive.
Mullards GZ34s are getting very silly though, especially considering that as you say - being the highest quality and lowest resistance valve, are ironically the least valve-y sounding! I can hear the difference - I had a Mesa Maverick with a solid-state/valve rectifier switch so you could compare it on the fly - but only really when the amp was pushed a bit.
In terms of reliability I have found the TAD GZ34 near indestructable, way better than Sovtek.
Originally Posted by ICBM
BTW those of you wanting to add some resitance in the GZ34 path would do well to consider two resistors in the anode feeds? This has the incidental advantage of lessening the stress on the valve, especially ones that have to contend with a (miswired, yes IC!) standby switch.
This is getting a bit complex for me. I think I will email my local amp tech and see what he quotes me for installing three different valued resistors (say 75, 100 and 125 ohms) which I can switch between. Thanks for your help everyone. I'll post again with results if I get this mod done.
I think you'd find more widely spaced values more useful... or a bypass switch to give you back the stock sound for maximum headroom.
Originally Posted by knuckleberryfinn
Definitely ask for at least 10W aluminium chassis-mount resistor too - although if you're wiring a couple in series (the most logical way of choosing two or more values), you could get away with slightly smaller ones... eg if you had two 50-ohm resistors in series with a switch to bypass one or both, you could use only 5W each.