A/D Conversion, and using ADAT/Spdif

[swayofpendulums]

Even after reading the wikipedia entries for these things I still don't know exactly when/why one would use ADAT or SPDIF. I have owned a firewire interface and I never even touched the ADAT or Spdif parts of it.

Also, I would like to know what analog to digital conversion is.

thanks,

Joe

 

[guitar zero]

ADAT or SPDIF can be used to link two interfaces, so if you wanted more channels of conversion than your current unit, you could link a second conversion unit via one of those cables, and run all channels simultaneously into your computer via the firewire. The A/D converters are simply taking your analog signal (think sound waves) and turning them into a digital signal (ones and zeros) for your computer to understand.

 

[KineticSound]

ADAT or SPDIF can be used to link two interfaces, so if you wanted more channels of conversion than your current unit, you could link a second conversion unit via one of those cables, and run all channels simultaneously into your computer via the firewire.

To simplify, ADAT or S/PDIF are simply means of transmitting digital audio data via a particular protocol. Just as a 1/4" phone jack or XLR jack on your interface carries an analog signal via its particular cable, the ADAT or S/PDIF jack and corresponding cable carries that signal already converted to its digital format.

Obviously, the benefit here is twofold... first (and most importantly), the signal doesn't have to be converted from digital to analog and back to digital again. Second, in the case of ADAT, you can move a lot of digital audio signals at once via one cable - not unlike the firewire cable that transmits many channels of digital audio from your interface to your computer.

ADAT actually stands for Alesis Digital Audio Tape, a term used when Alesis first started making machines that recorded 8-tracks that recorded to High8 casettes. Back then, most digital converters (especially those built into the backs of ADAT machines) weren't the best, so Alesis allowed digital I/O via what they called "ADAT Optical Interface" to allow us to use our own outboard converters. Over time, this has just come to be known as "ADAT" ins and outs. S/PDIF means "Sony / Phillips Digital InterFace" and was essentially the consumer-grade version of the AES/EBU digital protocol.

S/PDIF carries a 2-channel signal; ADAT can carry either 2-channel or 8-channel signals.

 

[swayofpendulums]

I see!

thanks for the info guys.

- Joe

 

[aarowsmith]

adat is very useful because it is cheaper interface for your computer

ADAT is still in use today because it is both cheaper and convenient for carrying 8 channels at once in pure digital format over what they call the "Lightpipe ADAT" optical interface, digitally cleaner than most other stand alone interfaces including some of the cheap 24 bit sound cards on the market. The ADAT machine is still a good analog to digital converter for your computer sound card and mixer.

The original 16 and 20 bit ADAT machines have 1/4" and RCA analog inputs 8 in/out as well as ELCO balanced +4 connectors, just perfect for your computer sound card with an ADAT optical input , the ADAT machine can be your analog to digital interface from your analog mixer to your computer.

You can transfer 16/20/24 bit rate audio in 8 or 4 digital audio channels at once, depending on the sampling rate on one ADAT optical input/output. For sampling rates of 24 bit 96khz, 4 channels are possible over one ADAT optical interface. That is why the new 24 bit hard drive ADAT machine uses multiple optical inputs/outputs to get 24 channels of 24 bit 96khz digital audio. Of course you can get all 8 channels in 24 bit 44khz or 48khz over one optical, these are some of the limitations of the ADAT optical interface.

The ADAT a/d converters were made very well and still are the industry standard. In fact the ADAT original 16 bit converters stand up to the very best CD players, so yes they can and do sound better than most CD players. The a/d and d/a converters still sound great today.

But the new 24 bit ADAT is still very expensive and also very expensive to archive (back up) that much more data on even more hard drives, etc, etc.

By the way ADAT machines that are 16 bit and 20 bit use SVHS tapes only, not HI-8 tapes, other machines like Tascam uses the HI-8 format tape, but they are much smaller and less reliable than the SVHS ADAT tapes used in both the Alesis and Fostex machines and others that use ADAT format.

Unless you live in a dust bowl and buy el' cheapo' SVHS brand tapes, then you might have problems with Adat. But if you keep the heads clean and serviced well, then ADAT SVHS tape machines are very reliable. I use them for live recordings even still today because of convenience and stability.

And ADAT machines are still MUCH better sounding then the new portable 8 track DAW digital recorders.

You can rack mount an ADAT machine easily, and it is quite compact, even by today's standards.

ADAT is Great for live use or recording without a computer in the studio. And it is fast to setup and easy to backup to.

Even with cheap hard drive prices the way they are, you can still easily buy two SVHS tapes to archive for way less money than buying a new hard drive, about $2 to $5 a tape and make a copy of your 8 tracks etc with out buying yet another hard drive.

Archiving ADAT is easy as popping in a new SVHS tape, hard drives are more money and are a pain when you lose a terabyte of audio!!! You lose a tape, its no big deal if you have a backup tape, and or you backed it up to a computer as well which you should. Make Three back ups!!!

An ADAT machine is especially now, a cheap way to go if you just want to get clean analog to digital audio transfers 8 channels into your computer sound card.

Your computer must have of course a ADAT optical input/output, such as an E-MU 1212m is a good PCI sound card on the cheap, get a used ADAT machine for about a $100 to $200 and you can make good quality recordings and get 8 channel a/d from your outboard mixer/gear into your ADAT and finally into your computer on your hard drive. You can edit the audio and send it back out ADAT if you want back to the ADAT machine to bring it with you.

And This is a big plus, ADAT machines can be synced together and you can make up to 16 ADAT recording/playback machines perfectly synced up together as one 128 track machine, and or if you have 16 optical ADAT inputs on your sound card you could have 128 digital inputs/outputs interface for your computer, why would you need this excess', I do not know??? Cheers'...................

 

[xlarge]

I believe I read that if I use the SPDIF connection, that will bypass the A/D converters? Is that true and is that also true with ADAT?

 

[gcapel]

I believe I read that if I use the SPDIF connection, that will bypass the A/D converters? Is that true and is that also true with ADAT?

Most of the time if your interface has an ADAT input and analog inputs the ADAT inputs are additional.

 

[aarowsmith]

Yes and you can use any ad/da converter on the market

I believe I read that if I use the SPDIF connection, that will bypass the A/D converters? Is that true and is that also true with ADAT?

Yes and you can use any ad/da converter on the market when you use the digital output.

Anytime you use a digital connector it will always bypass the internal converters.

This gives you the option of using outboard converters that sound better than, but the price and the sky is the limit on what you can pay for really fancy great sounding ad/da converters.

I find, if you like the sound of a 16bit 48khz DAT machine, then the older SVHS ADAT machines will sound just as good or better.

The 20 bit ADAT machines sound a little better, and of course the new 24 bit machines sound even better.

I just like the portability of any ADAT machine without the worry of software issues and computer interface hassles.

ADAT machines are self contained recording devices that work very well most of the time, just take care of them and they will work and sound great.