Wavebourn Audio Research Laboratories

The Wavebourn Audio Research Laboratories is working now on research and further development of high end line of equipment Edelweiss-3 preparing it to manufacturing.

Wavebourn Edelweiss-3 Power Amp Plus Overview

The Wavebourn Edelweiss-3 Power Amp Plus is a high-end, single-ended Class A1 vacuum tube power amplifier designed by Anatoliy Lisovskiy of Wavebourn Audio Research Laboratories. Part of the Edelweiss-3 series, it targets audiophiles seeking high-quality sound with innovative design features at a more affordable price point compared to typical high-end audio equipment. The series is being designed to contain Preamp Plus, a high end preamp that can output 20 mA to drive headphones, and several versions of Power Amp Plus for loudspeakers and headphones.

Key Features and Specifications

• Power Output:
  • Available in two versions:
    • 3W per channel (Click for youtube video) for 96 dB/W/M high-sensitivity speakers, using 9-pin output tubes.
    • 6W per channel (Click for youtube video) for 92 dB/W/M speakers, using octal output tubes.
  • An experimental "Assisted Single-Ended" version (Click for youtube video) can switch between:
    • 6W per channel (true single-ended, for 92 dB speakers).
    • 12W per channel (assisted single-ended, for 90 dB speakers).
• Tubes:
  • 9-pin version: Supports EL82, SV83, EL84, 6P14P, 6P15P, and 6P18P.
  • Octal version: Supports EL34, KT77, KT88, KT120, 6L6GC, and Russian 4P10S (similar to Raytheon VT127).
  • 8CB11 video pentode driver for enhanced performance.
• Adjustable Auto-Bias:
  • Features an adjustable auto-bias system with digital gauges (accessible under the bottom grill) for fine-tuning bias to suit various output tubes, ensuring optimal performance and longevity.
  • When swapping tubes (e.g., EL84 for 6P15P), the auto-bias control must be turned fully counter-clockwise before swapping, then gradually adjusted using the digital gauges to prevent damage and ensure proper operation.
• Inputs and Outputs:
  • Input: 0 dB (0.775V) RCA, 50K stereo impedance.
  • Outputs: Dual outputs for 4-6 Ohm (low ohm) and 8-12 Ohm (high ohm) speaker loads.
• Output Impedance Adjustment:
  • Features continuous variable output impedance adjustment from negative 3.8 Ohm to positive 3.8 Ohm, passing through zero ohmp. This renders the traditional "damping factor" metric obsolete, providing active servo-control for enhanced woofer performance, particularly in bass.
• Frequency Response: 10 Hz–90 kHz (within -3 dB), from 20 Hz full power, ensuring excellent frequency extension.
• Soft Clipping: Incorporates soft asymmetric saturation for near-inaudible clipping, mimicking a "too loud" sound without harsh distortion.
• Headphone Capability:
  • Doubles as a headphone amplifier with headphone output control, capable of driving a wide range of headphones, from highly sensitive dynamic headphones to power-hungry planar headphones, with clean, transparent sound.
• Build:
  • Hand-built in the USA, often sold as prototypes to fund R&D.
  • Uses MOSFET voltage regulators for stable, low-noise operation, alongside Schottky diodes for filament rectification, ensuring a compact design with minimal hum.

Design and Technology

• Class A1 Single-Ended (SE): Operates in pure Class A1 (or assisted SE in the experimental version), delivering a clean, warm sound with low intermodulation distortion and an "airy, liquid" midrange, ideal for jazz and female vocals.
• Feedback Loops: Three nested feedback loops, with the current loop bridged for adjustable output impedance, enhance bass control and speaker damping, challenging the stereotype of weak bass in SE tube amps.
• Tube Versatility: The adjustable auto-bias system supports a wide range of tubes, allowing audiophiles to experiment with sonic characteristics (e.g., EL82, SV83 for 9-pin; EL34, KT88 for octal).
• Modern Engineering: Adopts a modern approach not only through the use of contemporary components like MOSFET voltage regulators and rectified filament power, but also by implementing nested feedback loops that the designer experimented with using an analog computer, ensuring quiet, reliable operation while combining vintage tube warmth.

Performance Highlights

• Sound Quality:
  • Praised for detailed and defined bass, pure and sweet midrange, and transparent soundstage with excellent 3-dimensional image focus, competing with more expensive single-ended triode (SET) amps.
  • Excels with high-sensitivity speakers (96 dB for 9-pin, 92 dB for octal), or less sensitive 90 dB speakers in Assisted SE version.
  • The continuous variable output impedance adjustment optimizes speaker control, delivering superior bass definition and woofer damping.
• Headphone Performance: Recognized as the best headphone amp of 2021 by The Headphone Experience YouTube channel, praised for its clean, dynamic performance across a wide range of headphones, from sensitive dynamics to planar models.
• Soft Clipping: Handles overdrive gracefully, maintaining sound quality at peak power without harsh distortion, as demonstrated in YouTube reviews.
• Tube Compatibility: When swapping tubes like SV83/6P15P (lower screen grid voltage ratings: 150V typical, 330V max) for EL84/6P14P, the auto-bias must be carefully adjusted to avoid damage. Tubes like EL83 are incompatible due to potential damage.

Pricing and Availability

• MSRP: Pre-COVID prototypes (e.g., CV1127 version) were sold for approximately $800 USD. Post-COVID pricing may be higher due to inflation, but specific current pricing is unavailable.
• Availability:
  • Both 9-pin (3W, 96 dB speakers) and octal (6W, 92 dB speakers) versions are equally available, primarily as pre-production prototypes hand-built by Anatoliy Lisovskiy.
  • The experimental Assisted Single-Ended version (6W/12W switchable) is also available, with details on YouTube.
  • Full production models were planned, but updates are limited due to the designer’s focus on other projects (such as UV-C disinfection devices during COVID-19).
• Sales: Prototypescan be available via platforms like eBay, US Audio Mart, Ubuy, and Facebook Marketplace with some units circulating in 2024.

Reviews and Reception

• Dick Olsher (Blackdahlia, June 2024): Praised the amp’s bass definition, midrange purity, and soundstage transparency with high-sensitivity speakers. Noted superior bass control over other SET amps but highlighted limitations with power-hungry speakers.
• The Headphone Experience (YouTube): Named it the best headphone amp of 2021, emphasizing its versatility for both speakers and headphones.
• User Feedback: Owners report high satisfaction with efficient speakers and passive preamps, particularly praising the adjustable output impedance for optimizing speaker performance.

Additional Context

• Designer Background: Anatoliy Lisovskiy, educated at Tomsk University of Control Systems and Radio Electronics, transitioned from solid-state to tube amp design in 2002 after experiencing a single-ended triode amp. His designs blend vintage tube warmth with modern engineering for affordability and performance.
• Prototypes: The Edelweiss-3 series includes power amps and preamps, with prototypes sold to fund R&D. These units are hand-crafted, reflecting an iterative design process.
• Limitations:
  • Not suited for low-sensitivity speakers (e.g., 90 dB JBL, except in assisted SE mode) requiring higher power for realistic loudness.
  • Prototypes may lack aesthetic polish, prioritizing performance.
  • Tube swapping requires careful bias adjustment to avoid damage, particularly when using tubes with differing voltage ratings.

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