Detail 01
Rectifier tube
Handles the amp's power supply conversion. What you hear from it is response under load, not preamp character.
Product detailSKU #1274319722312
MESA/Boogie5U4GB Rectifier Tube
Independent shopping perspective
The Korena take
MESA/Boogie 5U4GB rectifier tube. A replacement part for amps specified to run a 5U4GB. Buy it to fix an amp, not to modify one.
Strong match
Who this is for
- Replacing a failed 5U4GB in a tube amp
- Carrying a backup rectifier for touring rigs
- Restoring an amp to its specified tube complement
Consider the trade-offs
When to look elsewhere
- Solid-state or hybrid amps with no rectifier socket
- Players chasing a tone change rather than a repair
- Anyone who has not confirmed their amp's rectifier type
What matters in use
The specifications, translated
Catalog numbers tell only part of the story. These are the details most likely to change how this product feels, sounds, or fits into a setup.
Detail 02
5U4GB type
A specific rectifier type. Substituting another type without checking the amp's spec risks damage.
Detail 03
MESA/Boogie branded
Sold under MESA's part number, so it matches the factory complement in amps that call for it.
Detail 04
$39 single tube
Cheapest routine consumable in a tube amp. Worth keeping a spare rather than losing a gig to one.
Final check
Know before you order
- 01One tube per order. Two-rectifier amps need a pair.
- 02Verify the amp specifies a 5U4GB — rectifier types are not universal.
- 03Let the amp fully discharge, or have a tech do the swap.
Product questions
Before you decide
Straight answers to the questions shoppers most often ask about this product.
01Is a 5U4GB the same as a 5AR4?
No. They are different rectifier types with different characteristics. Fit whichever one your amp specifies rather than assuming they swap.
02How do I know when a rectifier tube is failing?
Common signs are the amp losing volume, cutting out, or not powering up properly. A tech can confirm with a tube tester.
03Does this need to be matched?
No. Matching applies to output tube pairs. A rectifier is a single tube in the power supply.
04Will this work in a non-MESA amp?
Yes, if that amp specifies a 5U4GB. The MESA branding is the supplier, not a compatibility restriction.
