Rectifier valves are used in a large number of vintage and reissue guitar amplfiers.
For example the GZ34 (5AR4) rectifier from JJ Electronics.
This version of the GZ34 has a thick glass envelope and robust electrodes making it the perfect workhorse for those guitar amplfiers which use tube rectification.
Examples of guitar amplifiers which use the GZ34 (5AR4) rectifier tube are the Fender 66 Custom Deluixe and the Fender Pro Reverb and the Fender Princton Reverb Reissue but there are many others. In fact it’s become quite chic to adda rectifier tube to a new guitar amplifier design. People love that ‘retro’ feel!
Difference Between the GZ34 and the 5AR4
That’s simple. There is none! They are just different numbering systems for identical valves.
The GZ34 can also substitute for the 5U4 and 5Y3 rectifier valve.
Why Use a Valve Rectifier Such as the GZ34?
Good question. These are big, hot bottles which can be replaced by a few pence worth of silicon rectifier. The latter will do a BETTER job than the GZ34 rectifier valve.
So why do designers still use valves in the rectifier section?
The first thing to realise is that the GZ34 is NOT in the signal chain. It’s there simply to change AC to DC. A process called rectification.
As mentioned, this is easily done with 10p worth of diodes.
The reason GZ34 (etc) are still used is interesting. They are pretty bad at doing the job they are intended to do! That is, change AC to DC. If the amplifier is loaded (say by hitting a heavy chord on the old axe) the DC will ‘sag’ because the rectifier can’t keep up. In contrast a diode rectifier will barely sag. (sagging means the DC voltage drops before recovering.) Guitarists have come to like this effect, hence the demand for valve rectification.
And of course, back in the day there were no decent solid state rectifiers so GZ34 (etc) were the only game in town. There are still tens of thousands of vintage amplifiers out there which use GZ34 rectifier tubes and so they are still made and available.
So now you know!
Dying to know more? There’s a good article here: http://www.guitarplayer.com/amplifiers/1017/whats-the-big-deal-about-tube-rectifiers/23811