Compatibillity - iMac and Altec Lansing ADA885 THX

BKMTKZ wrote:

Is this Altec Lansing speaker system compatible with my soon-to-be delivered iMac?

The iMac's digital audio output supports 5.1 DolbyDigital, but
it's a TOSLINK (optical S/PDIF) signal rather than the coaxial
S/PDIF required by the ADA885.

You'll need an S/PDIF optical-to-coax converter, for example:

[Optical to coaxial converter|http://www.amazon.com/Cables-Go-Optical-Coaxial-Converter/dp/B0002GV8 76/ref=pd bbs2?ie=UTF8&s=electronics&qid=1200091705&sr=8-2]

[Bidirectional opto <-> coax converter |http://www.amazon.com/Midiman-M-Audio-Coaxial-Bi-Directional-Converter/dp/B000 06J074/ref=pd bbs_sr1?ie=UTF8&s=electronics&qid=1200091705&sr=8-1]

A USB or Firewire audio interface with an S/PDIF coax output
would also do the trick, but would probably cost more.

Looby

BKMTKZ wrote:
Looby,

... what type of cable would I need to run from the converter into the iMac?

You'd need a TOSLINK digital optical cable -- with a mini-TOSLINK connector
on the iMac end and (probably) a regular TOSLINK connector at the converter.

They make such cables -- but I'd suggest a cable with a "normal" TOSLINK
connector on both ends plus a mini-to-normal adapter plug at the iMac end.
You can probably find everything at RadioShack (including the converter), or
check http://www.monoprice.com for better prices and a wide selection:

[mini-to-normal TOSLINK Cable|http://www.monoprice.com/products/product.asp?c id=102&cp_id=10229&cs_id=1022902&pid=1572&seq=1&format=2]

[mini-to-normal TOSLINK Adapter|http://www.monoprice.com/products/product.asp?c id=104&cp_id=10423&cs_id=1042301&pid=2671&seq=1&format=2]

[normal-to-normal TOSLINK Cable|http://www.monoprice.com/products/product.asp?c id=102&cp_id=10229&cs_id=1022901&pid=2764&seq=1&format=2]

[optical-to-coax converter -- CHEAP!|http://www.monoprice.com/products/product.asp?c id=104&cp_id=10423&cs_id=1042302&pid=2948&seq=1&format=2]

...shop 'til ya drop,

Looby

I, too, have recently purchased an iMAC and want to use my Altec Lansing, model ADA890. Planning to get all of the above to convert, but I was wondering how exactly does everything plug into the iMAC? I thought to plug the converted S/PDIF line from the subwoofer into the audio-in port (which apparently can also be an S/PDIF stereo mini phono jack) on the iMAC. Then to plug the "front analog" connection from the subwoofer into the headphone jack on the iMAC. Not sure if I will need to connect the 2 as I have described or if only the S/PDIF is needed. We'll see, once the converter and cables have arrived.

Thanks for the input.

fauxdobe wrote:

I thought to plug the converted S/PDIF line from the subwoofer into the audio-in
port (which apparently can also be an S/PDIF stereo mini phono jack) on the iMAC.

You have me confused. My understanding is that the coaxial S/PDIF connector on
the ADA885/ADA890 speaker systems is the audio signal FROM the computer's
digital audio-output port, (i.e., the iMac's "headphone" combo-jack).

The manufacturer's documentation is dreadfully confusing -- but it's clear that
the S/PDIF signal is an output from the computer and an input to the DolbyDigital
decoder in the subwoofer box.

http://www.altec-lansing.com/downloads/ADA890_MAN.pdf

http://www.anandtech.com/multimedia/showdoc.aspx?i=1523&p=3

Looby

BKMTKZ wrote:

This is a silly question. Does the mini-TOSLINK connector
insert into the headphone (output) jack on the iMac?

Not silly, it's far from obvious -- and Apple doesn't document
it very well, if at all.

Yes. the "headphone" output is a "combo jack" that will accept
either a 3.5 mm analog stereo plug or a 3.5 mm digital optical
TOSLINK plug. In either case, the headphone jack is output-only.

The "Line In" jack is also an analog/digital "combo jack" that
accepts the same two types of plugs -- for input-only.

Looby

FYI, I have one of these exact same converters in use in one of my home theater setups and it works as advertised--perfectly.

I'm looking for some external sound for my iMac, but I was hoping to get a Subwoofer only (like my iSub which Apple killed).

Any ideas?

i think i understand now - the connection will only go from the s/pdif on the subwoofer through the converter to the headphone jack on the iMac. there will be no other cables running from the subwoofer to the iMac... yes? it's just that there were so many other connections before to the PC... i'm awaiting the converter/cables arrival. Thanks, again.

fauxdobe wrote:

i think i understand now - the connection will only go from the s/pdif on the subwoofer
through the converter to the headphone jack on the iMac. there will be no other cables
running from the subwoofer to the iMac... yes?

Yes, that is correct. The subwoofer cabinet is more than just a speaker; it also
contains a DolbyDigital decoder that processes the s/pdif input bitstream and
converts it into six separate analog signals -- one for each speaker.

The iMac just supplies the encoded 5.1 signal; it doesn't know/care whether
the signal is going to a "DolbyDigital receiver" in a high-end audio system or
to an integrated all-in-one speaker system with a built-in decoder.

The optical-to-coax converter box has no intelligence; it just converts pulses
of light from the iMac's optical output into electrical pulses on the coax cable.

...bits is bits,

Looby

sorry to belabor this topic. but the set-up did not work for me. I connected a coax RCA cable to the subwoofer s/pdif, then to the new converter. Connected converter to the new optical cable then to the adapter and into the iMac headphone jack. Also plugged converter into power. No sound. Used an RCA cable I had - will get a new one to see if that is the problem. Any thoughts? The speakers work if I just plug directly into headphone jack, although I don't get the subwoofer/surround sound.

fauxdobe wrote:

... No sound. Used an RCA cable I had - will get a new one to see if that is the problem.

Don't know what the problem could be; the connections you describe all
seem correct -- and BKMTKZ reports success with an identical setup on
a very similar ADA885 speaker system.

Strictly speaking, the S/PDIF coax should be 75 ohm video cable of the
type commonly used to connect composite video signals from a VCR
to a TV -- but in a pinch, I've used ordinary RCA audio cables with no
problem (but only on short runs).

...do you see red light at the end of the optical cable?

Looby

I purchased a digital coaxial cable w RCA connection - Monster cable, interlink datalink 100 ( for "digital audio signal transfer"). Still no go...
Yes, I see a red light at the end of the adapter (connected to the toslink cable).
The speakers test as correctly working.
Any thoughts? Different cable?