Bryston BP-173 line preamplifier Specifications

Sidebar 1: Specifications

Description: Solid-state stereo preamplifier with remote control & headphone amplifier. Inputs: 4 single-ended (RCA), 1 single-ended Record (RCA), 2 balanced (XLR). Input impedance: 6.5k ohms (RCA), 4.5k ohms (XLR, inverting and non-inverting). Outputs: 1 single-ended variable (RCA), 1 single-ended fixed (RCA), 2 pairs balanced (XLR), 1 headphone (1/4", 6.35mm TRS). Control connectors: female DB9 for full two-way RS-232 (RJ12) suite; two 3.5mm mono (TS) miniplug DC triggers (12V); one auxiliary IR input with external IR receiver terminated with 3.5mm plug. Output impedance: not specified. Maximum output level: not specified. 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.
Serial number of unit reviewed: 000042.
Prices: $3995; BR2 remote control, $375; MM and DAC modules, $750 each; TF-2 step-up transformer, $1500. Approximate number of dealers: 295. 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:

Ortofan's picture

... "superbly well engineered" and "it is difficult to see how a preamplifier could perform any better on the test bench", is it sufficient to derive the full benefit of 24-bit hi-res recordings?
A noise and distortion level of 0.001%/-100dB is barely equivalent to 16-bit resolution. Even the -120dB level only equates to about 20-bit resolution. The LSB for 24-bit encoding is on the order of a level of 0.00001%/-140dB. Does any preamp come close(r) to achieving this level of performance?

dalethorn's picture

Mind-boggling. So whatever the preamp is capable of with the best-case 1 khz test tone, you run a typical 24-bit recording through it and try to hear the preamp's contribution to the sound? No argument here, just trying to imagine how all that breaks down in the real world.

Gnib's picture

I`m very curious about this follow-up on the DAC and phono modules.

dalethorn's picture

"Cubed models employ an array of 12 active devices for the first 6dB of gain. Developed by the late Dr. Ioan Alexandru Salomie, this array acts as "a super-linear" input buffer to filter out audio- and radio-frequency noise, particularly anomalies that originate in the power line, reducing the overall noise and distortion to less than 0.001%."

Well, I thought Ortofan's questions were simple enough, but the array (no pun intended) of issues aren't going to make things easy. Ignoring any photo stages (can I?), the "array of 12 active devices" acting on the "power line anomalies" is interesting. I'd prefer to filter my power elsewhere, but who knows? Maybe these guys have tricks that their competitors don't.

allhifi's picture

Cubed's IBG (Input Buffer/Gain) circuit may be advantageous in main amplifier stages but may not be particularly suitable for preamp's 'Input' stage.

Bryston's 'Cubed' series amplifier's clearly have an articulation/ resolution capability previous series lacked.

Interestingly, the "SST" series was a MAJOR improvement over ST series, but by many accounts, the SST2 was a step back?
Apparently, changes were made to the 'Input Stage' in the SST2 -not well received by many accounts. Yet it "measured" better to Bryston ! Go figure.
Come (near) full-circle, the new "3" series employs a circuit that, interestingly, has Bryston talking 'audiophile' language previously dismissed as superfluous, imaginary -not relevant/important -or "measurable" Go figure.

I suspect IBG-circuit doesn't correlate well in line-stage applications.
While many line-stage (preamp) designer's appear to be employing lower-and-lower gain 3,6, 9 db., Bryston continues with 12-18 db.? designs.

Stick with the 3B/4B3 (Cubed) amps; quite an accomplishment for Bryston.

peter jasz

allhifi's picture

dalehorn: I suspect you are referring to Bryston's noise level/vs./source resolution ?

If so, the "breakdown" in the real-world is obvious via listening evaluations.


dalethorn's picture

Interesting - In any case, these proprietary techniques don't reveal enough to do much besides just listening for any anomalies. If I were engineering these things, I'd like to explore ways to both shape and filter noise (if that makes sense), to try to make it less apparent psychoacoustically. How that would look from a whole-system perspective I have no idea.

allhifi's picture

Indeed, what you say makes complete sense (re: noise attenuation)

It's unclear why makers don't consider using 'Balanced' power/ transformers in their designs -or AC Re-generation, as noted in ML's No.52 preamp.

The Balanced (Symmetrical) AC power supply I'm using (Blue Circle MR-800/1200) offers up excellent 'performance' with any/all components connected/powered. (I use on for 'sources', the other for amplification)

I have recently acquired an Exact Power SP-15 -sitting idle currently.
The SP-15 has a single, substantial 1.8-2KVa that may prove beneficial for main amplification -eventually to replace the 1200 watt Blue Circle.

The improvements in (particular lower/mid frequency) resolution is dramatic, and most welcome -when compared to wall AC power.

Yet, at busy AC-usage times of the day, one can easily hear the polluted line's impact upon SQ; a lumpy, slow sound. It happens regularly.

I suspect an AC Re-generator (PS Audio P-3) would work extremely well in low-power applications, particularly 'digital' gear where SQ improvements are incredible.