Hard disk vs CD transport through external DAC

I wonder if any of you savvy people can explain the following to me?

I have a Benchmark DAC1 to which I have connected my Roksan Kandy Mk III CD player (via digital coax) and an Apple TV (via optical cable). The music on the Apple TV is synced to it's hard disk, not streamed, to eliminate any interference issues. I have AB'd several pieces of music and without doubt the CD transport and DAC combination sounds better than the hard disk and the same DAC (not a lot, but certainly noticeable).

That doesn't make sense to me. I would expect that the mechanical movement of the CD transport could only serve to detract from the source material. Now, I do realize that a hard disk also contains a moving head but somehow because it's several orders of magnitude faster and more precise than the CD transport I assumed it's operation would not have a perceptible effect on the digital audio stream at the output stage. Was that a foolish assumption? Is it possible there is some kind of interference from the other consumer grade electronics in the Apple TV that would affect the music?

Could someone with a better understanding of electronics than me offer an explanation?

 

I'm not 100% certain on this one, but I think that hard disks are not as accurate as you believe. I think they rely on high rotation speeds to deliver data which hasn't been read correctly the first time. In other words, they're doing a lot of error-checking and error-correction, but because they're so fast it doesn't matter; until you get to time-dependent data like music, where all the error-correction becomes audible.

 

I've wondered about this too as my bargain basement MArantz SE 63 delivers a far better sound quality through my NOS DAC (Blue Light Plastic Box Thingie) than my computer digital output from M-Audio Delta 1010 through the same DAC. Incidentally the M-Audio Delta 1010 cost three times as much as the MArantz CD Player. I have almost given up on using my computer to deliver HiFi!

Incidentally I have also tried the computer analogue output Via the M-Audio DAC and this was even worse!!!

 

Interesting.
I'm on the fence with regard to HD's as the source to my main HiFi.
Reviews like this will keep me there for a lot longer.

I have found that the better the transport, the better the sound.
so IME something even better than the Roskan would hammer the HD even more convincingly.
This can be DAC dependant and some say the very expensive DAC's are less critical to jitter.

 

Anyone had a play with a solid state hard drive?

 

It could just be that apple tv is an over hyped piece of crap...

my £6 usb toslink widget into my cd player dac via my laptop sounds better than my cd player straight.

 

Dosh, I take it you are using iTunes to RIP your CDs ... Are you RIPing them using the standard 128kbs AAC encoding? If so, you are losing a huge amount of the musical data.
Try changing the setting for AAC to 320Kbs, or better still Lossless encoding. It takes up much more room (a factor of approx 10x more per RIPed CD) on your hard drive, but the results are worth it.
You can alter the settings in the following tab selection ... iTunes/Preferences/Advanced/Importing; then go to the "Import Using" tab and select AAC or Apple Lossless.
Cheers ... Andy

 

imho, its all to do with the attention given to timing/clocking by the manufacturers.

yes, there could be difference in lossy encoding
yes, there is prospect of interference from other electronics in a computer

and, delivery from solid state memory ought to have prospect of being better than either spinning hard disk or spinning CD, but surely, so much depends on what timing information signal the dac is given relative to the other encoding/transmission noise.

I'm happy with what AudioSynthesis do with their Ncode from their CD transport to their Dax Decade dac, but would like to enjoy the same benefit from a solid state storage/delivery device.

 

Thanks for the replies. Just to clarify I rip most of my music in lossless, and certainly those pieces I was using to test with. I use high bitrate AAC for a few things that were recorded poorly to begin with, or have been compressed a lot, or otherwise don't have much dynamic variation or harmonic content.

Solid state HD is an interesting suggestion. Unfortunately not one I am in position to test myself.

As far as I understand it as long as music remains in the digital domain, interference isn't an issue. Therefore the only things that could affect quality are loss of bits/error correction or rounding errors in sample rate or bit rate conversions. I checked the lossless pieces I was testing and they were ripped from the CD at 44100Hz and 16 bits so that should rule out conversion issues.

So maybe its as thrudge suggested, there are actually so many read errors it does affect the music. I'm not sure how I could test that. That leaves me with no explanation for how sq225917 can bet better sound out of his laptop than his CD unless his CD transport is so poor (or knackered at least) that it's making things worse.

I'd be interested to hear more of other people's experiences.

 

Thanks Ditton, I made that last post before reading yours. I hadn't considered timing issues. The Benchmark DAC1 is supposed to use some novel approach to eliminating clock jitter but the technical explanations go over my head. Perhaps it can only reduce them and if I was using a different DAC the problem may become even more pronounced.

I have a decent external audio interface for my computer, that should have a better clock then the Apple TV, I'll try hooking that into the hifi and seeing if there's much difference.

 

I think this area has been somewhat over-hyped. For high quality hifi the technology is simply not there yet. I'm certainly not going to entrust my music collection to the vagaries of some HD box. Anyone who's had a PC for a few years knows just how unreliable HD storage can be. And why should I waste my time doing back-ups – as someone said 'CDs are already backed-up!'

I'm quite happy to wait a few years until there's solid state storage of sufficient quality, capacity and reliability. Also until broadband speeds are significantly faster and less variable, and the infrastructure software is of much better quality and tailorable to the way I want to use it.

 

dosh, everything on my laptop is ripped with Exact audio Copy and output via digital, anything out of the analogue outs sounds shit, no better than my Sony-pod.

Playing a file copied to harddrive as wav and playing the same wav extracted via EAC shows a significant difference, it's easily noticable back to back, EAC is better.

if you scroll down on this page http://www.audioholics.com/educatio...ynamic-comparison-of-lps-vs-cds-part-4-page-6 they show a few measurements for the same track by Roxy Music via cd direct and from an EAC rip, the differneces are significant to say the least.

I guess Cd error correction isn't as perfect as we are lead to believe...

re my cd player, it's a very heavily modified Cambridge Audio 840c and it sounds simply superb, however EAC ripped lossless into the on board DAC still sounds better, a touch more dynamic with a more 'listen into' quality, kinda clean vs dirty vinyl in effect.

If i had to lay it anywhere i'd say the cd transport doesn't make a perfect read and the DAC can only deal with what it is dealt.

 

Solid state discs will make no difference. The data is asynchronous until a chip in the sound card reads it out of a buffer and clocks it. This clocking operation which produces a synchronous data stream will have a small amount of jitter dependent on the quality of the clock.

Every wire, every component and every contact between that chip and the DAC chip in your DAC will add a little bit of jitter.

If you want to reduce jitter, you need to create the synchronised signal using a very very high quality clock and as closely as possible to the input of the DAC chip.

Now let me see, can I think of a device that does this....



Finally there is the issue of electrical noise which is unrelated to the digital data which is generated inside a PC or a TV and will find its way into your DAC if you are using a wire connection. This can have all sorts of deleterious effects by polluting the power supplies in the DAC and other nefarious activities.

You may get a better sound by using a glass optical connection as this will eliminate the electrical noise.

The Transporter avoids interference from the PC by using wi-fi and by careful internal design so that its own digital circuits cannot pollute the analogue outputs.

 

£6 usb toslink widget, works for me, my DAC sound better than the transporter anyway.

 

SSD v HDD? Doesnt matter, they are both solid state to a degree. The read and write buffers of a hdd are solid state.

The quality loss is likley due to electronic noise. If you had a HDD (or SDD) source with a high quality output to a dac you will be quids in.