Bryston BP-173 Line Preamplifier
By Larry Greenhill
Introduction
This equipment report focuses on the Bryston BP-173 line preamplifier. The review highlights the author's experience with the component, emphasizing flexibility in audio system setup and the unique design philosophy behind Bryston's "Cubed" series.
Description
The Bryston BP-173 is a solid-state line preamplifier priced at $3995, positioned between Bryston's BP-6 and BP-26 models. It features an array of 12 active devices for the first 6dB of gain, designed to act as a super-linear input buffer, reducing noise and distortion. The unit offers seven inputs (five single-ended RCA, two balanced XLR) and balanced and single-ended outputs. Front panel controls include input selection, Power, Mute, Bypass, Record, and Balance, along with an IR receiver, headphone output, and a volume knob. The "Cubed" nomenclature refers to the evolution of Bryston's product naming conventions.
Specifications
Inputs: 4 single-ended (RCA), 1 single-ended Record (RCA), 2 balanced (XLR). Input impedance: 6.5k ohms (RCA), 4.5k ohms (XLR).
Outputs: 1 single-ended variable (RCA), 1 single-ended fixed (RCA), 2 pairs balanced (XLR), 1 headphone (1/4", 6.35mm TRS).
Control Connectors: RS-232, two 3.5mm DC triggers (12V), auxiliary IR input.
Line-stage gain: Variable RCA/XLR: 12/18dB; Fixed RCA in/out: 0dB; Fixed XLR in/out: 6dB.
Frequency response: 20Hz–20kHz, ±0.05dB.
THD+N (20Hz–20kHz, 1V RMS for XLR): <0.0025%.
IMD (60Hz, 7kHz in 4:1 ratio): <0.0003%.
Signal/noise: >102dB (RCA), >108dB (XLR).
Power consumption: 2W standby, 32W idle, 32W full power.
Dimensions: 17" (430mm) or 19" (483mm) W by 4.55" (116mm) H by 13" (330mm) D.
Weight: 11 lbs (5kg).
Finishes: Black, Silver.
Warranty: 20 years (analog circuits & components), 5 years (digital components).
Manufacturer: Bryston Limited, 677 Neal Drive, Peterborough, Ontario K9J 6X7, Canada. Tel: (705) 742-5325. Web: www.bryston.com.
Setup and Listening
Installation was straightforward. The reviewer used the BP-173 with a Constellation Stereo 1.0 power amplifier and a Mark Levinson No.534 amplifier. The unit performed well without any discernible change in sound quality during the review period, indicating no need for a warm-up or burn-in period. Initial listening impressions noted an "etched and edgy" vocal sound with Stevie Nicks, but this was resolved when paired with the Mark Levinson No.534, which provided a more neutral tonal balance, transparency, and clear highs. The bass response was described as strong and extended. The Bryston preamplifier also excelled with percussion recordings, clearly separating instruments and reproducing dynamic contrasts.
Measurements
The Bryston BP-173 demonstrated excellent performance in measurements. The preamplifier preserved absolute polarity and had very low output impedance. Frequency response was within specification. Channel matching was superb, even into lower impedances. Distortion levels were consistently low across the audioband, with minimal rise at the frequency extremes. Intermodulation distortion was also exceptionally low. The measurements indicated that the BP-173 is a superbly engineered preamplifier.
Key Measurement Highlights:
- Gain: 17.5dB (balanced/unbalanced to balanced), 11.6dB (unbalanced to unbalanced).
- Input Impedance: 6.8k ohms (unbalanced), 10k ohms (balanced).
- Output Impedance: 690 ohms (unbalanced), 340 ohms (balanced).
- Headphone Output Impedance: 72 ohms.
- Frequency Response: 20Hz–20kHz, ±0.05dB.
- THD+N: Below 0.0025% at 1kHz into 100k ohms.
- Signal/Noise Ratio: >92dB (A-weighted).
- Channel Separation: >108dB below 2kHz, decreasing to 80dB at 20kHz.
Comparisons
The BP-173 was compared with other high-end preamplifiers, including Bryston's own BP-26 and the Mark Levinson ML-7 and ML-526. While the BP-173 matched the dynamics and bass response of some higher-priced competitors, the Mark Levinson No.526 offered superior clarity, air, transparency, and transient response. However, the BP-173 was noted as a significant value proposition, offering performance close to that of the much more expensive No.526 at a fraction of the cost.
Conclusions
The Bryston BP-173 is highly recommended as a high-value, line-level preamplifier. It delivers engaging, detailed, and tonally captivating sound that approaches reference quality. Its deep bass extension, dynamic range, soundstaging, and speed are notable. Despite lacking built-in phono or digital inputs and internet connectivity in its standard configuration, the BP-173 offers exceptional performance, especially when paired with a compatible high-quality power amplifier. It is considered a bargain preamplifier that is strongly recommended after audition.
Associated Equipment
Analog Sources: Linn Sondek LP12 turntable, Day-Sequerra 25th Anniversary FM Reference tuner, Sutherland Engineering Vibe phono preamplifier.
Digital Sources: Bryston BCD-1 CD player, Bryston BDP-3 media player, Oppo BPD-103 universal BD player, Lenovo P50 ThinkPad computer.
Power Amplifiers: Constellation Audio Inspiration Stereo 1.0, Mark Levinson No.534.
Loudspeakers: Quad ESL-989, Revel Ultima Salon2.
Cables: Wireworld, Bryston, Mark Levinson, Pure Silver Cable, Red Rose Silver One, Totem Acoustic Sinew, Coincident Speaker Technology, QED X-Tube 400, Ultralink Excelsior.
Accessories: JL Audio CR-1 electronic crossover, Apple iPhone 6, Apple iPad, Torus Power RM 20 power conditioner, Salamander Designs Synergy System Twin-width S40 Rack.
