ASRC confusion

[Ciunas Audio]

.... I mean, trusting the input timing is probably OK in studio environments where a certain standard is expected, but for domestic playback where latency isn't a problem, and the quality of the source signal is unknown, surely a modest buffer is the way to go. Lots of "DAC designers" are doing it...

Go, sonddek, you tell them how to do it. As a matter of fact why not do it yourself - there's a niche in the market. And you can use that software program to control it - you know the one line software program you wrote earlier. I'm sure you can do the same one line programming for buffer management, it's a classic.

 

[Ciunas Audio]

I didn't know it!

Oh,OK

What I have just found is a large number of 50ohm coaxial cables. Since RCA appears to be ~50Ohms, why don't we use that instead?

Yes, a good question. What has happened in the industry is that a lot of SPDIF DACs & transports have a schizophrenic approach to this transmission of the SPDIF signal. Maybe because the standard is schizophrenic?

What you find inside these devices is no regard for impedance matching - after the RCA socket, they stick a 75ohm R in there, which is wrong, & consider that's it's covered. So they are neither adhering to 50ohm or to 75ohm impedance - they are all over the place.

 

[Paul R]

What I have just found is a large number of 50ohm coaxial cables. Since RCA appears to be ~50Ohms, why don't we use that instead?

Because the S/PDIF standard specifies 75R and phonos...

50 Ohm is radio, 75 Ohm is traditionally baseband video. I presume the specifiers went with 75 Ohms because it's everywhere and phono because they work fine for analogue video at 75 Ohms and consumers are familiar with them. And you can see cable reflections when you use analogue video...

Paul

 

[Ciunas Audio]

Anyway, enjoy your Saturday night, all
Have a good Christmas

 

[darrylfunk]

Using standard chipsets is fine. What's surprising is not knowing what 'buffer' means. Pretty confused about ASRC too.

re. the chipset point i made, i know that, you know that and jkeny knows that....he tried to say that i frowned upon it but that wasn't my point.

my point was that it's application note level stuff.

still bet you wont get any polite conversation or sense from him....he's a troll.

 

[sonddek]

Go, sonddek, you tell them how to do it. As a matter of fact why not do it yourself - there's a niche in the market. And you can use that software program to control it - you know the one line software program you wrote earlier. I'm sure you can do the same one line programming for buffer management, it's a classic.

You've missed the point: I'm not a brilliant inventor like you, I'm just describing what many budget DAC makers have already done.

Does your DAC have an input buffer to isolate it from transport jitter like some well-known budget DACs? If not, why not? It's quite alright to say you lacked the expertise or you hoped your customers' transport clocks would be better than your DAC's clock. I just think we should be told because otherwise it looks like all this transportfoo is a cache-sexe for a questionable DAC design.

 

[mudlark]

Because the S/PDIF standard specifies 75R and phonos...

50 Ohm is radio, 75 Ohm is traditionally baseband video. I presume the specifiers went with 75 Ohms because it's everywhere and phono because they work fine for analogue video at 75 Ohms and consumers are familiar with them. And you can see cable reflections when you use analogue video...

Paul

They didn't go with 75 Ohms, in my view, they went with coax cable (of a particular design/dimensions) which has the characteristic impedence of 75 Ohms.

The bnc connectors, cable end and chassis can be easily made in 75 Ohm characteristics and has many benefits. The conductor is covered by dielectric, ithas a locking collar and so shouldbe quiteresistant to corrosion.

The down side appears to be that they are expensive and a bit fiddly.

 

[adamdea]

Haha, what rubbish
SPDIF standard requires 75ohm characteristic impedance. the standard certainly doesn't specify RCA phono connectors as they are nowhere near a characteristic impedance of 75ohm

Come on guys this is digital audio 101???????

I'm beginning to think about the time wasting posts that you guys are indulging in here. If you can't get such simple basics correct then ..............?

Glad we've cleared his up

Merry Christmas all