[boead]

My dilemma is that my PC is about 25 feet from the stereo. I can either run a long RCA cables (which I already made with Belden wire that sound ok) OR I have to run long digital connections. Either Optical or Coaxial RCA.
I’m not even sure is you can get or make a 25-30 foot coaxial cable or optical TOSLINK.
Is there an inherent limit to how long a digital wire can be? I mean a point which degraded sound quality becomes significant?
I found that the longest a USB cable is sold is about 16 feet. Why? Can a USB cable for an audio device be longer then 16 feet?

Is it best to use an external DAC for a Computer close to the computer and use a long RCA to the preamp
OR
Is it best to use a long digital cable from the computer to the DAC at the rack with short IC’s to the preamp?

[gongos]

If you get a buffered USB cable you can run one 30+ feet.

[boead]

If you get a buffered USB cable you can run one 30+ feet.

Explain ‘buffered’ USB cable? I’ll google it too.

I’ve heard some negative comments about USB DAC’s being less musical (or Audiophile quality) then they should be when compared to similar DAC that use coaxial.

Any truth to that?

Any opinion on the Scott Nixon DAC+USB or the original DAC+

[gongos]

A buffered cable does exactly that--buffers the signal so there's no loss. I switched from a Modwright 999es to a USB converter to a Empirical Audio modded DAC. The latter cost half as much and is more musical to my ears. I wouldn't switch back if the 999es was $500. I've never used a straight USB DAC. Scott Nixon has a demo of his USB DAC.

[kfr01]

Check this product out...

USB --> 150ft + Cat5 --> USB...

I'm going to buy one for my new HT room.

http://www.cablestogo.com/product.asp?cat%5Fid=1501&sku=29341

Anyone have any experience with it?

[IronLion]

In a month or so Belkin will release a wireless USB hub that I am going to get to solve the same problem.  It will allow me to put my USB Soundcard away from my laptop and still have my computer hooked up to it (so the signal would go from my laptop to wireless transmitter to wireless hub to USB soundcard to Bel Canto DAC2).

[kfr01]

In a month or so Belkin will release a wireless USB hub that I am going to get to solve the same problem.  It will allow me to put my USB Soundcard away from my laptop and still have my computer hooked up to it (so the signal would go from my laptop to wireless transmitter to wireless hub to USB soundcard to Bel Canto DAC2).

Reeealllly!? That'd be perfect.  

Thanks!

[kbuzz3]

I use this dac with about 18 feet of usb cable. Very good sound for little money. Worth a try out without losing your shirt. reccomened

[boead]

I ordered this USB Active Extension in a 16 foot length.  http://www.usbcable.com/cat24.htm  
 
I also ordered a 15 foot USB cable AND a 10 foot extension (non-buffered).  
 
I’ll try these configurations.  
 
PC > 15’ USB cable > 16’ active extension > USB DAC > 3’ RCA (MIT S3) > Preamp
 
PC > 15’ USB cable > 10’ extension > USB DAC > 3’ RCA (MIT S3) > Preamp
 
PC > 15’ USB cable > USB DAC > 12’ RCA (MIT S3) > Preamp
 
PC > 2’ USB cable > USB DAC > 35’ RCA (DIY Belden wire) > Preamp
 
And we’ll see how it sounds with my M-Audio USB DAC. If it’s ok I’d like to try the Scott Nixon USB DAC+, I LIKE tubes –or- this USB DAC from Red Wine Audio.

http://www.redwineaudio.com/USB_Select.html

This unit WITHOUT an analog output stage is $399 which means all this is for the purpose of converting the USB to SPDIF.

He eliminates the USB power, converts to 12V so it can work on battery which is mounted inside.
( he says… this removes the noisy USB port's power supply out of the equation (which is derived from the computer's switch-mode power supply), as well as the length of USB cable that it would have to travel between the computer and DAC…)

He also replace the SPDIF output resistor with Caddock MK-132 precision metal film resistor, direct wiring of the SPDIF output signal to a high-bandwidth 75-ohm BNC digital output jack which I’m not thrilled with! And he adds dampening material to the crystal oscillator which sets the clock for SPDIF, this is from M-Audio.

Lastly he increases the power supply rail capacitance with the use of Black Gate capacitor, and replaces the USB CODEC chip’s critical voltage line decoupling capacitors with Black Gate NX-Hi-Q caps

All this so far just for USB to SPDIF conversion, obviously the most important thing.


If you want an analog output too, he adds this for $100; He completely bypasses of the opamp in the stock analog output stage.  The L and R output signals are now directly from the internal DAC's output stage and sent to the RCA output jacks via Black Gate NX-Hi-Q coupling caps.
So the only other thing he’s using from the M-Audio board is the Audiophile 2496 converter.

He also includes a battery charger that plugs into the back. The charger has a ‘charged’ indicator light. Batteries are replicable and said to last 6 to 8 hours.
For an extra $50 he has a slightly larger enclosure and batters with longer life span up to 24 hours.

Not a bad package for $499 and many seem to like it.


Something to consider with the Scott Nixon. With the upgraded power supply its $575 and then you need a power cord! That’s another $125 to $200 easy! So realistically the SN is $700++ and what about a nice NOS tube, that’s another $50.

[lcrim]

Just saw this thread, and wanted to post about this subject.  
There was a bit of discussion over on the Asylum re: optical usb  cable.  The product is at this address   http://www.usb-shop.com/opticis.html.
I have not tried it because I don't need 33ft. extention, which is currently the shortest length available.  John Swenson, among others was very favorably impressed w/ it.  The isolation fron RMI/EFI afforded by optical connection is thought to cause the improvement.  Search the PC sound forum there  on optical usb for more discussion.

About USB DACs in general,  if the implementation is done in a way that utilizes I2S directly to the DAC chip w/o a conversion to SPDIF, there can be a noticeable reduction in jitter.   Having spoken w/ Scott Nixon about his implementation, I know that the receiver chip talks directly to the DAC chip in I2S w/o a conversion to SPDIF.  I don't know about other implementations.
Hope this helps.

[boead]

Just saw this thread, and wanted to post about this subject.  
There was a bit of discussion over on the Asylum re: optical usb  cable.  The product is at this address   http://www.usb-shop.com/opticis.html.
I have not tried it because I don't need 33ft. extention, which is currently the shortest length available.  John Swenson, among others was very favorably impressed w/ it.  The isolation fron RMI/EFI afforded by optical connection is thought to cause the improvement.  Search the PC sound forum there   ...

I’m leaning towards a used DAC from a select few manufacturers so far. Meridian, CAL, Audio Note and a coupe of others. These DAC’s retailed for $2000 or more and commonly sell for about $500 at Audiogon. The same price as a Scott Nixon TubeDAC+ USB.

My onboard sound device has an optical output. I found a Glass optical cable at 30’ which is the longest Glass toslink I could find.

I can also use a 75-ohm coaxial but would then need to use a PCI or USB device to obtain a coaxial digital out. Still, its not a big deal but I’d prefer a Glass optical for convenience.

What’s the contentious on 75-ohm coaxial vs. Glass optical fiber?

A 30’ Glass optical is about $120. A 30’ Belden 75-ohm coaxial is about $50.

How important/significant is the PC device (onboard Realtek, Intel or whomever) that outputs the digital signal? On an older motherboard I was using a couple of years ago that had an optical Intel TOSLINK, the quality difference compared to an M-Audio Delta DIO ($325) PCI card was small. The Delta DIO also has coaxial which sounded somewhat nicer then the glass optical when using an MIT T3 digital coaxial ($125 cable).

Still, the Scott Nixon USB DAC looks like a nice package. I asked about a demo unit but he says people are keeping the demos too long and he’s lost track of who has it and was getting frustrated and wanted to call the unit back in.
I’m sorry Scott has lost control of his demo but I’d still like to try it before I buy it, he doesn’t have a return policy so that’s not a option either. Also the USB DAC doesn’t have any other type of input so its forever a USB device. By the time he adds a coaxial input the cost of the unit is too high.

[lcrim]

boead:
The cable that I provided a link to is not a digital cable per se but a USB cable that utilizes the optical format to transmit its data.  The possibility that EMI/RFI can interfere w/ USB communications is eliminated.  The translater device that creates the optical signal then becomes of great interest.  The discussion is at this address  http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=10850&highlight=optical+usb&r=&session=

[boead]

boead:
The cable that I provided a link to is not a digital cable per se but a USB cable that utilizes the optical format to transmit its data.  The possibility that EMI/RFI can interfere w/ USB communications is eliminated.  The translater device that creates the optical signal then becomes of great interest.  The discussion is at this address  http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=10850&highlight=optical+usb&r=&session=

Thanks Larry, I understood.

That’s fine if I want a USB DAC and if I’m concerned about distance on a USB cable. I’m going to try out a buffered USB cable and I’ll even try none at all. Scott said that a long 20+ foot USB cable he made worked just fine. No need for a complex and expensive device to convert to optical and then back again for 30 feet. Maybe for 100 feet or more.

My experience comparing polly TOSLINK and glass showed a significant increase in fidelity with the glass optical and only marginal increase with coaxial over glass with 1 meter runs. I believe that the longer you go the better the optical becomes compared to coaxial. I think a 30 foot glass optical is likely better then coaxial. But I’m only guessing. Once thing is for sure, Glass optical at 30’ are a lot more costly then polly but still relatively cheap compared to the cost of quality brand IC’s.