[gaby]

I have an apple MacBook pro of late 2008, it has a combination analog/optical output. I am using it now as optical connected to the digital input of a very high quality home theater preamp/processor.  What I need to know is if the digital output from this port is a bit perfect digital representation of the audio I will be playing or how I can ensure the purity of this signal. Or if it would be better to use the USB port and connect to a DAC and then to the home theater.  I want to have the purest digital signal from the computer and bypass any sound processing, mixing or alteration inside the pc.

 

[cel4145]

Well, for home theater, you should use HDMI if you are using blu-ray at all for audio. And also on an HT receiver, if you don't run it in a pure, direct mode, the audio typically goes through DSP even if you input analog from a DAC. It has to convert the analog back to digital, and then back again. So without some pure direct mode that bypasses that, no benefit on using an external DAC vs. sending the digital signal directly to your receiver.

I don't know about your Mac, but people can argue a lot about which is better, optical or USB. I wouldn't stress about it if you end up buying a good DAC. And you could always get one with USB and optical and judge for yourself.

 

[Randle81]

A good stand alone DAC will give you a better sound. How much is the question. Whether it sounds better over usb or optical is dac dependant but if you are into high resolution audio a usb connection will let you play greater than 24/192

 

[PurpleAngel]

  I have an apple MacBook pro of late 2008, it has a combination analog/optical output. I am using it now as optical connected to the digital input of a very high quality home theater preamp/processor.  What I need to know is if the digital output from this port is a bit perfect digital representation of the audio I will be playing or how I can ensure the purity of this signal. Or if it would be better to use the USB port and connect to a DAC and then to the home theater.  I want to have the purest digital signal from the computer and bypass any sound processing, mixing or alteration inside the pc.

 
Might depend on what Home Theater pre-amp/processor your using and how much your willing to spend for an external DAC.
Schiit has the Bifrost DAC for $350, plus tax/shipping.
 
The software program used on the Mac, to play the music files, might also have an effect on audio quality.
(but i know little about Mac audio)
 
For a PC the USB provides a very slightly cleaner digital audio signal, over a standard optical setup, for a PC.
On a PC you have the option of setting optical to bypass sound card feature, which USB does automatically.
Not sure if a Mac is the same.

 

[Jeangenie]

whats the source of your files?? Mac's (pre 2013) have a limit on what they can output via optical, whereas USB is unlimited

 

[Randle81]

  whats the source of your files?? Mac's (pre 2013) have a limit on what they can output via optical, whereas USB is unlimited

Toslink optical in general is limited to 24-bit/192kHz which is a hardware cap (and may be less depending on your connections and DAC). Whereas USB is limited by the capability of the DAC. Some will limit at 24-bit/92kHz. Many newer ones. 32-bit/384kHz. Each have their own technical advantages. I like the isolation provided by optical, many think USB provides a sound with less jitter, but will spend big dollars to isolate it. But here is the reality check - most people don't have much music that runs at greater than 16-bit/44kHz and will only dabble into hi-res. Personally I'd advise having a go with a good second-hand USB DAC. If you like the difference it makes - keep it. If you don't notice much, then sell it for similar to what you bought it for and move on.

 

[gaby]

Thanks for the information you all.  I always thought optical was better than USB, but I will check specs to verify the limits of each on my particular setup.  What I have not found is a PC laptop with optical port, I have only seen this on the Mac. I used the optical port on the Mac because it permits me to go digital directly into my HT preamp/processor which have a HQ DAC, so I save on a separate USB DAC.  But if the optical port output has some limitations in comparison with USB and I cannot bypass the sound card, then I will reconsider.

 

[cel4145]

Thanks for the information you all.  I always thought optical was better than USB, but I will check specs to verify the limits of each on my particular setup.  What I have not found is a PC laptop with optical port, I have only seen this on the Mac. I used the optical port on the Mac because it permits me to go digital directly into my HT preamp/processor which have a HQ DAC, so I save on a separate USB DAC.  But if the optical port output has some limitations in comparison with USB and I cannot bypass the sound card, then I will reconsider.

I think you are probably right. PC laptops seemed to have moved away from those mini optical ports. But they do typically have HDMI. Does your HT preamp/processor have that? No reason not to use HDMI instead.