O2 AMP + ODAC

[r010159]

 I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
Thanx.

 
I have been having a conversation with an embedded software engineer (the types that make things like DACs professionally) and some recording engineers. Here is what I learned so far. I will update this as my conversation develops. (The long version is followed by the short version).
 
The long story:
 
There is USB class 1 and class 2 implementations. Class 1 requires no special device driver. Class 2 does require its own driver, but it is a more accurate way of transferring information using USB. In other words, there is much less jitter (distortion) with class 2 devices. And custom drivers for this are only available for the Mac and Linux. As a consequence, very few DACs support class 2 designs. The ODAC is class 1 design that uses one of the few chips that support 24-bit data.
 
All PCM/SPDIF/I2S DACs have the most accurate timing by the nature of the chips used in their design. Next are class 2 designs. Next are USB class 1 designs operating in isochronous mode, which is the case with the ODAC. Then finally there are older USB designs which are, according to one engineer, "crap".
 
All DACs that are designed to faithfully reproduce the audio signal will sound the same. But some DACs introduce a type of distortion that makes the music more pleasant to the ear. This is where they can differ in how they sound. Please note that the latter DACs do not reproduce the sound accurately on purpose. For instance, this is the reason why there are those of use who like tube amps. Tube amps generate distortion by introducing the pleasing even harmonics to the sound. I also think this is how DAC manufactures can differentiate their DAC from other DACs.
 
In recording studios, the difference between a budget properly designed DAC (to the numbers like THD, SNR, FR) and high-end DACs (like the Benchmark DAC) is noticeable but not anywhere near as great as the difference between a good budget DAC and a poorly implemented one. We are talking the difference between inches compared to feet here. IMO I think the ODAC fits in the category of a good budget DAC.
 
The short version: The difference is in older poorly implemented USB and those of current day USB. For current day USB chip implementations, they are all the same.
 
Am I verbose or what?? 

 
 
PS: I will ask about the differences between asynchronous compared to isochronous implementations of USB.

EDIT: Class 2 USB is not natively supported in Windows. But this person said it may be in Mac OS and Linux. I just checked and they both do.

 

[r010159]

I have asked John Seaber of JDS Labs the question on the difference between asynch and adaptive implementations of data transfer with USB. I am paraphrasing since I did not receive his permission to quote him. He said that adaptive works better with some operating systems like that which is used for portable devices. Otherwise asych offers no audible difference over adaptive because of how ADC chips are implemented nowadays. The Mac OS happens to work just as well with both transfer methods.
 
This stuff is definitely interesting! Thank goodness for the Internet.

EDIT: The Tenor TE7022L chip that the ODAC uses is known to be a good chip. Internally it reclocks the audio information to reduce jitter, like the other better chips do. So adaptive approaches. (compared with asynchronous) can provide good results depending on how the circuit is implemented. (This information is from another source)

 

[adydula]

For the reference to the SQ being affected with the O2/ODAC....
 
That's note correct at all.....I don't want to get into a this cable is better than that cable...that should be for a separate thread about USB cables In general.
 
Any well made USB cable with a ferrite bead will do very very well....with no real discernible difference between them,
 
Belkin has a nice cable with a ferrite bead and doesn't break the bank.
 
All the best
Alex

 

[Whitecitadel]

I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
Thanx.

Some DAC's rely on he timing from the USB port, and if it's oscillator is prone to wander it could affect your DaC timing. Perhaps that what is meant by bad port as different implementations may or may not have accurate timings on the USB?

No such problem with odac as it has it's own internal oscillator.

 

[Solrighal]

. Belkin has a nice cable with a ferrite bead and doesn't break the bank.

Got a link for that by any chance?

 

[krismusic]

Am I verbose or what?? 

Really interesting and clearly explained. Even I understood.

 

[jring]

  I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
Thanx.

 
Hi,
 
under normal operating conditions and using a USB cord with a ferrite bead I have not seen problems - on a lot of different boxes with different operating systems and hardware.
 
I have seen problems in highly abnormal conditions like having too many power hungry devices on the same USB hub of my laptop - Vcc was down to 4 dot something Volts and ODAC was misbehaving but I wouldn't blame it. Also when programming Arduino boards on the same USB hub and the arduino does funny things with the USB data and clock pins ODAC started skipping - also I can't blame it.
 
In both cases plugging the ODAC into another USB port of my laptop fixed the problem - one could of course also just remove the other device acting up but I tend to like to listen to good music while hacking.
 
Joachim

 

[Solrighal]

So the ferrite bead is an essential component?

 

[AsianBatman]

So the ferrite bead is an essential component?

 
I'm using a ferrite bead usb right now, but did not see any difference between one without a ferrite bead. I just happen to have one laying around. 

 

[jring]

   
I'm using a ferrite bead usb right now, but did not see any difference between one without a ferrite bead. I just happen to have one laying around. 

 
Once again in normal conditions the ferrite bead will not have any effect. If your USB power is very noisy either because of lots of HF generating components inside your PC or your cell on channel search right beside it, it might prevent you from hearing effects due to the noisy power.
 
Joachim

 

[AsianBatman]

   
Once again in normal conditions the ferrite bead will not have any effect. If your USB power is very noisy either because of lots of HF generating components inside your PC or your cell on channel search right beside it, it might prevent you from hearing effects due to the noisy power.
 
Joachim

 
Yes. I completely understand that. I'm just putting in my experience. 

 

[adydula]

A cable with a ferrite bead is not essential.
 
Its a good idea to have a cable with a ferrite bead just for insurance.
 
It really will not help or improve the quality of sound, but if there is any RFI it will help eliminate this unwanted RF from entering into the DAC from the PC or any
induced RFI from electrical devices.
 
The ODAC has additional filtering but the ferrite bead on the cable is a good idea.
 
Here is a mini USB that is good and again is rather affordable:
 
http://www.amazon.com/Belkin-Series-5-Pin-Mini-B-Cable/dp/B007XZX8F4/ref=sr_1_12?ie=UTF8&qid=1397613982&sr=8-12&keywords=belkin+mini+usb+cable
 
Alex

 

[Whitecitadel]

So the ferrite bead is an essential component?

I personally consider it a bit of a"seat belt". If you don't have an issue, it's redundant, if you do have an issue it's going to save you.

(Being careful here as I am new!)
If you read some odac articles on "the internet", you can see someone once wrote:

There is some measurable improvement from using a USB cable with a ferrite "choke" at the ODAC end of the cable.

I have no opinion either way, just pointing out what I read. The Belkin cable looks a good option.

Enough about the chokes, more about me placed order yesterday with Stefan at head'n'hifi so just need to wait for the post pixies them get the soldering iron out... (And I think his cable cones with a choke anyway)

Just need to try and contain my enthusiasm for using a b3-80 larger enclosure to keep the batteries, or trying to squeeze the odac in under the PCB so I can save the batteries as others have done. Need to just get it together first I think before I go too crazy with elaborate plans...

 

[Solrighal]

Thanks guys. My mind is now at ease. I'll buy a set cable and see how it goes. Since I'm using a Mac mini with no audio stuff in the vicinity I don't foresee a problem.

And yes, Walter's cable does use a ferrite bead.

 

[MaciekN]

Would you guys think that analog crossfeed is a worthy addition to O2? If not, what else you'd wish it had?