[EliasGwinn]

Tosehee,

I'm not sure what basis their conclusion was made upon, but we have tested the optical output of a MacBook and have concluded that it is, in fact, bit-transparent. We proved this by playing an audio file which was actually a pre-known, pseudo-random bit sequence, and using an Audio Precision to monitor the digital output and compare the bits to the original sequence. If the audio was unprocessed, the sequences should match perfectly. The optical output was providing digital output which was bit-for-bit exact to the original audio file.

Thanks,
Elias

 

[tosehee]

Thanks again.

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Tosehee, I'm not sure what basis their conclusion was made upon, but we have tested the optical output of a MacBook and have concluded that it is, in fact, bit-transparent. We proved this by playing an audio file which was actually a pre-known, pseudo-random bit sequence, and using an Audio Precision to monitor the digital output and compare the bits to the original sequence. If the audio was unprocessed, the sequences should match perfectly. The optical output was providing digital output which was bit-for-bit exact to the original audio file. Thanks, Elias

 

[cansman]

Dear Elias,

I re-read the Benchmark Wiki on Mac OSX. I missed this earlier but ONLY under the Audio MIDI Setup page does it actually state to put ALL volume controls on devices, input and output, to 100%:

"It also has volume controls for each device and signal path (that is, input and output). It is recommended, however, to keep these volume controls at 100%."

Also, in the above screenshot where Built-in Output is set to Digital Out, notice BOTH System Output and Default Output are set to Built-in Output (naturally, this is the default if there are no other devices connected to the Mac). This implies however that both System and Default Outputs are optically streamed out of the Mac to the Benchmark. I presume this somehow ensures bit-perfect streaming.

Consequently, since I'm using the USB mode, the System and Default Outputs should also be set to Benchmark 1.0 to mimic the above setting to ensure bit-perfect streaming. This might explain why I was hearing verying sound qualities in the different settings, as stated in my earlier post.

Unfortunately, I have only my ears to guide me (I completely agree with Benchmark stance on the subjectivity of human listening perception!). I do not have the techinical equipment nor the expertise to verify the above statements. That's where I need your clarification.

If my observations are accurate, my recommendations are as follows (I'm only trying to help and clarify

):

1. Could you please expand the Benchmark Wiki section on Mac OSX to include USB use (in particular to recommend users to set System and Default Outputs to Benchmark 1.0).

2. Also, this is not stated in the web-site or elsewhere but under system preferences>sound>sound effects, Alert volume should also be set to 100%, with 'user interface sound effects' and 'play feedback when volume is changed' both checked (once again this needs to be verified).

3. Would the instructions to put Mac OSX volume control to the maximum on the web and instruction manual be expanded to include the above observations.

Thank you for reading this post. This is my last initiated post regarding Mac OSX sound settings.

Warm regards,
cansman

 

[EliasGwinn]

Cansman,

I really appreciate your feedback on these articles. I figured that, as computer technology is dynamic and evolutionary, so must my articles. Therefore, I am relying heavily on people such as yourself to 'keep it in check'. Thank you.

I would like to perform the tests on these settings soon, but I'm not sure when I will be able to get around to it. I am currently digging my way through a buried desk...but once I get some priority tasks taken care of, I will try this and report back (and update the article on the website).

Thanks again, cansman, and everyone else who keeps the flow of information alive and exciting.

Elias

 

[cansman]

Hi Elias,

Thank you for your reply - I look forward to the test results! This will indeed help Mac OS X users like myself have the confidence of the best setting for the DAC1 USB.

Cheers,
cansman

 

[Soundproof]

To all who have participated in this thread - A Big THANKS!
Lots of useful information, lots of myths examined, quite a few discounted.

As one in the process of moving my music to hard disk storage, at full resolution, this has made things a lot clearer.

A question on the potential difference of quality between the optical connection and the USB connection.
Stereophile has examined the Grace m902. Wes Philips was dissatisfied with the sound he heard through the USB connection, and was given the advice by John Atkinson that it should be ditched. This due to fears of ground loop induced hum. http://stereophile.com/headphones/406grace/index1.html

In other comments, including re. the Benchmark, they've made it clear that they prefer the optical connection.
Meanwhile - and true to audiophilia indeterminacy - accepted belief at AudioAsylum is that optical TosLink is inferior to USB.

Any thought here, Elias? What are your own experiences with the two connection methods? Any differences?

I use, and will be using, Macs to port out my music to both a Benchmark DAC1 USB I have connected to one sound system, and a Grace m902 I'm also using, and would like to hear your opinion on this particular topic: USB vs. TosLink optical - advantages/disadvantages.

 

[Crowbar]

Comments like this on Toslink are meaningless without context!
As has been said a million times around head-fi, Toslink transmitter and receiver components have high intrinsic jitter that exceeds that of S/PDIF and USB. Measurements by someone at an RF lab posted at the diyhifi forums confirm this. The only advantage of Toslink is ground loop prevention--but you shouldn't have ground loops on properly constructed and used equipment in the first place (and with S/PDIF transformer isolation also gets rid of ground loops). If your source is a PC, then you may also get some electrical noise over the USB connection.
In the case of a DAC like this one, you probably can't hear any difference in regards to the jitter, since the ASRC attenuates it by a large amount.
All of this is stuff that has been covered on head-fi already.
By the way, most stuff posted on the AA forums is fairy tales, so I suggest you go to more respectable places, or shortly you'll be buying gold conductor cables and cryo-treated connectors.

 

[Soundproof]

Are you referring to the Stereophile reviewers' opinion?

I'm just asking yours. Or actually that of Elias at Benchmark.

Between the points of attitude I'm able to cull the facts that:

1. Toslink has high intrinsic jitter, exceeding that of S/PDIF and USB,
2. That ground loop may be prevented.
3. And that some electrical noise may be transmitted down the USB wire.

Hey - that's pretty helpful - though somewhat at variance with JA and WS at Stereophile.

I agree with your opinion on Audio Asylum. It's a myth factory. And no - you won't see me buying gold conductor cables.

 

[EliasGwinn]

Soundproof,

We have done several listening and bench tests comparing the various digital inputs of the DAC1 USB. All tests indicate that all four digital inputs perform equally with the DAC1 USB.

This isn't generally the case, for instance, with all D-to-A converters and/or other digital audio receiving devices. It usually depends on galvanic isolation, PLL design, etc.

Luckily, you won't have to worry about any of that with the DAC1. For example, I am using a Lynx AES16 PCI interface which offers 16 channels of AES digital audio I/O to and from my computer. It is a very well built card...well respected in the industry. I use it to stream digitally to my DAC1 USB for doing audio editing with my digital audio workstation. However, when I listen to iTunes, etc, I simply use the USB port -> DAC1 USB so that I don't have to reconfigure the AES16. The USB port works and sounds just as well!! Which makes me

!!

Thanks,
Elias

 

[rmh1]

Any chance that there will be a DAC1-USB released without the headamp? That would save a bit of cash for those of us with amps already. Probably not the original intent of the DAC1, but the USB version is obviously a hit around here and I (and probably others) might be more inclined to buy it if I could save the cash for balanced cables, etc. Just an idea.

Cheers

 

[EliasGwinn]

Rmh1,

We currently do not have any plans to make a DAC1 USB without the headphone amp. Sorry...

Thanks,
Elias

 

[choariwap]

sir,

i just bought a dac1 usb and i'm very pleased with it

one thing though, the one i got is an ROHS compliant version. there is a page in the manual that states that ROHS compliant versions are less reliable in the long term, so much so that extended warrantee only goes to 2 years instead of 5.

1. does this mean that the life expectancy of my dac1 is only 2 years? thats a pretty short time for a 1375 usd dac.
2. have you been getting a lot of RMAs for ROHS compliant products?
3. what sort of failures are there?
4. what should i do to preserve the life of my dac1? i've read that lead free solder doesnt do well if thermal cycled.. does the auto standby feature drop temps?
5. what was the lead free solder and manufacturing treatment used for the dac1 usb?

i'm more than a little nervous about this.

thanks!

ps: i'm not a heavy user, just a home user. listen to it for around 3-4 hours twice a week on weekdays and 8-16 hours total over the weekend.

 

[EliasGwinn]

We have no reason to believe that the life-expectancy of the ROHS compliant DAC1's are any shorter then the non-ROHS versions (which we are no longer manufacturing).

The reason for the shortened warranty is because the ROHS regulation standards includes the use of lead-free solder. This has been known to cause 'tin whiskers', which could lead to short-circuits, and potentially damage the unit. The only known method of preventing 'tin whiskers' is adding lead - hence the dilemma. Every company which manufacturers electronics to be sold in the EU and other ROHS-compliant country is experiencing the same dilemma.

So far, since the transition to ROHS-only manufacturing, we have not seen any increase in RMA's or failed units. However, it would be catastrophic to any small company if the lead-free solder failed and they had to recall every single unit made - especially if the majority of the products were sold abroad.

Thermal cycling may increase the chances of failure. Therefore, it is recommended to keep the unit powered up continuously. The auto-standby feature of the DAC1 USB will not cause the unit to cool, so it does not present a problem.

Thanks,
Elias

ps. If you feel that the lead-free solder regulation is a bad idea, please write to the appropriate government representatives of your country and tell them to modify the ROHS standards to allow lead-based solder.

 

[EliasGwinn]

Cansman,

I got a chance to put the MacBook on the bench. It seems to be bit-transparent independent of what 'System Output' is set to.

Also, I noticed that iTunes was able to achieve bit-transparency at 44/24, which is new to this version (7.3.1). It is still NOT bit-transparent at 24-bits with other sample-rates. (I don't have any idea why it would be like this, but

...thats a question for Apple).

Thanks,
Elias

 

[gregeas]

Elias,

Since you're still here after all these months, I wanted to run a new product idea by you.

I can't be the only one who has the need for a new type of digital two-channel pre-amp. Essentially what I'm envisioning is a full set of digital inputs, a high-quality converter like the one in the DAC1, and remote controlled input switching and volume (with a nice analog pot). While you're at it make it full rack width...

Right now I'm using my Slimdevices Transporter for this; it converts digital signals from my cable box and PS3 and of course handles PC music playback with an excellent UI. It does the job pretty well -- conversion is very nice --but doesn't have an analog volume control, and the inputs can't easily be switched remotely (the process requires multiple button presses). So I've had to keep my pre-amp in the rack to make the system user friendly.

So really the only differences between what I'm proposing and the DAC1 are a remote control and perhaps more a few more inputs for consumer audio. If this product existed I could get rid of my pre-amp altogether and pair my digital pre-amp with my amps directly... Sweet.

I thought about getting a nice audiophile pre-pro, but I'd be paying for extra channels of conversion and video features I don't need.