DAC with digital (BNC) output

vetinry

Member
2010-10-29 2:41 pm
Good evening
I'm having a few problems configuring my system and wondered if anyone could help
I've recently purchased a Bryston SP1.7 receiver, which, becuase it's the pro model has a BNC input rather than optical via toslink.
I am just researching a DAC to feed my squeezebox signal into the by passed analogue inputs of the Bryston, but completely forgot that if I want to hook up a 5.1 source (such as a Humax digital box) with only optical outputs, I would be a bit stuck.
I've seen that you can buy optical to coaxial converters (no idea how damaging they are to the digital signal, but I wondered if there were any DACs which I could use with my squeezebox but which could also feed a digital signal to the Bryston via BNC
Can anyone help?
Steve
 
you dont want a DAC, you want an audio interface or transport. something like an RME HDSP9652 PCIE card perhaps, or the RME fireface 400 (both of these have 5.1 pass through). cheaper units are available, but this one is pretty nice and will run via firewire from the computer, but also standalone with your squeezebox. you could also get a hiface USB to BNC.
 

alexcp

Member
Paid Member
2009-06-09 8:55 pm
HiFiOcean.com
Well, not entirely different - otherwise it wouldn't work at all! The connector is different; BNC has higher signal level, but the level of RCA is within the acceptable range for BNC; BNC is normally 24-bit while for RCA 24-bit is optional and 20-bit is standard; and BNC has no built-in copy protection. Nothing on this list is critical for a system that currently uses TOSLINK for multichannel audio.
 
I fail to see any relevance of RCA being 24bit or 20 bit, its a matter of not being possible to maintain the 75ohms standard. spdif 'works' on 2 wires, or a minijack, doesnt mean it does the job even close to spec. RCA or BNC with built in copy protection??....what? no connector type can possibly have built in copy protection its a completely passive device
 

vetinry

Member
2010-10-29 2:41 pm
Thanks for the replies.
The PC is no where near my listening area anymore, so I'm not sure that the first options would be of any use.
As you will probably tell from this next statement, I'm definitely not an expert in this at all.
From what I've read, I thought that BNC formed part of the AES standard rather than the SPDIF path and that a BNC connection allows for a slightly better signal path than SPDIF coaxial or optical.

I guess I was hoping that there might be a DAC with digitial pass through function, which might preserve the digital signal and enable me to use the BNC connector.

The back of the Bryston has several coaxial connectors and so if I can't find a high quality connection path, am I best to simply use an optical to coaxial converter?

Or am I missing the point entirely.

I'm not sure what DACs are in the Bryston, but do you still think I'd see a benefit placing a DAC between the SB and pre amp for stereo listening?

Cheers

Steve
 

alexcp

Member
Paid Member
2009-06-09 8:55 pm
HiFiOcean.com
Steve, you are right: BNC connectors are as per AES/EBU. SPDIF is a consumer version of AES/EBU. The differences I was referring to above are between the standards, not connectors. The two standards are more or less compatible electrically; you plug AES/EBU device into SPDIF, and it will work.

qusp makes a good point saying that a proper BNC connector in principle should allow better impedance matching and better quality. For the same reason, a BNC-to-BNC cable preserves the signal over much longer distance than an RCA-to-RCA. However, SPDIF is extensively used in consumer audio products of all prices ranges that get excellent reviews. You don't really need anything more for connecting a HUMAX box to a receiver. My thinking was that if you want a good DAC with digital passthrough, allowing yourself to choose from those with SPDIF output would give you a much wider selection.

By the way, TOSLINK is identical to SPDIF but uses plastic optical fiber instead of 75 ohm coaxial cable. Some people believe TOSLINK introduces more jitter compared to the coaxial cable. A good summary of the differences between AES/EBU, SPDIF and TOSLINK can be found in wikipedia.
 
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vetinry

Member
2010-10-29 2:41 pm
Hi Alex
Thanks very much for the reply and for providing clarity.
I was trying to find a DAC with digital outputs yesterday and the only one I've discovered so far is the Cambridge Audio DAC magic. Are there any other contenders, or even DIY versions?
Steve
 

vetinry

Member
2010-10-29 2:41 pm
Hi Sonic
I did actually mean digital outputs. I am looking for a DAC, which will also provide a pass through function so that I can send toslink to it and then pass through in a form that can enter my Bryston (no optical).
I know I'm a nooby, but I have just about sussed out that Digital to Analogue usually means digital in analogue out :)

Steve
 

vetinry

Member
2010-10-29 2:41 pm
Thanks for the link.
Having searched extensively for a DAC with digital pass through, I've come back to the DAC magic - it seems quite well reviewed and has the functionality I'm looking for - no AES but does have a coaxial digital output which will take my 5.1 humax signal and send straight through to the Bryston.
Cheers
Steve