- Written by John E. Johnson, Jr.
- Published on 15 April 2013
We reviewed the Bryston BDA-1 Outboard DAC in June, 2011. It demonstrated excellent sound quality and bench test results. Now comes the latest iteration in their DAC line, the BDA-2. The DAC is still balanced (through the use of two DAC chipsets), has lower distortion, and best of all (as you will see), they have added an asynchronous USB input (the type that you would connect to your computer via a USB port).
- Design: Stereo DAC
- DACs: Two 32 Bit AKM
- Codecs: WAV, FLAC, AIFF, WMA, MP3
- MFR: 20 Hz - 20 kHz, - 0.1 dB
- THD+N: 0.001%
- Sampling: Up to 24 Bit / 192 kHz
- Inputs: USB Class 2, 4x SPDIF (2 BNC, 2 RCA), 2x Optical (TOSLINK), AES/EBU, RS-232
- Outputs: RCA Single Ended, XLR Balanced, SPDIF Bypass (RCA)
- Dimensions: 1.75" H x 17" W x 11.25" D
- Weight: 39.5 pounds
- MSRP: $2,395 (Remote Control Optional)
- SECRETS Tags: Bryston, DACs, Asychronous USB, Audio
Compared to the BDA-1, the BDA-2 uses 32 bit DACs (AKM). Over the past couple of years, I have seen manufacturers who produce digital components moving towards the 32 bit arena. Of course, there are no 32 bit music or movie sound tracks, but 32 bits gives the DAC some headroom so that no bits are truncated during processing. In other words, you get the full benefit of the current 24 bit sound, and 16 bit music is a breeze.
The DAC is balanced circuitry, having a stereo DAC for each of the outputs, with one channel of the stereo DAC being used for the + side of the signal, and the other channel for the - side. This is for the XLR analog balanced output. If you use the RCA analog output, only one channel of the DAC is used for each of the two RCA output jacks. In general, balanced circuitry is a good thing to have, since you get common mode rejection of any electrical interference that gets into the circuit, and also because there is twice the voltage output, which means lower overall noise, since the voltage is higher than the noise floor.
The front panel has indicators for the bitstream word depth and sampling frequency, e.g., 44.1, 48, 88.2, 96, 176.4, and 192 kHz. The input is selected by pressing one of the eight buttons on the right hand side, with the power on/off button to the far right. The eight inputs include two Toslink optical, two S/PDIF BNC, two S/PDIF RCA, one XLR, and USB. Lastly, there is a button to turn on upsampling, which allows for a more shallow slope in the cutoff filter.
Bryston explains the technology behind the BDA-2:
"The main motivation for the BDA-2 was to improve the USB input to allow for asynchronous USB and up to 192/24 bit high resolution playback. Asynchronous decoding uses the high quality high precision digital clock in the BDA-2 rather than utilizing the clock in the source computer. Timing is critical in a DAC to reduce jitter (timing) errors in the digital bitstream.
"We evaluated a number of DAC’s and chose the AKM 4399 due to its sonic qualities, excellent measured performance and potential for DSD decoding (software required).
"Most quality DAC chips perform well so what makes the BDA-2 unique in the market is the serious attention paid to many other parameters such as independent power supplies for the digital and analog sections, fully discrete Bryston proprietary analog circuitry, transformer coupled digital inputs, circuit board trace routing, independent circuit board traces for the analog and digital sections, grounding optimization for improved noise floors, proprietary part selection, multiple digital inputs (8 total) etc.
"The result is a DAC that in our opinion measures and performs at a state of the art level at a very reasonable price."
The rear panel is shown below.
From the left are two XLR analog outputs, two RCA unbalanced analog outputs, a S/PDIF output (if you want to have the digital signal pass through to another component), a USB-2 input, one XLR balanced input, two BNC S/PDIF inputs, and two RCA S/PDIF inputs. There is also a trigger connector for automatically turning on the DAC when you turn on your transport (if the transport has a trigger output). The RS-232 port is for updating firmware. There is a grounded AC receptacle at the far right.
I tested the BDA-2 with an OPPO BDP-105 (as a transport, with the RCA digital coax output going to the RCA coax input on the Bryston BDA-2), Pass Labs XP-20 preamplifier, Classé CA-M600 power amplifiers, and Carver Mark IV ribbon speakers. Cables were Wireworld. Much of my music these days is in the SACD format, but I used the CD layer as the digital output to the BDA-2 in those cases.
Piano is a difficult instrument to reproduce, not only because its lowest note is 28 Hz, but the attack has intense transients. No better way to test this than with Rachmaninov, in this case, his 24 Preludes (London 443 841-2).
Vladimir Ashkenazy knows how to play Rachmaninov, and his dexterity as well as his interpretation are flawless. The sound was flawless as well. The Bryston delivered clarity to the attack transients, and they sounded unrestrained, testimony not only to the DAC chipset, but also to the output stage.
Ah Mozart! Violin Concertos, produced by the rapidly-becoming-famous Norwegian recording company 2L (SACD 2L38). The violinist soloing amongst the other strings and brass can get lost if there is significant IM distortion. As you will see in the bench test results, IM in the BDA-2 was almost non-existent. Thus, not only was the soloist Marianne Thorsen quite separate, she was still delicately integrated into the overall music. The SACD's high resolution capability was a gift to her playing in a note so high in the register, it must have been near the highest note playable on a violin. And it was clean, clean, clean . . . astonishingly so. Again, the 32 bit DAC and fine output stage of the BDA-2 really make a huge difference when listening to music like this.
Bach, Beethoven, and Brahms make up the "Three B's" of classical fare, but if one tried to create the "Three H's" using Haydn as a member, who would the other two be? Certainly, he is of the same genius as the B's, and this SACD recording of some of his string quartets (Praga Digitals 16136) demonstrates his prowess as a composer, rather than simply that he was prolific in output.
The four stringed instruments were placed across the soundstage, and easily identified in their position. Again, if there were significant IM distortion, the soundstage placement would have been much more of a blend, and the strings would have sounded harsh.
In summary, I would classify the Bryston BDA-2 as detailed and neutral, with nary an audible hint of distortion.
On the Bench
All distortion measurements were within an 80 kHz bandwidth, and I used the XLR balanced outputs of the BDA-2 DAC. All digital test signals were at -5 dB unless otherwise stated.
At 16/44.1, 1 kHz sine wave, and 0 dB, the output was 3.9 volts, which is the maximum voltage the unit can produce. Distortion was 0.002%.
With the same signal at -5 dB, which is a more realistic level, the output was 2.2 volts, and distortion was 0.004%. If you compare these results with the BDA-1, you can see that the BDA-2 has a small, but measurable improvement. (Note however, that the "transport" for the BDA-1 tests was the BDP-1 music server.)
Using 19 kHz and 20 kHz sine waves, at 16/44.1, there were only two small side bands near the fundamentals, and there was no visible B-A peak at 1 kHz.
IM distortion came in at 0.005%, using a 16/44.1 test signal.
The measured frequency response for 16/44.1 was 10 Hz - 19 kHz, ± 0.1 dB, with a 0.8 dB roll-off between 19 kHz and 20 kHz.
The results for 24/96 and 24/192 were the same, so I will illustrate just the 24/192 graphs.
At 1 kHz, THD+N was 0.009%. This is truly excellent!
With 19 kHz and 20 kHz, there were no visible side bands, and there was a visible B-A peak 104 dB below the fundamentals.
IMD at 24/192 was 0.002%.
The measured frequency response at 24/192 was flat to about 25 kHz, followed by a decline of 7 dB out to 90 kHz.
Now, here is a 1 kHz sine wave digital signal played from my computer connected to the BDA-2 through the USB input. The distortion is the same as with the coax input, but notice the improved noise floor, which is significantly lower than with the coax input.
I also measured the jitter reduction of the DAC by inducing a specified amount of jitter in a 10 kHz sine wave and measuring the jitter in the signal from the S/PDIF output jack on the BDA-2. With the signal jittered at 531 picoseconds, the output had a measured jitter of 448 picoseconds, which is a 16% reduction. In other words, the DAC could reduce the jitter with its asynchronous design, by 16%. This is a new measurement for consumer A/V reviews, so we have to wait and see how this compares with other DACs tested down the road.
The Bryston BDA-2 is a very fine outboard DAC. It improves upon the BDA-1 in distortion, and adds an asynchronous USB input to be used for playing music with a digital output to the DAC. A few years ago, you could not get this performance at $5,000, so at $2,395, this DAC is a no brainer for consideration.