Ray Tubes SELECT 5U4

The rectifier turns the AC from your wall into the DC your amplifier runs on, and it shapes the sound more than most listeners expect. The SELECT 5U4 is a new-production full-wave rectifier that Ray Tubes builds to its own audio specifications and keeps only when it ranks among the best of its batch.

The rectifier tube, chosen by listening.

The Design

SELECT takes the reliability and consistency of Ray Tubes' CORE line as its starting point and aims at one thing: more nuanced sound. Ray Tubes builds each tube with manufacturing partners to its own audio specifications, then sells only the best tubes from each batch; Ray Tubes says fewer than 5% of production meets its standard. Audio engineers with decades of experience take part in the selection from start to finish, including listening sessions in real-world conditions.

Every Ray Tubes tube passes a seven-step process in three phases. Phase one checks reliability: soldering inspection under a microscope and a 24-hour burn-in. Phase two measures critical parameters, matches tubes by current draw, and tests for microphonics. Phase three is an amplifier test with listening by Ray Tubes' sound engineers, plus targeted expert listening sessions on randomly chosen tubes. Measurements are recorded under each tube's serial number.

How It Sounds

Ray Tubes says the SELECT 5U4 helps create a sound that is smooth on top, full through the midrange, and grounded in natural bass. Its contribution is subtle but essential: composed bass with textural integrity and natural decay; mids with richness and organic flow, so vocals gain body and presence; and smooth, refined treble that reduces grain and adds clarity and air to cymbals and string overtones.

Where It Fits

The 5U4 is a common full-wave rectifier in tube amplifier power supplies. Its twin-diode design uses a shared cathode and two anodes to convert both halves of the AC cycle. Ray Tubes points out that audiophiles sometimes overlook rectifiers, though like power and signal tubes they can shape an amplifier's character. Check your amplifier's manual for the rectifier type before swapping, since rectifier choice affects supply voltage. Ray Tubes publishes a compatibility list, and we can check your amp with you.

Warranty and Break-In

Ray Tubes' One Year Warranty covers manufacturing defects for twelve months, tied to the original invoice and the serial number on the box, so it transfers to a new owner. Give new tubes 48 to 96 hours of use to break in; early quirks such as slight background noise or imbalance usually fade as hours accumulate. The tube comes with a user handbook with burn-in guidelines and a certificate of authenticity and warranty.

Press Recognition

Ray Tubes' tubes have drawn reviews from Positive Feedback, Stereophile, and HiFi.nl. Reviews of the SELECT 5U4 itself are on the way. Read HiFi.nl's review of Ray Tubes

Wondering whether the SELECT 5U4 suits your amplifier? Give us a call. We'll check your amp's tube complement with you.

Specifications

• Tube type: 5U4, full-wave twin-diode rectifier
• Socket: 4-pin
• Filament: 5 V, 3 A
• Peak inverse plate voltage: 1550 V
• Peak plate current: 800 mA
• Absolute maximum peak reverse plate voltage: 1500 V
• Absolute maximum peak plate current: 750 mA
• Capacitor input filter, range A: 300 V AC RMS per plate; 35 Ω transformer winding resistance per plate; 40 µF maximum input capacitance; 245 mA DC output current; 290 V DC output
• Capacitor input filter, range B: 450 V AC RMS per plate; 85 Ω transformer winding resistance per plate; 40 µF maximum input capacitance; 220 mA DC output current; 470 V DC output
• Choke input filter: 550 V AC RMS per plate; 10 H input choke; 225 mA DC output current; 440 V DC output
• Availability: Single tube
• Includes: User handbook with burn-in guidelines; certificate of authenticity and warranty
• Warranty: One year, transferable