[SilverEars]

  A real difference in level suggests that the source (computer?) is not sending bitperfect audio and attenuating it a little.  But if you mean it just sounds like a lower level, but measures the same, there are effects (like jitter) that can  cause subjective perception of level changes.  If all is designed well asynchronous USB should always beat TOSLINK optical.  However, it is not always true all things are designed well.
 
The measures you mention are all useful in attenuation RF, but the USB ground is generally unfiltered, so is connected to the ground of a very noisy source: a computer chassis.  So the only way to be sure can be galvanic isolation.
 
With some very expensive equipment, it is hard to prove, but it would be interesting to try subjectively.
 
Yes our ears are sensitive to jitter, more so than a lot of test equipment (including Audio Precision).  However some kinds of jitter just cause THD, and so cannot be differentiated from THD, others cause noise.  So the ear is crucial in the design and tuning of audio equipment, but cannot replace measurement in finding and curing problems.

I was actually looking into galvanic isolation to see if it will benefit audibly as I don't believe my usb output is noisy(only way to tell is to measure) enought to affect the DAC circuit.  On the ODAC thread, a fellow has measured his laptop's usb port close to the monitor, and in this case, there were EMI from the monitor it was picking up since it was near by.  It can be checked if there is an audible difference at the same time it can be checked electrically by taping into the usb port.  Below is measurements of noisy supply, and with a linear supply the noise has reduced.  Second is test with an isolator.  Once again, this all depends on if this noise is affecting the analog output to be audible.
 

 
 

  I'm at least half sure that a battery may be overkill but hey have fun! I would love to do battery power electronics as well. Here is ground pollution from my VGA monitor, not sure about how newer monitors would work. Rig this time is Monitor >Fujitsu Lifebook-> ODAC->ADC-> Adum4160 isolator-> Lifebook. Taking out the monitor gives me a clean spectrum.
 
Maybe the rigs you have been using are cleaner then most but I find that its not the case with some of us which may explain some's negative experiences with the ODAC.Just making a Y cable to inject extra power may not get you the results you really want as you are really concerned with common mode noise which though the ODAC does an okay job, it won't withstand ground loops. Well, whether you believe me ain't my problem so YMMV. 
 
The really bad pollution you see in the previous graph comes from a small switch mode PSU for the Acer. Coupled with the fact that the usb port happens to be exceptionally close to the power input and bam, distortion. In desktops this may come from power built PSUs or you have some crazy graphics(or monitors) or some crappy fans or whatever polluting your usb. 

 

 

[jagwap]

C.A.P.S.  -->  http://www.computeraudiophile.com/section/c-p-s-489/

Empirical Audio Off Ramp 5 -->  http://www.empiricalaudio.com/products/off-ramp-converter

Audiophilleo and Pure Power  -->  http://www.audiophilleo.com/en/default.aspx

Interesting that the audiophilleo and off-ramp also have galvanic isolation as well as the conversation to SPDIF.

I would still be interested in a head to head between these and a USB isolator.

 

[ALRAINBOW]

I have all of them and the ISO helps but not as much as the set does.

 

[jagwap]

I have all of them and the ISO helps but not as much as the set does.

Interesting...
 
If the clock of these devices is better than the one in the DAC… Nope, still doesn't make sense.  SPDIF should be more jittery than asynchronous USB… Hey sometimes what sounds better does not get an obvious immediate explanation.

 

[ALRAINBOW]

There is so many posts on why and how. I do not claim to really know
But my brain knows fast. As with the hdvd800
Without the USB converters it sound nice
But with it the trebles clears up and the low end does too.
It overall makes it much better. If you use a ref track it's easy to know. But if the music is not well done it's much harder and maybe not worth it. The AES does DSD as well as PCM
But spidif only PCM.
It helps without any DAC I have tried
Al

 

[wisemanja]

  A Couple Of HDVD 800 Unboxing Hiccups
 
Though it is now working flawlessly and performing delightfully, I just wanted to share a couple of irritations that occurred to me yesterday as I opened up my Sennheiser HDVD800 DAC/amp.
 

• There was NO power cord!  Yes, it needs one.  The end going into the amp has to be that keystone shape of a rectangle with corners sawed off (see picture below).    I stole one from a Dell computer.  A person buying this $2,000 amp is likely to receive it in the mail on a work day and, despite mounting anticipation, is not likely to open it until dinner is done and kids are off to bed.  Radio Shacks and other plug places are closed by then.  Frustration abounds! (However, I must admit to discovering a new audiophile business opportunity... premium HDVD 800 power cords, at $350 a piece, made of pure Unobtainium braided into Gordian knots, improving sound greatly, and filling this need admirably, or at least expensively!)  
• The driver installation routine in the live PC manual on the supplied DVD did not work. These were needed to make my PC route its signal to its USB port and into the USB DAC input on the HDVD 800.   A call to Sennheiser Technical Support revealed that there is no on-line posting of these drivers.  I was invited to write an email to shouston of Technical Support (as in "How the Sam Houston am I supposed to get this thing to work if the driver does not install!?")  Skipping the live manual page with its installation icon to click on the screen, I went to the individual files on the disk and eventually got it to run the installation program.

 

 
The HDVD 800 comes with not one, not two, but THREE instruction manuals, each written in a dfferent two languages (6 in all!).  I suspect that as a convenience to Sennheiser, they wanted to have a box that could be sent to any country, and since power cords differ by country, they simply elected to not include any (or maybe I am behind the times... I recall when gadgets stopped including printed instructions in favor of disks or on line, and then when they stopped including USB connections, as those are becoming common.)  Maybe I'm just behind the power (cord) curve!
 
Oh, well... all's well that ends well.

 
The cardboard liner that runs around the outside edge of the HDVD800 as it sits inside the box is hollow. The power cord is shipped INSIDE of that liner. Many people have missed this.
 
Also, if you are using asynchronous USB, any half ways decent USB will work. I have compared a $500 USB cable that I own with a $1.95 USB cable I bought later. Normally because of jitter issues, the more expensive cable would perform better on other units. I was amazed that with Asynch mode, I couldn't hear any difference on the HDVD800. So I kept the $1.95 cable and sold the $500 one as I no longer needed it.
 
-Jeff

 

[ruthieandjohn]

Thanks for the tip @wisemanja, but no. I went to the box, took out that liner, had to unstick one of two clear circular stickers at diagonal corners to open the liner to look inside, but... Nothing! (I DID hear a little chuckle in the air as I looked, though!! )

 

[AlanHell]

Thanks for the tip @wisemanja, but no. I went to the box, took out that liner, had to unstick one of two clear circular stickers at diagonal corners to open the liner to look inside, but... Nothing! (I DID hear a little chuckle in the air as I looked, though!!

)

I got mine in Bay&Bloor radio with a bit of discount (about $100) and I did not have the power cord either.
 
I guess now I know where the discount comes from~~

 

[ruthieandjohn]

Does anyone know what the output power vs. impedance is for the Sennheiser HDVD800?
 
I read (somewhere, I think in Sennheiser literature) that it puts out 480 mW into 600 ohms, but no amounts were given for lower headphone impedances.
 
Question becomes important if you are trying to figure out if the HDVD800 can drive, for example, the HiFiMAN HE-6, which at least some folks say benefits from an amp that can drive 5,000 mW into the HE-6 impedance (about 38 ohms as I recall).
 
Thanks!

 

[thomascrown]

Thanks for the tip @wisemanja, but no. I went to the box, took out that liner, had to unstick one of two clear circular stickers at diagonal corners to open the liner to look inside, but... Nothing! (I DID hear a little chuckle in the air as I looked, though!!

)

Mine was included in the shipping box arrived to the store, outside the "sale" box.

 

[Priidik]

  Does anyone know what the output power vs. impedance is for the Sennheiser HDVD800?
 
I read (somewhere, I think in Sennheiser literature) that it puts out 480 mW into 600 ohms, but no amounts were given for lower headphone impedances.
 
Question becomes important if you are trying to figure out if the HDVD800 can drive, for example, the HiFiMAN HE-6, which at least some folks say benefits from an amp that can drive 5,000 mW into the HE-6 impedance (about 38 ohms as I recall).
 
Thanks!

I read somewhere that that  the nominal impedance for HDVD800 was around 50 ohms (at 1khz ?), and its voltage output can be taken from the power rating to 600ohm headphones, which is 17V rms or 24V p-p from 4-pin out. 
With HE-6 impedance (z) of 50ohm the output voltage will be divided approx 50-50 with the headphones (and amp), only ~8.5V goes to hp-s, then power generated at hp-s is about 1.4W.
That is if the the output current isn't limited.
More importantly the damping factor is too low for low z hp-s, and it shows. Even HE400 are better off from a mid-tier amp with low z; from Senn amp the bass lacks control.

 

[62ohm]

I tried the Shure SRH1540 the other day, and I have to admit, even the WA7 sounds better than the Senn amp for the Shure. Though I was surprised by how well the Senn amp drives the LCD-2.

 

[yates7592]

I recently bought a HDVA600 at a good price on Ebay (so there is no DAC of course). The only DAC I have at present is a Yulong D100. I'll be using HD800's and Cardas Clear balanced cable, going balanced out from D100 into HDVA600, then 4-pin balanced out to HD800.

I like the D100 a lot, but whilst its been good enough for me in the past, it's not high-end stuff, so I'm not sure how it will match with HDVA600. Do you guys think this pairing will be ok, either in the short-term, or the long-term, compared to HDVD800 alone?

If not positive thoughts, can you recommend another neutral DAC that I could pair with my HDVA600? I can't tell you yet how it sounds with the D100 because the HDVA600 hasn't arrived......

 

[SilverEars]

  I read somewhere that that  the nominal impedance for HDVD800 was around 50 ohms (at 1khz ?), and its voltage output can be taken from the power rating to 600ohm headphones, which is 17V rms or 24V p-p from 4-pin out. 
With HE-6 impedance (z) of 50ohm the output voltage will be divided approx 50-50 with the headphones (and amp), only ~8.5V goes to hp-s, then power generated at hp-s is about 1.4W.
That is if the the output current isn't limited.
More importantly the damping factor is too low for low z hp-s, and it shows. Even HE400 are better off from a mid-tier amp with low z; from Senn amp the bass lacks control.

Yes, the problem with HE-6, is that it needs lots of power, and if the amp has output impedance since HE-6 is 50, it will take significant amount of power.  This is one of the reasons why people scratch their heads.  0 output impedance would be preferable if there isn't gobs of power.  
 
For the 800, the lowest it dips is like low 300ohms, and there is the bass resonace peak that speakers have.  Here is the thing, the 800's impedance response is reactive, I don't know how it fares with 50ohm output impedance reactively.  Wouldn't it shift the resonance?  Therefore, change the FR?

 

[kazsud]

I recently bought a HDVA600 at a good price on Ebay (so there is no DAC of course). The only DAC I have at present is a Yulong D100. I'll be using HD800's and Cardas Clear balanced cable, going balanced out from D100 into HDVA600, then 4-pin balanced out to HD800.

I like the D100 a lot, but whilst its been good enough for me in the past, it's not high-end stuff, so I'm not sure how it will match with HDVA600. Do you guys think this pairing will be ok, either in the short-term, or the long-term, compared to HDVD800 alone?

If not positive thoughts, can you recommend another neutral DAC that I could pair with my HDVA600? I can't tell you yet how it sounds with the D100 because the HDVA600 hasn't arrived......

How much did you get the hdva600 for if you don't mind me asking?