Bryston BP-173 line preamplifier Phono & DAC modules June 2019

Larry Greenhill reviewed the BP-173's phono & DAC modules in June 2019 (Vol.42 No.6):

After reviewing Bryston's BP-173 line preamplifier ($3995) in June 2018, I returned the review sample to Bryston to have its optional DAC and moving-magnet phono modules installed ($750 each). I was curious to hear if these options would maintain the high standard set by this component, which is included in Stereophile's "Recommended Components."

When the BP-173 returned, it looked unchanged. But when I removed its top plate, I saw that two new daughterboards had been installed above the motherboard: the DAC module on the right, the phono module on the left. The new high-resolution DAC module has two TosLink inputs and two transformer-isolated coaxial S/PDIF inputs, selectable from the front panel. The data are directly passed on to a single AKM 4490 DAC, which has a single-ended output. Unlike Bryston's flagship standalone D/A processor, the BDA-3 ($3495), this new card doesn't decode DSD data. The new card's specified total harmonic distortion plus noise in the audioband is 0.002%, an improvement over Bryston's previous add-on DAC modules, made for their BP-26 preamplifier.

The BP-173's moving-magnet phono module employs two-stage RIAA equalization; James Tanner, Bryston's vice-president of marketing, sent me a graph that shows the EQ section's extreme accuracy. An optional rumble filter is available with a factory order, or in the field with a change of capacitors.

Adding these modules to the BP-173 changes its input architecture. The base model has seven line-level analog inputs—two balanced (XLR) and five unbalanced (RCA), with one of the latter designated Record. Adding the MM phono module drops this to six line-level inputs and assigns the MM phono input to the pair of RCA jacks labeled Input 2. (Once the phono module is installed, Input 2 can only be used with a turntable.) Installing the DAC module also changes the input count: It activates the preamp's two TosLink digital inputs—D1 and D2—and allows the pair of RCA jacks labeled Input 1 to be used as two distinct S/PDIF digital inputs: D3 and D4. But even with the DAC module installed, as long as no S/PDIF digital sources are connected, Input 1 can still be used as a line-level analog input.

Setting up the upgraded BP-173 was straightforward, with no glitches encountered. I ran an unbalanced S/PDIF interconnect (RCA) from my Bryston BCD-1 CD player to the left-channel jack of the Bryston's input 1 (D3), and a single BNC-to-RCA interconnect (footnote 1) from my Bryston BDP-3 media player to the right-channel jack of the BP-173's input 1 (D4). And because I needed to use Bryston's TF2-30 moving-coil step-up transformer ($1500) to boost the 0.2mV output of my Spectral Reference MC cartridge for the MM phono module's input, I ran unbalanced interconnects (RCA) from the TF2-30 to the right and left jacks of the BP-173's input 2 (phono).

The BP-173's DAC upgrade grabbed my attention from the get-go. I was surprised by its slam, snappy transient response, and transparency. Driving the Mark Levinson No.534 power amplifier, the expanded BP-173 produced engaging, detailed, tonally captivating, utterly natural sound. The sound of the vibraphone that accompanies the male vocal ensemble Cantus in John Atkinson's recording of "Introit: Benedicta sit Sancta Trinitas," from Cantus (CD, Cantus CTS-1207), was translucent, liquid, and glowing. At the end of the Piè Jesu of John Rutter's Requiem, in the recording by the Turtle Creek Chorale led by Timothy Seelig, the DAC clearly depicted the sopranos' lilting voices over the pipe organ's massive pedal chord (CD, Reference RR-75CD). The ominous bass synth in "Silk Road," from I Ching's Of the Marsh and the Moon (CD, Chesky WO144), pressurized my room. With "Gabriel's Oboe," from Ennio Morricone's film score for The Mission, as arranged by Ralph Ferris for the chamber ensemble Ethel (MP3 file recorded from SiriusXM Radio's weekly show Living American), the BP-173 drew me in as has no other audio component. The augmented BP-173 reproduced the full power of the violins' fierce, fast pattern, coupled with pounding drums and brass, in Bruckner's Symphony 9, with Claudio Abbado conducting the Lucerne Festival Orchestra (24/48 download and CD, Deutsche Grammophon 479 3441/HDtracks).

At first the BP-173's phono module sounded more neutral than I liked, but I soon realized that it was allowing me to focus on the music longer than usual, with less fatigue. This was particularly true with the score for Glory (LP, Virgin America 91329-1), composed and conducted by James Horner and produced and mixed by Shawn Murphy. I relaxed, drawn into the orchestral dynamics and the lilting voices of the Boys Choir of Harlem in "Call to Arms," one of the most melodic of Horner's compositions for film. The soundstage was wide and deep, with the fife and snare drum set in a distinctly different layer from the singers.

Bryston's new phono module also did well by Russian ballet music, including Dance of the Knights from Prokofiev's Romeo and Juliet, with Erich Leinsdorf conducting the Los Angeles Philharmonic (direct-to-disc LP, Sheffield Lab 8), and the suite from Shostakovich's The Age of Gold, with Leopold Stokowski conducting the Chicago Symphony (LP, RCA Living Stereo LSC-3133). The phono module reproduced the rich orchestral timbres, silky strings, intense and driving rhythms, and wide, deep soundstages captured on both of these recordings.

The Bryston preamp's new phono section inspired me to revisit some of my favorite jazz LPs, including Michel Legrand's Legrand Jazz (LP, Columbia CL-1250), particularly his arrangement of Thelonious Monk, Cootie Williams, and Bernie Hanighen's "'Round Midnight," with Herbie Mann (flute), John Coltrane (tenor sax), Miles Davis (trumpet), Eddie Costa (vibes), Paul Chambers (double bass), and Kenny Dennis (drums). I'd never heard Davis's solo trumpet come through so distinctly, so clearly, and so beautifully.

How did the upgraded BP-173 sound in comparison with other preamplifiers I had on hand? As noted in my review of the BP-173 in June 2018, matching it to the right amplifier—in my case, a Mark Levinson No.534—was critical. That done, the upgraded BP-173's dynamics, punchy bass, slam, and soundstage depth matched those of my Mark Levinson ML-7 preamplifier and easily bettered those of Bryston's BP-26. However, neither the upgraded BP-173 nor the ML-7 attained the transparency, transient response, and freedom from midrange grain of the Mark Levinson No.526 preamp, which costs considerably more ($20,000).

That said, the BP-173's optional modules exude top build quality and engineering excellence. They use high-quality PCBs with no point-to-point wiring. They should last for years and be easy to service. Adding these modules requires no changes to the front or rear panel, and no new connectors or switches. Low-level phono-cartridge signals or digital datastreams can be managed with the existing front-panel controls and/or Bryston's optional BR-2 remote control ($375). However, audiophiles who stream their libraries of digital music will bemoan the DAC's lack of a USB or HDMI input and user-selectable PCM filters. More important, the DAC module can't decode DSD files.

Bryston's à la carte upgrade plan may at first produce sticker shock, as a fully maxed-out BP-173 costs a total of $7370: $3995 for the base preamplifier, $375 for the BR-2 remote, $1500 for the DAC and phono modules, and $1500 for the TFA-30 step-up transformer (if you use an MC cartridge). But that's still less than the cost of 17 of the 22 other solid-state preamps listed in Class A of "Recommended Components"—and at $750, the integrated DAC module costs only 22% of the price of the BDA-3, but sounds as good, I felt, with PCM files.

Bryston's optional phono and DAC modules and BR-2 remote control greatly increase the BP-173's strengths while maintaining the high standard set by the base model. They integrate high-quality phono and DAC functions without the need for separate components and their interconnects, and they sure save shelf space. For most BP-173 owners, these upgrades should be no-brainers.—Larry Greenhill

Footnote 1: Because the Bryston BDP-3's S/PDIF output has a BNC jack, I used a Bryston LV61S BNC-to-RCA 75 ohm coaxial cable ($120).

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.