Key Features
The Power 3 is a push-pull, ultralinear design using eight KT88 output valves per monoblock, arranged in four matched pairs operating in parallel push-pull configuration. The circuit topology follows a three-stage architecture: four 6922 dual-triode valves handle input and voltage amplification, two 5687 dual-triode valves act as high-voltage driver cathode followers, and the eight KT88s form the output stage. The 5687 driver stage is a detail that merits particular note — the 5687 runs at considerably higher anode voltages than the 6922 and provides the current drive necessary to control the grids of eight output valves cleanly and without compression, a requirement that less generously specified designs can fail to meet at high output levels. Pearl tube coolers are fitted to the 5687 valves as standard, visible in the photographs, to manage the thermal load on these particularly hot-running devices.
The output transformers are Sonic Frontiers’ own design, wound in-house, and are a major contributor to the amplifier’s measured performance. Stereophile’s measurements recorded an output impedance of 0.17–0.22 ohms across the audio band — exceptionally low figures for a valve amplifier, translating to a damping factor in excess of 50 — and a frequency response that extends from 5Hz to 75kHz at 1W. These are figures that approach or surpass many solid-state amplifiers of the period, and reflect the quality of transformer design rather than simply the output valve configuration.
Rated power output is 220 watts into 8, 4, or 2 ohm loads — the output transformer is configurable for different impedances by the dealer, and this pair is currently set for 8Ω operation. In Stereophile’s measurements, the amplifier was found to produce predominately second-harmonic distortion, which is the character of distortion most commonly associated with valve amplifiers operating in push-pull and is generally regarded as the most musically benign distortion signature. The signal-to-noise ratio is specified at 110dB, and input sensitivity at 2.2V balanced.
Signal inputs are provided in both balanced XLR and single-ended RCA formats, both accessible on the rear panel alongside a mute switch. Input impedance is 198kΩ balanced, ensuring compatibility with virtually any preamplifier. The speaker output is a balanced configuration — as the rear panel warning clearly states — using four binding posts per monoblock supporting positive, negative, and ground connections; buyers should read the owner’s manual carefully regarding loudspeaker connection to this output stage. A standby circuit is provided, allowing the amplifier to be held at reduced operating temperature between listening sessions without a full cold start each time. Two screws are all that is required to remove the top section of the chassis for access to the bias adjustment points — a practical consideration that reflects Sonic Frontiers’ attention to the needs of the end user.
Idle power consumption is 375W per monoblock, rising to 580W at rated output. These figures are important for two reasons: they determine running costs in use, and they indicate the significant thermal output of each unit. Adequate ventilation above, behind, and to the sides of each monoblock is essential.
Important Owner’s Notes
Valve maintenance: Each Power 3 monoblock uses eight KT88 output valves, four 6922 input/driver valves, and two 5687 driver valves — fourteen valves per monoblock, twenty-eight in total for the pair. KT88 output valves have a finite service life that depends on usage, and a full replacement set for a pair of Power 3s represents a significant cost that prospective buyers should factor into their ownership planning. KT88 valves remain in current production from several manufacturers including Gold Lion, Electro-Harmonix, Psvane, and Shuguang, and are widely available. The 6922 and 5687 are also currently available. Individual bias adjustment points are provided for each output valve, and biasing should be carried out after any valve change. Sonic Frontiers’ manual is straightforward on this procedure and the relevant tools are included with the amplifiers.
Heat and ventilation: Each Power 3 monoblock consumes 375W at idle and 580W at full output. This is a substantial thermal load, and the amplifiers run very hot. They must be positioned with clear space above and to all sides, and must never be placed in enclosed equipment racks or on shelving with restricted airflow. They are not suitable for positioning near heat-sensitive furniture or equipment. Children and pets should be kept away from the amplifiers when in use.
Technical Specifications
(Source: HiFi Engine manual listing; Stereophile Power 3 review specifications sidebar (October 2000); cross-referenced with Sonic Frontiers Power 3 operating manual via Pearl HiFi archive)
- Type: Monoblock push-pull ultralinear valve power amplifier
- Valve Complement (per monoblock): 8 × KT88 (output); 4 × 6922 (input/driver); 2 × 5687 (driver cathode follower)
- Power Output: 220W into 8Ω, 4Ω, or 2Ω (1% THD, 20Hz–20kHz)
- Frequency Response: 5Hz–75kHz (±0.5dB at 1W); 15Hz–60kHz (±0.5dB at 220W)
- Total Harmonic Distortion: 1%
- Signal to Noise Ratio: 110dB
- Input Sensitivity: 2.2V (balanced or single-ended)
- Voltage Gain: 25.6dB into 8Ω; 22.6dB into 4Ω
- Input Impedance: 198kΩ (balanced); 99.3kΩ (single-ended)
- Output Impedance: 0.17–0.22Ω (20Hz–20kHz, as measured by Stereophile)
- Damping Factor: >50
- Inputs: XLR balanced; RCA single-ended; Mute switch
- Output: Balanced speaker terminals (4 posts: +, −, GND × 2)
- Output Impedance Setting: 8Ω (current configuration, as confirmed on rear panel)
- Power Consumption: 375W idle; 580W at rated output (per monoblock)
- Dimensions (W × H × D): 460 × 230 × 560mm (per monoblock)
- Weight: 45kg per monoblock (90kg total for pair)
- Serial Number: 106494 (confirmed from rear panel)
- Year of Production: 1996–1999
- Country of Origin: Canada (made by Sonic Frontiers Inc, Oakville, Ontario)
- Original US Retail Price: $9,999 per pair
Why Buy From Us
With over 40 years of experience in the Hi-Fi industry, we are well placed to assess and test equipment of this type. Every item we list is fully inspected and tested before sale — this pair was checked by Andrew in our workshop.
When you buy from us you can expect:
- Full inspection and testing prior to listing — not simply a visual check
- A 3-month guarantee on every item we sell
- Transparent descriptions with no omissions
- Professional packaging to ensure safe delivery
- After-sales support available by phone or email should you have any questions
Please note that specialist packing arrangements will apply to this item owing to the exceptional size and weight of the amplifiers — each monoblock weighs 45kg. Please contact us prior to purchase to discuss delivery arrangements.
Summary
A matched pair of Sonic Frontiers Power 3 monoblock valve power amplifiers in immaculate condition — the flagship product of one of Canada’s most respected valve amplifier manufacturers, and a design that competed at the highest level of the market during its production life. 220 watts per monoblock from eight KT88 output valves, exceptionally low output impedance for a valve amplifier, balanced and single-ended inputs, and a build quality that reflects serious engineering throughout. Prospective buyers should note the heat and ventilation requirements, the valve maintenance considerations, and the significant weight of each unit. This is a matched pair listed as a single lot. Please feel free to get in touch with any questions prior to purchase.
