Rectifier tubes play a crucial role in vacuum tube amplifiers, converting AC voltage to DC voltage to power the amplifier circuits. For audiophiles seeking to fine-tune their sound, rectifier tube rolling—experimenting with different rectifier tubes—can be a rewarding endeavor. Among the vast landscape of rectifier tubes, the 274 and 5R4 families are popular choices, each offering unique sonic characteristics. This article delves into a detailed comparison of the 274 and 5R4 tubes, exploring their differences, sonic signatures, and suitability for various audio setups. We will also touch upon other related rectifier types like 5U4G and GZ34 to provide a broader context for audiophiles looking to optimize their tube amplifier performance.
Rectifier tube rolling is a common practice among enthusiasts aiming to tailor the sound of their amplifiers. Different rectifier tubes can impart subtle yet noticeable changes to the overall sonic character, influencing factors such as warmth, soundstage, dynamics, and detail retrieval. This exploration is especially relevant for amplifiers like Woo Audio’s WA series and custom-built OTL amps, where rectifier tube swaps are easily implemented and sonically impactful.
Let’s embark on a journey to understand the nuances of these rectifier tubes, starting with an overview of some notable examples from the original review.
Western Electric 422A
The Western Electric 422A, a premium variant of the 5U4G, is often lauded as a top-tier rectifier. Known for its exceptional sonic qualities, the 422A delivers a hauntingly beautiful tone, characterized by expansive air, precise layering, and remarkable transparency. Its frequency extension is exceptional, reaching deep into the bass and soaring in the highs. The midrange is palpable and lucid, contributing to a holographic 3D soundstage and imaging. Listeners often describe its transients as liquid and its overall balance as neither overly warm nor bright. Priced at a premium, the WE422A is considered a reference tube for many discerning audiophiles.
GEC U52/5U4G/CV575
The GEC U52, a British-made tube also compatible with 5U4G circuits, stands as a close second to the WE422A in many audiophile circles. Sharing many sonic traits with the 422A, the U52 is perhaps slightly warmer with a more euphonic decay. It maintains impressive speed, transparency, and soundstage, making it another nearly perfect rectifier. The U52’s sonic signature is described as warm yet airy, with extended treble, deep bass, and a grain-free presentation. Its British tone, reminiscent of GEC 6AS7G power tubes, makes it a synergistic match for headphones like the Sennheiser HD 800. Like the WE422A, the GEC U52 is a premium tube that can evoke an emotional listening experience.
Mullard/Cossor CV378/GZ37 (Fat Bottle GZ37)
The Mullard/Cossor CV378, also known as the fat bottle GZ37, is another highly regarded British rectifier tube. Offering a warmer sound than the GEC U52, the fat bottle GZ37 provides more bass body and punch while retaining good speed and transparency. Its smooth transients and grain-free presentation contribute to a liquid sonic character. While warmer and less airy than the U52, its slight fullness and tubey midrange make it well-suited for brighter setups and headphones like the T1 or HD 800. This tube excels with jazz and vocals, delivering a natural timbre and classic tube warmth. Compared to the later, more common skinny bottle GZ37, the fat bottle version is considered superior in bass texture, resolution, and overall speed.
Mullard GZ34/5AR4 (Metal Base)
The metal base Mullard GZ34/5AR4 stands out for its cool tonality while preserving tube warmth and euphony. This 1950s tube delivers a liquid-like decay and grain-free presentation, coupled with transparency and excellent treble extension. Its midrange is neutral with a slightly forward character, and the soundstage and imaging are commendable. The metal base GZ34 is also noted for its dynamic capabilities and ability to add neutrality to an amplifier, making it a versatile choice for various music genres. Its bass performance is described as amazing, with clean decay, good texture, and deep extension. This tube is particularly recommended for slightly sluggish amps or warmer headphones, offering a “minty coolness” that enhances clarity and dynamism. Its long lifespan is another notable attribute.
Mullard GZ34/5AR4/CV1377 (Black Base)
The black base Mullard GZ34/5AR4, a later iteration from the 1960s, maintains a similar sonic signature to its metal base predecessor but with some distinctions. While the “minty cool” sound is still present, it leans towards a colder, more solid-state-like presentation. The decay is fast and clean, but lacks the liquidity of the metal base version. Transparency is slightly reduced, with occasional grain. The treble, while extended, can be harder, and the soundstage is narrower. The midrange may sound leaner, and the bass, though punchy, is less extended and textured compared to the metal base. However, the black base GZ34 remains a good option for those seeking a neutral and faster sound, and it retains the long lifespan associated with the GZ34 family.
Brimar 5R4GY/CV717
The Brimar 5R4GY/CV717 is a warm and euphonic rectifier tube, similar in character to the GZ37 family. On warmer amplifiers, it can be very lush and laid-back, offering a syrupy midrange. However, it pairs well with brighter headphones due to its treble roll-off. Compared to GZ37 tubes, the Brimar 5R4GY is positioned between the Cossor GZ37 and the Mullard GZ37 in performance. It surpasses the skinny bottle GZ37 in transparency, tonal richness, and soundstage dimensionality. While not as fast as some rectifiers, its natural decay and timbre make it excellent for vocals and slower music genres. The Brimar 5R4GY is praised for delivering high performance at a relatively accessible price, offering transparency and tonal richness comparable to more expensive tubes.
Philips 5R4GYS
The Philips 5R4GYS is often touted as an excellent 5U4G variant. Sharing similarities with the Brimar 5R4GY, it offers euphonic warmth and a sweet midrange but with more air and treble extension. However, this added treble can initially present some hardness, requiring a burn-in period to smooth out. After burn-in, the Philips 5R4GYS delivers a warm yet dynamic and faster sound compared to the Brimar. It is considered more balanced overall, with very good imaging and PRaT. While its soundstage depth might not match the Brimar, it provides a versatile performance upgrade over stock 5U4G tubes at a reasonable price point.
RCA 5R4GY
The RCA 5R4GY from the 1940s offers a distinct sonic profile compared to other 5R4 variants. Leaning towards a more neutral and treble-oriented sound, it evokes similarities to the brighter sound signature of Eddie Current amplifiers. The RCA 5R4GY delivers airy treble, an open midrange, and a large soundstage, albeit with lighter bass. Its tonality is colder yet retains some warmth, with a forward and clear midrange. The soundstage is expansive with excellent instrument separation, though layering may not be as dimensional as top-tier tubes. Its fast decay contributes to an almost solid-state-like presentation but without harshness. While detailed and clear, some may find it lacking in timbre and tonal richness, and potentially having a slight treble emphasis.
Emission Labs (EML) 274B Mesh Plate
The Emission Labs (EML) 274B mesh plate is a modern production tube popular among 274B amplifier owners. Known for its warm sound, the EML 274B mesh plate offers a wide, holographic soundstage with a magical quality. It is warmer than the Sophia 274B and has less bass presence, but excels in soundstage width and airiness. The treble is smooth, and the midrange is warm without being overly colored. Compared to the EML 5U4G, it shares a similar warmth but has more treble, less body, and a slightly faster, more separated sound. While detailed and clear, it prioritizes soundstage and a sweeter presentation, making it a compelling option for listeners who value these qualities.
Shuguang 274B
The Shuguang 274B, a current production Chinese tube, is often included as a stock tube in new amplifiers. However, sonically, it is generally considered a lower-tier option. The Shuguang 274B is described as grainy and harsh, with a congested soundstage and a confused overall sound lacking in coherence. Detail retrieval is limited, and the sound can be fatiguing despite a muddy midrange. It is generally not recommended for critical listening and is best used for initial amplifier burn-in or basic testing purposes.
Key Differences: 274 vs 5R4 Tubes
While both 274 and 5R4 tubes function as rectifiers, there are important distinctions that impact their application and sonic characteristics.
- Voltage Drop: 5R4 tubes generally have a higher voltage drop compared to 274 tubes. This means that using a 5R4 in place of a 274 (or 5U4G) might result in a slightly lower B+ voltage in the amplifier circuit.
- Current Handling: 274 tubes, particularly the 274B variant (which is electrically similar to the 5U4G), are typically designed to handle higher current demands than 5R4 tubes.
- Sonic Signature: Based on the reviews, 5R4 tubes (like Brimar and RCA 5R4GY) often lean towards a warmer, more euphonic, and sometimes slower sound. They can be excellent for adding richness and smoothness, particularly beneficial for brighter systems or genres like jazz and vocals. 274 tubes, especially premium NOS versions or modern production like EML, can offer a broader range of sonic characteristics, from warm and holographic (EML 274B) to more neutral and balanced (like some 274B variants not explicitly reviewed here but related to 5U4G types). The Shuguang 274B is an outlier in terms of negative sonic attributes and is not representative of the 274 family’s potential.
Choosing Between 274 and 5R4 Tubes
The best choice between a 274 and 5R4 tube (or their variants like 5U4G and GZ34) depends on several factors:
- Amplifier Compatibility: Always ensure the rectifier tube is compatible with your amplifier’s specifications. Check the amplifier manufacturer’s recommendations regarding compatible rectifier types. While many amplifiers designed for 5U4G can often accept 274B and some 5R4 types, it’s crucial to verify compatibility to avoid damage.
- Desired Sound Signature: Consider your preferred sonic characteristics. If you seek warmth, smoothness, and a romantic tube sound, 5R4 tubes like Brimar or Philips 5R4GY might be excellent choices. If you desire a more balanced, detailed, or holographic sound, exploring 274B tubes or premium 5U4G variants like WE422A or GEC U52 could be more rewarding.
- Headphone and System Synergy: Match the rectifier tube to your headphones and overall system. Warmer rectifier tubes can complement brighter headphones, while neutral or faster rectifiers might pair well with warmer or darker headphones.
- Budget: Rectifier tubes vary significantly in price. Premium NOS tubes like WE422A and GEC U52 are expensive, while more common NOS 5R4GY or modern production EML tubes are more accessible. Balance your sonic aspirations with your budget.
Conclusion
The world of rectifier tubes offers a fascinating avenue for audiophiles to explore and refine their listening experience. When comparing 274 and 5R4 tubes, it’s evident that both families offer valuable sonic options. 5R4 tubes often bring warmth and euphony, while the 274 family, particularly when considering its broader compatibility with 5U4G types, encompasses a wider spectrum of sonic possibilities, from highly refined and balanced to lush and holographic.
Ultimately, the best way to determine the ideal rectifier tube for your system and preferences is through experimentation. Tube rolling, while sometimes subtle, can lead to meaningful improvements and personalized sound tailoring. Explore reputable sources for NOS and modern production tubes, and enjoy the journey of discovering the perfect rectifier to elevate your audio enjoyment.
References
- Dubstep Girl’s Massive 5AR4/5R4/5U4G Rectifier Review/Comparison! http://www.head-fi.org/t/648547/dubstep-girls-massive-5ar4-5r4-5u4g-rectifier-review-comparison
- WA22 rectifier shootout. http://www.head-fi.org/t/428570/woo-audio-amp-owner-unite/20325
- WA22 rectifier comparison. http://www.head-fi.org/t/428570/woo-audio-amp-owner-unite/13755
- 5R4 comparison. http://www.audioasylum.com/audio/tubes/messages/24/248138.html
- WA22 lets roll some tubes done mod burnning in. http://www.head-fi.org/t/451678/wa22-lets-roll-some-tubes-done-mod-burnning-in
- Woo6 owners rectifier tube rolling options. http://www.head-fi.org/t/242539/woo6-owners-rectifier-tube-rolling-options
- Woo Audio WA6-WA6SE tubes comments pictures and advice. http://www.head-fi.org/t/587285/woo-audio-wa6-wa6se-tubes-comments-pictures-and-advice
- some WE422A notes. http://www.head-fi.org/t/428570/woo-audio-amp-owner-unite/10755
- 2359glenn studio. http://www.head-fi.org/t/600110/2359glenn-studio
- DNA Stratus 2A3 amplifier first impressions. http://www.head-fi.org/t/609800/dna-stratus-2a3-amplifier-first-impressions
