I have a couple of simple queries. I’m using optical out on my imac straight to a chord mojo dac. My simple signal path is source–this mac—built in output. 1) Am i right in saying that as long as i get the purple lights on each stage i’m guaranteed 100% that a bit perfect signal is being sent to my dac via optical? 2) Are AAC albums also bit perfect? If it helps i use exclusive mode on and integer mode. @support
The final thing which is unrelated when using an external hard drive for manual backups will any decent quality HD do or should i look for something in particular?
AAC is a lossy format like MP3. Lossy formats never produce bit perfect output.
Use any reputable brand, nothing special is required. Many here swear by Western Digital drives and caution against Seagate but my experience with Seagate has been fine. Always have more than one backup though, preferably one off site.
Hi Tor, with chord dacs they employ a DPLL digital phase lock loop. This means optical in is clocked by the internal FPGA and jitter is totally eliminated. The end result is that optical in is the same as usb in. Usb is clocked by the internal FPGA. Could Carl confirm if optical out from my imac to chord mojo is 100% bit perfect with purple lights on signal path and exclusive mode and integer mode enabled? Tor says maybe but Tony says yes. I do need to confirm this point with 100% accuracy. many thanks. Mohab
On any DAC I have heard (including MSB signature dac, and close to 50 others). The coaxial/BNC are_ALWAYS_ better compared to optical. It is easy to hear the difference in my opinion. But you are happy; I’m not trying to tell you not to be happy. But I’m fairly sure the Chord dac’s will give you improved performance over coaxial or AES/EBU. USB can be better, but never heard any USB implementation on a DAC that beats the coaxial one.
On high end DACs this is solved for the other inputs as well via isolation. And you of course try to avoid any direct connection between DAC and computer with massive fans and iffy power supply. This is why I just don’t get why the Nucleus is not delivered with a good linear power supply from the get go.
Edit:
I’m just sharing my own experience. If you love the optical - be happy and continue to use it
In fact as optical is galvanically isolated computer “noise” is no longer an issue. Usb cleaners, reclockers, usb to spdif convertors just add unwanted RF noise before the dac IMHO.
This is why I use a network player; hence no cables from computer to DAC.
I have previously been using a very good USB to SPDIF bridge: Audiobyte Hydra Z with Hydra ZPM power supply. Then you get galvanic isolation between computer and DAC. And this is the main reason I love Roon, audio over ethernet, magic.
Thanks Tor continue to enjoy!! I just wish one of the moderators would answer my original question below.
I’m using optical out on my imac straight to a chord mojo dac. My simple signal path is source–this mac—built in output. 1) Am i right in saying that as long as i get the purple lights on each stage i’m guaranteed 100% that a bit perfect signal is being sent to my dac via optical?
While not all file formats are themselves lossless (not Roon’s problem), Roon will send all of these formats to your endpoints bit perfectly, if there is no DSP enabled and if the chain itself is capable if bit perfect playback.
If there is something affecting bit perfect playback in your chain (dodgy cable for example) then you will most definitely know , with audible dropouts or stuttering or pops etc etc.
Hi Sean my question was to do with method of transfer here optical. I’ve had two differing points of view. One stating a definite yes and another experienced member stating that optical may not transfer digital audio in a bit perfect manner all the time. I have an imac with optical out and a redundant laptop which i may sell if i can get an answer from the moderators. One question seems to have spiralled out of control here.
Roon is 100% capable of bit perfect transfer over optical - any format that it can play.
You will probably know Rob Watts simple but effective test for this which can avoid all this discussion.
Play a DSD64 album via DoP over optical (if your TOSlink cable is capable of PCM176kHz).
If you have no audible dropouts or stuttering or pops, everything is cool. You can verify this test with Rob Watts too. This test applies to any software , not just Roon. It’s a solid bit perfect playback test of a chain.
I completely agree with you Sean but with answers like this i want a definite response from the moderators who are Roon. I have an HP laptop which was going to be a usb source which i will sell once i confirm this and use my imac optical out. I may just pm a moderator.
I don’t know how to conduct a DoP64 test i only ever play redbook cd album format not even mqa. I’m very happy this way. Is it normal to pm a moderator here? thanks Sean nice to chat again. I’m almost certain you are right about bit perfect optical i just want to eliminate the doubt triggered off by that reply. An mscaler and new hugo2 are arriving soon hence the obsession with detail here.
Download the free DSD64 samples from the below link. If you never hear a dropout or pop or stutter, your entire TOSlink chain (from software to DAC input) is playing bit perfectly.
Lossy formats sacrifice information from the original recording, that’s what “lossy” means. Hence they are not “bitperfect”, but we don’t use that word in this case, we just say lossy.
The transfer of information from Roon Core to the endpoint is usually bitperfect, and that includes optical. This statement doesn’t mean that a transfer is always bitperfect, things can go wrong. A CD is bitperfect, but the FedEx guy delivering the CD from Amazon might drop it and back over it with his truck. But in normal circumstances, optical is bitperfect. That’s not what we worry about with optical.
Optical often has high jitter, which causes distortion. This is rooted in a bad decision in the design of SPDIF (optical is a kind of SPDIF) which made the source and therefore the transfer responsible for timing. That is not the case with asynchronous transfer mechanisms like asynch USB and network. But some DAC manufacturers put aside the SPDIF standard and take responsibility for timing, including Chord which was mentioned above.
There is concern with elevctrical noise being transferred through the cable, maybe through the ground/shield. Optical eliminates this.
So that’s why Rob Watts of Chord can say he prefers optical, because his DAC is not susceptible to jitter and avoids noise.
So which is preferable depends on your DAC. All these discussions about transfer mechanisms depend on what the DAC is sensitive to.
