Quick Dacmagic Question


New member
Aug 10, 2019
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Hopefully someone can help me here. I'm going to be using the dacmagic with my acer laptop and have been reading many things about usb vs optical. The general consensus appears to be that optical is superior.

My laptop supports s/pdif through the headphone jack so I'm assuming I could use a mini toslink to toslink cable to connect to the dacmagic's optical input, and this would be better?

However I'm confused as I thought the purpose of a standalone dac was to bypass the inferior onboard soundcard, which is what connecting via usb does. Unless I'm missing here something wouldn't connecting via the headphone jack still be utilising the laptops soundcard? Could somebody explain to me exactly how connecting this way would work and what it would mean in terms of audio quality vs usb connection?

Any help much appreciated, thanks.


New member
Mar 28, 2011
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The S/PDIF output on the laptop just enables the digital audio to go out unprocessed by the internal card but I don't think it's any better than USB. If you had an asynchronous USB (like the DACMagic Plus) then there would be even more reason to use USB over S/PDIF.

Digital does still get messed with on computers though which is why it's worth trying to get a bit-perfect output by using ASIO or WASAPI. This is pretty easy if you are using Foobar, not so much with iTunes.

Here is what Cabridge Audio say:

"The ATF technology used in the 840C/740C/DacMagic intrinsically re-clocks all the data, removing jitter in the process and is ideal for this kind of use.

It uses a very high stability local clock (a metal can oscillator) which is used to generate the timing of the upsampled data, this happens aysnchronously to the incoming clock (and its jitter) so that the output data is locked to this clock instead, which also drives the DACs.
With ATF the principle is to regenerate new data points using a polynomial curve fit over time. The data points are generated to a new clock that is not linked to the incoming one other than via a slow digital PLL.
What actually happens is millions of data points are generated internally and the one that coincides with the local clock used.
This gives very high jitter reduction and is better (certainly in our opinion!) than any analog PLL trying to recover a clock from the SPDIF stream itself as the main jitter reduction technique."

John Duncan

Well-known member
I still heard a bit of electrical noise when plugged in via USB, but it wasn't really much to worry about (certainly compared to the racket it made out of the 3.5mm audio with the laptop plugged into the mains). You wouldn't get this with optical. TBH though, I think USB's a rather more stable connection physically.


Thanks for the replies I just needed some confirmation that when a mini toslink - toslink cable is plugged into the headphone jack it is detected and the s/pdif operation "takes over" from the onboard soundcard, rather than simply converting the signal or something.

I'm sure I read a quote by cambridge audio in the faq somewhere that said optical would be the better choice, so it appears there are still conflicting opinions. I will be using a 5 metre cable whether it's usb or optical if this makes much difference (I read usb is fine up to, but not more than 5m.)

I'm already using WASAPI with foobar, I will be trying both usb and optical to try and decide myself if there are any discernable differences (to my ears at least.)


Well-known member
FWIW I asked CA and J River which they thought was the optimum connection between my laptop and DAC, both answers were USB using the CA ASIO driver installed. I found it sounds slightly more dull using the optical connection.


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