This is IWISTAO's Blogger,and for IWISTAO HIFI MINIMART, which is about Tube Amplifier,Output Transformer, Power Transformer, Speaker enclosure, and Bluetooth Technology, HIFI Audio and related accessories and the information like as Bluetooh Speaker, HIFI Bluetooth Earphone,HIFI Bluetooth Audio, HIFI Bluetooth Tube Acoustics,, and other populor electronics consumer products,.etc.
Looking for the Perfect 8-inch Speaker Enclosure for Your DIY Project?
If you're ready to assemble your own speaker, take a look at this! IWISTAO offer a pair of high-quality 2-way bookshelf speaker cabinets, designed for easy customization and built with premium materials.
These solid wood enclosures feature a sturdy dovetail joint construction and diamond-cut corners, providing both durability and an elegant aesthetic. The natural wood finish, enhanced with a layer of varnish, gives the cabinets a classic, timeless look. The internal volume is approximately 26L, ideal for 8-inch drivers.
Customizable to Fit Your Components
If you have specific speaker units in mind, simply let us know the dimensions or provide us with the design drawings, and we'll custom-cut the speaker holes to your specifications. This ensures the perfect fit for your drivers.
Example Build:
One example build would be using the GRS RT1.R-8 Hi-Res Neo Ribbon Tweeter for the high frequencies and the Dayton Audio SIG225-4 8" Signature Series woofer for the low frequencies. These components are available for purchase both online and at local retailers. Don't forget to add a suitable crossover to complete your setup. Once assembled, you'll be ready to enjoy high-quality sound.
In the world of audio amplification, few topologies are as revered and debated as the Single-Ended (SE) Class A amplifier. Known for its circuit simplicity and sonic purity, the SE amplifier uses a single active device to amplify the entire audio waveform. This approach avoids the crossover distortion inherent in push-pull designs and is celebrated for producing a rich tapestry of even-order harmonics, which many listeners find musically pleasing and natural.
This article explores the design of a classic SE amplifier, pairing two legendary tubes: the 6SL7 high-mu twin triode as the driver and the iconic EL34 power pentode for the output stage. This combination promises a journey into the heart of vintage audio, delivering a sound that is both powerful and nuanced.
The Heart of the Preamp: Understanding the 6SL7
The first stage of amplification is critical, as it sets the tonal foundation for the entire amplifier. For this role, we've chosen the 6SL7, a tube with a long and storied history in both Hi-Fi and guitar amplification.
The Tung-Sol 6SL7, a modern production of the classic high-mu twin triode
The 6SL7-GT is a high-mu twin triode designed for use in resistance-coupled circuits as a voltage amplifier or phase inverter.
— General Electric 6SL7-GT Datasheet
When implemented correctly in a circuit designed for its parameters, the 6SL7 is known for producing a warm and smooth sound, making it a favorite for the input stages of audio equipment where tonal character is paramount .
Why the 6SL7 is a Great Driver for the EL34
To drive a power tube like the EL34 to its full output, the driver stage must provide sufficient voltage swing. The 6SL7';s high amplification factor makes it perfectly suited for this task. A single 6SL7 triode section can easily take a standard line-level signal (around 1-2V) and amplify it to the ~20-40V peak-to-peak signal required at the EL34's control grid.
Furthermore, the 6SL7 exhibits excellent linearity, which ensures that the signal passed to the power stage is a clean, uncolored replica of the input, preserving the integrity of the music before the final power amplification and its associated harmonic coloration.
The Powerhouse: The Iconic EL34 Pentode
The EL34 is arguably one of the most famous power tubes in audio history. It is a pentode, meaning it has three grids (control, screen, and suppressor), which gives it high power sensitivity and efficiency.
The "British Sound" Embodied
The EL34 is the cornerstone of the ";British Sound." It powered legendary amplifiers from manufacturers like Marshall and Orange, shaping the sound of rock music from the 1960s onwards. Its sonic signature is often described as aggressive and forward, with a rich midrange and excellent headroom that allows for blistering, dynamic performances .
This character—a powerful and articulate voice—makes it not only a giant in the guitar world but also a compelling choice for high-fidelity audio, where it can deliver music with authority and presence.
The Marshall Plexi, an iconic amplifier that defined the "British Sound" with its EL34 power stage
Operating the EL34 in a Single-Ended Configuration
While most famous for its use in push-pull circuits, the EL34 performs exceptionally well in a single-ended Class A design. In this topology, the entire signal is handled by one tube, biased to be constantly conducting. This requires careful management of its operating point to avoid exceeding its maximum plate dissipation, which is typically rated at 25 watts .
A key design choice is whether to run the EL34 in pentode mode or triode mode (by connecting the screen grid to the plate).
Pentode Mode: Delivers higher power output and efficiency, retaining the classic, punchy pentode character.
Triode Mode: Results in lower power output, lower distortion, and a lower output impedance, leading to a sound that is often described as smoother and more refined.
For this project, we will focus on the pentode connection to leverage the EL34's full power and characteristic tone.
Designing the Amplifier Circuit: Key Considerations
Building a stable and great-sounding amplifier requires careful attention to the operating points of each stage and the selection of key components like the output transformer.
The Driver Stage: Setting the 6SL7's Operating Point
The operating point, or Quiescent point (Q-point), defines the tube';s idle state. A well-chosen Q-point ensures the tube operates in its most linear region, minimizing distortion. A typical operating point for a 6SL7 in a preamp stage, derived from datasheets, is:
For an SE Class A amplifier, the tube idles at its maximum dissipation. The goal is to set an idle current that is high enough for Class A operation without exceeding the 25W plate dissipation limit. For example, with a plate voltage of 350V, the maximum idle current would be I = P/V = 25W / 350V ≈ 71mA. A safe and common practice is to idle at around 70-90% of max dissipation.
Let's choose a conservative idle point:
Plate Voltage (Va): 350V
Plate Current (Ia): 60mA
This results in an idle plate dissipation of 350V * 0.060A = 21 watts, which is safely within the 25W limit. The required negative grid voltage for this operating point can be found on the EL34's plate characteristic curves and is typically achieved with a cathode bias resistor.
The Output Transformer: The Critical Link
The output transformer (OPT) is perhaps the most critical component in a tube amplifier. Its functions are twofold:
A single-ended output transformer with an air-gapped core, essential for handling DC idle current
Visualizing Performance: Plate Curves and Load Lines
To truly understand how the power stage will behave, engineers use plate characteristic curves and load lines. A plate curve graph plots plate current (Ip) versus plate voltage (Vp) for various fixed control grid voltages (Vg). The load line is a line drawn on this graph that represents the load presented by the output transformer. The slope of the load line is equal to -1/Z_p.
So, what does this amplifier sound like? The final sound is a beautiful synergy of its parts. The 6SL7 provides a clean, warm, and detailed signal to the power stage. The EL34, operating in Class A, takes this signal and imbues it with its characteristic richness and authority. The single-ended topology adds a layer of second-order harmonic distortion that is inherently musical, creating a sound that is lush, three-dimensional, and engaging.
You can expect a powerful bass response, a detailed and articulate midrange where the EL34 truly shines, and clear, extended highs. For Hi-Fi listening, it will present music with a sense of realism and emotional weight. For a guitar amplifier, it will offer a touch-sensitive response, transitioning from clean tones to a sweet, singing overdrive as you dig in—the hallmark of a great single-ended design .
Conclusion: A Timeless Combination for the Modern Builder
The 6SL7-driven EL34 single-ended amplifier is more than just an electronics project; it';s an exploration into the art of sound reproduction. It combines a high-gain, linear driver with a powerful and characterful output tube in a topology celebrated for its sonic purity. While it may not be the most efficient design in terms of power consumption, its reward is a sound that is deeply musical and satisfying.
For the modern DIY audio enthusiast, this classic pairing offers a direct connection to the golden age of tube amplification, resulting in a piece of equipment that is as rewarding to build as it is to listen to.
Down by the Salley Gardens Full Version from a Big Vacuum Tube Amplifier
Although this vacuum tube amplifier generates a lot of heat, it has an unexpected benefit—keeping you cozy during winter evenings. Imagine the warmth of the amplifier complementing your favorite music as you relax. Why not brew a cup of coffee, settle into a comfortable chair, and enjoy the beautiful melodies filling the room? Truly, isn’t this one of life’s simple pleasures?
Michael Jackson's iconic song "Bad" from IWISTAO HIFI Power Amplifier 80Wx2 Stereo NAP140
The IWISTAO HIFI Power Amplifier 80Wx2 Stereo NAP140 is a product that audiophiles will find particularly intriguing. Modeled after the legendary Naim NAP140, this amplifier carries the essence of what makes Naim amplifiers so revered in the audio community. Often compared to Linn turntables in their iconic status, Naim amplifiers are known for their warm and mellow tones, delivering a listening experience that captures the hearts of true music enthusiasts.
Despite its understated appearance, the Naim NAP140 has gained a cult following for its ability to provide a rich and immersive audio experience. While the price of Naim amplifiers can be steep, those who appreciate expert craftsmanship and superior sound quality find the investment worthwhile. This amplifier isn’t just a device; it’s an experience. Once you’ve listened to it, it’s hard to imagine settling for anything else.
Personally, I hold the NAP140 circuit in high regard, comparable to my affection for the iconic 1969 circuit. While the sound quality of the NAP140 is on par with the 1969 circuit, it surpasses it in terms of output power. A defining characteristic of the NAP140’s architecture is its predominantly second-harmonic distortion, which lends it a tonal quality reminiscent of the charming warmth of tube amplifiers. However, unlike tube amplifiers, the NAP140 achieves this harmonic richness with remarkable efficiency and precision.
The IWISTAO HIFI Power Amplifier brings the essence of the Naim NAP140 to a wider audience, offering a taste of its renowned mellow and soft sound. For those who value musicality and tonal charm, this amplifier is a compelling option that bridges the gap between classic designs and modern accessibility.
A demo video showcases the amplifier’s performance using Michael Jackson's iconic song "Bad." You can view it here to experience the sound quality for yourself.
Friend Don't Cry from IWISTAO 5.25 Inch Coaxial Speaker LS50
This is a 5.25 inch coaxial empty speaker cabinet with solid wood. Exquisite craftsmanship, pure sound quality, high density and strong anti-resonance ability.
