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PostPosted: Mon Jun 05, 2017 5:20 am 
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Joined: Tue Oct 30, 2007 10:18 am
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Location: ottawa, ON, CA
I have a CD player that can of course provide regular output through RCA jacks......but there is also a single RCA out marked digital out. Are there cables to connect the RCA digital out from the CD player to the USB input of a DAC? Audioquest or a similar quality and reasonably affordable type cable? Thanks. Andrew


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PostPosted: Mon Jun 05, 2017 5:29 am 
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Joined: Wed Aug 08, 2012 4:17 pm
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Location: Winnipeg, MB, CA
that would be a coax connection. Your dac will likely have the input and cables are abundantly available.


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PostPosted: Mon Jun 05, 2017 6:22 am 
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Joined: Wed Oct 10, 2012 10:07 am
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Location: Repentigny, QC, CA
You need an adapter, with usb input only DAC, BUT.

I quote from Quora:
Can you buy an adapter to convert coaxial cable to USB?
Yes... But not one that simply lets you run the same kind of signal.

There are certainly adapters such as a USB TV stick that will allow you to convert a television signal to something your computer can use.

If you're looking to use different wiring to run cable for a USB device, the issue you'd be facing in creating one is that coaxial cable has a conductor and a ground, whereas USB is a 4 wire setup, carrying data and power.

Let's say that the coaxial would carry just data and you could use a wall wart for the 5v power, I guess you could potentially make one.

Then your second issue would be in matching the data signal to make USB understand what exactly is being sent through the coax. It's most likely a lot more complicated than it looks at first glance.

If you were strictly running USB data (green and white) through the coax with a 5v power injection into the adapter.. Maybe.


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PostPosted: Mon Jun 05, 2017 6:26 am 
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Joined: Sat Jul 04, 2009 6:08 pm
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Location: Montreal, QC, CA
It depends on what inputs your USB DAC has. If it only has a USB input, then you are SOL. If it has a USB input AND also a digital input or 2, one of them will probably be a Coax or Toslink (optical) input. All you need is a proper DIGITAL coax cable (75 ohm) to connect the 2.

If not, them what you are looking for is a Digital to Digital Coax to USB converter, something I have never seen because everyone wants Digital to Analog or Analog to Digital conversions at the same time and because the 2 digital protocol are different.


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PostPosted: Mon Jun 05, 2017 6:55 am 
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Joined: Fri Mar 25, 2016 12:47 pm
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Location: Leduc, AB, CA
Why would you want to do this? The only designed/engineered digital connector changeovers are digital coax and digital BNC, as they are both SPDIF specification. USB is not compatible with any of the non-USB inputs on a DAC. USB connections are two-way; all others are one-way. The lion's share of DACs have been designed to accept SPDIF coax output from a CD player/CD transport's coax output. Optical has to go to Optical and XLR has to go to XLR. The USB input on your DAC is specifically designed to accept a digital signal from your computer so that you can stream music from the internet. The DAC's USB input has a special additional circuit built in to accommodate the extra timing requirements of the computer's signal. USB inputs on DACs are a very recent development of the digital mainstream of playback, designed to take advantage of the extended bandwidth afforded by internet streaming of music from sources such as Tidal.

In layman's terms, your idea would be akin to the tail waging the dog. Even if you could find such a cable combination, or manage this with gender converters of some sort, you could potentially cause some damage, if not to your DAC, then to your speakers if distortion levels suddenly ramp up as the connection finalizes.

In practical terms, if your DAC is more than a few years old, that USB input on the back is more likely for control purposes, i.e., a wired internet remote control, and has no ability to process a music stream. If you have completely run out of digital inputs on your DAC, you may have to institute a unplug/replug scenario between sources, with the DAC temporarily turned off and the input selector of your preamp pointed elsewhere with the volume set to zero, please!


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PostPosted: Mon Jun 05, 2017 11:09 am 
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Joined: Tue Oct 30, 2007 10:18 am
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Location: ottawa, ON, CA
OK thanks everyone. Sounds like I just have two incompatible pieces: my DAC is only designed to receive a USB signal - no other inputs possible. My CD player only has an RCA for digital out.

I won't worry about it and for now just connect my CD player straight to the integrated amp.


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PostPosted: Mon Jun 05, 2017 1:55 pm 
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Joined: Thu Sep 17, 2015 2:08 pm
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Location: victoria, BC, CA
This would be a total long shot and probably isn't possible anyway, but .. if your DAC has an IIS/I2S input points on it's circuit board you could add an optical/coax receiver board:

http://www.ebay.ca/itm/142031681322?_tr ... EBIDX%3AIT

If you know an electronics expert who could DIY this, might be worth a gamble. I think these boards are usually meant for China made DAC kits that have the IIS/I2S input solder points.


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PostPosted: Tue Jun 06, 2017 1:07 pm 
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Location: Vernon, BC, CA
Heads up for next time...stating the make and model of the equipment in question can go a long way to helping us help you.


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PostPosted: Tue Jun 06, 2017 3:49 pm 
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Joined: Fri Mar 25, 2016 12:47 pm
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Location: Leduc, AB, CA
You shouldn't feel down by any stretch. Have you tried transferring any of your CD's onto your computer? You could then play them back through your DAC into your amp; the sound quality might be better this way, especially if your DAC is new and your CD player is relatively old. These are the kinds of "give it a try" exercises that very often lead to a lot of new learning and good old fashion hobby fun. If this "works" for you, check out Tidal; I believe they still offer a free 30 day trial. All kinds of possibilities mushrooming here, perhaps. Cheers!


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