This is MOTU 2408 MkIII, an audio interface. It's a frustrating thing.
It was originally released
in 2003, but despite being over twenty years old it's still pretty good. It has
eight balanced 1/4" audio inputs, a bunch of ADAT, TDIF, and SPDIF ports, and
it records 24-bit audio at 44, 48, 82, and 96khz.
But it's a pain to get working with modern computers. The original MOTU
2408 MkI came out in 1999, slightly before FireWire, at a time when USB was
restricted to USB 1.0, so it connected up to contemporary PCs and Macintoshes
with a PCI card. What's a PCI card? Ask your parents. They might remember their own parents fiddling around with PCI cards.
The 2408 MkII and MkIII had the same system. To their credit
MOTU continued to update the drivers, but as of 2025 the only Apple Macintosh
with PCI slots is the Mac Pro, and MOTU's drivers haven't been updated for
modern Apple Silicon processors. MOTU's next interface was the 828, but that
used Firewire, which is another story entirely.
It would be nice to still use the 2408. And there is hope! Even without a
computer connection the 2408 still works as an audio interface. In standalone
mode analogue audio that comes in through the 1/4" jacks is routed out to the
ADAT, TDIF, and SPDIF ports. SPDIF folds everything down to two-channel
stereo, but ADAT and TDIF transmit eight
channels of audio at 44 or 48khz, or four channels at 82 and 96khz.
What would be nice is a simple dongle that could pump ADAT to a computer,
preferably something cheaper than an entirely new modern audio interface with
an ADAT input. There are lots of USB interfaces that output ADAT, but a dearth of interfaces with ADAT inputs.
There is one exception, the
MiniDSP MCHStreamer,
which is available either as an unclad circuit board or in a little box. I'm
not a farmer, so I bought the version that comes in a box. This is what it
looks like:
NB I bought it with my own money and have no commercial relationship with
MiniDSP. It shipped from Hong Kong and is, as far as I can tell, exempt from
UK customs duty, although even if it isn't the price isn't onerous. The boxed
version is currently listed at $115, shipping $35, which is about £110. The
kit version (which is assembled, it just doesn't have a case) is $10 cheaper.
Is it just a Raspberry Pi or something, with special firmware? Could
you make one yourself? I have no idea, and possibly, in that order.
The MCHStreamer is essentially a tiny little computer board that converts a bunch of digital audio formats in real time. The boxed version only supports ADAT and SPDIF, although I assume that's only because the internal
headers are covered by the case. It's powered by USB, and it's small enough to
rest on top of the 2408.
Getting it to work isn't straightforward, although it's still easy. I have a
Macintosh. The first step is to download the firmware bundle and plug the
MCHStreamer into the computer. At that point you have to upload the correct
firmware into the box. In the following screenshot I've picked ADAT:
Step two involves plugging the included optical cable - the package includes
two optical cables and a USB cable, which is a nice touch - into the 2408's
BANK A optical ADAT output:
Step three involves booting up the 2408 and fiddling with the SELECT and SET
buttons. For the SOURCE I picked the audio inputs. Confusingly the LEDs imply
that the audio is routed to ADAT BANK C, but no, the audio is output to all
three ADAT banks.
For the CLOCK I picked 44khz, internal. Baby steps. I then plugged a radio
into input 3, just to see if it worked, and also because I wanted to make sure
that it was transmitting on discrete channels and not just 1+2 as a stereo pair.
Then I popped open Audio MIDI Setup and set the MCHStreamer to pick up
clock from the 2408's ADAT signal:
Why do you have to do this? If you don't - and I tried it - the signal is
crackly. My understanding is that the optical audio protocol isn't
like computer networking. It doesn't send packets of data, it just sends a
string of bytes, and the receiver has no idea where each byte begins unless it
has a clock signal from the source. The result is a kind of audio chaos that
sounds awful. Does that sound like a plausible explanation? That's how my mind envisages it. Sometimes my mind plays tricks on me, but deep down there is a brave heart. In my mind.
Synchronising the MCHStreamer to ADAT clock was flaky. At first. I can't tell if it just
takes a long time, or if there's a quasi-random factor, but at first it didn't
work. After cycling through the 2408's clock options it did eventually hook
up, and remained hooked up, although curiously after the first run (pictured
above) it only synchronised at 48khz. And yet once it worked, it stayed
working. Maybe it's a first-run thing. Perhaps I just didn't have the optical cables plugged in all the way.
After setting all this up I opened Logic, and lo and behold, MCHStreamer ADAT
was an input source, with eight channels of audio:
I clicked the input monitoring icon and voila, I could hear a signal coming
from the 2408, and I could select each of the eight channels and record audio
from them.
As a proof of concept I used it to record the following piece of music, which has a mixture of audio tracks from my modular synthesiser and some virtual instruments:
Sadly one thing missing from this setup is the 2408's original monitoring hardware, which was housed on the PCI card and acted as a mini-mixer.
Still, if you happen to have an ancient MOTU 2408 lying around doing
nothing, it can be returned to service as an eight-channel audio interface
with a simple ADAT to USB box that powers itself from the USB port.
Alternatively, if you want to use the 2408 as a crude mixer you could power the MCHStreamer with a powered USB hub.
In theory you could bypass all of this malarky by plugging the 2408 into the ADAT input of another audio
interface. But the cheaper good-quality audio interfaces don't
have ADAT ports, and the more expensive interfaces are much more capable than
the 2408, so why bother?
If the MCHStreamer was $35 and just a tiny little USB dongle with USB at one
end and a pair of optical ports at the other it would be even more superb,
although it has to be said that the population of people who have a
twenty-year-old MOTU 2408 lurking in a cupboard probably isn't large enough to
justify the research and development outlay. If it had a built-in DAC and a
3.5" headphone output it would also be useful for the tiny, tiny population of
people who want to use a PlayStation 3 with a computer monitor that doesn't
have built-in speakers, but again that's a small constituency. There are dozens of us. Dozens.
