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Why Use a Valve Rectifier in a Guitar Amplifier?

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 amplifiers which use tube rectification.

Examples of guitar amplifiers which use the GZ34 (5AR4) rectifier tube are the Fender 66 Custom Deluxe and the Fender Pro Reverb and the Fender Princeton Reverb Reissue but there are many others. In fact it’s become quite chic to add a rectifier tube to a new guitar amplifier design. Guitarists love that ‘retro’ feel and sound!

Difference Between the GZ34 and the 5AR4.

That’s simple. There is none! They are just different numbering systems for identical valves.

Why Use a Valve Rectifier Such as the GZ34?

Good question. These are big, hot bottles which can easily be replaced by a few pence worth of silicon rectifier. In theory, the latter will actually do a BETTER job than the GZ34 rectifier valve. So there is obviously more to this than meets the eye. 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. But it still affects the sound of the amp.

The reason valve rectifiers like the GZ34 are still used is because of the way they behave when they receive a large signal. If the amplifier is loaded (say by hitting a heavy chord) the DC will ‘sag’ because the rectifier can’t quite keep up. There is a very small delay before it gets up to speed. In contrast a diode rectifier will barely sag. (sagging means the DC voltage drops before recovering.) Guitarists really like this sag effect, because it softens the attack at the front end of the chord or note.

And of course, back in the day there were no decent solid state rectifiers so valve rectifiers 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!

If you want to replace GZ34 on your amp we recommend JJ tubes, click the link below to purchase.

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