When I was doing DAC reclocking 10 years ago, I found my player was still affecting the sound. I still can't figure it out what would be the cause of that. This is probably the greatest mystery of audio industry. Anyone who can solve the puzzle should be awarded. As Ian said, the EMI could be the cause, but we need to exploit more.
Ian has designed a very sophisticated FIFO that definitely should remove any jitter caused by the source signal. Despite this, some people state that they, even with the FIFO, still hear differences between sources, cables and even player software. As Ian writes, it could possibly be induced and/or conducted noise causing the differences - so it is possible that the effect of the induced and/or conducted noise is greater than that of the source-induced jitter - and thus optical isolation might actually be a more fruitful avenue to explore, rather than a FIFO.
Note that I am definitely not advocating that the effect of the induced and/or conducted noise is greater than that of the source-induced jitter - I am only saying that as long as we don't have any reliable data, we are groping in the dark and might be barking up the wrong tree. Or we might well be chasing a non-existent phantom - that is why I tend to advocate an evidence-based approach...
And the fist step, at least to me, would be to verify the observations objectively.
Just some basic jitter measurements with different sources would probably be a good start in verifying the effect - but it also seems that some people don't believe in measurement results no matter how they are done.
Ian,
I don't entirely share your scepticism about optical - considering a part of my career was spent in getting gigabits per second transmitted thousands of kilometres, without unrecoverable data loss or jitter issues.
There is a write-up of an interesting experiment using a Corning USB 3 optical cable.
I don't entirely share your scepticism about optical - considering a part of my career was spent in getting gigabits per second transmitted thousands of kilometres, without unrecoverable data loss or jitter issues.
There is a write-up of an interesting experiment using a Corning USB 3 optical cable.
Julf, i'm no expert. Never will be.
But if i'm correct, in the case of a i2s fifo/dual xo, we are talking about kb's per second over a distance of 1 metre max?
I can see how optical transmitters/receivers would benefit over a distance of a 1000 miles. But in a audio component, would al the extra parts, psu's etc. not be a waste because these parts also produce distortion of its own within the enclosure?
If this is so, we are back to your statement in post 3678, place the dac far away from any other electronics.
Or do i need to see it otherwise.
"Problem" is, i see the fifo/dual xo as part of my dac. So it will always be in the same enclosure. As for the most of us i think.
Ps. Or am i interpeting it all wrong and are you talking about putting the source (in my case raspberry pi) as far away as possible from the dac and fifo/xo
But if i'm correct, in the case of a i2s fifo/dual xo, we are talking about kb's per second over a distance of 1 metre max?
I can see how optical transmitters/receivers would benefit over a distance of a 1000 miles. But in a audio component, would al the extra parts, psu's etc. not be a waste because these parts also produce distortion of its own within the enclosure?
If this is so, we are back to your statement in post 3678, place the dac far away from any other electronics.
Or do i need to see it otherwise.
"Problem" is, i see the fifo/dual xo as part of my dac. So it will always be in the same enclosure. As for the most of us i think.
Ps. Or am i interpeting it all wrong and are you talking about putting the source (in my case raspberry pi) as far away as possible from the dac and fifo/xo
Zoef
+1 to this experience. I finally am seeing no impact of the PC hdw/softw on the sound. To get there it is a BBB > I2S > isolator and master clock > Ian I2S to PCM > then short ufl cable to DAC which sits with it's shunt regs in their own box surrounded by copper. BBB of course on separate ground scheme to all the isolated components. Also needs vibration dampening. This was not the case with USB and all in one box where I was constantly fussing with the PC trying to get the good stuff.
It sounds very clean/natural & I can listen for hours. Some of what I perceived as 'magic' is gone, but I think that once you get used to it there is no turning back.
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Indeed - and that is one of my points. Compared to transatlantic data cables (that embed the clock in the signal using quadrature modulation), the connections we are talking about here are not very demanding.
Even over a distance of 10 cm optics provide galvanic isolation - in case the error mechanism is ground-induced noise. But once again, first we need to find out what the problem really is (and if there is a problem at all) before we can address it.
I try to keep "distortion" and "noise" apart, because the mechanisms and effects are different. Yes, the extra parts cause some additional EMF noise - but it is pretty small compared to the stuff already there, as all you need is an optical receiver.
In this case yes, as the discussion started from some people stating that they still hear a difference from different sources and player software despite the FIFO. So clearly the cause can't be source clock-related jitter. All that remains is ground-induced electrical noise (that an optical connector would remove) and induced EMF (that shielding can remove). So until we understand and verify the source of the audible differences, we don't know which approach yields the best results - clock domain isolation, galvanic isolation or EMF shielding.
But to reiterate - the first step is to verify that there really is a problem...
Did you do "before" and "after" tests with each step? Just curious to find out which step was the most significant.
Great Question
I am constantly guilty of non engineering rigor to truly understand where the impact came. And I agree, I wish someone with the tools would get to root cause(s).
I made several steps in one leap. I can say that even with the isolator and the physical setup, with USB the pc was still a factor in the sound. I suspect that all of these steps contributed, but usb still created something that the isolation could not totally eliminate.
I made the beginners leap. I read that it was good to do "some" shielding. So i shielded the h#ll out of it. LOL from the compartements with copper and mu metal to all internal wires. Even the output transformers of the dac where put in extra mu metal cases with resin. Overkill would be a understatement ha!
Well it was a nice winter project......
But never again. .....i think
Well it was a nice winter project......
But never again. .....i think
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[emoji33] [emoji33] i think i made a major #@$$&
I don't have the pi on a separate ground..................
Yes, it is hand soldered
I use Runeaudio with Rpi2.
Runeaudio can be remotecontrolled via a browser on pc or smartphone.
But I dont like smartphone.
I designed my own mobile remotecontroll with rpi2 640*480 screen powered by li-ion battery.
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Hey MeiT, that remote looks banging! Are you able to provide some more details on what hardware and software components you used?
How did you make the enclosure!? Very slick.
