Bryston BDA-1 d/a mystery

Any BDA-1 processor possessors out there ? 

Currently investigating modding a  BDA-1 for a friend.

Unfortunately, Bryston  obfuscates much of their topology  by unobtanium service manuals and schematics. Which is the exact opposite situation of major players like Philips and Sony.

The Bryston BDA-1  d/a processor (released late 2009) is contains two Cirrus Logic  CS4398 dac chips. Each CS4398 is a dual-differential device that outputs L and R stereo channels.

The Audiocircle site has the official Bryston forum. There, officials from Bryston can comment on their products. For the BDA-1, they claim each 4398 is used per  channel. 

The company's sales literature on this product notes its use of "Dual 192K/24Bit Crystal DAC’s"

You can browse thru some of the of the device's manuf literature here:

The BDA-1 is the only digital device (CD player or d/a processor) that uses 2xCS4398
 ... and CTR+ F for "CS4398". Every other device on this fairly comprehensive list uses only one CS4398.

Unlike some of Cirrus Logic's competitors (Wolfson TI, AD), the Cirrus dac is not capable of mono-mode. So it can't be used, as a single device, to output a dual-diff mono channel (e.g., L or R). In fact, no Cirrus/Crystal dac -- ttbomk -- ever featured a mono mode including the 4398's immediate ancestor, the 4397.

So either it is stacked or Bryston is using only one of the two provided channel outputs (e.g., AOUTA- ,  AOUTA+ ) It's like using using two stereo amps for "dual mono". You feed the preamp L to one  stereo amp and preamp R to the other  stereo amp.  So ...  one of the  stereo amp channels is left dangling and never used. This can be done but it's rare.

Actually, there is one more  possibility for the dual CS-4398 use: one for std outs; the other for balanced outs. If you look at the photos of the PCB, this looks like the most likely scenario.

Why all the fuss? Well,  If a respected long-time high-end manuf can make such claims -- honest mistake or deliberate marketing hype of "dual dac chips " -- what / who else is pulling our legs with similar claims? 

Or did Bryston ACTUALLY   work out how to get the CS4398 to output a dual-diff mono signal for each chip?



Can’t answer.  I have the DAC3, which I love, but it uses AKM chip.

I will note that the Bryston Audiocircle Forum is extremely unhelpful.  I had bought the BDP-3 and eventually sold if off in frustration over many issues.  I joined that Forum to raise these issues and I was routinely ignored, with many of my queries deleted.  They only want rah rah fan’s posting there

mahler123: I posted on this issue at the AC Bryston sub-forum using very nuanced language. So far, no censorship.

Meanwhile, if anyone here on Audiogon has a BDA-1, can remove the cover and simply perform a few non-destructive tasks, perhaps we can dig into the mystery. Ahem ... "help" Bryston out.

--- remove cover and take closeup photos of the PCB (both sides); post here on Audiogon

--- use a DMM in "ohm" mode to trace the test-point connections. The test points are the round "via" holes that are ubiquitous in modern surface-mount PCB design.

Here is close-up of the BDA-1 pcb (photo taken by in their review).