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Advantages of USB -> coax / toslink -> DAC vs. USB -> DAC

Roen

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#1
I've seen some setups utilizing a digital to digital converter then connecting to a DAC. Is there any particular reason (besides DAC not accepting USB) to do such a setup?
 

Veri

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#2
I've seen some setups utilizing a digital to digital converter then connecting to a DAC. Is there any particular reason (besides DAC not accepting USB) to do such a setup?
Might give like 1 SINAD more than plain USB, in general there's a slight improvement, although sometimes more significant.

Will you hear this as an actual difference? Considering a good USB-SPDIF bridge usually costs upwards of $100, the price of a modi3/tone board, I would say it's really not worth the cost. If you need the galvanic isolation of optical/spdif or have obvious noise problems via USB, the purchase of such a device might make sense. It would also be prudent to order one via amazon for example, so you can return if you can't discern any difference.

Personally I detest the additional conversion box and interconnect needed, compared to a single direct connection. I used to do usb to converter to coax to DAC, but since getting Topping DX3 I used the bundled USB cable and it was so easy, flawless and problem-free I never went back to a more elaborate set-up. Not worth the cable hassle.
 

RayDunzl

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#3
I've seen some setups utilizing a digital to digital converter then connecting to a DAC. Is there any particular reason (besides DAC not accepting USB) to do such a setup?
Yes, my other stuff that precedes the DAC doesn't accept USB.

I convert USB from the PC to Optical, because the data switch doesn't accept USB, nor the DEQ2496, nor the miniDSP OpenDRC-DI, which come before the DAC (which does have an unused USB input) in the signal chain.

All my other sources are Optical or coax S/PDIF. TV / Cable Box / HDRadio / CD and Video players / Roku (via TV)

I don't "listen" from the PC, or rarely do, but I do use it for test/mesurement.
 
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#4
It only makes sense if your DAC doesn't have usb input, or the usb input on your DAC is so bad and usb input on the other device is so much better that you have to add the device to compensate.

Otherwise, adding more gear and conversions to the chain can only further degrade the signal or cause problems. There is no magic here.
 

andreasmaaan

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#5
It just depends on the quality of the USB input on your DAC vs the quality of the USB-SPDIF converter.

Most decent USB DACs, even cheap ones, have excellent USB inputs, in which case adding such a device is unnecessary and could marginally improve or marginally degrade performance, depending on the device.

Many myths abound regarding USB audio. If you're considering purchasing a specific USB DAC and want to know whether an additional USB-SPDIF converter is warranted, the best thing to do is look (or ask here) about its performance. If a DAC's USB performance is sub-standard, it's probably not worth buying it given how many DACs do this so well.
 
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#6
Cable length is another use case. You can run SPDIF cables much farther than USB.
 

RayDunzl

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#7

tlr

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#8
Might give like 1 SINAD more than plain USB, in general there's a slight improvement, although sometimes more significant.
What the technical reason an external USB-SPDIF converter would have better performance than built in USB?
 

Veri

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#9
What the technical reason an external USB-SPDIF converter would have better performance than built in USB?
I'm just going by the measurements so far when amir tested both USB and coax as with the EL Dac, Khadas tone board, ..

In a perfect DAC it should be the same.
 
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#10
Just saying "it may add 1 SINAD" doesn't make any sense. Why do people assume the USB interface on a dedicated spdif converter is always better than the USB interface on any given DAC? The people selling the device may want you to believe that, but there is no reason it must be true. If some vendor is selling both dacs and spdif converters, probably they use the exact same usb implementation in both (unless they one product is very old and the other very new).

Some usb interfaces are better and some are worse. The USB interface on a given DAC may well be much better than the one on a dedicated spdif converter, in which case you just degraded your signal.

You aren't avoiding the "overhead" of usb in either case. You're just moving it from your DAC to a dedicated device earlier in the chain. Digital audio over usb is still there. The only way to remove usb is to not have a usb connection at all in the chain, i.e. dedicated spdif outs on your source.
 

RayDunzl

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#11
<-- doesn't sweat the digits
 

graz_lag

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#12

graz_lag

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#13
This applies to me only maybe but after several back & forth with /without my Weiss USB S/PDIF bridge, my ears suggest me to keep it the path to the DAC, both, the NAD M51 and Topping DX7s.
Very short USB cable : 500 mm
75 ohms coax cable from Supra, Sweden, 1 meter long
Entirely subjective I know, without solid justification from an engineering standpoint ...
 

Veri

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#14
Just saying "it may add 1 SINAD" doesn't make any sense. Why do people assume the USB interface on a dedicated spdif converter is always better than the USB interface on any given DAC? The people selling the device may want you to believe that, but there is no reason it must be true. If some vendor is selling both dacs and spdif converters, probably they use the exact same usb implementation in both (unless they one product is very old and the other very new).

Some usb interfaces are better and some are worse. The USB interface on a given DAC may well be much better than the one on a dedicated spdif converter, in which case you just degraded your signal.

You aren't avoiding the "overhead" of usb in either case. You're just moving it from your DAC to a dedicated device earlier in the chain. Digital audio over usb is still there. The only way to remove usb is to not have a usb connection at all in the chain, i.e. dedicated spdif outs on your source.
In general it doesn't hurt to isolate into s/pdif, and often has a small improvement in measurements. Likely it'll sound the exact same as Usb so I agree one shouldn't bother, but generally there really was a small improvement looking at amir's work...
 

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