Ray Tubes RESERVE 300B

SELECT is the best 300B most listeners will ever need. RESERVE is the one you've always wanted: a bespoke, small-batch directly heated triode that Ray Tubes designs from start to finish for hi-fi audio.

SELECT is the tube you need. RESERVE is the tube you've always wanted.

The Design

RESERVE is where Ray Tubes pulls out every stop. Each tube is designed from start to finish for hi-fi audio and made in small batches, and Ray Tubes says fewer than 5% of production qualifies. The glass bulb is shaped for better heat dissipation and longevity, the metals are high-purity to reduce the chance of flaws, and the vacuum is pulled slowly rather than quickly. A Magic Coating of monocrystalline carbon improves electron flow, helps shed heat, and blocks noise, and the pins are gold-plated. Each tube carries a unique identifier that tracks it through testing.

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.

How It Sounds

Ray Tubes describes the RESERVE 300B as delivering warm, elastic low frequencies, a delicate, layered midrange, clear, smooth highs, and rich detail, with a moderate dynamic range and a wide, well-defined soundstage with a good sense of space. Bass is textured and delicate, suited to jazz and folk, the midrange is full-bodied and emotional with vocals and strings in particular, and the treble is clear, airy, and gentle. Monthly Audio's Kim Mun-bu called it a true reference 300B, and Steve Huff said the sound improved when he swapped in a set.

Where It Fits

The 300B was introduced in 1938 and powered the cinemas of Hollywood's Golden Age. Audiophiles have valued it for decades for its low noise and good reliability. Check your amplifier's manual for the tube type, then choose a single tube, a matched pair, or a matched quad for your output stage. Have your amplifier's bias checked whenever you change output tubes.

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. If one tube in a matched pair or quad fails, Ray Tubes replaces the whole set. 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. Each tube comes with a user handbook with burn-in guidelines and a certificate of authenticity and warranty.

Press Recognition

• Monthly Audio, Kim Mun-bu (September 2025), reviewing the RESERVE 300B. Kim called it the most complete 300B currently available and a true reference 300B. Read the review at Monthly Audio
• Hifi Huff, Steve Huff (September 2025), in his Cary Audio 300 SEI review. Huff wrote that swapping in a set of RESERVE 300B tubes noticeably improved the sound. Read the review at Hifi Huff

Wondering whether the RESERVE 300B suits your amplifier, or how many tubes you need? Give us a call. We'll check your amp's tube complement with you.

Specifications

• Tube type: 300B
• Socket: 4-pin
• Output power: 6.6 W
• Filament: 5 V, 1.2 A
• Max anode voltage: 480 V
• Max anode dissipation: 40 W
• Cathode current: 100 mA self-bias; 70 mA fixed bias
• Input capacitance: 9 pF
• Output capacitance: 4.3 pF
• Transfer capacitance: 15 pF
• Static conditions: 300 V anode, -60 V grid, 60 mA anode current
• Transconductance: 5.5 mA/V
• Internal resistance: 0.7 kΩ
• Amplification factor: 3.85
• Construction: Gold-plated pins; monocrystalline carbon Magic Coating; optimized bulb shape
• Availability: Single, matched pair, or matched quad
• Includes: User handbook with burn-in guidelines; certificate of authenticity and warranty
• Warranty: One year, transferable