ADAT Explained- S/PDIF Toslink x16?

[ampsarus]

Hello esteemed slutz- I thought to post this in the general forum, but somehow it seems too general for that discussion.

Could your collective wisdoms please enlighten this mook? Easy as 1-2-3 I'm sure.

Is the ADAT protocol just a multiplexed S/PDIF? Or is it a different animal?
I'm keen enough to see that the connectors are the same as Toslink, (smart)
but I don't know if it's just the same protocol x16, i.e if a 2-ch. stereo stream of ADAT is the same thing as S/PDIF on Toslink.

Finally, I have heard some say ADAT is useless, poor sounding "prosumer crap" while others think it is fine if not ideal.

I hope this question is clear enough, TIA for your enlightenment! I'd never ask this at the store!


Much appreciated, TIA

[DrDeltaM]

No, optical spdif is different protocol from ADAT. A 2channel ADAT stream won't be recognised by an optical spdif interface.

There's nothing wrong with the ADAT protocol by itself (tho it doesn't seem ideal for clocking). I has a bad name cuz of the ADAT machines of back in the days.

[d_fu]

Originally Posted by ampsarus

Is the ADAT protocol just a multiplexed S/PDIF? Or is it a different animal?

Different... In any case, ADAT has 8 channels, not 16.

Finally, I have heard some say ADAT is useless, poor sounding "prosumer crap" while others think it is fine if not ideal.

The ADAT protocol as such (isolated from the ADAT tape machines) is just as good or bad as the signal it's transmitting. It's a purely digital transfer, as is SPDIF.


Daniel

[ampsarus]

Thanks for your responses guys.

I understand 2-chs. of ADAT can't be sent to a S/PDIF input and vice-versa. What I meant to ask was is the ADAT stream 16/44.1 PCM? Will 2-ch.s of ADAT look the same on a scope and sound the same as 2-chs. on your average S/PDIF?

"It's a purely digital transfer, as is SPDIF"

That is all fine and well but what about jitter and other implementation issues? Is it not true that not all S/PDIF interfaces are created equal?

Thanks for the answers guys! thumbsup

[tINY]

ADAT optical is not S/PDif. I don't know how you are going to look at an optical signal on a scope, either.....



-tINY

[ampsarus]

Originally Posted by tINY

ADAT optical is not S/PDif. I don't know how you are going to look at an optical signal on a scope, either.....



-tINY

Before and after the transmitter/receiver.

[nicpope]

Both ADAT and spdif are digital signals. There is no quality difference. I don't remember what the max. sample rate is for spdif because I've never used a spdif connection, but ADAT has a max of 48khz/24 bit unless you get into bit splitting but then its four channels per cable and goes up to 96k/24 bit.

That is all fine and well but what about jitter and other implementation issues? Is it not true that not all S/PDIF interfaces are created equal?

Jitter is introduced into the signal when you have multiple devices converting between analog and digital (also vice versa) that are running on different clock sources. Its not a question of how good either clock is, merely that neither of them will ever be exactly 100% the same. Jitter has nothing to do with how you pass a digital signal.

Not all spdif interfaces are created equal, but it is the converters in them that are not equal, not the digital interface. The whole reason that such (relatively)high quality digital gear can be had so cheaply is that once it becomes digital nothing short of SERIOUS error will change it until you try to make it analog again.

[kafka]

Originally Posted by ampsarus

Thanks for your responses guys.

I understand 2-chs. of ADAT can't be sent to a S/PDIF input and vice-versa. What I meant to ask was is the ADAT stream 16/44.1 PCM? Will 2-ch.s of ADAT look the same on a scope and sound the same as 2-chs. on your average S/PDIF?

"It's a purely digital transfer, as is SPDIF"

That is all fine and well but what about jitter and other implementation issues? Is it not true that not all S/PDIF interfaces are created equal?

Thanks for the answers guys! thumbsup

ADAT is 8 channels of 44.1kHz or 48kHz. To transmit 88.1kHz or 96kHz, 2 channels are muxed together. 176.2kHz or 192kHz - 4 channels. Bit depth can be 16,18,20,22 or 24 bits. In practice, it's just about always 24 bits these days. There are also channels for the ADAT 32-bit time code and MIDI, as well as some others that I won't get into.

As far as sound quality goes, it's digital - meaning, there is no degradation. It is not an ADC, nor a DAC - ergo, jitter is not an issue. It's just a way of getting the bits from one box to another. It's up to the box to take samples in a timely manner, or sequence them into a playout buffer, or store them, or whatever. If you have sound quality problems, it's your ADC or DAC. It has nothing to do with the ADAT protocol itself.

One benefit over AES/EBU is that ADAT carries 8 channels of data, while AES/EBU only carries 2. Another benefit is that it works over optical, eliminating interference with clocking (i.e. which would cause transfer drops, as opposed to jitter) due to grounding problems.

[ampsarus]

Thanks again for the info guys, big help! thumbsup

[JayT]

Originally Posted by nicpope

...
Jitter is introduced into the signal when you have multiple devices converting between analog and digital (also vice versa) that are running on different clock sources. Its not a question of how good either clock is, merely that neither of them will ever be exactly 100% the same. Jitter has nothing to do with how you pass a digital signal.

Nope. But not for Sampling-Jitter. You describe synchronisation problems (interface-jitter).They are harmless, since they sound so terrible and can easily be heard.

Sampling-Jitter comes from the clock or the clock source. It the clock-generator is not stable enough you get sligthly time-shifted samples during recording.Since all clocks (even the cheap ones) are relatively good (since semiconducters improved a lot the last years) it can't be heard so easily.

The clock-source (eg. when you use the adat for synchronisation) can therefore also add some jitter. Thats because the longer the line (optical & copper) the more "round corners" the rectangle signal gets. So there is not a clear difference between 0 and 1. Easily spoken. Wiki it.

Jitter exists on all digital systems (spdif, adat,....) and their connections
(optical, coax,...).

But hey, these are small details and often more a point of religion and believe istead of real problems.


Since ADAT nowadays is mostly "ADAT-Lightpipe" 24 bit optical 8 channel
max. 48kHz it can not be easily "connected" to SPDIF 16bit 2 channel
coax max. 48kHz. But the differences (logically) are not so big.
Thats why nearly every new soundcard knows adat and spdif-optical.

greets from austria. JayT.