USB Bridge

The goal for USB receiver is to get data and reformat it for use by DAC circuit. There is nothing fancy there, All magic happens later in clock recovery, digital filtering and actual D/A conversion. There are new new features still coming out. But this all is WITHIN DAC BOX! It is impossible to keep clock stable with low jitter if it is located further than a couple inches from D/A chip. This means that all this magic should happen within few square inches of a single circuit board. This has nothing to do with USB protocol processing.

So all the USB bridges on the market are a waste of money and offer no benefit to the internal USB solution all DACs already have? All of the USB Regen and Remedy products are all a waste of money and offer no benefit? So when I hear any improvement from such devices it is all in my imagination?
 
So all the USB bridges on the market are a waste of money and offer no benefit to the internal USB solution all DACs already have? All of the USB Regen and Remedy products are all a waste of money and offer no benefit? So when I hear any improvement from such devices it is all in my imagination?

Exactly right. They just used in case if DAC does not have internal USB interface (usually older or pro-audio devices). Any data stream extracted from USB still needs to be re-clocked and processed inside DAC unit.

It does not mean that there are no poorly designed DACs which incorrectly process data via USB (you can find some examples reading measurement section of Stereophile reviews). But they are broken to begin with and their place is in garbage bin regardless of original price. If software developers or hardware designers could not simply implement well written standard from decade ago, they should be immediately fired.
 
So, are we saying the latest XMOS chip doesn't bring anything new to the table? Like I mentioned I'm in the market for a DDC to be used with a vintage Dac and wonder if the latest XMOS solutions are worth the premium. I suspect not for redbook.
 
Exactly right. They just used in case if DAC does not have internal USB interface (usually older or pro-audio devices). Any data stream extracted from USB still needs to be re-clocked and processed inside DAC unit.

It does not mean that there are no poorly designed DACs which incorrectly process data via USB (you can find some examples reading measurement section of Stereophile reviews). But they are broken to begin with and their place is in garbage bin regardless of original price. If software developers or hardware designers could not simply implement well written standard from decade ago, they should be immediately fired.

Of course the DAC itself is of the most importance for any digital to analog conversion. This is where you should spend your money.

I do not agree the USB interface is not critical to sound quality. I do agree that the best solution is to have a good USB interface internal to your DAC. I do agree having a short connection between the USB interface and the DAC processor is important but mostly this is true for the raw I2s interface. A USB interface that converts to PCM and transmits over SPDIF is not nearly as distant critical (this would also rule out DSD transfer). So if you have the latest XMOS and TCXO components in your internal USB interface an external one won’t provide any improvement (with a few other assumptions included). If you have a DAC that has a USB interface that is a couple of generations back, an external USB converter with the latest components absolutly will improve audio performance of your digital files as they sound coming out of your DAC. It is not subtle and it sounds like you should try it for yourself.
 
So, are we saying the latest XMOS chip doesn't bring anything new to the table? Like I mentioned I'm in the market for a DDC to be used with a vintage Dac and wonder if the latest XMOS solutions are worth the premium. I suspect not for redbook.

In my experience the latest USB interface with current XMOS and TCXO will make all digital files sound better than any USB interface from a few generations ago.
 
I mean not generations, but say Gustard U12 is $170 on Amazon with Prime shipping and I believe it comes with proper drivers.
 
Of course the DAC itself is of the most importance for any digital to analog conversion. This is where you should spend your money.

I do not agree the USB interface is not critical to sound quality. I do agree that the best solution is to have a good USB interface internal to your DAC. I do agree having a short connection between the USB interface and the DAC processor is important but mostly this is true for the raw I2s interface. A USB interface that converts to PCM and transmits over SPDIF is not nearly as distant critical (this would also rule out DSD transfer). So if you have the latest XMOS and TCXO components in your internal USB interface an external one won’t provide any improvement (with a few other assumptions included). If you have a DAC that has a USB interface that is a couple of generations back, an external USB converter with the latest components absolutly will improve audio performance of your digital files as they sound coming out of your DAC. It is not subtle and it sounds like you should try it for yourself.

There is another issue of computer noise that has not been addressed in this thread . To isolate the DAC from the computer you need to use a AOIP or a optical Toslink .
One good solution for USB is the PS audio LANRover .
 
Of course the DAC itself is of the most importance for any digital to analog conversion. This is where you should spend your money.

I do not agree the USB interface is not critical to sound quality. I do agree that the best solution is to have a good USB interface internal to your DAC. I do agree having a short connection between the USB interface and the DAC processor is important but mostly this is true for the raw I2s interface. A USB interface that converts to PCM and transmits over SPDIF is not nearly as distant critical (this would also rule out DSD transfer). So if you have the latest XMOS and TCXO components in your internal USB interface an external one won’t provide any improvement (with a few other assumptions included). If you have a DAC that has a USB interface that is a couple of generations back, an external USB converter with the latest components absolutly will improve audio performance of your digital files as they sound coming out of your DAC. It is not subtle and it sounds like you should try it for yourself.

If you use SPDIF, you need to do clock recovery all over again. Thus it almost does not matter how good is clock in USB interface. The same thing is about HDMI audio de-embedders. Both only work well if DAC has very good clock recovery circuit or ASRC along with independent clock. It is somewhat easier to achieve if all components use a single word clock. In this case there is no need for buffers, just good PLL to reduce signal front incertaintly (commonly called jitter). My DAC uses ASRC and I saw huge difference in distortion between it being on or off. I can imagine that this can be heard too. But if DAC circuit is bad, nothing really helps it. Do not waste your money and get a DAC that has no design error. They are affordable enough today.
 
I mean not generations, but say Gustard U12 is $170 on Amazon with Prime shipping and I believe it comes with proper drivers.
The U12 is an established and proven product but has the previous generation XMOS (U8) which is fine but has about half the processing capability of the newer XU208. I’m also not sure it has the latest clock but I know they are totally acceptable. Depending on what USB interface you have now, I think you can’t go wrong with the Gustard U12.
 
If you use SPDIF, you need to do clock recovery all over again. Thus it almost does not matter how good is clock in USB interface. The same thing is about HDMI audio de-embedders. Both only work well if DAC has very good clock recovery circuit or ASRC along with independent clock. It is somewhat easier to achieve if all components use a single word clock. In this case there is no need for buffers, just good PLL to reduce signal front incertaintly (commonly called jitter). My DAC uses ASRC and I saw huge difference in distortion between it being on or off. I can imagine that this can be heard too. But if DAC circuit is bad, nothing really helps it. Do not waste your money and get a DAC that has no design error. They are affordable enough today.

Absolutly agree. In my case my main DAC is a Modwright Elyse which I absolutly love the sound it provides for my digital files in my system. Maybe it is partly due to the great anolog output design, maybe it is the PS design but I’m sure it is also due to the digital circuit design utilizing the PCM1794. The PCM1794 is strange choice as it is H/W controlled which is not the normal choice these days but does give the designer many controls not common with other chips. It also means it can’t process I2s or DSD but I really don’t care as I really like this DAC and 24/192 is fine with me (actually 24/96 is fine with me). So even though I am still relying on the internal clock because I’m interfacing with SPDIF I still hear a substantial improvement with this new USB interface. The internal USB in the Elyse is an Optoma NuForce which is not real common, and uses unique drivers but has a decent reputation. The new Breeze sounds better as I described at the beginning of this thread. It is not subtle.

Now if I can just get Dan Wright to design and build an Elyse II with all the latest developments. I’m sure he will once the dust settles just a little. One thing I hope he does not touch is his analog output circuit of the Elyse as it makes beautiful music!
 
The U12 is an established and proven product but has the previous generation XMOS (U8) which is fine but has about half the processing capability of the newer XU208. I’m also not sure it has the latest clock but I know they are totally acceptable. Depending on what USB interface you have now, I think you can’t go wrong with the Gustard U12.

I have none, using Toslink out of a, vintage now, Creative SB notebook card which I'm not very confident in, so any more or less decent USB DDC out to coax should be an improvement. The DAC in question has no USB. I don't do hires or DSD, so even previous XMOS should be adequate I would think.
 
I have none, using Toslink out of a, vintage now, Creative SB notebook card which I'm not very confident in, so any more or less decent USB DDC out to coax should be an improvement. The DAC in question has no USB. I don't do hires or DSD, so even previous XMOS should be adequate I would think.

What external DAC do you have? The reason I ask is the money may be better spent on the DAC itself rather than the USB interface.
 
It's a Parasound D/AC-1000, just bought it to experiment with so just need an interface. Not to mention I would probably have to spend in 4 digits to get to the same level of performance. I have other more modern DACs with USB, but I've been curious about these vintage multibit DACs, and it does not disappoint.
 
Last edited:
If you actually read the FLAC papers, the first ones to come out on it, that is where the idea for FAC came from but instead of losing the data - one could make a 'Container' type system just like *.zip, etc. use.

I'm sorry, but I don't see your point. Container is just that - a container, think of a cardboard box with Christmas decorations kept in a closet with a "Christmas decorations" label on it. Same idea.
 
I'm sorry, but I don't see your point. Container is just that compression - a container, think of a cardboard box with Christmas decorations kept in a closet with a "Christmas decorations" label on it. Same idea.

FLAC is just like ZIP. You can actually take text file and compress it with FLAC. After you decompress it - it will be the same text file. In that regard it works like ZIP, RAR or any other lossless compression tool. The only difference is that algorithm is optimized for audio data allowing a bit better compression ratio than plain ZIP. That is why when you use FLAC to compress DoP encoded DSD file, after expanding it is successfully played by DSD DAC. No bits are lost in the process.
 
FLAC is just like ZIP. You can actually take text file and compress it with FLAC. After you decompress it - it will be the same text file. In that regard it works like ZIP, RAR or any other lossless compression tool. The only difference is that algorithm is optimized for audio data allowing a bit better compression ratio than plain ZIP. That is why when you use FLAC to compress DoP encoded DSD file, after expanding it is successfully played by DSD DAC. No bits are lost in the process.

Thanks, I'm well aware of how compression works. It is just using a JPEG analogy was wrong and then that container comment just seemed random.
 
So, are we saying the latest XMOS chip doesn't bring anything new to the table? Like I mentioned I'm in the market for a DDC to be used with a vintage Dac and wonder if the latest XMOS solutions are worth the premium. I suspect not for redbook.


the new XMOS u208 is superior. I use a gustard u12 and I recently had a singxer su-1 u208 based DDC in my system it improved the sonics of both my RDC 7.1 and schiit yggdrisil

gvl I have heard great thing about that parasound dac- I believed its a pcm63k which is an impressive chip. using a DDC out to digital coax spdif will give you a great increase in fidelity compared to optical out of an on board or PCI sound card.

many flock to the many new USB DACs because of the ease, but there is something to be said for the value of using older spdif/aes based DACs with an external DDC, dollar for dollar I think a used parasound/theta etc 90s DAC paired with a u208 DDC would be killer.

a friend of mine uses a CAL tube DAC with a gustard u12. the performance was much better with the more precise gustard than spdif out of onboard.



I too believe that USB interfaces only increase in quality with new chipsets & technology

the actually DAC chips themselves don't follow this trend. newer is not always better. its all in the design, you can still get superior sound out of near 20 year old chips pcm63/tda15xx etc
 
the new XMOS u208 is superior. I use a gustard u12 and I recently had a singxer su-1 u208 based DDC in my system it improved the sonics of both my RDC 7.1 and schiit yggdrisil

gvl I have heard great thing about that parasound dac- I believed its a pcm63k which is an impressive chip. using a DDC out to digital coax spdif will give you a great increase in fidelity compared to optical out of an on board or PCI sound card.

I had it for a couple of days and I think it is fantastic. And even if you consider the cost of the 96kHz/24bit upgrade kit and a decent DDC it is still less expensive than say a comparable Schiit multibit DAC, even used. I did try it with a coax out of my CDP SPDIF, and while not a night and day difference it sounded better than optical out from the sound card when listening to a FLAC rip of the same CD, but probably that will be the extent of improvement with a good DDC.
 
the new XMOS u208 is superior. I use a gustard u12 and I recently had a singxer su-1 u208 based DDC in my system it improved the sonics of both my RDC 7.1 and schiit yggdrisil

gvl I have heard great thing about that parasound dac- I believed its a pcm63k which is an impressive chip. using a DDC out to digital coax spdif will give you a great increase in fidelity compared to optical out of an on board or PCI sound card.

many flock to the many new USB DACs because of the ease, but there is something to be said for the value of using older spdif/aes based DACs with an external DDC, dollar for dollar I think a used parasound/theta etc 90s DAC paired with a u208 DDC would be killer.

a friend of mine uses a CAL tube DAC with a gustard u12. the performance was much better with the more precise gustard than spdif out of onboard.



I too believe that USB interfaces only increase in quality with new chipsets & technology

the actually DAC chips themselves don't follow this trend. newer is not always better. its all in the design, you can still get superior sound out of near 20 year old chips pcm63/tda15xx etc

Do you know how XMOS became a standard in USB audio? When XMOS made their new multicore DSP, they decided that it is necessary to give an example of its use for interface data processing. For that purpose their developers wrote USB client code running on that DSP. And they make it open source and available for free. That is why everyone jumped in and started using this software as base of their own design running on XMOS processor. Before that manufacturers were just too lazy to write USB client code. There is nothing in XMOS chips that is not available in other processors for embedded systems. And some DAC makers successfully use TI or other chips to process audio data.
 
Back
Top Bottom