[JakeJ]

Hi Folks,

Noob to both computer music servers and Apple computers.  Over the Holidays I bought a used Apple iMac G5 1.8 GHz 2 GB RAM and a 160 GB HDD with a Superdisk, OS is Leopard 10.5.8.  Works great but here's my particular issue; I have the iMac connected to my P3A DAC via optical toslink and I have no sound. 

If I unplug the iMac end sound comes out of the built in speakers and the System Preferences\Sound\Output changes from "Digital Audio" to "Internal Speakers", vise versa when plug it back in.

When I unplug the toslink cable from the DAC I have bright red light at the end.  The DAC has an LED indicator for each input and it stays red never turning green for a lock condition.  When I cycle the input selector in the P3A it gets an instant lock on the I2S input from the P1A.

I did try unplugging the I2S cable to make sure it wasn't due to the DAC not supporting two devices connected simultaneously.

Bad input on the DAC?

[neekomax]

I'd start by opening your Audio MIDI Setup application and checking to see if your DAC is being recognized (Applications>Utilities>Audio MIDI Setup). Maybe others have some alternative options for you...

[srb]

I'd start by opening your Audio MIDI Setup application and checking to see if your DAC is being recognized (Applications>Utilities>Audio MIDI Setup).

It is not a USB or FireWire DAC, so it will not be "recognized" by the computer because it is not acting like an external soundcard but merely being driven by the internal optical digital audio output from the Mac.
 
It does sound like it should work as the Audio Preferences are indicating the digital output is selected and you do have a light at the end of the cable.  Do you have any CD or DVD player that you can use to try to send an optical input to the DAC?  I would also try another Toslink cable in case there is some fracture or anomaly that is allowing light to be transmitted but not allowing the signal to be locked onto?
 
Steve

[neekomax]

Oops. Duh.

[JakeJ]

Thanks for the tip, srb.  Just checked my CEC transport and it does have a toslink output so I'll check that and report back.  Unfortunately I have but one cable at the moment.

Back in a jiffy.

[JakeJ]

Rats, just realized the cable is mini-Toslink to Toslink so I can't connect the CEC to the P3A without an adapter.

For cable testing purposes I can use my home theater kit and connect it between my Oppo DVD player and my Sony pre-pro to see if that's the issue, eh?  It is just a $6 cable.

[srb]

Rats, just realized the cable is mini-Toslink to Toslink so I can't connect the CEC to the P3A without an adapter.

For cable testing purposes I can use my home theater kit and connect it between my Oppo DVD player and my Sony pre-pro to see if that's the issue, eh?  It is just a $6 cable.

I thought maybe you were using a Mini-Toslink to Toslink adapter, as some people have experienced no sound or dropouts using adapters, but it sounds like you're using a Mini-Toslink to Toslink cable with no adapter.
 
So how would you test the Mini-Toslink to Toslink cable between your Oppo and Sony pre-pro, as I would assume they are both full size Toslink?
 
I have also read that some earlier iMacs had a lower intensity Toslink optical output that gave some problems of either no sound or dropouts particularly when using adapters but that's heresay and I have no actual experience with that particular iMac series.
 
Any chance you also have an Airport Express which has a Mini-Toslink output?
 
Steve

[JakeJ]

Yeah, I put the cart before the horse again.  No worky.  The bottom line is I'll have to buy something to figure this out.

[tabrink]

 
This what I use with spectacular results!


http://www.lifatec.com/toslink2.html

[JakeJ]

I checked out the Airport Express.  Sorry for the denseness but how is this applicable?

This is the device I looked at and I realize there are other models.
http://store.apple.com/us/product/MB321/AirPort-Express-AirTunes#overview

[JakeJ]

I checked out that link for the Silflex cables and they look well constructed plus they are reasonably priced as I have checked out Wireworld Supernova 6 and that comes in at $180 for a 2 meter cable.  I especially like the armored version    but wonder if it is extremely stiff.

[srb]

I checked out the Airport Express.  Sorry for the denseness but how is this applicable?

This is the device I looked at and I realize there are other models.
http://store.apple.com/us/product/MB321/AirPort-Express-AirTunes#overview

I wasn't recommending that you go out and get one, but if you already had one it could be used for troubleshooting.  There's actually only one model of Airport Express, the other one is an Airport Extreme.  Although it can function as a wireless router like an Airport Extreme, it is more limited by having only one wired LAN port compared to four and doesn't have the range of the Extreme.
 
But many people like myself already have a wireless network router and use the Airport Express soley for wireless iTunes streaming.  It has the same combination analog/optical output like the Mac so it can be used to to test the Mini Toslink-Toslink cable as well as the P3A DAC's optical input.  It doesn't have anything to do with the Mac's internal digital output, so it works whether the Mac is set to internal speakers or digital output.
 
I actually have three of them for other rooms beyond the main system and they can be used casually with their internal DAC/analog output or with the Mini-Toslink output to an external DAC for better sound.  One disadvantage is that it can only do 16/44.1 files compared to the Mac doing 24/96 out of it's optical port.
 
Although out of the box they can only stream iTunes, with a third party piece of software called Airfoil ($25) it can also stream audio from other programs.  It can also function as a wireless Print Server for a USB printer. 
 
Some people also use the Apple TV to stream audio, video or both.
 
Steve

[JakeJ]

Thanks for enlightening me, Steve.  I picked up this iMac off Craigslist for $120 thinking it would be a cheap ticket to a music server.  Just a simple way to have background music with out the commercials that FM has, wasn't really thinking "CD quality".

I did think of another test I could try.  Connect the Mini-Toslink to the iMac and the Toslink to the Sony and see if that works.  Short of getting a different known good cable, which I will try to do, I may call the local Apple store and see if they are willing to help me troubleshoot this.

Thanks to all for helping so far.  I'll report back with further investigations and the results.

[HAL]

Have you tried connecting the TOSLINK cable from the iMac to the P-1A, using the I2S Bus to the P-3A that you know works? 

Also in the iMac audio settings does it have selections for bitstream or LPCM output?  It should be LPCM to work with the P-1A or P-3A.

Just some thoughts.

[JakeJ]

Hi HAL,

"Conveniently" the P1A does not have a Toslink input, only coax, AES/EBU, and I2S.  I'll have to look for that LPCM setting.

[JakeJ]

Did not find a setting for LPCM/bitstream.  Looked under System Prefs and Midi Devices in Utilities group.  Am I missing something?  This is a 2004 iMac G5 OSX Leopard.

More questions.  Will this iMac stream audio out via USB?  Can it stream audio out via WiFi and is there a device to convert from WiFi to S/PDIF RCA?  Which form of connection from computer, Apple or PC, to the stereo introsuces the lowest jitter?

[HAL]

I am not a Mac person, so just thinking about general troubleshooting of sound devices.

If the iMac OSx can install drivers like the M2Tech hiFace or hiFace Evo USB driver that runs on the MacMini with OSx it should be able to do USB output.  Friends have used the M2Tech hiFace Evo with the MacMini with very good results.  Both of these will convert USB to coaxial S/PDIF to run the P-3A. 

The P-3A will work with any S/PDIF or I2S Bus PCM input from 16bit/44.1KHz to 24bit/96KHz in my setup with a PC and hiFace.  The TOSLINK input drives it correctly. 

Your idea of using another device like a CD player with TOSLINK output should show if the input section is working.  You can also try the coaxial input to the P-3A to see if it works with the same transport.  That would narrow down the problem to the TORX receiver in the P-3A if the coaxial input works. 

[JakeJ]

Update - Just hooked up the iMac in my HT and music comes through just fine so it's not the cable or the iMac it's the Toslink connector (or the associated circuitry) in my Perpetual Technologies P3A DAC!

Solves that mystery.

[JakeJ]

Update 2

I took the P3A apart today and solder joints look fine and I could see no other anomalies so I thought I'd try to get a close up photo of the connector itself.
 

Looks pretty beat up plus that looks like a spider's egg nest on the right.  I think I'll try and replace the connector just for fun and see if it works.